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Archive for the ‘Explanatory’ Category

The History of Hematology and Related Sciences

Curator: Larry H. Bernstein, MD, FCAP

 

The History of Hematology and Related Sciences: A Historical Review of Hematological Diagnosis from 1880 -1980

 

Blood Description: The Analysis of Blood Elements a Window into Diseases

Diagnosing bacterial infection (BI) remains a challenge for the attending physician. An ex vivo infection model based on human fixed polymorphonuclear neutrophils (PMNs) gives an autofluorescence signal that differs significantly between stimulated and unstimulated cells. We took advantage of this property for use in an in vivo pneumonia mouse model and in patients hospitalized with bacterial pneumonia. A 2-fold decrease was observed in autofluorescence intensity for cytospined PMNs from broncho-alveolar lavage (BAL) in the pneumonia mouse model and a 2.7-fold decrease was observed in patients with pneumonia when compared with control mice or patients without pneumonia, respectively. This optical method provided an autofluorescence mean intensity cut-off, allowing for easy diagnosis of BI. Originally set up on a confocal microscope, the assay was also effective using a standard epifluorescence microscope. Assessing the autofluorescence of PMNs provides a fast, simple, cheap and reliable method optimizing the efficiency and the time needed for early diagnosis of severe infections. Rationalized therapeutic decisions supported by the results from this method can improve the outcome of patients suspected of having an infection.

Monsel A, Le´cart S, Roquilly A, Broquet A, Jacqueline C, et al. (2014) Analysis of Autofluorescence in Polymorphonuclear Neutrophils: A New Tool for Early Infection Diagnosis. PLoS ONE 9(3): e92564.
http://dx.doi.org:/10.1371/journal.pone.0092564

This study was designed to validate or refute the reliability of total lymphocyte count (TLC) and other hematological parameters as a substitute for CD4 cell counts. Participants consisted of two groups, including 416 antiretroviral naive (G1) and 328 antiretroviral experienced (G2) patients. CD4+ T cell counts were performed using a Cyflow machine. Hematological parameters were analyzed using a hematology analyzer. The median ± SEM CD4 count (range) of participants in G1 was 199 ± 10.9 (5–1840 cells/μL) and the median ± SEM TLC (range) was 1. 61 ± 0.05 (0.07–6.63 × 103/μL). The corresponding values among G2 were 421 ± 15.8 (13–1801) and 2.13 ± 0.04 (0.06–5.58), respectively. Using a threshold value of 1.2 × 103/μL for TLC alone, the sensitivity of G1 was 88.4% (specificity (SP) 67.4%, the positive predictive value (PPV) 53.5% and negative predictive value (NPV) of 93.2% for CD4 , 200 cells/μL, the sensitivity for G2 was 83.3%, SP 85.3%, PPV 23.8%, and NPV of 93.2%. Using multiple parameters, including TLC , 1.2 × 103/μL, hemoglobin , 10 g/dL, and platelets , 150 × 103/L, the sensitivity increased to 96.0% (SP, 82.7%; PPV, 80%; NPV, 96.7%) among G1, while no change was observed in the G2 cohort. TLC , 1.2 × 103/μL alone is an insensitive predictor of CD4 count of , 200 cells/μL. Incorporating hemoglobin , 10 g/dL, and platelets , 150 × 103/L enhances the ability of TLC , 1.2 × 103/μL to predict CD4 count , 200 cells/μL among the antiretroviral-naïve cohort. We recommend the use of multiple, inexpensively measured hematological parameters in the form of an algorithm for predicting CD4 count level.

Evaluating Total Lymphocyte Counts and Other Hematological Parameters as a Substitute for CD4 Counts in the Management of HIV Patients in Northeastern Nigeria. BA Denue, AU Abja, IM Kida, AH Gabdo, AA Bukar and CB Akawu.
Retrovirology: Research and Treatment 2013:5 9–16 http://dx.doi.org:/10.4137/RRT.S11562

Sepsis is a syndrome that results in high morbidity and mortality. We investigated the delta neutrophil index (DN) as a predictive marker of early mortality in patients with gram-negative bacteremia. Retrospective study. The DN was measured at onset of bacteremia and 24 hours and 72 hours later. The DN was calculated using an automatic hematology analyzer. Factors associated with 10-day mortality were assessed using logistic regression. A total of 172 patients with gram-negative bacteremia were included in the analysis; of these, 17 patients died within 10 days of bacteremia onset. In multivariate analysis, Sequental organ failure assessment scores (odds ratio [OR]: 2.24, 95% confidence interval [CI]: 1.31 to 3.84; P = 0.003), DN-day 1 ≥ 7.6% (OR: 305.18, 95% CI: 1.73 to 53983.52; P = 0.030) and DN-day 3 ≥ DN day 1 (OR: 77.77, 95% CI: 1.90 to 3188.05; P = 0.022) were independent factors associated with early mortality in gram-negative bacteremia. Of four multivariate models developed and tested using various factors, the model using both DN-day 1 ≥ 7.6% and DN-day 3 ≥ DN-day 1 was most predictive early mortality. DN may be a useful marker of early mortality in patients with gram-negative bacteremia. We found both DN-day 1 and DN trend to be significantly associated with early mortality.

Delta Neutrophil Index as a Prognostic Marker of Early Mortality in Gram Negative Bacteremia. HW Kim, JH Yoon, SJ Jin, SB Kim, NS Ku, SJ Jeong,
et al. Infect Chemother 2014;46(2):94-102. pISSN 2093-2340·eISSN 2092-6448
http://dx.doi.org/10.3947/ic.2014.46.2.94
Various indices derived from red blood cell (RBC) parameters have been described for distinguishing thalassemia and iron deficiency. We studied the microcytic to hypochromic RBC ratio as a discriminant index in microcytic anemia and compared it to traditional indices in a learning set and confirmed our findings in a validation set. The learning set comprised samples from 371 patients with microcytic anemia mean cell volume (MCV < 80 fL), which were measured on a CELL-DYN Sapphire analyzer and various discriminant functions calculated. Optimal cutoff values were established using ROC analysis. These values were used in the validation set of 338 patients. In the learning set, a microcytic to hypochromic RBC ratio >6.4 was strongly indicative of thalassemia (area under the curve 0.948). Green-King and England-Fraser indices showed comparable area under the ROC curve. However, the microcytic to hypochromic ratio had the highest sensitivity (0.964). In the validation set, 91.1% of microcytic patients were correctly classified using the M/H ratio. Overall, the microcytic to hypochromic ratio as measured in CELL-DYN Sapphire performed equally well as the Green-King index in identifying thalassemia carriers, but with higher sensitivity, making it a quick and inexpensive screening tool.
Differential diagnosis of microcytic anemia: the role of microcytic and hypochromic erythrocytes. E. Urrechaga, J.J.M.L. Hoffmann, S. Izquierdo, J.F. Escanero. Intl Jf Lab Hematology Aug 2014. http://dx.doi.org:/10.1111/ijlh.12290

Achievement of complete response (CR) to therapy in chronic lymphocytic leukemia (CLL) has become a feasible goal, directly correlating with prolonged survival. It has been established that the classic definition of CR actually encompasses a variety of disease loads, and more sensitive multiparameter flow cytometry [and polymerase chain reaction methods] can detect the disease burden with a much higher sensitivity. Detection of malignant cells with a sensitivity of 1 tumor cell in 10,000 cells (10–4), using the above-mentioned sophisticated techniques, is the current cutoff for minimal residual disease (MRD). Tumor burdens lower than 10–4 are defined as MRD-negative. Several studies in CLL have determined the achievement of MRD negativity as an independent favorable prognostic factor, leading to prolonged disease-free and overall survival, regardless of the treatment protocol or the presence of other pre-existing prognostic indicators. Minimal residual disease evaluation using flow cytometry is a sensitive and applicable approach which is expected to become an integral part of future prospective trials in CLL designed to assess the role of MRD surveillance in treatment tailoring.

Minimal Residual Disease Surveillance in Chronic Lymphocytic Leukemia by Fluorescence-Activated Cell Sorting. S Ringelstein-Harlev, R Fineman.
Rambam Maimonides Med J. Oct 2014   5 (4)  e0027. http://dx.doi.org:/10.5041/RMMJ.10161

Natural Killer cells (CD3-CD16+CD56+) are a major players in innate immunity, both as direct cytotoxic effectors as well as regulators for other innate immunity cell types. We have shown that, using the FlowCellect™ human NK cell characterization kit, one can achieve accurate phenotyping on a variety of sample types, including whole blood samples. Using the same kit to perform an NK cell cytotoxicity test, we demonstrate that unbound K562 target cells can be clearly distinguished from those that have been engaged by CD56+ NK cells, and each of these populations can be further investigated for viability using the eFluor 660® dye.

Analysis of NK cell subpopulations in whole blood

Analysis of NK cell subpopulations in whole blood

Analysis of NK cell subpopulations in whole blood

A

Proportion of K562 target cells bound to NK cells

Proportion of K562 target cells bound to NK cells

In a 5:1 effector cell:target cell population, 8% of the K562 cells were bound to NK cells (Figure 3B). 84% of the bound K562 cells were viable (Figure 3C) stained with fixable viability dye), while 96% of the unbound K562 cells were viable (Figure 3D). (B,C,D not shown)

Characterization of Natural Killer Cells Using Flow Cytometry.
EMD Millipore is a division of Merck KGaA, Darmstadt, Germany.

Red blood cell distribution width (RDW) is increased in liver disease. Its clinical significance, however, remains largely unknown. The aim of this study was to identify whether RDW was a prognostic index for liver disease. Retrospective: 33 patients with non-cirrhotic HBV chronic hepatitis, 125 patients with liver cirrhosis after HBV infection, 81 newly diagnosed primary epatocellular carcinoma (pHCC) patients, 17 alcoholic liver cirrhosis patients and 42 patients with primary biliary cirrhosis (PBC). Sixty-six healthy individuals represented the control cohort. The relationship between RDW on admission and clinical features: The association between RDW and hospitalization outcome was estimated by receiver operating curve (ROC) analysis and a multivariable logistic regression model. Increased RDW was observed in liver disease patients. RDW was positively correlated with serum bilirubin and creatinine levels, prothrombin time, and negatively correlated with platelet counts and serum albumin concentration. A subgroup analysis, considering the different etiologies, revealed similar findings. Among the patients with liver cirrhosis, RDW increased with worsening of Child-Pugh grade. In patients with PBC, RDW positively correlated with Mayo risk score. Increased RDW was associated with worse hospital outcome, as shown by the AUC [95% confidence interval (CI)] of 0.76 (0.67 – 0.84). RDW above 15.15% was independently associated with poor hospital outcome after adjustment for serum bilirubin, platelet count, prothrombin time, albumin and age, with the odds ratio (95% CI) of 13.29 (1.67 – 105.68). RDW is a potential prognostic index for liver disease.

Red blood cell distribution width is a potential prognostic index for liver disease
Z Hua , Y Suna , Q Wanga , Z Han , Y Huang , X Liu , C Ding, et al.
Clin Chem Lab Med 2013; 51(7):1403–1408.
http://dx.doi.org:/10.1515/cclm-2012-0704

Blood Plasma and Red Blood Cells

Whole blood consists of red and white blood cells, as well as platelets suspended in a liquid referred to as blood plasma. According to the American Red Cross, plasma is 92% water and makes up 55% of blood volume. The permeability of blood plasma is equal to 1.

Red blood cells make up slightly lower blood volume than blood plasma — about 45% of whole blood. As you probably already know, these types of blood cells contain hemoglobin, which in turn consists of iron that helps transport oxygen throughout the body. The permeability of red blood cells is slightly less than 1,
(1 – 3.9e-6). Or to put it in words, red blood cell particles are diamagnetic.

Due to their magnetic properties, red blood cells may be separated from the plasma via a magnetophoretic approach. If the blood were to be in a channel subject to a magnetophoretic force, we could control where the red blood cells and the plasma go within the channels. In other words, because the red blood cells have different permeability, they can be separated from the flow channel. However, such methodology is beyond the year 1980.

Timeline of Major Hematology Landmarks

1877 Paul Ehrlich develops techniques to stain blood cells to improve microscopic visualization.

1897 The Diseases of Infancy and Childhood contains a 20-page chapter on diseases of the blood and is the first American pediatric medical textbook to provide significant hematologic information.

1821–1902 Rudolph Virchow, during a long and illustrious career, demonstrates the importance of fibrin in the blood coagulation process, coins the terms embolism and thrombosis, identifies the disease leukemia, and theorizes that leukocytes are made in response to inflammation.

1901 Karl Landsteiner and colleagues identify blood groups of A, B, AB, and O.

1907 Ludvig Hektoen suggests that the safety of transfusion might be improved by crossmatching blood between donors and patients to exclude incompatible mixtures. Reuben Ottenberg performs the first blood transfusion using blood typing and crossmatching in New York. Ottenberg also observes the Mendelian inheritance of blood groups and recognizes the “universal” utility of group O donors.

1910 The first clinical description of sickle cell published in medical literature.

1914 Sodium citrate is found to prevent blood from clotting, allowing blood to be stored between collection and transfusion.

1924 Pediatrics is the first comprehensive American publication on pediatric hematology.

1925 Alfred P. Hart performs the first exchange transfusion.

1925 Thomas Cooley describes a Mediterranean hematologic syndrome of anemia, erythroblastosis, skeletal disorders, and splenomegaly that is later called Cooley’s anemia and now thalassemia.

1936 Chicago’s Cook County Hospital establishes the first true “blood bank” in the United States.

1938 Dr. Louis Diamond (known as the “father of American pediatric hematology”) along with Dr. Kenneth Blackfan describes the anemia still known as Diamond-Blackfan anemia.

1941 The Atlas of the Blood of Children is published by Blackfan, Diamond, and Leister.

1945 Coombs, Mourant, and Race describe the use of antihuman globulin (later known as the “Coombs Test”) to identify “incomplete” antibodies.

1954 The blood product cryoprecipitate is developed to treat bleeds in people with hemophilia.

1950s The “butterfly” needle and intercath are developed, making IV access easier and safer.

1961 The role of platelet concentrates in reducing mortality from hemorrhage in cancer patients is recognized.

1962 The first antihemophilic factor concentrate to treat coagulation disorders in hemophilia patients is developed through fractionation.

1969 S. Murphy and F. Gardner demonstrate the feasibility of storing platelets at room temperature, revolutionizing platelet transfusion therapy.

1971 Hepatitis B surface antigen testing of blood begins in the United States.

1972 Apheresis is used to extract one cellular component, returning the rest of the blood to the donor.

1974 Hematology of Infancy and Childhood is published by Nathan and Oski.

As I write today my hospital celebrates its 150th anniversary. Great Ormond Street Children’s Hospital was founded on 14 February 1852 by the visionary Dr Charles West followed his belief that hospital care allied to research in children’s diseases would reduce child mortality from above 50% by the age of 15 years. It is foolish to believe that we can progress in medicine without a knowledge of the past and that much of life is based upon experience. When putting together a series of articles on the history of haematology, initially published in BJH, this was the main raison d’être, along with the belief that the practice of medicine has become increasingly serious but should also be fun and interesting and even occasionally uplifting to the spirit.

The central problem of any survey of the history of haematology is usually the question of balance. Achieving a degree of balance among themes and topics that will be satisfactory to practicing haematologists/physicians with an interest in blood diseases is essentially impossible. Our preference has been for themes of general interest rather than those of a purely scientific view into a field that has led the way in understanding the molecular basis of human disease.

  1. M. Hann, London, 2002; O. P. Smith, Dublin, 2002.

Origins of the Discipline `Neonatal Haematology’, 1925-75

In every modern neonatal intensive care unit (NICU), haematological problems are encountered daily. Many of these problems involve varieties of anaemia, neutropenia or thrombocytopenia that are unique to NICU patients. A characteristic aspect of these unique problems is that, if the neonate survives, the haematological problem will remit and will not recur later in life, nor will it evolve into a chronic illness (although the problem might occur in a future newborn sibling). This characteristic comes about because the common haematological problems of NICU patients are not genetic defects but are environmental stresses (such as infection, alloimmunization or a variety of maternal illnesses) that are imposed on a developmentally immature haematopoietic system.

In the USA, and in some parts of Europe, the unique haematological problems that occur among NICU patients are diagnosed and treated by neonatologists, not by paediatric haematologists. Although these haematological conditions were generally first described by haematologists, the conditions occur, obviously, in neonates. Thus, the neonatologist, who is familiar with intensive care management of neonates, has also become familiar with the diagnosis and management of the neonate’s common haematological disorders. A growing number of neonatologists have sought specific additional training in haematology, with the goals of discovering the mechanisms underlying the unique haematological problems of NICU patients and improving the management and outcome of the patients who have these conditions. These physicians have remained as neonatologists and they do not practice paediatric haematology, although their research contributions certainly come under the purview of haematology, or more precisely under the discipline of `neonatal haematology’. In many places in Europe, it is the haematologists rather than the neonatologists who have an academic and clinical interest in neonatal haematology.

The roots of the discipline of neonatal haematology can be traced to the early application of haematological methods to animal and human embryos and fetuses, such as found in the reports of Maximow (1924) and Wintrobe & Schumacker (1936). The clinical underpinnings of this discipline include reports of anaemia (Fikelstein, 1911) and jaundice (Blomfeld, 1901; YlppoÈ, 1913) among neonates.

Before the 1930s, very few studies and very few published clinical case reports originated from premature nurseries. Such nurseries had dubious beginnings, which were criticized by some physicians as more resembling circus exhibitions than medical care wards (Bonar, 1932). These units generally had mortality rates greatly exceeding 50% on the day of admission, with the majority of the first-day survivors having late deaths or serious long-term morbidity.

It was not until publication of the review of premature nursery care at the Children’s Hospital of Michigan, in 1932, that it was clear that some units had instituted systematic attempts to monitor and improve outcomes. A special care nursery had been established at the Children’s Hospital in 1926 and, in 1932, Drs Marsh Poole and Thomas Cooley reported their experience in that unit (Poole & Cooley, 1932). The report included  incubator design with temperature and humidity control, growth curves of patients on various feeding practices, mortality statistics and attempts to determine causes of death.

At the time premature nursery care was beginning to merit academic credentials, reports were published of haematological problems that were unique to the neonate. These papers included the seminal publication on erythroblastosis fetalis by Drs Diamond (Fig 1), Blackfan and Baty (Diamond et al, 1932), and the report of sepsis neonatorum at the Yale New Haven Hospital by Ethyl C. Dunham (Fig 2) (Dunham,

1933).

The first major textbook devoted to clinical haematology, as well as the first textbook of neonatology, contained very little information about what are today’s common NICU haematological problems. For instance, in the first edition of Clinical Hematology by Dr Maxwell M. Wintrobe (Fig 3), of the Johns Hopkins University Hospital (Wintrobe, 1942), several topics related to paediatric haematology were reviewed, but discussions of the haematological problems of neonates were limited to three – erythroblastosis fetalis, haemorrhagic disease of the newborn and the `anaemia of prematurity’. Similarly, Premature Infants: A Manual for

Physicians, the original neonatology textbook, published in 1948 by Dr Ethyl C. Dunham (Fig 2; Dunham, 1948), had only a few pages devoted to haematological problems – the same three discussed by Dr Wintrobe. Also, the classic neonatology text book, `The Physiology of the Newborn Infant’, published in 1945 by Dr Clement A. Smith, contained almost no discussion of haematological problems (Smith, 1945). hrombocytopenia, which is now diagnosed among 25-30% of NICU patients, and neutropenia, now diagnosed in 8-10% of NICU patients, were not mentioned.

The first article published in Paediatrics (1948) dealing with a neonatal haematological problem was in volume two, in which Dr Diamond detailed his technique for performing a replacement transfusion (which later became known as an `exchange’ transfusion) as a treatment for erythroblastosis fetalis (Diamond, 1949). The second paper published by Paediatrics containing aspects of neonatal haematology was 1 year later, when Sliverman & Homan (1949) described leucopenia among neonates with sepsis. Most of the 25 infants they described, who were treated at Babies Hospital in New York over an 11-year period, had `late-onset’ sepsis, beginning after 3 days of life. They reported 14 neonates with Escherichia coli sepsis and four with streptococcal or staphylococcal sepsis, and observed that leucopenia occurred occasionally among these patients but was uncommon. (Indeed, today neutropenia remains uncommon in `late-onset’ sepsis, but common in congenital or `early onset’ sepsis.)

Louis K. Diamond, MD, at Children's Hospital, Boston,

Louis K. Diamond, MD, at Children’s Hospital, Boston,

Louis K. Diamond, MD, at Children’s Hospital, Boston, MA. , date unknown (obtained with the kind assistance of Charles F. Simmons, MD, Harvard University).

Diagnosing neutropenia, anaemia or thrombocytopenia in a neonate obviously requires knowledge of the expected normal range for neutrophil concentration, haematocrit and platelet concentration in the appropriate reference population. Early contributions to neonatal haematology included the publications of these reference ranges. The landmark studies included the range of blood leucocyte and neutrophil concentrations in neonates published in 1935 by Dr Katsuji Kato from the Department of Paediatrics at the University of Chicago (Kato, 1935). He tabulated the leucocyte concentrations and differential counts of 1081 children, ranging from birth to 15 years of age. A striking finding of his report (Fig 4) was the very high neutrophil counts during the first hours and days of life. Blood neutrophil concentrations among neonates with infections were published during the early and mid-1970s by Dr Marietta Xanthou (Fig 5) at the Hammersmith Hospital in London (Xanthou, 1970, 1972), and by Drs Barbara Manroe and Charles Rosenfeld (Fig 6) at the University of Texas Southwestern Medical Center in Dallas, Texas (Manroe et al, 1977).

Normal values for haemoglobin, haematocrit, erythrocyte indices and leucocyte concentrations were refined by DeMarsh et al (1942, 1948), and in a series of publications in the early 1950s in Archives of Diseases of Children by Gairdner et al (1952a, b). These were followed by observations on human fetal haematopoiesis by Thomas and Yoffey in the British Journal of Haematology (Thomas & Yoffey, 1962, 1964), and by the work on blood volume during the 1960s (Usher et al, 1963, Usher & Lind, 1965; Yao et al, 1967, 1968). Normal ranges for blood platelet counts in ill and well preterm and term infants were published in the early 1970s (Sell et al, 1973; Corrigan, 1974).

The first publication addressing the problem of neutropenia accompanying fatal early onset bacterial sepsis was that of Tygstrup et al (1968). This was a report of a near-term male with congenital Listeria sepsis who lived for only 4 h. The platelet count was 80*109/l and the leucocyte count was 13´7*109/l, but no granulocytes were observed on the differential count, which consisted of 84% lymphocytes, 8% monocytes and 8% leucocyte precursors. A sternal marrow aspirate was taken of the infant shortly before death that revealed myeloblasts, promyelocytes and myelocytes, but no band or segmented neutrophils.

An important advance in understanding the blood neutrophil count during neonatal sepsis occurred with the back-to-back papers in Archives of Diseases of Childhood in 1972 by Dr Marietta Xanthou of Hammersmith Hospital, London (Xanthou, 1972), and Drs Gregory and Hey of Babies’ Hospital, Newcastle upon Tyne (Gregory & Hey, 1972). Both papers reported that neonates who had life threatening (or indeed fatal) infections became neutropenic prior to death. Dr Xanthou reported 35 ill preterm and term babies within their first 28 d of life. Twenty-four were ill but not infected, and these had normal blood neutrophil concentrations and morphology. However, among the 11 who were ill with a bacterial infection, neutrophilia was observed in the survivors, but neutropenia, a `left shift’, and toxic granulation were observed in the non-survivors. Consistent with this observation, Gregory and Hey reported three neonates who died with overwhelming bacterial sepsis and noted that all had profound neutropenia. Neutrophilia was common among the survivors and neutropenia, a “left shift’, and specific neutrophil morphological changes were seen among those who subsequently died.

A pivotal publication that launched the search for mechanistic information and successful treatments was that of Dr Barbara Manroe, a fellow in Neonatal Medicine, and her mentor Dr Charles Rosenfeld (Fig 6) from the University of Texas, South-western, Parkland Hospital in Dallas, Texas (Manroe et al, 1977). They evaluated 45 neonates who had culture-proven group B streptococcal infection and found that 39 had abnormal leucocyte counts: 25 neutrophilia and 14 neutropenia, and that 41 had a `left shift’. This paper was the first to quantify the `left shift’ using a method that has since become popular in neonatology – the ratio of immature neutrophils to total neutrophils on the differential cell count.

From these beginning, hundreds of studies using experimental models and clinical observations and trials were published, detailing the kinetic and molecular mechanisms accounting for this common variety of neutropenia. Marked improvements in the survival of neonates with this condition have come about through combined efforts, including early maternal screening for GBS carriage, early anti-microbial administration to ill neonates, non-specific antibody administration and a variety of measures to improve supportive care of neonates with early onset sepsis.

In the early 1930s, Dr Helen Mackay worked as a paediatrician in Mother’s Hospital, a maternity hospital located in the north-east section of London. Acting on the observation of Lichtenstein (1921) that infants of subnormal birth weight regularly became anaemic in the first months of life, she measured and reported serial heel-stick haemoglobin levels on 150 infants during their first 6 months. Thirty-nine of these infants weighed under five pounds at birth (six were under four pounds), 52 weighed five to six pounds, and 59 weighed six pounds and upwards. She showed that babies of the lightest birth weights had the most rapid fall in haemoglobin and that these fell to lower levels than those of babies of heavier birth weight (MacKay et al, 1935). Figure 7 contrasts this fall in babies weighing `3-4 lbs odd at birth’ with those weighing `5 lbs odd at birth’.

Her attempts to prevent the anaemia of prematurity failed,  but her work constituted the first clear definition of the `anaemia of prematurity’ and showed that iron administration did not prevent this condition. In the early 1950s, Douglas Gairdner, John Marks and Janet D. Roscoe, of the Department of Pathology of Cambridge Maternity Hospital, published pioneering studies in blood formation in infancy (Gairdner et al, 1952a, b). Studying 105 blood samples and 102 bone marrow samples, they concluded that `erythropoiesis ceases when the oxygen saturation just after birth increases from about 65% in the umbilical vein to .95% just after birth’. Publications by Dr Irving Schulman, in the mid- to late 1950s, defined three phases of the anaemia of prematurity and provided a mechanistic explanation for the anaemia (Schulman & Smith, 1954; Schulman, 1959). His work illustrated that the early and intermediate phases of this anaemia occur in the face of relative iron excess and are unaffected by prophylactic iron administration.

Haemoglobin levels during the first 25 weeks of life among

Haemoglobin levels during the first 25 weeks of life among

Haemoglobin levels during the first 25 weeks of life among neonates in London [by permission; Archives Diseases of Children, (MacKay, 1935)].

In 1963, Dr Sverre Halvorsen of the Department of Paediatrics at Rikshospatalet in Oslo, Norway (Fig 9), provided an underlying explanation for the observations made by MacKay, Gairdner and Schulman (Halvorson, 1963). He observed that, compared with the blood of healthy adults, umbilical cord blood of healthy neonates had a high erythropoietin concentration, but the concentration was considerably higher in the plasma of severely erythroblastotic, anaemic infants. Among the healthy infants, erythropoietin levels fell to unmeasurably low concentrations after delivery, but levels remained elevated in hypoxic and cyanotic infants. Dr Per Haavardsholm Finne, also of the Children’s Department, Paediatric Research Institute and Department of Obstetrics and Gynaecology at Rikshospitalet in Oslo, observed high oncentrations of erythropoietin in the amniotic fluid and the umbilical cord blood after fetal hypoxia (Finne, 1964, 1967).

In subsequent studies, Dr Halvorsen observed lower plasma erythropoietin concentrations in the cord blood of preterm infants at delivery than in term neonates at delivery (Halvorsen & Finne, 1968). These observations supported the concept of Gairdner et al (1952a, b) that the postnatal fall in erythropoiesis (the `physiologic anaemia’ of neonates) is as a result of an increase in oxygen delivery to tissues following birth and is mediated by a fall in circulating erythropoietin concentration. The observations gave rise to the postulate that the `anaemia of prematurity’ was an exaggeration of this physiological anaemia and involved a limitation of preterm infants to appropriately increase erythropoietin production.

Many landmark reports of haematological findings of neonates that were published between 1925 and 1975 were not detailed in this review because they were outside the restricted topics selected.

Robert D. Christensen, MD, Gainesville, FL
Brit J Haem 2001; 113: 853-860

Towards Molecular Medicine; Reminiscences of the Haemoglobin Field

When historians of medicine in the twentieth century start to piece together the complex web of events that led from a change of emphasis of medical research from studies of patients and their organs to disease at the levels of cells and molecules they will undoubtedly have their attention drawn to the haemoglobin field, particularly the years that followed Linus Pauling’s seminal paper in 1949 which described sickle-cell anaemia as a `molecular disease’. These are personal reminiscences of some of the highlights of those exciting times, and of those who made them happen.

One of my first patients serving the RAMC was a Nepalese Ghurka child who was kept alive from the first few months of life with regular blood transfusion without a diagnosis. Henry Kunkel published a paper which described how, using electrophoresis in slabs of starch, he had found a minor component of human haemoglobin (Hb), Hb A2, the proportion of which was elevated in some carriers of thalassaemia. After several weeks spent knee deep in potato starch, we found that the Ghurka child’s parents had increased Hb A2 levels and, hence, that she was likely to be homozygous for thalassaemia. I was hauled up before the Director General of Medical Services for the Far East Land Forces and told that I could be court marshalled for not getting permission from the War House (Office) to publish information about military personnel. `And, in any case’, he added, `it is bad form to tell the world that one of our pukka regiments has bad genes; don’t do it again’.

Just before the end of my National Service I arranged to go to Johns Hopkins Hospital in Baltimore to train in genetics and haematology. I was told that I was wasting my time working on haemoglobin because there was `nothing left to do’. `Start exploring red cell enzymes’, he suggested. On arriving in Baltimore in 1960 it turned out that human genetics, and the haemoglobin field in particular, were bubbling with excitement and potential. The only lessons for those contemplating careers in medical research from this chapter of academic and military gaffs are that, regardless of the working conditions, when there are sick people there are always interesting research questions to be asked.

The excitement of the haemoglobin field in 1960 reflected the chance amalgamation of several disciplines in the 1950s, particularly X-ray crystallography, protein chemistry, human genetics and haematology.

From the early 1930s the structure of proteins became one of the central problems of biochemistry. At that time, the only way of tackling this problem was by X-ray crystallography. In 1937 Felix Haurowitz suggested to Max Perutz (Fig 1) that an X-ray study of haemoglobin might be a good subject for his doctoral thesis. He was given some large crystals of horse methaemoglobin which gave excellent Xray diffraction patterns.

Max Perutz

Max Perutz

However, there was a major snag; an X-ray diffraction pattern provided only half the information required to solve the structure of a protein, that is the amplitudes of diffracted rays, while the other half, their phases, could not be determined. But in 1953, they discovered that it could be solved in two dimensions by comparison of the diffraction patterns of a crystal of native haemoglobin with that of haemoglobin reacted with mecuribenzoate, which combines with its two reactive sulphydryl groups. In short, to solve the structure in three dimensions required the comparison of the diffraction patterns of at least three crystals, one native and two with heavy atoms combined with different sites on the haemoglobin molecule. In 1959 this approach yielded the first three-dimensional model of haemoglobin, at 5´5 AÊ resolution.

Protein chemistry evolved side-by-side with X-ray crystallography during the 1950s. In 1951 Fred Sanger solved the structure of insulin, a remarkable tour de force which showed that proteins have unique chemical structures and amino acid sequences. Sanger had perfected methods for fractionation and characterization of small peptides by paper chromatography or electrophoresis. In 1956 Vernon Ingram (Fig 2), who, like Max Perutz, was a refugee from Germany, was set the task of studying the structure of haemoglobin from patients with sickle-cell anaemia. Ingram separated the peptides produced after globin had been hydrolysed with the enzyme trypsin, which cuts only at lysine and arginine residues. Although these amino acids accounted for 60 residues per mol of haemoglobin, only 30 tryptic peptides were obtained, indicating that haemoglobin consists of two identical half molecules. Re-examination of the amino-terminal sequences of haemoglobin by groups in the United States and Germany showed 2 mols of valine ± leucine and 2 mols of valine ± histidine ± leucine per mol of globin. These findings, which were in perfect agreement with the X-ray crystallographic results, suggested that haemoglobin is a tetramer composed of two pairs of unlike peptide chains, which were called α and β.

A seminal advance, and one which was to mark the beginning of molecular medicine, was the chance result of an overnight conversation on a train journey between Denver and Chicago. Linus Pauling, the protein chemist, and William Castle (Fig 3), one of the founding fathers of experimental haematology, were returning from a meeting in Denver and Castle mentioned to Pauling that he and his colleagues had noticed that when red cells from patients with sickle-cell anaemia are deoxygenated and sickle they show birefringence in polarized light.

Five generations of Boston haematology. Seated is William Castle. Standing (left to right) are Stuart Orkin, David Nathan and Alan Michelson. The picture on the left is of Dean David Edsall of Harvard Medical School who established the Thorndyke Laboratory at the Boston City Hospital. He was succeeded by Dean Peabody, who recruited both George Minot, who won the Nobel Prize for his work on pernicious anaemia, and William Castle, who should have also received it.

Pauling guessed that this might reflect a structural difference between normal and sickle-cell haemoglobin which could be detected by a change in charge. He gave this problem to one of his postdoctoral students, a young medical graduate called Harvey Itano. At that time they knew that a Swede, Arne Tiselius, had invented a machine for separating proteins according to their charge by electrophoresis. As there was no machine of this kind in Pauling’s laboratory, Itano and his colleagues set to and built one. Eventually they found that the haemoglobin of patients with sickle-cell anaemia behaves differently to that of normal people in an electric field, indicating that it must have a different amino acid composition. Even better, the haemoglobin of sickle-cell carriers was a mixture of both types of haemoglobin. This work was published in Science in 1949, under the title `Sickle-cell anaemia: a molecular disease’.

Perutz and Crick suggested to Ingram that he should apply Sanger’s techniques of peptide analysis to see if he could find any difference between normal and sickle cell haemoglobin. After digesting haemoglobin with trypsin, Ingram separated the peptides by electrophoresis and chromatography in two dimensions to produce what he later called `fingerprints’. He recalls that his first efforts looked like a watercolour that had been left out in the rain. But gradually things improved and he was able to show that the fingerprints of Hbs A and S were identical except for the position of one peptide. Using a method that had been developed a few years earlier by Pehr Edman, which allowed a peptide to be degraded one amino acid at a time in a stepwise fashion, Ingram found that this difference was due to the substitution of valine for glutamic acid at position 6 in the β chain of Hb S.

As well as demonstrating how a crippling disease can result from only a single amino acid difference in the haemoglobin molecule, this beautiful work had broader implications for molecular genetics. Although nothing was known about the nature of the genetic code at the time, the findings were compatible with the notion that the primary product of the β-globin gene is a peptide chain, a further development of the one-gene-one-enzyme concept, suggested earlier by Beadle and Tatum from their studies of Neurospora, and a prelude to the later studies of Yanofsky on Escherichia coli, which were to confirm this principle.

With the advent of simple filter paper electrophoresis, haemoglobin analysis became the province of clinical research laboratories during the 1950s and `new’ abnormal haemoglobins appeared almost by the week. Although many scientists were involved it was Hermann Lehmann (Fig 4) who became the father figure. Like Handel, Hermann was born in Halle and, also like the composer, made his home in Great Britain. He came to England as a refugee and at the beginning of the Second World War had a short period of internment as a `friendly alien’ at Huyton, close to Liverpool, an experience shared with many others, including Max Perutz. He travelled widely during his later war service in the RAMC and developed a wide international network which enabled him to discover 81 haemoglobin variants during his career.

Harvey Itano and Elizabeth Robinson showed that Hb Hopkins 2 is an a chain variant. Hence, it was now clear that there must be at least two unlinked loci involved in regulating haemoglobin production, a and b. The discovery of the λ and δ chains of Hbs F and A2, respectively, meant that there must be at least four loci involved. Subsequent family studies and analyses of unusual variants resulting from the production of δβ or λβ fusion chains led to the ordering of the non-α globin genes.

It had been known for some years that children with severe forms of thalassaemia might have persistent production of HbF and it was found later that some carriers might have elevated levels of Hb A2. The seminal observation in favour of this notion came from the study of patients who had inherited the sickle-cell gene from one parent and thalassaemia from the other. Sickle-cell thalassaemia was first described by Ezio Silvestroni and his wife Ida Bianco in 1946, although at the time they could not have known the full significance of their finding.  Phillip Sturgeon and his colleagues in the USA found that the pattern of haemoglobin production in patients with sickle-cell thalassaemia is quite different to that of heterozygotes for the sickle-cell gene; the effect of the thalassaemia gene is to reduce the amount of Hb A to below that of Hb S, i.e. exactly the  opposite to the ratio observed in sickle-cell carriers. As it was known that the sickle-cell mutation occurs in the β globin gene, it could be inferred that the action of the thalassaemia gene was to reduce the amount of β globin production from the normal allele. Indeed, from the few family studies available in 1960 there was a hint that this form of thalassaemia might be an allele of the β globin gene. Another major observation that was made in the mid-50 s was the association of unusual tetramer haemoglobins, β4 (Hb H) and λ4 (Hb Bart’s), with a thalassaemia phenotype. In 1959 Vernon Ingram and Tony Stretton proposed in a seminal article that there are two major classes, α and β, just as there are two major types of structural haemoglobin variants. They extended the ideas of Linus Pauling and Harvey Itano, who had suggested that defective globin synthesis in thalassaemia might be due to `silent’ mutations of the β globin genes, and postulated that the defects might lie outside the structural gene in the area of DNA in the connecting unit. work on the interactions of thalassaemia and haemoglobin variants in the late 1950s had moved the field to a considerably higher level of understanding than is apparent in the earlier papers of Pauling and Itano. In any case, in their paper Ingram and Stretton generously acknowledged the ideas of other workers, including Lehmann, Gerald, Neel and Ceppellini, that had allowed them to develop their conceptual framework of the general nature of thalassaemia. This interpretation of events, and the input of scientists from many different disciplines into these concepts, is supported by the published discussions of several conferences on haemoglobin held in the late 1950s.

Historical Review. Towards Molecular Medicine; Reminiscences of the Haemoglobin Field. D. J. Weatherall, Weatherall Institute of Molecular Medicine, University of Oxford. Brit J  Haem 115:729-738.

The Emerging Understanding of Sickle Cell Disease

The first indisputable case of sickle cell disease in the literature was described in a dental student studying in Chicago between 1904 and 1907 (Herrick, 1910). Coming from the north of the island of Grenada in the eastern Caribbean, he was first admitted to the Presbyterian Hospital, Chicago, in late December 1904 and a blood test showed the features characteristic of homozygous sickle cell (SS) disease. It was a happy coincidence that he was under the care of Dr James Herrick (Fig 1) and his intern Dr Ernest Irons because both had an interest in laboratory investigation and Herrick had previously presented a paper on the value of blood examination in reaching a diagnosis (Herrick, 1904-05). The resulting blood test report by Dr Irons described and contained drawings of the abnormal red cells (Fig 2) and the photomicrographs, showing irreversibly sickled cells.

People with positive sickle tests were divided into asymptomatic cases, `latent sicklers’, and those with features of the disease, `active sicklers’, and it was Dr Lemuel Diggs of Memphis who first clearly distinguished symptomatic cases called sickle cell anaemia from the latent asymptomatic cases which were termed the sickle cell trait (Diggs et al, 1933).

Prospective data collection in 29 cases of the disease showed sickling in all 42 parents tested (Neel, 1949), providing strong support for the theory of homozygous inheritance. A Colonial Medical Officer working in Northern Rhodesia (Beet, 1949) reached similar conclusions at the same time with a study of one large family (the Kapokoso-Chuni pedigree). The implication that sickle cell anaemia should occur in all communities in which the sickle cell trait was common and that its frequency would be determined by the prevalence of the trait did not appear to fit the observations from Africa. Despite a sickle cell trait prevalence of 27% in Angola, Texeira (1944) noted the active form of the disease to be `extremely rare’ and similar observations were made from East Africa. Lehmann and Raper (1949, 1956) found a positive sickling test in 45% of one community, from which homozygous inheritance would have predicted that nearly 10% of children had SS disease, yet not a single case was found. The discrepancy led to a hypothesis that some factor inherited from non-black ancestors in America might be necessary for expression of the disease (Raper, 1950).

The explanation for this apparent discrepancy gradually emerged. Working with the Jaluo tribe in Kenya, Foy et al (1951) found five cases of sickle cell anaemia among very young children and suggested that cases might be dying at an age before those sampled in surveys. A similar hypothesis was advanced by Jelliffe (1952) and was supported by data from the then Belgian Congo (Lambotte-Legrand Lambotte-Legrand, 1951, Lambotte-Legrand, 1952, Vandepitte, 1952). Although most cases were consistent with the concept of homozygous inheritance, exceptions continued to occur. Patients with a non-sickling parent of Mediterranean ancestry were later recognized to have sickle cell-β thalassaemia (Powell et al, 1950; Silvestroni & Bianco, 1952; Sturgeon et al, 1952; Neel et al, 1953a), a condition also widespread in African and Indian subjects that presents a variable syndrome depending on the molecular basis of the β thalassaemia mutation and the amount of HbA produced.

Phenotypically, there are two major groups in subjects of African origin, sickle cell-β+ thalassaemia manifesting 20-30% HbA and mutations at 229(A,G) or 288(C,T), and sickle cell-β0 thalassaemia with no HbA and mutations at IVS2-849(A,G) or IVS2-1(G,A). In Indian subjects, a more severe β thalassaemia mutation IVS1-5(G,C) results in a sickle cell-β+ thalassaemia condition with 3-5% HbA and a relatively severe clinical course.

Other double heterozygote conditions causing sickle cell disease include sickle cell-haemoglobin C (SC) disease, (Kaplan et al, 1951; Neel et al, 1953b), sickle cellhaemoglobin O Arab (Ramot et al, 1960), sickle cellhaemoglobin Lepore Boston (Stammatoyannopoulos & Fessas, 1963) and sickle cell-haemoglobin D Punjab (Cooke & Mack, 1934). The latter condition was first described in siblings in 1934, who were reinvestigated for confirmation of HbD (Itano, 1951), the clinical features reported (Sturgeon et al, 1955) and who were finally identified as HbD Punjab (Babin et al, 1964), representing a remarkable example of longitudinal observation and investigation in the same family over 30 years.

The maintenance of high frequencies of the sickle cell trait in the presence of almost obligatory losses of homozygotes in Equatorial Africa implied that there was either a very high frequency of HbS arizing by fresh mutations or that the sickle cell trait conveyed a survival advantage in the African environment. There followed a remarkable period in the 1950s when three prominent scientists were each addressing this problem in East Africa, Dr Alan Raper and Dr Hermann Lehmann in Uganda and Dr Anthony Allison in Kenya. It was quickly calculated that mutation rates were far too low to balance the loss of HbS genes from deaths of homozygotes (Allison, 1954a). An increased fertility of heterozygotes was proposed (Foy et al, 1954; Allison, 1956a) but never convincingly demonstrated. Raper (1949) was the first to suggest that the sickle cell trait might have a survival advantage against some adverse condition in the tropics and Mackey & Vivarelli (1952) suggested that this factor might be malaria. The close geographical association between the distribution of malaria and the sickle cell gene supported this concept (Allison, 1954b) and led to an exciting period in the history of research in sickle cell disease.

The first observations on malaria and the sickle cell trait were from Northern Rhodesia where Beet (1946, 1947) noted that malarial parasites were less frequent in blood films from subjects with the sickle cell trait. Allison (1954c) drew attention to this association, concluding that persons with the sickle cell trait developed malaria less frequently and less severely than those without the trait. This communication marked the beginning of a considerable controversy.Two studies failed to document differences in parasite densities between `sicklers’ and `non-sicklers’ (Moore et al, 1954; Archibald & Bruce-Chwatt, 1955) and Beutler et al (1955) were unable to reproduce the inoculation experiments of Allison (1954c). Raper (1955) speculated that some feature of Allison’s observations had accentuated a difference of lesser magnitude and postulated that the sickle cell trait might inhibit the establishment of malaria in non-immune subjects. The conflicting results in these and other studies appear to have occurred because the protective effect of the sickle cell trait was overshadowed by the role of acquired immunity. Examination of young children before the development of acquired immunity confirmed both lower parasite rates and densities in children with the sickle cell trait (Colbourne & Edington, 1956; Edington & Laing, 1957; Gilles et al, 1967) and it is now generally accepted that the sickle cell trait confers some protection against falciparum malaria during a critical period of early childhood between the loss of passively acquired immunity and the development of active immunity (Allison, 1957; Rucknagel & Neel, 1961; Motulsky, 1964). The mechanism of such an effect is still debated, although possible factors include selective sickling of parasitized red cells (Miller et al, 1956; Luzzatto et al, 1970) resulting in their more effective removal by the reticulo-endothelial system, inhibition of parasite growth by the greater potassium loss and low pH of sickled red cells (Friedman et al, 1979), and greater endothelial adherence of parasitized red cells (Kaul et al, 1994).

The occurrence of the sickle cell mutation and the survival advantage conferred by malaria together determine the primary distribution of the sickle cell gene. Equatorial Africa is highly malarial and the sickle cell mutation appears to have arisen independently on at least three and probably four separate occasions in the African continent, and the mutations were subsequently named after the areas where they were first described and designated the Senegal, Benin, Bantu and Cameroon haplotypes of the disease (Kulozik et al, 1986; Chebloune et al, 1988; Lapoumeroulie et al, 1992). The disease seen in North and South America, the Caribbean and the UK is predominantly of African origin and mostly of the Benin haplotype, although the Bantu is proportionately more frequent in Brazil (Zago et al, 1992). It is therefore easy to understand the common misconception held in these areas that the disease is of African origin.

However, the sickle cell gene is widespread around the Mediterranean, occurring in Sicily, southern Italy, northern Greece and the south coast of Turkey, although these are all of the Benin haplotype and so, ultimately, of African origin. In the Eastern province of Saudi Arabia and in central India, there is a separate independent occurrence of the HbS gene, the Asian haplotype. The Shiite population of the Eastern Province traditionally marry first cousins, tending to increase the prevalence of SS disease above that expected from the gene frequency (Al-Awamy et al, 1984). Furthermore, extensive surveys performed by the Anthropological Survey of India estimate an average sickle cell trait frequency of 15% across the states of Orissa, Madhya Pradesh and Masharastra which, with the estimated population of 300 million people, implies that there may be more cases of sickle cell disease born in India than in Africa. The Asian haplotype of sickle cell disease is generally associated with very high frequencies of alpha thalassaemia and high levels of fetal haemoglobin, both factors believed to ameliorate the severity of the disease.

The promotion of sickling by low oxygen tension and acid conditions was first recognized by Hahn & Gillespie (1927) and further investigated by others (Lange et al, 1951; Allison, 1956b; Harris et al, 1956). The morphological and some functional characteristics of irreversibly sickled cells were described (Diggs & Bibb, 1939; Shen et al, 1949), but the essential features of the polymerization of reduced HbS molecules had to await the developments of electron microscopy (Murayama, 1966; Dobler & Bertles, 1968; Bertles & Dobler, 1969; White & Heagan, 1970) and Xray diffraction (Perutz & Mitchison, 1950; Perutz et al, 1951). The early observations on the inducement of sickling by hypoxia led to the first diagnostic tests utilizing sealed chambers in which oxygen was removed by white cells (Emmel, 1917), reducing agents such as sodium metabisulphite (Daland & Castle, 1948) or bacteria such as Escherichia coli (Raper, 1969). These slide sickling tests are very reliable with careful sealing and the use of positive controls, but require a microscope and some expertise in its use. An alternative method of detecting HbS utilizes its relative insolubility in hypermolar phosphate buffers (Huntsman et al, 1970), known as the solubility test. Both the slide sickle test and the solubility test detect the presence of HbS, but fail to make the vital distinction between the sickle cell trait and forms of sickle cell disease. This requires the process of haemoglobin electrophoresis, which detects the abnormal mobility of HbS, HbC and many other abnormal haemoglobins within an electric field.

The contributions of several workers on the determinants of sickling (Daland & Castle, 1948), birefringence of deoxygenated sickled cells (Sherman, 1940) the lesser degree of sickling in very young children which implied that it was a feature of adult haemoglobin (Watson, 1948) led Pauling to perform Tiselius moving boundary electrophoresis on haemoglobin solutions from subjects with sickle cell anaemia and the sickle cell trait. The demonstration of electrophoretic and, hence, implied chemical differences between normal, sickle cell trait and sickle cell disease led to the proposal that it was a molecular disease (Pauling et al, 1949). The chance encounter between Castle and Pauling who shared a train compartment returning from a meeting in Denver in 1945, its background and implications, has passed into the folklore of medical research (Conley, 1980; Feldman & Tauber, 1997).

The nature of this difference was soon elucidated. The haem groups appeared identical, suggesting that the difference resided in the globin, but early chemical analyses revealed no distinctive differences (Schroeder et al, 1950; Huisman et al, 1955). Analyses of terminal amino acids also failed to reveal differences, although an excess of valine in HbS was noted but considered an experimental error (Havinga, 1953). The development of more sensitive methods of fingerprinting combining high voltage electrophoresis and chromatography allowed the identification of the essential difference between HbA and HbS. This method enabled the separation of constituent peptides and demonstrated that a peptide in HbS was more positively charged than in HbA (Ingram, 1956). This peptide was found to contain less glutamic acid and more valine, suggesting that valine had replaced glutamic acid (Ingram, 1957). The sequence of this peptide was shown to be Val-His-Leu-Thr-Pro-Val-Glu-Lys in HbS instead of the Val-His-Leu-Thr-Pro-Glu-Glu-Lys in HbA (Hunt & Ingram, 1958), a sequence which was subsequently identified as the amino-terminus of the b chain (Hunt & Ingram, 1959). This amino acid substitution was consistent with the genetic code and was subsequently found to be attributable to the nucleotide change from GAG to GTG (Marotta et al, 1977).

Haemolysis and anaemia. The presence of anaemia and jaundice in the first four cases suggested accelerated haemolysis, which was supported by elevated reticulocyte counts (Sydenstricker et al, 1923) and expansion of the bone marrow (Sydenstricker et al, 1923; Graham, 1924). The bone changes of medullary expansion and cortical thinning were noted in early radiological reports (Vogt & Diamond, 1930; LeWald, 1932; Grinnan, 1935). Drawing on a comparison of sickle cell disease and hereditary spherocytosis, Sydenstricker (1924) introduced the term `haemolytic crisis’ that has persisted in the literature to this day, despite the lack of evidence for such an entity in sickle cell disease. The increased requirements of folic acid and the consequence of a deficiency leading to megaloblastic change was not noted until much later (Zuelzer & Rutzky, 1953; Jonsson et al, 1959; MacIver & Went, 1960).

The haemoglobin level in SS disease of African origin is typically between 6 and 9 g/dl and is well tolerated, partly because of a marked shift in the oxygen dissociation curve (Scriver & Waugh, 1930; Seakins et al, 1973) so that HbS within the red cell behaves with a low oxygen affinity. This explains why patients at their steady state haemoglobin levels rarely show classic symptoms of anaemia and fail to benefit clinically from blood transfusions intended to improve oxygen delivery.

Graham R. Serjeant
Sickle Cell Trust, Kingston, Jamaica
Brit J Haem 2001; 112: 3-18

The Immune Haemolytic Anaemias

The growth in knowledge of the scientific basis of haemolytic anaemias, which have been a main interest of the author, has been remarkable, as have consequent advances in the practice of medicine since the mid-1930s. At that time, the cause and mechanism of important disorders such as the acquired antibody determined (immune) haemolytic anaemias, haemolytic disease of the newborn, hereditary spherocytosis and paroxysmal nocturnal haemoglobinuria were unknown or but partially understood.

According to Crosby (1952), William Hunter of London, in an article on pernicious anaemia published in 1888, was the first to use the term `haemolytic’ to denote an anaemia caused by excessive blood destruction. By the turn of the century, the term was being widely used in clinical literature. Peyton Rous, in his comprehensive review `Destruction of the red blood corpuscles in health and disease’ (Rous, 1923), concluded that the generally held view in the early 1930s was that about one-fifteenth of the erythrocyte mass was destroyed daily. Rous was aware of the pioneer work of Winifred Ashby (1919), who, by following the survival of serologically distinct but compatible transfused erythrocytes, had found that normal erythrocytes might live for up to 100 d in the recipients’ circulation. Subsequent work using radioactive chromium (51Cr) as an erythrocyte label, showed that Ashby’s data and conclusions were in fact correct, i.e. that normal erythrocytes in health circulate in the peripheral blood for approximately 110 d. Erythrocyte labelling with 51Cr also had a further advantage over the Ashby method in addition to enabling the life-span of the patients’ erythrocytes to be assessed in the circulation by surface counting, to detect and measure the accumulation of radioactivity in the spleen and liver, and thereby assess the organs’ role in haemolysis

In the first decade of the twentieth century Widal et al (1908a) and Le Gendre & Brulea (1909) reported that autohaemoagglutination was a striking finding in some cases of icteare heamolytique acquis, and also Chauffard & Trosier (1908) and Chauffard & Vincent (1909) had described the presence of haemolysins in the serum of patients suffering from intense haemolysis. The conclusion was that abnormal immune processes, i.e. the development of auto-antibodies damaging the patients’ own erythrocytes, might play a part in the genesis of some cases of acquired haemolytic anaemia. This was indeed antedated by the classic observations of Donath & Landsteiner (1904) and Eason (1906) on the mechanism of haemolysis in paroxysmal cold haemoglobinuria.

That blood might auto-agglutinate when chilled had been described by Landsteiner (1903) and that an unusual degree of the phenomenon might complicate some types of respiratory disease was reported by Clough & Richter (1918) and later by Wheeler et al (1939). A few years later Peterson et al (1943) and Horstmann & Tatlock (1943) reported that cold auto-agglutinins at high titres were frequently found in the serum of patients who had suffered from the then so called primary atypical pneumonia.

Stats & Wasserman’s (1943) review on cold haemagglutination was a valuable contribution to contemporary knowledge. They listed in a table as many as 94 references to papers published between 1890 and 1943 in which cold haemagglutination had been described. In 32 of the papers the patients referred to had suffered from increased haemolysis

Recognition that cold auto-antibodies played an important role in the pathogenesis of some cases of haemolytic anaemia led to the concept that auto-immune haemolytic anaemia (AIMA) might usefully be classified into warm antibody or cold-antibody types, according to whether the patient is forming (warm) antibodies which react (perhaps optimally) at body temperature or (cold) antibodies which react strongly at low temperatures (e.g. 48C) but progressively less well as the temperature is raised and are perhaps inactive at 37oC. The clinical syndrome suffered by the patient would depend not only on the amount of antibody produced but also on its temperature requirement. Another important advance in understanding has been the realization that both types of AIHA could develop in association with a wide range of underlying disorders (secondary AIHA) as well as `idiopathically’, i.e. for no obvious cause (primary AIHA). The author’s own experience was summarized in a review (Dacie & Worlledge, 1969): 99 out of 210 cases of warm AIHA were judged to be secondary as were 39 out of 85 cases of cold AIHA. Petz & Garratty (1980), summarized the data from six centres: 55% out of a total of 656 cases had been reported as secondary. They listed the disorders with which warm antibody AIHA had been associated as chronic lymphocytic leukaemia, Hodgkin’s disease, non-Hodgkin’s lymphomas, thymomas, multiple myeloma, Waldenstrom’s macroglobulinaemia, systemic lupus erythematosus, scleroderma, rheumatoid arthritis, infectious disease/ childhood viral disorders, hypogammaglobulinaemia, dysglobulinaemias, other immune deficiency syndromes, and ulcerative colitis.

Conley (1981), in an interesting review of warm-antibody AIHA patients seen at the Johns Hopkins Hospital, emphasized how important it was to carry out a careful enquiry into the patient’s past history and also to undertake a prolonged follow-up. He stated that a retrospective review of 33 patients whose illnesses in the past have been designated `idiopathic” had revealed an associated immunologically related disorder in 19 of them. An additional three patients had developed a lymphoma 2±10 years after they had developed AIHA. As already referred to, warm-antibody AIHA is now known to complicate a wide range of underlying diseases, particularly malignant lymphoproliferative disorders, other auto-immune disorders and immune deficiency syndromes. What proportion of patients suffering from a lymphoproliferative disorder develop AIHA is an interesting question. Duehrsen et al (1987) stated that this had occurred in 12 out of 637 patients. Early data on the incidence of a positive DAT in SLE were provided by Harvey et al (1954) – in six out of 34 patients tested the DAT had been positive. Later, Mongan et al (1967), who had studied a large number of patients suffering from a variety of connective tissue disorders, reported that the DAT had been positive in 15 out of 23 patients with SLE, none of whom, however, had suffered from overt haemolytic anaemia. It has also been realized since the 1960s that warm-antibody AIHA may develop in patients suffering from a variety of immune deficiency syndromes, both congenital and acquired.

It was in the mid-1960s that it was realized that, in a significant proportion of patients thought to have `idiopathic’ warm-antibody AIHA, the development of the causal auto-antibodies had been triggered in some way by a drug the patient was taking. The first drug implicated was the antihypertensive drug a-methyldopa (Aldomet) (Carstairs et al, 1966a,b). Following the finding that treating hypertensive patients with a-methyldopa led to the formation of anti-erythrocyte auto-antibodies in a significant percentage of patients, renewed interest was taken in the possibility that other drugs might have the same effect. Two main hypotheses have been advanced in relation to how certain drugs in some patients appear to have caused the development of anti-erythrocyte auto-antibodies. One hypothesis was that the drug or its metabolites act on the immune system so as to impair immune tolerance; the other was that the drug affects antigens at the erythrocyte surface in such a way that a normally active immune system responds by developing anti-erythrocyte antibodies. Clearly, too, the patient’s individuality must be an important factor, for only a proportion of patients receiving the same dosage of the offending drug for the same period of time develop a positive DAT and only a small percentage develop overt AIHA.

An interesting development in the history of the immune haemolytic anaemias was the realization in the mid-1950s that, rather rarely, haemolysis was brought about by the patient developing antibodies that were directed against a drug the patient had been taking and that the erythrocytes were in some way secondarily involved. The first drug to be implicated was Fuadin (stibophen), which had been used to treat a patient with schistosomiasis (Harris, 1954, 1956). The patient’s serum contained an antibody that agglutinated his own or normal erythrocytes and/or sensitized them to agglutination by antiglobulin sera; however, this occurred only in the presence of the drug.

In the late 1940s, several accounts of patients with AIHA who had persistently low platelet counts were published, e.g. Fisher (1947) and Evans & Duane (1949); and it was suggested that the patients might have been forming autoantibodies directed against platelets. This concept was further developed by Evans et al (1951). Eight out of their 18 patients with AIHA were thrombocytopenic; four had clinically obvious purpura. Evans et al (1951) suggested that there exists `a spectrum-like relationship between acquired haemolytic anaemia and thrombocytopenic purpura’; also that `on the one hand, acquired haemolytic anaemia with sensitization of the red cells is often accompanied with thrombocytopenia, while, on the other hand, primary thrombocytopenic purpura is frequently accompanied with red cell sensitization with or without haemolytic anaemia’. Many further case reports of AIHA accompanied by severe thrombocytopenia have since been published

There are two features in the blood film of a patient with an acquired haemolytic anaemia which indicate that he or she is suffering from AIHA; one is auto-agglutination, the other is erythrophagocytosis. Spherocytosis, although often present to a marked degree, is of course found in other types of haemolytic anaemia.

The pioneer French observations on auto-agglutination already referred to were generally overlooked until the late 1930s, and serological studies seem seldom to have been undertaken until the publication of Dameshek & Schwartz’s (1938b) report in which they described the presence of `haemolysins’ in cases of acute apparently acquired haemolytic anaemia. Dameshek & Schwartz (1940) summarized contemporary knowledge in an extensive review. They concluded that it was not improbable that haemolysins of various types and `dosages’ were in fact responsible for many cases of human haemolytic anaemias, including congenital haemolytic anaemia, which they suggested might be caused by the `more or less continued action of an haemolysin’.

Six years were to pass before the concept that an abnormal immune mechanism played a decisive role in some cases of acquired haemolytic anaemia was clearly demonstrated by Boorman et al (1946), who reported that the erythrocytes of five patients with acquired acholuric jaundice had been agglutinated by an antiglobulin serum, i.e. that the newly described antiglobulin reaction or Coombs test (Coombs et al, 1945) was positive, while the test had been negative in 28 patients suffering from congenital acholuric jaundice. This work aroused great interest and was soon confirmed.

Until the 1950s, the auto-antibodies responsible for AIHA were generally concluded to be `non-specific’. According to Wiener et al (1953), `Red cell auto-antibodies react not only with the individual’s own red cells but also with the erythrocytes of all other human beings. The substances on the red blood cell envelope with which the auto-antibodies combine are agglutinogens like the ABO, MN and RhHr systems, except that, in the former case, the blood factors with which the auto-antibodies react are not type specific but are shared by all human beings.’ They suggested that the auto-antibodies might be directed to the `nucleus of the RhHr substance’. Earlier work had, however, indicated that the sensitivity of normal group-compatible erythrocytes to a patient’s auto-antibody might vary considerably (Denys & van den Broucke, 1947; Kuhns & Wagley, 1949). That auto-antibodies might have a clearly defined Rh specificity, e.g. anti-e, was described by Race & Sanger (1954) in the second edition of their book. Referring to Wiener et al (1953), they wrote: `This beautifully clear investigation made the present authors realize that a curious result obtained by one of them (Ruth Sanger) in 1953 in Australia had after all been true; the serum of a man who had died of a haemolytic anaemia 3000 miles away contained anti-e; his cells were clearly CDe-cde’. A similar finding, i.e. an auto-anti-e, was described by Weiner et al (1953).

A further development in the unravelling of a complicated story was the realization that some of the antibodies which appeared to be specific were reacting with more basic antigens, although showing a preference for specific antigens, i.e. some specific auto-antibodies appeared to be less specific than their allo-antibody counterparts. Moreover, some antibodies, reacting with specific antigens, have been shown to be partially or completely absorbable by antigen negative cells.

Many apparently `non-specific’ antidl antibodies have been shown to be not strictly `nonspecific’ but to react with antigens of very high frequency, e.g. to be anti-Wrb, anti-Ena, anti-LW or anti-U. Issitt et al (1980)) listed six additional very common antigens that had been identified as targets for anti-dl auto-antibodies, i.e. Hr, Hro, Rh34, Rh29, Kpb and K13.

In relation to human acquired haemolytic anaemia, the discovery in the late 1940s and 1950s that many cases were apparently brought about by the development of damaging anti-erythrocyte antibodies led to intense interest and speculation into the why and how of auto-antibody formation. Of seminal importance at the time were the experiments and theoretical arguments of Burnet (Burnet & Fenner, 1949; Burnet, 1957, 1959, 1972) and the studies on transplantation immunity of Medawar (Billingham et al, 1953; Medawar, 1961). Of particular interest, too, was the report by Bielschowsky et al (1959) of the occurrence of AIHA in an inbred strain of mice – the NZB/BL strain. Remarkably, by the time the mice were 9-months-old the DAT was positive in almost every mouse. Burnet (1963) referred to the gift of the mice to the Walter and Eliza Hall Institute of Medical Research, Melbourne as `the finest gift the Institute has ever received’.

Exactly how is it that auto-antibodies reacting with an erythrocyte surface antigen result in the cell’s premature destruction? The possible role of auto-agglutination in bringing about haemolysis was emphasized by Castle and colleagues as the result of a series of studies carried out in the 1940s and 1950s. As summarized by Castle et al (1950), an antibody which appears to be incapable of causing `lysis in vitro might bring about the following sequence of events in vivo. (1) Red cell agglutination in the peripheral blood; (2) red cell sequestration and separation from plasma in tissue capillaries; (3) ischaemic injury of tissue cells with release of substances that increase the osmotic and mechanical fragilities of red cells locally; (4) local osmotic lysis of red cells or subsequent escape of mechanically fragile red cells into the blood stream where the traumatic motion of the circulation causes their destruction’.

We can expect, as the years pass, that more and more will be known as to the intricate mechanisms that bring about self-tolerance and the mechanisms underlying the occurrence of auto-immune disorders in general, including the role of infectious agents, drugs and genetic factors. Patients with immune haemolytic anaemias can be expected to benefit from the new knowledge; for in parallel with a better understanding as to how immune self-tolerance breaks down will hopefully be the development of more effective drugs and therapies aimed at controlling the breakdown.

The Immune Haemolytic Anaemias: A Century of Exciting Progress in Understanding.  Sir John Dacie, Emeritus Professor of Haematology.
Brit J Haem 2001; 114: 770-785.

A History of Pernicious Anaemia

This is a review of the ideas and observations that have led to our current understanding of pernicious anaemia (PA). PA is a megaloblastic anaemia (MA) due to atrophy of the mucosa of the body of the stomach which, in turn, is brought about by autoimmune factors.

A case report by Osler & Gardner (1877) in Montreal could be that of PA. This anaemic patient had numbness of the fingers, hands and forearms; the red blood cells were large; at autopsy the gastric mucosa appeared atrophic and the marrow had large numbers of erythroblasts with finely granular nuclei. The increased marrow cellularity had also been noted by Cohnheim (1876).

Ehrlich (1880) (Fig 1) distinguished between cells he termed megaloblasts present in the blood in PA from normoblasts present in anaemia as a result of blood loss. Not only were large red blood cells noted in PA, but irregular red cells, ? poikilocytes, were reported in wet blood preparations by Quincke (1877). Megaloblasts in the marrow during life were first noted by Zadek (1921). Hypersegmented neutrophils in peripheral blood in PA were described by Naegeli (1923) and came to be widely recognized after Cooke’s study (Cooke, 1927). The giant metamyelocytes in the marrow were described by Tempka & Braun (1932).

Paul Ehrlich

Paul Ehrlich

Fig 1. Paul Ehrlich (Wellcome Institute Library, London).

The association between PA and spinal cord lesions was described by Lichtheim (1887) and a full account was published by Russell et al (1900), who coined the term `subacute combined degeneration of the spinal cord’ (SCDC) although they were not convinced of its relation to PA. Arthur Hurst at Guy’s Hospital, London, confirmed the association of the neuropathy with PA and added, too, the association of loss of hydrochloric acid in the gastric juice (Hurst & Bell, 1922). Cabot (1908) found that numbness and tingling of the extremities were present in almost all of his 1200 patients and 10% had ataxia. William Hunter (1901) noted the prevalence of a sore tongue in PA, which was present in 40% of Cabot’s series.

In 1934, the Nobel Prize in medicine and physiology was awarded to Whipple, Minot and Murphy. Was there ever an award more deserved? They saved the lives of their patients and pointed the way forward for further research. What was there in liver that was lacking in patients with PA? The effect of liver in restoring the anaemia in Whipple’s iron-deficient dogs was by supplying iron which is  abundant in liver.

Liver given by mouth also provides Cbl and folic acid. But patients with PA cannot absorb Cbl, although some 1% of an oral dose can cross the intestinal mucosa by passive diffusion; this, presumably, is what happened when large amounts of liver were eaten. Beef liver contains about 110 mg of Cbl per 100 g and about 140 mg of folate per 100 g. Cbl is stable and generally resistant to heat; folate is labile unless preserved with reducing agents. The daily requirement of Cbl by man is l-2 mg. The liver diet, if consumed, had enough of these haematinics to provide a response in most MAs.

George Richard Minot

George Richard Minot

George Richard Minot (Wellcome Institute Library, London).

The availability of liver extracts brought about interest in the nature of the haematological response. An optimal response required a peak rise of reticulocytes 5±7 d after the injection of liver extract and the height of the peak was greatest in those with severe anaemia; the flood of reticulocytes was as a result of a synchronous maturation of a vast number of megaloblasts into red cells. There is a steady rise in the red cell count to reach 3 x 1012/l in the 3rd week (Minot & Castle, 1935). Many liver extracts did not have enough antianaemic factor to achieve this and some assayed by the author had only 1-2 mg of Cbl.  It took another 22 years for a pure antianaemic factor to be isolated, although, admittedly, the Second World War intervened; in 1948, an American group led by Karl Folkers and an English group led by E. Lester-Smith published, within weeks of each other, the isolation of a red crystalline substance termed vitamin B12 and subsequently renamed cobalamin.

The structure of this red crystalline compound was studied by the nature of its degradation products and by X-ray crystallography. It soon became apparent that there was a cobalt atom at the heart of the structure and this heavy atom was of great aid to the crystallographers, so much so that, with additional information from the chemists, they were the first to come up with the complete structure. To quote Dorothy Hodgkin: `To be able to write down a chemical structure very largely from purely crystallographic evidence on the arrangement of atoms in space – and the chemical structure of a quite formidably large molecule at that – is for any crystallographer, something of a dream-like situation’. As Lester-Smith (1965) pointed out, it also required some 10 million calculations. In 1964, Dorothy Hodgkin was awarded the Nobel Prize for chemistry.

Barker et al (1958) published an account of the metabolism of glutamate by a Clostridium. The glutamate underwent an isomerization and an orange-coloured co-enzyme was involved that turned out to be Cbl with a deoxyadenosyl group attached to the cobalt.

This Cbl co-enzyme, deoxyadenosylCbl, is the major form of Cbl in tissues; it is also extremely sensitive to light, being changed rapidly to hydroxoCbl. DeoxyadenosylCbl is concerned with the metabolism of methylmalonic acid in man (Flavin & Ochoa, 1957). The other functional form of Cbl is methylCbl involved in conversion of homocysteine to methionine (Sakami & Welch, 1950). Both these pathways are impaired in PA in relapse.

Cbl consists of a ring of four pyrrole units very similar to that present in haem. These, however, have the cobalt atom in the centre instead of iron and the ring is called the corrin nucleus. The cobalamins have a further structure, a base, termed benzimidazole, set at right angles to the corrin nucleus and this may have a link to the cobalt atom (base on position).

By the time Cbl had been isolated from liver it was already known that it was also present in fermentation flasks growing bacteria such as streptomyces species. Other organisms gave higher yields so that kilogram quantities of pure Cbl were obtained; these sources have replaced liver in the production of Cbl. By adding radioactive form of cobalt to the fermentation flasks instead of ordinary cobalt, labelled Cbl became available (Chaiet et al, 1950). The importance of labelled Cbl is that it made it possible to carry out Cbl absorption tests in patients, to design isotope dilution assays for serum Cbl, to design ways of assaying intrinsic factor (IF), to detect antibodies to IF and even to measure glomerular filtratration rate, as free Cbl is excreted by the glomerulus without any reabsorption by the renal tubules.

William Castle at the Thorndike Memorial Laboratory, Boston City Hospital, devised experiments to explore the relationship between gastric juice, the anti-anaemic factor that Castle assumed, correctly, was also present in beef, and the response in PA. The question Castle asked was `Was it possible that the stomach of the normal person could derive something from ordinary food that for him was equivalent to eating liver?’.

The experiment in untreated patients with PA consisted of two consecutive periods of 10 d or more during which daily reticulocyte counts were made. During the first period of 10 d, the PA patient received 200 g of lean beef muscle (steak) each day. There was no reticulocyte response. During the second period, the contents of the stomach of a healthy man were recovered 1 h after the ingestion of 300 g of steak; about 100 g could not be recovered. The gastric contents were incubated for a few hours until liquefied and then given to the PA patient through a tube. This was done daily. On day 6 there was a rise in reticulocytes reaching a peak on day 10, followed by a rise in the red cell count. The response was similar to that obtained with large amounts of oral liver.

Thus, Castle concluded that a reaction was taking place between an unknown intrinsic factor (IF) in the gastric juice and an unknown extrinsic factor in beef muscle. Whereas Minot & Murphy (1926) found that 200-300 g of liver daily was needed to get a response in PA, 10 g liver was adequate when incubated with 10-20 ml normal gastric juice (Reiman & Fritsch, 1934). Castle’s extrinsic factor is the same as the anti-anaemic factor that is Cbl, and IF is needed for its absorption. Presumably the gastric juice in PA lacks IF.

The elegant studies of Hoedemaeker et al (1964) in Holland using autoradiography of frozen sections of human stomach incubated with [57Co]-Cbl showed that IF was produced in the gastric parietal cell. The binding of Cbl to

the parietal cell was abolished by first incubating the section with a serum containing antibodies to IF. The parietal cell in man is thus the source of both hydrochloric acid and IF. The parietal cell is the only source of IF in man as a total gastrectomy is invariably followed by a MA due to Cbl deficiency. IF is a glycoprotein with a molecular weight of 45 000.

Assay of protein fractions of serum after electrophoresis showed that endogenous Cbl is in the position of α-1 globulin. Chromatography of serum after addition of [57Co]-Cbl on Sephadex G-200 showed that Cbl was attached to two proteins, one eluting before the albumin termed transcobalamin I (TCI) and the other after the albumin termed transcobalamin II (TCII). Charles Hall showed that, when labelled Cbl given by mouth is absorbed, it first appears in the position of TCII and later in the position of TCI as well (Hall and Finkler, l965). They concluded that TCII is the prime Cbl transport protein carrying Cbl from the gut into the blood and then to the liver from where it is redistributed by both new TCII as well as TCI. Congenital absence of a functional TCII causes a severe MA in the first few months of life owing to an inability to transport Cbl. Most of the Cbl in serum is on TCI because it has a relatively long half-life of 9±10 d, whereas the half-life of TCII is about 1.5 h. Thus, in assaying the serum Cbl level, it is mainly TCI-Cbl that is being assayed.

With the availability of labelled Cbl, Cbl absorption tests began to be widely used in the 1950s. The commonest method was the urinary excretion test described by Schilling (1953). Here, an oral dose of radioactive Cbl is followed by an injection of 1000 mg of cyano-Cbl. The free cyano-Cbl is largely excreted into the urine over the next 24 h and carries with it about one third of the absorbed labelled Cbl.

Parietal cell antibodies (Taylor et al, 1962) are present in serum in 76-93% of different series of PAs and in the serum of 36% of the relatives of PA patients. The antibody is present in sera from 32% of patients with myxoedema, 28% of patients with Graves’ disease, 20% of relatives of thyroid patients and 23% of patients with Addison’s disease. Parietal cell antibodies are found in between 2-16% of controls, the high 16% figure being in elderly women. There is a higher frequency of PA in women, the female to male ratio being 1.7 to 1.0. The parietal cell antibody is probably important in the production of gastric atrophy. Thyroid antibodies are present in sera from 55% of PAs, in sera from 50% of PA relatives, in 87% of sera from myxoedema patients, in 53% of sera in Graves’ disease and in 46% of relatives of patients with thyroid disease.

There is a high frequency of PA among those disorders that have antibodies against the target organ. Thus, among 286 patients with myxoedema, 9.0% also had PA (Chanarin, 1979), as compared with a frequency of PA of about 1 per 1000 (0.01%) in the general population. Of 102 consecutive patients with vitiligo,
eight also had PA.

Patients with acquired hypogammaglobulinaemia are unable to make humoral antibodies; nevertheless, one third have PA as well. This cannot be as a result of action of IF antibodies and must be because of specific cell-mediated immunity. Tai & McGuigan (1969) demonstrated lymphocyte transformation in the presence of IF in six out of 16 PA patients and Chanarin & James (1974) found 10 out of 51 tests were positive.

Twenty-five patients with PA were tested for the presence of humoral IF antibody in serum and gastric juice and for cell-mediated immunity against IF. All but one gave positive results in one or more tests. It was concluded that these findings establish the autoimmune nature of PA and that the immunity is not merely an interesting byproduct.

Patients with PA treated with steroids show a reversal of the abnormal findings characterizing the disease. If they are still megaloblastic, the anaemia will respond in the first instance (Doig et al, 1957), but in the longer term Cbl neuropathy may be precipitated. The absorption of Cbl improves and may become `normal’ (Frost & Goldwein, 1958). There is a return of IF in the gastric juice (Kristensen and Friis, 1960) and a decline in the amount of IF antibody in serum (Taylor, 1959). In some patients there is return of acid in the gastric juice. Gastric biopsy shows a return of parietal and chief cells (Ardeman & Chanarin, 1965b; Jeffries, 1965). All this is as a result of suppression of cell-mediated immunity against the parietal cell and against IF. Withdrawal of steroids leads to a slow return to the status quo.

The author has dipped freely into the two volumes by the late M. M. Wintrobe. These are: Wintrobe, M.M. (1985) Hematology, the Blossoming of a Science. Lea & Febinge

A History of Pernicious Anaemia
I. Chanarin, Richmond, Surrey
Brit J Haem 111: 407-415
History of Folic Acid

1928 Lucy Wills studied macrocytic anaemia in pregnancy in Bombay, India

1932 Janet Vaughn studied macrocytic anemia associated with coeliac disease and idiopathic steatorrhea (1932) showed a response to marmite

1941 Folic acid extracted from spinach and is a growth factor for S. Faecalis

1941 pteroylglutamic acid synthesized at Amer Cyanamide – Pteridine ring, paraminobenzoic acid, glutamine –  PGA differed from natural compound in some respects

1945 PGA resolved the macrocytic anemia, but not the neuropathy

1979 Stokstad and associates at Berkeley obtained the first purified mammalian enzymes involved in synthesis

Folate antagonists inhibit tumor growth (Hitchings and Elion)(Nobel)

  • Misincorporation of uracil instead of thymine into DNA

Sidney Farber introduced Aminopterine and also Methotrexate for treatment of childhood lymphoblastic leukemia

  • MTX inhibits DHFR enzyme (dihydrofolate reductase) necessary for THF

Wellcome introduces trimethoprim (antibacterial), and also pyramethoprime (antimalarial)

Homocysteine isolated by Du Vineaud, but it was not noticed

Finkelstein and Mudd demonstrated the importance of remethylation for tHy and worked out the transsulfuration pathway

  1. Function of methyl THF is remethylation of homocysteine
  2. Synthesized by MTHFR
Metabolism of folate

Metabolism of folate

Metabolism of folate

Allosterically regulated by S-adenosyl methionine (Stokstad)

MTHF also inhibits glycine methyl transferase controlling excess SAM – transmethylation

JD Finkelstein

JD Finkelstein

James D Finkelstein

  • Homocysteinuria – mental retardation, skeletal malformation, thromboembolic disease; deficiency of cystathionine synthase (controls trans-sulfuration)
  • NTDs – pregnancy
  • Hyperhomocysteinemia and VD

AD Hoffbrand and DG Weir
Brit J Haem 2001; 113: 579-589

The History of Haemophilia in the Royal Families of Europe Queen Victoria.

On 17 July 1998 a historic ceremony of mourning and commemoration took place in the ancestral church of the Peter and Paul Fortress in St Petersburg. President Boris Yeltsin, in a dramatic eleventh-hour change of heart, decided to represent his country when the bones of the last emperor, Tsar Nicholas II, and his family were laid to rest 80 years to the day after their assassination in Yekaterinberg (Binyon, 1998). He described it as ‘ironic that the Orthodox Church, for so long the bedrock of the people’s faith, should find it difficult to give this blessing the country had expected’. ‘I have studied the results of DNA testing carried out in England and abroad and am convinced that the remains are those of the Tsar and his family’ (The Times, 1998a). Unfortunately, politicians and the hierarchy of the Russian Orthodox Church had argued about what to do with the bones previously stored in plastic bags in a provincial city mortuary. Politics, ecclesiastical intrigue, secular ambition, and emotions had fuelled the debate. Yeltsin and the Church wanted to honour a man many consider to be a saint, but many of the older generation are opposed to the rehabilitation of a family which symbolizes the old autocracy.

Our story starts, almost inevitably, with Queen Victoria of England who had nine children by Albert, Prince of Saxe-Coburg-Gotha. Victoria was certainly an obligate carrier for haemophilia as over 20 individuals subsequently inherited the condition (Figs 1 and 2). Princess Alice (1843–78) was Victoria’s third child and second daughter. Having married the Duke of Hesse at an early age, Alice went on to have seven children, one of whom, Frederick (‘Frittie’) was a haemophiliac who died at the age of 3 following a fall from a window.

Prince Leopold with Sir William Jenner at Balmoral in 1877

Prince Leopold with Sir William Jenner at Balmoral in 1877

Prince Leopold with Sir William Jenner at Balmoral in 1877. (Hulton Deutsch Collection Ltd.)

Alexandra was the sixth child and was only 6 years old when her mother and youngest sister died. ‘Sunny’, as she became known, was a favourite of Queen Victoria, who as far as possible directed her upbringing from across the channel: Alexandra (Alix) was forced to eat her baked apples and rice pudding with the same regularity as her English cousins. Alix visited her older sister Elizabeth (Ella) on her marriage to Grand Duke Serge and met Tsarevich Nicholas for the first time: she was 12 and not impressed. Five years later they met again and Alix fell in love, but by now she had been confirmed in the Lutheran Church and religion became the solemn core of her life.

Victoria had other aspirations for Alix. She hoped that she would marry her grandson Albert Victor (The Duke of Clarence) and the eldest son of the Prince of Wales (later Edward VII). The Duke was an unimpressive young man who was somewhat deaf and had limited intellectual abilities. If this arrangement had proceeded then Alix’s haemophilia carrier status would have been introduced into the British Royal Family and the possibility of a British monarch with haemophilia might have become a reality; however, the Duke died in 1892.

Nicholas and Alexandra. Alix and Nicholas were married in 1894 one week after the death of Nicholas’s father (Alexander III). In the same way that Victoria, with her personal aspirations of a marriage between Alix and the Duke of Clarence, had not considered the possibility of haemophilia, neither did the St Petersburg hierarchy consider a marriage to Nicholas undesirable. Haemophilia was already well recognized in Victoria’s descendants. Her youngest son, Leopold, had already died, as had Frittie her grandson. The inheritance of haemophilia had been known for some time since its description by John Conrad Otto (Otto, 1803). However, it was as late as 1913 before the first royal marriage was declined because of the risk of haemophilia, when the Queen of Rumania decided against an association between her son, Crown Prince Ferdinand, and Olga, the eldest daughter of Nicholas and Alexandra. The Queen of Rumania was herself a granddaughter of Queen Victoria and therefore a potential haemophilia carrier!

Alix was received into the Russian Orthodox Church, taking the name of Alexandra Fedorova. The first duty of a Tsarina was to maintain the dynasty and produce a male heir, but between 1895 and 1901 Alix produced four princesses, Olga, Tatiana, Maria and Anastasia. Failure to produce a son made Alix increasingly neurotic and she had at least one false pregnancy. However, in early 1904 she was definitely pregnant.

For a month or so all seemed well with little Alexis, but it was then noticed that the Tsarevitch was bleeding excessively from the umbilicus (a relatively uncommon feature of haemophilia). At first the diagnosis was not admitted by the parents, but eventually the truth had to be faced although even then only by the doctors and immediate family. Alix was grief stricken: ‘she hardly knew a day’s happiness after she realized her boy’s fate’. As a newly diagnosed haemophilia carrier she dwelt morbidly on the fact that she had transmitted the disease. These feelings are well known to some haemophiliac mothers but the situation was different in Russia in the early twentieth century. The people regarded any defect as divine intervention. The Tsar, as head of the Church and leader of the people, must be free of any physical defect, so the Tsarevich’s haemophilia was concealed. The family retreated into greater isolation and were increasingly dominated by the young heir’s affliction (Fig 3).

Up to a third of haemophiliac males do not have a family history of the condition. This is usually thought to be the result of a relatively high mutation rate occurring in either affected males or female carriers. None of Queen Victoria’s ancestors, for many generations, showed any evidence of haemophilia. Victoria was therefore either a victim of a mutation, or the Duke of Kent was not her father.The mutation is unlikely to have been in her mother, Victoire, who had a son and daughter by her first marriage, and there is no sign of haemophilia in their numerous descendants.

Victoire was under considerable pressure to produce an heir. The year before Victoria was born, Princess Charlotte, the only close heir to the throne, had died and the Duke of Kent had somewhat reluctantly agreed to marry Victoire with the aim of producing an heir. The postulate that the Queen’s gardener had a limp has not been substantiated!

The Duke of Kent had no evidence of haemophilia (he was 51 when Victoria was born) but did inherit another condition from his father (George III): porphyria. While a young man in Gibralter he suffered bilious attacks which were recognized as being similar to his father’s complaint.

Had Queen Victoria carried the gene for porphyria we might expect that she would have at least as many descendants with this condition as had haemophilia. Until recently only two possible cases of porphyria have been suggested amongst Victoria’s descendants: Kaiser Wilhelm’s sister and niece (MacAlpine & Hunter, 1969), but they could have inherited it from their Hohenzollern ancestor, Frederick the Great. A recent television programme (Secret History, 1998) claims to have identified two more cases in Victoria’s descendants, Princess Victoria, the Queen’s eldest daughter, and Prince William of Gloucester, nephew of George V. If these two cases are correct then they would tend to confirm that Victoria was indeed the daughter of the Duke of Kent, but the apparent lack of more cases in Victoria’s extended family is difficult to understand. The gene for acute intermittent porphyria has been isolated on chromosome 11. There is still plenty of scope for further genetic analysis on the European Royal Families!

We can only speculate as to the impact on European events over the last 150 years if the marriages within the Royal houses had been different. What is evident is the dramatic effect of haemophilia on the Royal Princes and their families.

Empress Alexandra at the Tsarevich’s bedside during a haemophiliac crisis

Empress Alexandra at the Tsarevich’s bedside during a haemophiliac crisis

Empress Alexandra at the Tsarevich’s bedside during a haemophiliac crisis in 1912. (Radio Times Hulton Picture Library.)

Richard F. Stevens
Royal Manchester Children’s Hospital
Brit J Haem 1999, 105, 25–32

`The longer you can look back ± the further you can look forward’: Winston Churchill in an address to The Royal College of Physicians, London 1944. At the time that Churchill was speaking in 1944, leukaemia was a fatal disease that had been identified 100 years before. The disease was described as the dreaded leukaemias, sinister and poorly understood.

Thomas Hodgkin chose a career in medicine and enrolled as a pupil at Guy’s Hospital in London. Being a Quaker, however, he could not enter the English universities of Oxford and Cambridge and decided to follow the medical courses at Edinburgh. At that times, Aristotelian and Hippocratic medicine were greatly influencing British physicians. Hodgkin, still a medical student, wrote a paper `On the Uses of the Spleen’ where he reported his beliefs on the purposes of the spleen: to regulate fluid volume, clean impurities from the body, supply expandability to the portal system. The subject was a presage of the disease that bears his name.

Hodgkin interrupted his studies at Edinburgh to spend a year in Paris where he met many people who had a great influence in his life and future activities. Among them, were Laennec (Hodgkin played an important role in bringing the stethoscope to Great Britain); Baron von Humboldt who introduced Hodgkin to the field of anthropology; Baron Cuvier, a distinguished anatomist and palaeontologist; and Thomas A. Bowditch, whose expeditions to Africa had a great impact on Hodgkin’s future activities.

In 1825, Thomas Hodgkin returned to London to join the staff at Guy’s Hospital, and in 1826 he was made `Inspector of the Dead’ and `Curator of the Museum of Morbid Anatomy’. In developing the museum he had accumulated, by 1829, over 1600 specimens demonstrating the effects of disease. The correlation of clinical disease to pathological material was quite new: from analyses of pathological specimens Hodgkin was able to describe appendicitis with perforation and peritonitis, the local spread of cancer to draining lymph nodes, noting that the tumour had similar characteristics at both sides, and features of other diseases.

In his historic paper `On Some Morbid Appearances of the Absorbent Glands and Spleen’ (Hodgkin, 1832), he briefly described the clinical histories and gross postmortem findings on six patients from the experience at Guy’s Hospital and included another case sent to him in a detailed drawing by his friend Carswell (Fig 2). In the very first paragraph he wrote: `The morbid alterations of structure which I am about to describe are probably familiar to many practical morbid anatomists, since they can scarcely have failed to have fallen under their observation in the course of cadaveric inspection’. Hodgkin’s studies had convinced him that he was dealing with a primary disease of the absorbent (lymphatic) glands. `This enlargement of the glands appeared to be a primitive affection of those bodies, rather than the result of an irritation propagated to them from some ulcerated surface or other inflamed texture – Unless the word inflammation be allowed to have a more indefinite and loose eaning, this affection – can hardly be attributed to that cause’ was stated on pages 85 and 86 of his 1832 paper. Hodgkin also mentioned that the first reference that he could find to this or similar disease was in fact by Malpighi in 1666.

Wilks (1865) described the disease in detail and, made aware by Bright that the first observations were done by Hodgkin, linked his name permanently to this new entity in a paper entitled `Cases of Enlargement of the Lymphatic Glands and Spleen (or Hodgkin’s Disease) with Remarks’ (Fig 3).

In 1837 Thomas Hodgkin was the outstanding candidate for the position of Assistant Physician at Guy’s Hospital in succession to Thomas Addison who had been promoted to Physician. After 10 years spent as Inspector of the Dead, he had published a great deal, including a two-volume work entitled The Morbid Anatomy of Serous and Mucous Membrane.

Hodgkin, acting in his other capacity, had sent Benjamin Harrison a report on the terrible consequences to native Indians of monopoly trading and on the inhuman treatment they received from officials of the Hudson Bay Company, of which Harrison was the financier. when the opportunity to appoint an Assistant Physician occurred, Harrison exercised an autocratic rule over the hospital and presided at the appointment made by the General Court. Thomas Hodgkin did not get the job and the next day he resigned all his appointments at Guy’s Hospital. Social medicine, medical problems associated with poverty, antislavery, concern for underpriviledged groups such as American Indians and Africans, as well as a strong sense of responsibility defined his life after this separation.

Sternberg (1898) and Reed (1902) are generally credited with the first definitive and thorough descriptions of the histopathology of Hodgkin’s disease. Based on the findings observed in her case series, Dorothy Reed concluded `We believe then, from the descriptions in the literature and the findings in 8 cases examined, that Hodgkin’s disease has a peculiar and typical histological picture and could thus rightly be considered a histopathological disease entity’.

During the successive decades, pathologists began to describe a broader spectrum of histological features. However, it was Jackson and Parker who, in scientific papers and in their well-known book Hodgkin’s Disease and Allied Disorders (Jackson & Parker, 1947), presented the first serious effort at a histopathological classification. They assigned the name `Hodgkin’s granuloma’ to the main body of typical cases. A much more malignant variant, usually characterized by a great abundance of pleomorphic and anaplastic Reed-Sternberg cells and seen in a relativelysmall number of cases was named `Hodgkin’s sarcoma’. A third, similarly infrequent, variant characterized by an extremely slow clinical evolution, a relative paucity of Reed-Sternberg cells and a great abundance of lymphocytes was termed `Hodgkin’s paragranuloma’. It was only approximately 20 years later that Lukes & Butler (1966) reported a characteristic subtype of the heterogeneous `granuloma’ category, to which they assigned the name `nodular sclerosis’. They also proposed a new histopathological classification, still in use to date, with an appreciably greater prognostic relevance and usefulness than the

previous Jackson-Parker classification.

The first human bone marrow transfusion was given to a patient with aplastic anemia in 1939.9 This patient received daily blood transfusions, and an attempt to raise her leukocyte and platelet counts was made using intravenous injection of bone marrow. After World War II and the use of the atomic bomb, researchers tried to find ways to restore the bone marrow function in aplasia caused by radiation exposure. In the 1950s, it was proven in a mouse model that marrow aplasia secondary to radiation can be overcome by syngeneic marrow graft.10 In 1956, Barnes and colleagues published their experiment on two groups of mice with acute leukemia: both groups were irradiated as anti-leukemic therapy and both were salvaged from marrow aplasia by bone marrow transplantation.

The topics of leukemias and lymphomas will not be discussed further in  this discussion.

The related references are:

Leukaemia – A Brief Historical Review from Ancient Times to 1950
British Journal of Haematology, 2001, 112, 282-292

The Story of Chronic Myeloid Leukaemia
British Journal of Haematology, 2000, 110, 2-11

Historical Review of Lymphomas
British Journal of Haematology 2000, 109, 466-476

Historical Review of Hodgkin’s Disease
British Journal of Haematology, 2000, 110, 504-511

Multiple Myeloma: an Odyssey of Discovery
British Journal of Haematology, 2000, 111, 1035-1044

The History of Blood Transfusion
British Journal of Haematology, 2000, 110, 758-767

Hematopoietic Stem Cell Transplantation—50 Years of Evolution and Future Perspectives. Henig I, Zuckerman T.
Rambam Maimonides Med J 2014;5 (4):e0028.
http://dx.doi.org/10.5041/RMMJ.10162

Landmarks in the history of blood transfusion.

1666 Richard Lower (Oxford) conducts experiments involving transfusion of blood from one animal to another

1667 Jean Denis (Paris) transfuses blood from animals to humans

1818 James Blundell (London) is credited with being the first person to transfuse blood from one human to another

1901 Karl Landsteiner (Vienna) discovers ABO blood groups. Awarded Nobel Prize for Medicine in 1930

1908 Alexis Carrel (New York) develops a surgical technique for transfusion, involving anastomosis of vein in the recipient with artery in the donor. Awarded Nobel Prize for Medicine in 1912

1915 Richard Lewinsohn (New York) develops 0.2% sodium citrate as anticoagulant

1921 The first blood donor service in the world was established in London by Percy Oliver

1937 Blood bank established in a Chicago hospital by Bernard Fantus

1940 Landsteiner and Wiener (New York) identify Rhesus antigens in man

1940 Edwin Cohn (Boston) develops a method for fractionation of plasma proteins. The following year, albumin produced by this method was used for the first time to treat victims of the Japanese attack on Pearl Harbour

1945 Antiglobulin test devised by Coombs (Cambridge), which also facilitated identification of several other antigenic systems such as Kell (Coombs et al, 1946), Duffy (Cutbush et al, 1950) and Kidd (Cutbush et al, 1950)

1948 National Blood Transfusion Service (NBTS) established in the UK

1951 Edwin Cohn (Boston) and colleagues develop the first blood cell separator

1964 Judith Pool (Palo Alto, California) develops cryoprecipitate for the treatment of haemophilia

1966 Cyril Clarke (Liverpool) reports the use of anti-Rh antibody to prevent haemolytic disease of the newborn

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Outline of Medical Discoveries between 1880 and 1980

Curator: Larry H Bernstein, MD, FCAP

This is the first of a two part series tracing the developments in medical diagnosis and treatment, and herein, tracing the scientific events of the 19th century that accelerated and created the emergent events that brought together physics, organic and physical chemistry, electronics, computational biology.

Part I. Anatomy and Physiology

The first Nobel Prize in Physiology was awarded to Ivan Pavlov for work on digestion in 1904.  The presentation speech refers to the groundbreaking work of Vesalius and Harvey in his presentation address, citing their passionate pursuit of knowledge.  He credits the work of a young American physician, William Beaumont, who served as the only doctor on Michigan’s Mackinac Island in the French and Indian war in 1822, and who observed the gastric secretion from the gastric fistula of a wounded soldier. (see John Karlawish, Open Wound, University of Michigan Press, 2011). This was the basis for the work by Pavlov on dogs that extends our understanding of the telationship of the central nervous system to the digestive processes.

The Nobel Prize in Physiology or Medicine 1906 was awarded jointly to Camillo Golgi and Santiago Ramón y Cajal “in recognition of their work on the structure of the nervous system”. Golgi first opened the field of neuroanatomy with the silver staining method, and Cajal contributed equally to establishing the foundation for this research of great complexity.

The Nobel Prize in Physiology or Medicine 1909 was awarded to Emil Theodor Kocher for his work on the physiology, pathology, and surgery  of the thyroid gland. It had already been established that the enlargement of the thyroid compresses the trachea, and that complete removal has morbid effects. It was expressed by Kocher in 1883 that removal of the thyroid as a consequence of surgery must leave behind a functioning portion of the gland.

This was later followed by the establishment of a great medical institution Dr. William Worrall Mayo, a frontier doctor, and his two sons, Dr. William J. Mayo and Dr. Charles H. Mayo, Mayo Clinic.

The elder Dr. Mayo emigrated from his native England to the United States in 1846. He became a doctor in 1850. In 1863 he was appointed a surgeon for the enrollment board in southern Minnesota, to examine recruits for the Union Army, and settled in Rochester, Minn. His dedication to medicine became a family tradition when his sons, Drs. William James Mayo and Charles Horace Mayo, joined his practice in 1883 and 1888, respectively.

In 1883, a tornado swept through Rochester leaving in its wake many deaths and injuries. Temporary hospital quarters were set up in offices and hotels. Nuns from the Sisters of St. Francis, a teaching order, were recruited as nurses. The experience inspired Mother Alfred Moes to request that the Drs. Mayo join with the Sisters to build the first general hospital in southeastern Minnesota. The 27-bed Saint Mary’s Hospital opened in 1889 as a result of this partnership.

mayo-brothers

mayo-brothers

As the demand for their services increased, they asked other doctors and basic science researchers to join them in the world’s first private integrated group practice. In 1919, the Mayo brothers dissolved their partnership and turned the clinic’s name and assets, including the bulk of their life savings, to a private, not-for-profit, charitable organization now known as Mayo Foundation. It is worth noting that the Mayo Clinic became a favored place to have thyroid surgery, as its location is in the “goiter belt”.

Patients discovered the advantages to a “pooled resource” of knowledge and skills among doctors. In fact, the group practice concept that the Mayo family originated has influenced the structure and function of medical practice throughout the world.

The Nobel Prize in Physiology or Medicine 1912 was awarded to Alexis Carrel “in recognition of his work on vascular suture and the transplantation of blood vessels and organs”. He demonstrated the technique used to suture together open vessels, and even to transplant whole organs from one animal to another with excellent results.

The Nobel Prize in Physiology or Medicine 1920 was awarded to August Krogh “for his discovery of the capillary motor regulating mechanism”.  Harvey had shown in 1628 that the blood traverses the circulation returning to the heart in one minute. Malpighi showed that blood passes from the artery to the vein by capillaries  in 1661.  Krogh demonstrated by very elegant experiments that the quantity of gas that diffuses across the pulmonary alveoli is the same amount of gas that is released to the alveolar space. The importance of this is that the investigations having the aim to determine the process by which the oxygen requirement of the tissues is satisfied.

The Nobel Prize in Physiology or Medicine 1922 was divided equally between Archibald Vivian Hill “for his discovery relating to the production of heat in the muscle” and Otto Fritz Meyerhof “for his discovery of the fixed relationship between the consumption of oxygen and the metabolism of lactic acid in the muscle”. One need not be a physiologist to recognize that muscular activity is essentially bound up with the development of heat, or even with combustion. AV Hill determined the time relationships of heat production in muscle contraction measured galvanometrically, and Otto Meyerhof determined the oxygen consumption in the production of lactic acid. The muscle is regarded as a machine that converts chemical energy to mechanical energy (tension) with the production of heat. The development of heat entirely fails to appear if the supply of oxygen to the muscle is cut off, while the development of heat during the actual twitch, is independent of the presence of oxygen (consistent with Meyerhof’s glycolysis). The relaxation phase is consistent with oxygen uptake during recovery.

Fletcher and Hopkins had shown earlier that muscle not only forms, but also uses lactic acid in the presence of oxygen. Meyerhof determined by parallel determination of the lactic acid metabolism and the oxygen consumption during the recovery of the muscle, which yielded the result that the oxygen consumption does not account for more than1/3 – 1/4 of the lactic acid formed. When lactic
acid is formed an equivalent amount of glycogen in muscle disappears, and when lactic acid disappears, the quantity of
carbohydrate increases by the difference between lactic acid and quantity used in oxygen consumption.

The Nobel Prize in Physiology or Medicine 1923 was awarded jointly to Frederick Grant Banting and John James Rickard
Macleod “for the discovery of insulin”.  In 1857, Claude Bernard discovered that the liver contains glycogen, which converted to glucose, enters the blood stream (and thereby, the urine). Glycosuria became a starting point for the study of diabetes. It is of interest that he could not produce glycosuria by ligation of the pancreatic duct. But in 1889 Mering and Minkowsky did an operation on dogs that removed the pancreas, resulting in glycosuria, and creating a disease comparable to diabetes in humans. If part of the pancreas was left behind, it failed to produce diabetes. Brown-Sequard had called attention to ductless organs in the 1880s that are glands. These were
endocrine glands secreting hormones. Langerhans had shown in 1869 that the pancreas has glands that have no secretion into the pancreatic ducts, and in the beginning of the 1890s Languese surmised that these glands were involved in diabetes mellitus. Schulze and Ssobolev had shown that ligation of the duct resulted in atrophy of the pancreas sparing the islets. Frederick Banting at this time postulated that trypsin degraded the hormone, and with Best and Collip, under MacLeod’s guidance, Banting pursued his idea, and the effective extract was obtained in 1921, and demonstrated in 1922.

Arch Anat Histol Embryol. 1993-1994;75:151-82.

[History of histology in Strasbourg].

Le Minor JM.

Since the cellular theory was formulated in 1839, the University of Strasbourg has held a pioneer place in histology. This new morphological science has had, since its origin, close relations with physiology, and from 1846 to 1871, an original histophysiological school was organized in Strasbourg. The microscope and the study of tissues were considered as a fundamental approach for the progress of biological and medical knowledge. After the German annexation of Alsace, the scientists from this school participated in the renewal of histology in Nancy, Montpellier, and Paris. In 1872, when the new German university was created, an anatomical institute regrouped all aspects of normal morphology: anatomy, histology, and embryology. This was the case until 1918. In 1919, when the Faculty of Medicine was reorganized after Alsace was restored to France, a specific chair and institute of histology were created. This was the beginning of a school of histophysiology which was internationally renowned in the rise of experimental endocrinology. Great discoveries followed one after another: folliculin in 1924 and demonstration of the duality of ovarian hormones, the prominent place of the anterior part of the hypophysis and the demonstration of prolactin in 1928, thyreostimulin in 1929, then study of the other stimulins. In 1946 a chair and institute of medical biology were created. In 1948, a service of electron microscopy was opened.
P. Bouin (1870-1962), M. Aron (1892-1974), J. Benoit (1896-1982), R. Courrier (1895-1986) et M. Klein (1905-1975), were among the famous scientists who worked in histology in Strasbourg in the
period after the French restoration.
The Nobel Prize in Physiology or Medicine 1947

Bernardo Alberto Houssay

“for his discovery of the part played by the hormone of the anterior pituitary lobe in the metabolism of sugar”

He had already begun studying medicine and, in 1907, before completing his studies, he took up a post in the Department of Physiology. He began here his research on the hypophysis which resulted in his M.D.-thesis (1911), a thesis which earned him a University prize.

In 1919 he became Professor of Physiology in the Medical School at Buenos Aires University. He also organized the Institute of Physiology at the Medical School, making it a center with an international reputation. He remained Professor and Director of the Institute until 1943.  He made a lifelong study of the hypophysis and his most important discovery concerns the role of the anterior lobe of the hypophysis in carbohydrate metabolism and the onset of diabetes.

The Nobel Prize in Physiology or Medicine 1950

Edward Calvin Kendall, Tadeus Reichstein and Philip Showalter Hench

“for their discoveries relating to the hormones of the adrenal cortex, their structure and biological effects”

As late as in 1854 the German anatomist, Kölliker, was able to claim in a review of the subject that although the function of the adrenals was still unknown, yet in certain respects great advances had been made. Two quite different parts were now distinguished, an outer part, a fairly firm cortex, and an inner, softer medulla. Kölliker classified the adrenal cortices as ductless glands, which we now call the endocrine organs.

Thomas Addison, the English doctor, observed a rare disease with a fatal course, which was characterized chiefly by anemia, general weakness and fatigue, disturbances in the digestive apparatus, enfeebled heart activity and a peculiar dark pigmentation of the skin. He published a paper 1n 1855, suggesting that this morbid picture made its appearance in persons the greater part of whose adrenals was destroyed. Subsequent experiments in animals showed that removal of the adrenals led to speedy death, the symptoms recalling those known from Addison’s disease.

In 1894 Oliver and Schäfer proved that the injection of a watery extract from the adrenals had extremely pronounced effects. Within a few years adrenaline had been produced from the extract, its composition had been ascertained, and its artificial production accomplished. The more detailed analysis showed effects of the same kind as those resulting on increased activity of the so-called sympathetic nervous system, which innervates internal organs such as the heart and vessels, the intestinal canal, etc.  Attempts to prevent by means of adrenaline the deficiency symptoms following on the removal of the adrenals failed completely. The explanation of this was given when Biedl and others showed that it is the cortex which is of vital importance, not the medulla.

The isolation of the cortin proved to be a difficult task, calling for the combined efforts of a number of research workers. Particularly important contributions were made in this field by Wintersteiner and Pfiffner, and also by Edward Kendall at the Mayo Clinic in Rochester, and Tadeus Reichstein in Basel, and their co-workers. As early as in 1934, Kendall and his group succeeded in preparing from cortex extract what was at first assumed to be pure cortin in crystalline form. They found that it contained carbon, hydrogen, and oxygen, and indicated its empirical formula. But that was only a beginning. There was no reason to suspect that the cortin was not homogeneous; as further experiments proved. In reality Kendall and his co-workers had produced a mixture of different substances closely related to one another, and their work represents the early steps in the crystallization of a whole series of cortin substances. There is at least one active cortical substance – the best known of them all, first named Compound E and now called cortisone or cortone – which was isolated at four different laboratories, among them Kendall’s and Reichstein’s.

As all the cortin substances are closely related to one another, Reichstein’s finding implies that, like the sex hormones, they belong to the large and important group of steroids. The D vitamins and the bile acids, like our most important heart remedies, the active substances in Digitalis leaves and Strophanthus seeds, are also intimately associated with the steroids

The six definitely active cortical hormones are characterized, inter alia, by a double bond in the steroid skeleton; if this double bond disappears, inactive substances are obtained. They differ very inconsiderably from each other chemically. They are built up of 21 carbon atoms, but the number of oxygen atoms in the molecule is three, four, or five. The position of the additional oxygen atoms in the molecule was first established by Reichstein and Kendall, and thus a way was opened for semisynthetic production e.g. from the more easily obtainable bile acids or material from a certain species of Strophanthus. This is of particular importance, since the yield from the adrenals is very poor, at most about 1:1,000,000.

Thanks to the work of Kendall and his school, it has emerged that the comparatively inconsiderable dissimilarities in the matter of the structure of the cortical hormones are accompanied by material differences in respect of the effect. Thus some act especially strongly on the metabolism of sugar, others on the salt and fluid balances, and there are also several other differences. This was illustrated when Compound E was first tested. Pfiffner and Wintersteiner, like the Reichstein group, found that the substance had no, or extremely inconsiderable, life-prolonging effects on animals deprived of the adrenals. On the other hand, Ingle, Kendall’s coworker, observed that it stimulated the muscular work of such animals very strongly.

In the April of 1949, Hench, Kendall, Slocumb and Polley published their experiences in respect of the dramatic effects of cortisone in cases of chronic rheumatoid arthritis. A rapid improvement set in, pains and tenderness in the joints abated or disappeared, mobility increased, so that patients who had previously been complete invalids could walk about freely, and their general condition was also favourably affected. Similar results were obtained with a preparation from the anterior lobe of the pituitary, the so-called ACTH (Adreno-Cortico-Tropic Hormone), which, as the name indicates, stimulates the adrenal cortex to increased activity.

The value of a discovery lies not only in the immediate practical results, but equally much in the fact that it points out new lines of research. This is strikingly illustrated by the research during the last few decades into the cortical hormones, which has already led to unexpected and important new results within widely different spheres.

Nobel Prize in Physiology or Medicine 1966

Charles Huggins

Endocrine-Induced Regression of Cancers

The net increment of mass of a cancer is a function of the interaction of the tumor and its soil. Self-control of cancers results from a highly advantageous competition of host with his tumor. There are multiple factors which restrain cancer – enzymatic, nutritional, immunologic, the genotype and others.Prominent among them is the endocrine status, both of tumor and host – the subjects of this discourse.

The second quarter of our century found the biological sciences much pre-occupied with two noble topics :

  • chemistry and physiology of steroids and
  • biochemistry of organo-phosphorus compounds.

The key to the puzzle of the steroid hormones in cancer was the isolation of crystalline estrone by Doisy et al.2 from extracts of urine of pregnant women. In the phosphorus field there were magnificent findings of hexose phosphates, nucleotides, coenzymes and high-energy phosphate intermediates. These wonderful discoveries provided the Zeitgeist for our work.

Through the portal of phosphorus metabolism we entered on a series of interconnected observations in steroid endocrinology. A program was not prepared in advance for this basic physiologic study. The work was fascinating and informative so that it provided its own momentum and served as an end in itself.

The prostatic cell does not die in the absence of testosterone, it merely shrivels. But the hormone-dependent cancer cell is entirely different. It grows in the presence of supporting hormones but it dies in their absence and for this reason it cannot participate in growth cycles.

A remarkable effect of testosterone is the promotion of growth of its target cells during complete deprival of food. Androstane derivatives conferred on the prostate of puppies a selective nutritional advantage during starvation of 3 weeks whereby abundant growth of this gland-occurred while there was serious cell breakdown in most of the tissues of the body.

At first it was vexatious to encounter a dog with a prostatic tumor during a metabolic study but before long such dogs were sought. It was soon observed that orchiectomy or the administration of restricted amounts of phenolic estrogens caused a rapid shrinkage of canine prostatic tumors.

The experiments on canine neoplasia proved relevant to human prostate cancer; there had been no earlier reports indicating any relationship of hormones to this malignant growth.

Kutscher and Wolbergs9 discovered that acid phosphatase is rich in concentration in the prostate of adult human males. Gutman and Gutman10 found that many patients with metastatic prostate cancer have significant increases of acid phosphatase in their blood serum. Cancer of the prostate frequently metastasizes to bone.

Human prostate cancer which had metastasized to bone was studied at first. The activities of acid and alkaline phosphatases in the blood were measured concurrently at frequent intervals. The methods are reproducible and not costly in time or materials; both enzymes were measured in duplicate in a small quantity (0.5 ml) of serum. The level of acid phosphatase indicated activity of the disseminated cancer cells in all metastatic loci. The titer of alkaline phosphatase revealed the function of the osteoblasts as influenced by the presence of the prostatic cancer cells that were their near neighbors. By periodic measurement of the two enzymes one obtains a view of overall activity of the cancer and the reaction of non-malignant cells of the host to the presence of that cancer. Thereby the great but opposing influences of, respectively, the administration or deprival of androgenic hormones upon prostate cancer cells were revealed with precision and simplicity. Orchiectomy or the administration of phenolic estrogens resulted in regression of cancer of the human prostate whereas, in untreated cases, testosterone enhanced the rate of growth of the neoplasm.

The first indication that advanced cancer can be induced to regress was the beneficial effect of oöphorectomy on cancer of the breast of two women. This empirical observation17 of Beatson in 1896 was remarkable since it was made before the concept of hormones had been developed. The beneficial action of removal of ovaries was not understood until steroid hormones had been isolated 4 decades later.

But why does breast cancer thrive in folks who do not possess ovarian function – in men, old women, and females who have had oöphorectomy?

Farrow and Adair observed that benefits of great magnitude frequently follow orchiectomy in mammary cancer in the human male. Thereby, they established that testis function can sustain mammary cancer.

A half century after the classic invention of Beatson it was found out that adrenal function can maintain and promote growth of human mammary cancer. The adrenal factor supporting growth of cancer was identified when it was shown that bilateral adrenalectomy (with glucocorticoids as substitution therapy) can result in profound and prolonged regression of mammary carcinoma in men and women who do not possess gonadal function. In developing the idea of adrenalectomy for treatment of advanced cancer in man we were considerably influenced by the discovery of Woolley et al. that adrenals can evoke cancer of the breast in the mouse.

Mammary cancers induced in the male rat by aromatics were not influenced by orchiectomy and hypophysectomy; by definition, these neoplasms are hormone-independent. In contrast to male rat, most mammary cancers of men wither impressively after deprival of supporting hormones.

The hormone-responsiveness of established mammary cancers induced in female rat by aromatics or ionizing radiation is identical; it was a newly recognized property of experimental breast cancers. Prior to this finding, clinical study of patients with mammary cancer was the only material available for investigation of hormonal-restraint of neoplasms of the breast.

In female rat, many but far from all of the induced mammary cancers vanished after removal of ovaries or the pituitary. In our experiments hypophysectomy was the most efficient of all methods to cure rat’s mammary cancer.

Malignant cells which succumb to hormone-deprival, by definition, are hormone-dependent. The quality of hormone-dependence resides in the tumor cells whereas their growth is determined by the host’s endocrine status.

Both man and the animals can have some of their cancer cells which are hormone-dependent while other neoplastic cells in the same organism are not endocrine-responsive.

The cure of a cancer after hormone-deprival results from death of the cancer cells whereas their normal analogues in the same animal shrivel but survive. It is a basic proposition in endocrine-restraint of malignant disease that cancer cells can differ in a crucial way from ancestral normal cells in response to modification of the hormonal milieu intérieur of the body.

Cancer is not necessarily autonomous and intrinsically self-perpetuating. Its growth can be sustained and propagated by hormonal function in the host which is not unusual in kind or exaggerated in rate but which is operating at normal or even subnormal levels.

The control of cancer by endocrine methods can be described in three propositions:

  • Some types of cancer cells differ in a cardinal way from the cells from which they arose in their response to change in their hormonal environment.
  • Certain cancers are hormone-dependent and these cells die when supporting hormones are eliminated.
  • Certain cancers succumb when large amounts of hormones are administered.

The Nobel Prize in Physiology or Medicine 1971

Earl W. Sutherland, Jr.

“for his discoveries concerning the mechanisms of the action of hormones”

Part II. Vitamins

The Nobel Prize in Physiology or Medicine 1929

Christiaan Eijkman “for his discovery of the antineuritic vitamin”

Sir Frederick Gowland Hopkins “for his discovery of the growth-stimulating vitamins”

When the 20th century began, the prevailing thought about nutrition rested on the importance of energy requirements, as elucidated by  Rubner, Benedict and others, in the United States, that entails the quantitative measurement of the food value of carbohydrates, fats, and proteins. But there was a misconception of the process in its detail. The quantitative studies of the energetics and of respiratory exchange were not sufficient to explain problems that arise as a result of deficiencies of micronutrients in food intake.  The complexity of these nutritional needs as we now view them is indeed astonishing.

There is a need for indispensable organic substances specific in nature and function of which the quantitative supply is so small as to contribute little or nothing to the energy factor in nutrition. These substances, following the suggestion of Casimir Funk, we have agreed to call vitamins.

In 1881, Lunin, and associate of Bungel noted that a diet of milk was not sufficient to sustain the life of mice, even if the caloric nutrients were adequate. The main lesson taken from the findings was concerned with inorganic nutrients had not been determined that would answer the question. A decade later, Socin, in Bunge’s group, concluded that the deficiency was in the quality of protein.  In an important paper by Professor Pekelharing in 1905 published an astonishing paper following on the work in Bungel’s lab. He noted that there is a substance in milk in small quantities that he was unable to identify that is essential for life.  It is noteworthy that Pekelharing records prolonged endeavours towards the isolation of a vitamin.

Eikman’s work came in the 1880s. He did not at first visualize beriberi clearly as a deficiency disease. The view that the cortical substance in rice supplied a need rather than neutralized a poison was soon after put forward by Grijns and ultimately accepted by Professor Eijkman himself.  The prevailing thinking about nutritional requirements was preoccupied by the methods of calorimetry at the turn of the century.  The idea of “deficiency diseases” was obscured as a result. There was no concept of an indispensable portion of the food supply other than calories, proteins and minerals until 1911-1912.  Hopkins was convinced that the science of nutrition had to come to terms with an explanation for scurvy and rickets, and he needed to use the new science of biochemistry, which was ongoing at Cambridge.

In 1906-1907, he carried out studies of feeding rats casein, along the lines of Bungel.s experiments, and he found variability in the results with different casein preparations.  He next washed the casein so that any soluble substance was extracted and the rats died, but if he added the extract they grew.  He also used butter, with results more favorable than casein, and lard, with unfavorable results.  At the same time he was studying polyneuritis in birds, which took up much time.  He know that he had to extract the substance, but was unaware of the fat solubility in 1910. He published his work in 1912. Soon after the publication of his work, and duting WWI, much research was done in US, by Osborn and Mendel at Harvard, and by McCollum at Johns Hopkins, and the vitamins were separated into “water soluble” and “fat soluble”.

The Nobel Prize in Physiology or Medicine 1937

Albert von Szent-Györgyi Nagyrápolt

“for his discoveries in connection with the biological combustion processes, with special reference to vitamin C and the catalysis of fumaric acid”

http://pharmaceuticalintelligence.com/2014/08/18/studies-of-respiration-lead-to-acetyl-coa/

Szent Gyorgyi was a biochemist who worked with Otto Warburg and others, and had a special interest in muscle metabolism. He delineated a portion of the Krebs cycle (Krebs was also associated with Warburg), that which involves the conversion of fumaric acid to succinate.  He also purified vitamin C (ascorbic acid) from paprika in his native region of Hungary. He later turned his interest to cancer research, for which he was honored by the MD Anderson Cancer Center.

The Nobel Prize in Physiology or Medicine 1934

George Hoyt Whipple, George Richards Minot and William Parry Murphy

“for their discoveries concerning liver therapy in cases of anaemia”

The Nobel Prize in Physiology or Medicine 1943

Henrik Carl Peter Dam “for his discovery of vitamin K”

Edward Adelbert Doisy “for his discovery of the chemical nature of vitamin K”

To further his studies of the metabolism of sterols, Dam obtained a Rockefeller Fellowship and worked in Rudolph Schoenheimer’s Laboratory in Freiburg, Germany, during 1932-1933, and later worked with P. Karrer, of Zurich, in 1935. He discovered vitamin K while studying the sterol metabolism of chicks in Copenhagen. When he returned to Denmark after WWII in 1946, Dam’s main research subjects were vitamin K, vitamin E, fats, cholesterol.

Part III.  Microbiology and Plague

The Nobel Prize in Physiology or Medicine 1901

Emil Adolf von Behring

“for his work on serum therapy, especially its application against diphtheria, by which he has opened a new road in the domain of medical science and thereby placed in the hands of the physician a victorious weapon against illness and deaths”

The Nobel Prize in Physiology or Medicine 1902

Ronald Ross

“for his work on malaria, by which he has shown how it enters the organism and thereby has laid the foundation for successful research on this disease and methods of combating it”

The Nobel Prize in Physiology or Medicine 1905

Robert Koch

“for his investigations and discoveries in relation to tuberculosis”

The Nobel Prize in Physiology or Medicine 1908

The Nobel Prize in Physiology or Medicine 1928

Charles Jules Henri Nicolle

“for his work on typhus”

The Nobel Prize in Physiology or Medicine 1939

Gerhard Domagk

“for the discovery of the antibacterial effects of prontosil”

The Nobel Prize in Physiology or Medicine 1945

Sir Alexander Fleming, Ernst Boris Chain and Sir Howard Walter Florey

“for the discovery of penicillin and its curative effect in various infectious diseases”

The Nobel Prize in Physiology or Medicine 1951

Max Theiler

“for his discoveries concerning yellow fever and how to combat it”

The Nobel Prize in Physiology or Medicine 1952

Selman Abraham Waksman

“for his discovery of streptomycin, the first antibiotic effective against tuberculosis”

The Nobel Prize in Physiology or Medicine 1954

John Franklin Enders, Thomas Huckle Weller and Frederick Chapman Robbins

“for their discovery of the ability of poliomyelitis viruses to grow in cultures of various types of tissue”

The Nobel Prize in Physiology or Medicine 1976

Baruch S. Blumberg and D. Carleton Gajdusek

“for their discoveries concerning new mechanisms for the origin and dissemination of infectious diseases”

Part IV.

Ilya Ilyich Mechnikov and Paul Ehrlich

“in recognition of their work on immunity”

The Nobel Prize in Physiology or Medicine 1919

Jules Bordet

“for his discoveries relating to immunity”

The Nobel Prize in Physiology or Medicine 1930 was awarded to Karl Landsteiner “for his discovery of human blood groups”.

In 1901, in the course of his serological studies Landsteiner observed that when, under normal physiological conditions, blood serum of a human was added to normal blood of another human the red corpuscles in some cases coalesced into larger or smaller clusters. This observation of Landsteiner was the starting-point of his discovery of the human blood groups. In the following year, i.e. 1901, Landsteiner published his discovery that in man, blood types could be classified into three groups according to their different agglutinating properties. These agglutinating properties were identified more closely by two specific blood-cell structures, which can occur either singly or simultaneously in the same individual.

Landsteiner’s discovery of the blood groups was immediately confirmed but it was a long time before anyone began to realize the great importance of the discovery. The first incentive to pay greater attention to this discovery was provided by von Dungern and Hirszfeld when in 1910 they published their investigations into the hereditary transmission of blood groups. Thereafter the blood groups became the subject of exhaustive studies, on a scale increasing year by year, in more or less all civilized countries. In order to avoid, in the publication of research on this subject, detailed descriptions which would otherwise be necessary – of the four blood groups and their appropriate cell structures, certain short designations for the blood groups and corresponding specific cell structures have been introduced. Thus, one of the two specific cell structures, characterizing the agglutinating properties of human blood is designated by the letter A and another by B, and accordingly we speak of «blood group A» and «blood group B». These two cell structures can also occur simultaneously in the same individual, and this structure as well as the corresponding blood group is described as AB.

The fourth blood-cell structure and the corresponding blood group is known as O, which is intended to indicate that people belonging to this group lack the specific blood characteristics typical of each of the other blood groups. Landsteiner had shown that under normal physiological conditions the blood serum will not agglutinate the erythrocytes of the same individual or those of other individuals with the same structure. Thus, the blood serum of people whose erythrocytes have group structure A will not agglutinate erythrocytes of this structure but it will agglutinate those of group structure B, and where the erythrocytes have group structure B the corresponding serum does not agglutinate these erythrocytes but it does agglutinate those with group structure A. Blood serum of persons whose erythrocytes have structures A as well as B, i.e. who have structure AB, does not agglutinate erythrocytes having structures A, B, or AB. Blood serum of persons belonging to blood group O agglutinates erythrocytes of persons belonging to any of the group.

The group characteristics are handed down in accordance with Mendel’s laws. The characteristics of blood groups A, B, and AB are dominant, and opposing these dominant characteristics are the recessive ones which characterize blood group O. An individual cannot belong to blood group A, B, or AB, unless the specific characteristics of these groups are present in the parents, whereas the recessive characteristics of blood group O can occur if the parents belong to any one of the four groups. If both parents belong to group O, then the children never have the characteristics of A, B, or AB. The children must then likewise belong to blood group O. If one of the parents belongs to group A and the other to group B, then the child may belong to group A or B or it may possess both characteristics and therefore belong to group AB. If one of the parents belongs to group AB and the other to group O, then in accordance with Mendel’s law of segregation the AB characteristic can be segregated and the components can occur as separate characteristics in the children.

Even while he was a student he had begun to do biochemical research and in 1891 he published a paper on the influence of diet on the composition of blood ash. To gain further knowledge of chemistry he spent the next five years in the laboratories of Hantzsch at Zurich, Emil Fischer at Wurzburg, and E. Bamberger at Munich.

In 1896 he became an assistant under Max von Gruber in the Hygiene Institute at Vienna. Even at this time he was interested in the mechanisms of immunity and in the nature of antibodies. From 1898 till 1908 he held the post of assistant in the University Department of Pathological Anatomy in Vienna, the Head of which was Professor A. Weichselbaum, who had discovered the bacterial cause of meningitis, and with Fraenckel had discovered the pneumococcus. Here Landsteiner worked on morbid physiology rather than on morbid anatomy. In this he was encouraged by Weichselbaum, in spite of the criticism of others in this Institute.

Up to the year 1919, after twenty years of work on pathological anatomy, Landsteiner with a number of collaborators had published many papers on his findings in morbid anatomy and on immunology. He discovered new facts about the immunology of syphilis, added to the knowledge of the Wassermann reaction, and discovered the immunological factors which he named haptens (it then became clear that the active substances in the extracts of normal organs used in this reaction were, in fact, haptens). He made fundamental contributions to our knowledge of paroxysmal haemoglobinuria.

He also showed that the cause of poliomyelitis could be transmitted to monkeys by injecting into them material prepared by grinding up the spinal cords of children who had died from this disease, and, lacking in Vienna monkeys for further experiments, he went to the Pasteur Institute in Paris, where monkeys were available. His work there, together with that independently done by Flexner and Lewis, laid the foundations of our knowledge of the cause and immunology of poliomyelitis.

http://www.nobelprize.org/nobel_prizes/medicine/laureates/1930/landsteiner-bio.html

His discovery of the differences and identification of the groups that were alike made it possible for blood transfusions to become a routine procedure.  This paved the way for many other medical procedures that we don’t even think twice about today, such as surgery, blood banks, and transplants.

While in medical school, Landsteiner began experimental work in chemistry, as he was greatly inspired by Ernst Ludwig, one of his professors. After receiving his medical degree, Landsteiner spent the next five years doing advanced research in organic chemistry for Emil Fischer, although medicine remained his chief interest. During 1886-1897, he combined these interests at the Institute of Hygiene at the University of Vienna where he researched immunology and serology. These fields were developing rapidly in the late 1800s as scientists explored numerous physiological changes associated with bacterial infection. Immunology and serology then became Landsteiner’s lifelong focus. Landsteiner was primarily interested in the lack of safety and effectiveness of blood transfusions.

Landsteiner is known as the “melancholy genius” because he was so sad and intense, yet he was so systematic, thorough, and dedicated. He wrote 346 papers during his long career contributing to many areas of scientific knowledge. He is considered the father of Hematology (the study of blood), Immunology (the study of the immune system), Polio research, and Allergy research.

The fundamental contribution of Robert A. Good to the discovery of the crucial role of thymus in mammalian immunity

Domenico Ribatti

Immunology. Nov 2006; 119(3): 291–295.

http://dx.doi.org:/10.1111/j.1365-2567.2006.02484.x

Robert Alan Good was a pioneer in the field of immunodeficiency diseases. He and his colleagues defined the cellular basis and functional consequences of many of the inherited immunodeficiency diseases. His was one of the groups that discovered the pivotal role of the thymus in the immune system development and defined the separate development of the thymus-dependent and bursa-dependent lymphoid cell lineages and their responsibilities in cell-mediated and humoral immunity.

Keywords: bursa of Fabricius, history of medicine, immunology, thymus

Robert A. Good (Fig. 1) began his intellectual and experimental queries related to the thymus in 1952 at the University of Minnesota, initially with paediatric patients. However, his interest in the plasma cell, antibodies and the immune response began in 1944, while still in Medical School at the University of Minnesota in Minneapolis, with his first publication appearing in 1945.

Robert Good

Robert Good

Figure 1

Robert A. Good with two young patients. Source: http://www.robertagoodarchives.com.

Good described a new syndrome that would carry his name: ‘Good syndrome: thymoma with immunodeficiency’.7 The clinical characteristics of Good syndrome are increased susceptibility to bacterial infections by encapsulated organisms and opportunistic viral and fungal infections. Subsequently, Good saw several patients with thymic tumours, which regularly presented with immunodeficiencies, leukopenia, lymphopenia and eosinophylopenia. Plasma cells, however, were not completely absent: the patient was severely hypogammaglobulinaemic rather than agammaglobulinaemic.

The association of thymoma with profound and broadly based immunodeficiency provoked Good’s group to ask what role the thymus plays in immunity.

Good and others found that the patients lacked all of the subsequently described immunoglobulins. These patients were found not to have plasma cells or germinal centres in their haematopoietic and lymphoid tissues. They possessed circulating lymphocytes in normal numbers.

In the mouse and other rodents, immunological depression is profound after thymectomy in neonatal animals, resulting in considerable depression of antibody production, plus deficient transplantation immunity and delayed-type hypersensitivity. Speculation on the reason for immunological failure following neonatal thymectomy has centred on the thymus as a source of cells or humoral factors essential to normal lymphoid development and immunological maturation.

Three independent groups of experiments showed that neonatal thymectomy has a significant effect on immunological reactivity: (i) the studies of Fichtelius et al. in young guinea-pigs showed that the depression of antibody response is slight, but significant; (ii) the experiments of Archer, Good and co-workers in rabbits and mice; and (iii) the studies by Miller at the Chester Beatty Research Institute in London.

Stutman, in Good’s laboratory, demonstrated that non-lymphoid thymomas induced the restoration of immunological functions in neonatally thymectomized mice and that when thymomas were grafted into allogenic hosts, immunological restoration was mediated by lymphoid cells of host type. Comparable results were obtained with free thymus grafts.

Cooper et al. postulated that a lymphoid stem cell population exists that is induced to differentiate along two distinct and separate cell lines related to two central lymphoid organs. In birds this developmental influence is exercised by the thymus and the bursa of Fabricius. Removal of one or both in the early post-hatching period has strikingly different influences on immunological function in the maturing animals. The thymus in the chicken functions exactly as does the thymus of the mouse. It represents the site of differentiation of a population of lymphocytes that subserve largely the functions of cell-mediated immunity.

The athymic children described by Di George, who lacked lymphoid cells in the deep cortical areas of the nodes but not at the peripheral areas, seemed the equivalent of the neonatally thymectomized mice and chickens. These patients had severe deficiencies of small T lymhocytes and profound deficiencies of all cell-mediated immunities, including delayed allergies, deficient allograft immunities and deficiencies in resistance to viruses, fungi and opportunistic infections.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1819567/

The Nobel Prize in Physiology or Medicine 1960

Sir Frank Macfarlane Burnet and Peter Brian Medawar

“for discovery of acquired immunological tolerance”

The Nobel Prize in Physiology or Medicine 1980

Baruj Benacerraf, Jean Dausset and George D. Snell

“for their discoveries concerning genetically determined structures on the cell surface that regulate immunological reactions”

Part V.

Biochemistry and Molecular Biology

The Nobel Prize in Physiology or Medicine 1922

Archibald Vivian Hill

“for his discovery relating to the production of heat in the muscle”

Otto Fritz Meyerhof

“for his discovery of the fixed relationship between the consumption of oxygen and the metabolism of lactic acid in the muscle”

The Nobel Prize in Physiology or Medicine 1931

Otto Heinrich Warburg

“for his discovery of the nature and mode of action of the respiratory enzyme”

http://pharmaceuticalintelligence.com/2012/11/02/otto-warburg-a-giant-of-modern-cellular-biology/

http://pharmaceuticalintelligence.com/2013/11/28/warburg-effect-revisited/

http://pharmaceuticalintelligence.com/2013/03/12/ampk-is-a-negative-regulator-of-the-warburg-effect-and-suppresses-tumor-growth-in-vivo/

http://pharmaceuticalintelligence.com/2012/10/17/is-the-warburg-effect-the-cause-or-the-effect-of-cancer-a-21st-century-view/

The Nobel Prize in Physiology or Medicine 1933

Thomas Hunt Morgan

“for his discoveries concerning the role played by the chromosome in heredity”

The Nobel Prize in Physiology or Medicine 1947

Carl Ferdinand Cori and Gerty Theresa Cori, née Radnitz

“for their discovery of the course of the catalytic conversion of glycogen”

The Nobel Prize in Physiology or Medicine 1953

Hans Adolf Krebs

“for his discovery of the citric acid cycle”

http://pharmaceuticalintelligence.com/2014/10/22/introduction-to-metabolic-pathways/

Fritz Albert Lipmann

“for his discovery of co-enzyme A and its importance for intermediary metabolism”

http://pharmaceuticalintelligence.com/2014/10/22/introduction-to-metabolic-pathways/

http://pharmaceuticalintelligence.com/2014/11/07/summary-of-cell-structure-anatomic-correlates-of-metabolic-function-2/

http://pharmaceuticalintelligence.com/2014/08/18/studies-of-respiration-lead-to-acetyl-coa/

http://pharmaceuticalintelligence.com/2013/01/26/portrait-of-a-great-scientist-and-mentor-nathan-oram-kaplan/

The Nobel Prize in Physiology or Medicine 1955

Axel Hugo Theodor Theorell

“for his discoveries concerning the nature and mode of action of oxidation enzymes”

http://pharmaceuticalintelligence.com/2014/08/18/studies-of-respiration-lead-to-acetyl-coa/

The Nobel Prize in Physiology or Medicine 1958

George Wells Beadle and Edward Lawrie Tatum

“for their discovery that genes act by regulating definite chemical events”

The Nobel Prize in Physiology or Medicine 1959

Severo Ochoa and Arthur Kornberg

“for their discovery of the mechanisms in the biological synthesis of ribonucleic acid and deoxyribonucleic acid”

Joshua Lederberg

“for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria”

The Nobel Prize in Physiology or Medicine 1962

Francis Harry Compton Crick, James Dewey Watson and Maurice Hugh Frederick Wilkins

“for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material”

The Nobel Prize in Physiology or Medicine 1963

Sir John Carew Eccles, Alan Lloyd Hodgkin and Andrew Fielding Huxley

“for their discoveries concerning the ionic mechanisms involved in excitation and inhibition in the peripheral and central portions of the nerve cell membrane”

The Nobel Prize in Physiology or Medicine 1964

Konrad Bloch and Feodor Lynen

“for their discoveries concerning the mechanism and regulation of the cholesterol and fatty acid metabolism”
http://pharmaceuticalintelligence.com/2014/10/25/oxidation-and-synthesis-of-fatty-acids/

The Nobel Prize in Physiology or Medicine 1965

François Jacob, André Lwoff and Jacques Monod

“for their discoveries concerning genetic control of enzyme and virus synthesis”

http://pharmaceuticalintelligence.com/2014/10/06/isoenzymes-in-cell-metabolic-pathways/

The Nobel Prize in Physiology or Medicine 1967

Ragnar Granit, Haldan Keffer Hartline and George Wald

“for their discoveries concerning the primary physiological and chemical visual processes in the eye”

The Nobel Prize in Physiology or Medicine 1968

Robert W. Holley, Har Gobind Khorana and Marshall W. Nirenberg

“for their interpretation of the genetic code and its function in protein synthesis”

The Nobel Prize in Physiology or Medicine 1969

Max Delbrück, Alfred D. Hershey and Salvador E. Luria

“for their discoveries concerning the replication mechanism and the genetic structure of viruses”

The Nobel Prize in Physiology or Medicine 1970

Sir Bernard Katz, Ulf von Euler and Julius Axelrod

“for their discoveries concerning the humoral transmittors in the nerve terminals and the mechanism for their storage, release and inactivation”

The Nobel Prize in Physiology or Medicine 1972

Gerald M. Edelman and Rodney R. Porter

“for their discoveries concerning the chemical structure of antibodies”

The Nobel Prize in Physiology or Medicine 1974

Albert Claude, Christian de Duve and George E. Palade

“for their discoveries concerning the structural and functional organization of the cell”

The Nobel Prize in Physiology or Medicine 1975

David Baltimore, Renato Dulbecco and Howard Martin Temin

“for their discoveries concerning the interaction between tumour viruses and the genetic material of the cell”
The Nobel Prize in Physiology or Medicine 1977

Rosalyn Yalow

“for the development of radioimmunoassays of peptide hormones”

The Nobel Prize in Physiology or Medicine 1978

Werner Arber, Daniel Nathans and Hamilton O. Smith

“for the discovery of restriction enzymes and their application to problems of molecular genetics”

Read Full Post »

Selected Contributions to Chemistry from 1880 to 1980

Curator: Larry H. Bernstein, MD, FCAP

 

FUNDAMENTALS OF CHEMISTRY – Vol. I  The Contribution of Nobel Laureates to Chemistry

– Ferruccio Trifiro

http://www.eolss.net/sample-chapters/c06/e6-11-01-04.pdf

This chapter deals with the contribution to the development of chemistry of all the Nobel Prize winners in chemistry up to the end of the twentieth century, together with some in physics and medicine or physiology that have had particular relevance for the advances achieved in chemistry. The contributions of the various Nobel laureates cited are briefly summarized. The Nobel laureates in physics dealt with in this chapter are those who made important contributions to ard the understanding of the properties of atoms, the development of theoretical tools to treat the chemical bond, or the development of new analytical instrumentation. The Nobel laureates in medicine or physiology cited here are those whose contributions have been in the area of using chemistry to understand natural processes, such as the physiological aspects of living organisms through electron and ion exchange processes, enzymatic catalysis, and DNA-based chemistry. Eight areas of thought or thematic areas were chosen into which the contributions of the Nobel laureates to chemistry can be subdivided.

  1. The Properties of Molecules

4.1. The Discovery of Coordination and Metallorganic Compounds

4.2. The Discovery of New Organic Molecules

4.3. The Emergence of Quantum Chemistry

  1. The Dynamics of Chemical Reactions

6.1. Kinetics of Heterogeneous and Homogeneous Processes

6.2. The Identification of the Activated State

  1. The Understanding of Natural Processes

8.1. From Ferments to Enzymes

8.2. Understanding the Mechanism of Action of Enzymes

8.3. Mechanisms of Important Natural Processes

8.4. Characterization of Biologically Important Molecules

  1. The Identification of Chemical Entities

9.1. Analytical Methods

9.2. New Separation Techniques

9.3. The Development of New Instrumentation for Structure Analysis

The Nobel Prize in Chemistry: The Development of Modern Chemistry

by Bo G. Malmström and Bertil Andersson*

http://www.nobelprize.org/nobel_prizes/themes/chemistry/malmstrom/

Introduction

1.1 Chemistry at the Borders to Physics and Biology

The turn of the century 1900 was also a turning point in the history of chemistry. A survey of the Nobel Prizes in Chemistry during this century provides a view toward important trends in the development of Chemistry at the center of the sciences, bordering onto physics, which provides its theoretical foundation, on one side, and onto biology on the other. The fact that chemistry flourished during the beginning of the 20th century is intimately connected with fundamental developments in physics.

In 1897 Sir Joseph John Thomson of Cambridge announced his discovery of the electron, for which he was awarded the Nobel Prize for Physics in 1906. It took a number of years before its relevance to chemistry was seen. In 1911 Ernest Rutherford, who had worked in Thomson’s laboratory in the 1890s, formulated an atomic model, which depicted a cloud of electrons circling around the nucleus. Rutherford had received the Nobel Prize for Chemistry in 1908 for his work on radioactivity.

In Rutherford’s atomic model the stability of atoms was at variance with the laws of classical physics. Niels Bohr from Copenhagen brought clarity to this dilemma in the distinct lines observed in the spectra of atoms, the regularities of which had been discovered in 1890 by the physics professor Johannes (Janne) Rydberg at Lund University. This was the basis for Bohr’s formulation (1913) of an alternative atomic model. Only certain circular orbits of the electrons are allowed. In this model light is emitted (or absorbed), when an electron makes a transition from one orbit to another. For this, Bohr received the Nobel Prize for Physics in 1922

Gilbert Newton Lewis next suggested in 1916 that strong (covalent) bonds between atoms involve a sharing of two electrons between these atoms (electron-pair bond). Lewis also contributed fundamental work in chemical thermodynamics, and his brilliant textbook, Thermodynamics (1923), written together with Merle Randall, is counted as one of the masterworks in the chemical literature. Lewis never received a Nobel Prize.

However, important work was published in the 1890s, considered by the first Nobel Committee for Chemistry (see Section 2). Three of the Laureates during the first decade, Jacobus Henricus van’t Hoff, Svante Arrhenius and Wilhelm Ostwald, are generally regarded as the founders of a new branch of chemistry, physical chemistry. Fundamental work was also recognized in organic chemistry and in the chemistry of natural products, which is clearly reflected in the early prizes. Further, the Nobel Committee, recognized the border towards biology in 1907, with the prize to Eduard Buchner “for his biochemical researches and his discovery of cell-free fermentation”.

  1. The First Decade of Nobel Prizes for Chemistry

So much fundamental work in chemistry had been carried out during the last two decades of the 19th century that a decision for the first several prizes was not easy.  In 1901 the Academy had to consider 20 nominations, but no less than 11 of these named van’t Hoff, who was selected. van’t Hoff had already established the four valences for the carbon atom in his PhD thesis in Utrecht in 1874, foundation work for  modern organic chemistry. But the Nobel Prize was awarded for his later work on chemical kinetics and equilibria and on the osmotic pressure in solution, published in 1884 and 1886.

In his 1886 work van’t Hoff showed that most dissolved chemical compounds give an osmotic pressure equal to the gas pressure they would have exerted in the absence of the solvent. An apparent exception was aqueous solutions of electrolytes (acids, bases and their salts), but in the following year Arrhenius showed that this anomaly could be explained, if it is assumed that electrolytes in water dissociate into ions. Arrhenius had already presented the rudiments of his dissociation theory in his doctoral thesis, which was defended in Uppsala in 1884 and was not entirely well received by the faculty. It was, however, strongly supported by Ostwald in Riga, who, in fact, travelled to Uppsala to initiate a collaboration with Arrhenius. In 1886-1990 Arrhenius did work with Ostwald, first in Riga and then in Leipzig, and also with van’t Hoff in Berlin. Arrhenius was awarded the Nobel Prize for Chemistry in 1903,  and he was also nominated for the Prize for Physics (see Section 1).

The award of the Nobel Prize for Chemistry in 1909 to Ostwald was chiefly in recognition of his work on catalysis and the rates of chemical reactions. Ostwald had in his investigations, following up observations in his thesis in 1878, shown that the rate of acid-catalyzed reactions is proportional to the square of the strength of the acid, as measured by titration with base. His work offered support not only to Arrhenius’ theory of dissociation but also to van’t Hoff’s theory for osmotic pressure. Ostwald was founder and editor of Zeitschrift für Physikalische Chemie, the publication of which is generally regarded as the birth of this new branch of chemistry.

Three of the Nobel Prizes for Chemistry during the first decade were awarded for pioneering work in organic chemistry. In 1902 Emil Fischer, then in Berlin, was given the prize for “his work on sugar and purine syntheses”. Fischer’s work is an example of the growing interest biologically important substances, and was a foundation for the development of biochemistry. Another major influence from organic chemistry was the development of chemical industry, and a chief contributor here was Fischer’s teacher, Adolf von Baeyer in Munich, who was awarded the prize in 1905 “in recognition of his services in the advancement of organic chemistry and the chemical industry, … ” His contributions include, in particular, structure determination of organic

Ernest Rutherford [Lord Rutherford since 1931], professor of physics in Manchester, was awarded the Nobel Prize for Chemistry in 1908. In his studies of uranium disintegration he found two types of radiation, named α- and β-rays, and by their deviation in electric and magnetic fields he could show that α-rays consist of positively charged particles. He had received many nominations for the Nobel Prize for Physics (see Section 1).

In 1897 Eduard Buchner, at the time professor in Tübingen, published results demonstrating that the fermentation of sugar to alcohol and carbon dioxide can take place in the absence of yeast cells. Louis Pasteur had earlier maintained that alcoholic fermentation can only occur in the presence of living yeast cells. Buchner’s experiments showed unequivocally that fermentation is a catalytic process caused by the action of enzymes, as had been suggested by Berzelius for all life processes. Because of Buchner’s experiment, 1897 is generally regarded as the birth date for biochemistry proper. Buchner was awarded the Nobel Prize for Chemistry in 1907, when he was professor at the agricultural college in Berlin. This confirmed the prediction of his former teacher, Adolf von Baeyer: “This will make him famous, in spite of the fact that he lacks talent as a chemist.”

  1. The Nobel Prizes for Chemistry 1911-2000

3.1 General and Physical Chemistry

The Nobel Prize for Chemistry in 1914 was awarded to Theodore William Richards of Harvard University for “his accurate determinations of the atomic weight of a large number of chemical elements”. In 1913 Richards had discovered that the atomic weight of natural lead and of that formed in radioactive decay of uranium minerals differ. This pointed to the existence of isotopes, i.e. atoms of the same element with different atomic weights, which was accurately demonstrated by Francis William Aston at Cambridge University, with the aid of an instrument developed by him, the mass spectrograph. For his achievements Aston received the Nobel Prize for Chemistry in 1922.

One branch of physical chemistry deals with chemical events at the interface of two phases, for example, solid and liquid, and phenomena at such interfaces have important applications all the way from technical to physiological processes. Detailed studies of adsorption on surfaces, were carried out by Irving Langmuir at the research laboratory of General Electric Company, who was awarded the Nobel Prize for Chemistry in 1932, the first industrial scientist to receive this distinction.

Two of the Prizes for Chemistry in more recent decades have been given for fundamental work in the application of spectroscopic methods (Prizes for Physics in 1952, 1955 and 1961) to chemical problems. Gerhard Herzberg, a physicist at the University of Saskatchewan, received the Nobel Prize for Chemistry in 1971 for his molecular spectroscopy studies “of the electronic structure and geometry of molecules, particularly free radicals”. The most used spectroscopic method in chemistry is undoubtedly NMR (nuclear magnetic resonance), and Richard R. Ernst at ETH in Zürich was given the Nobel Prize for Chemistry in 1991 for “the development of the methodology of high resolution nuclear magnetic resonance (NMR) spectroscopy”. Ernst’s methodology has now made it possible to determine the structure in solution (in contrast to crystals; cf. Section 3.5) of large molecules, such as proteins.

3.2 Chemical Thermodynamics

The Nobel Prize for Chemistry to van’t Hoff was in part for work in chemical thermodynamics, and many later contributions in this area have also been recognized with Nobel Prizes.  Walther Hermann Nernst of Berlin received this award in 1920 for work in thermochemistry, despite a 16-year opposition to this recognition from Arrhenius. Nernst had shown that it is possible to determine the equilibrium constant for a chemical reaction from thermal data, and in so doing he formulated what he himself called the third law of thermodynamics. This states that the entropy, a thermodynamic quantity, which is a measure of the disorder in the system, approaches zero as the temperature goes towards absolute zero. van’t Hoff had derived the mass action equation in 1886, with the aid of the second law which says, that the entropy increases in all spontaneous processes [this had already been done in 1876 by J. Willard Gibbs at Yale, who certainly had deserved a Nobel Prize].  Nernst showed in 1906 that it is possible with the aid of the third law, to derive the necessary parameters from the temperature dependence of thermochemical quantities. Nernst carried out thermo-chemical measurements at very low temperatures to prove his heat theorem. G.N. Lewis (see Section 1.1) in Berkeley extended these studies in the 1920s and his new formulation of the third law was confirmed by his student, William Francis Giauque, who extended the temperature range experimentally accessible by introducing the method of adiabatic demagnetization in 1933. He managed to reach temperatures a few thousandths of a degree above absolute zero and could thereby provide extremely accurate entropy estimates. He also showed that it is possible to determine entropies from spectroscopic data. Giauque was awarded the Nobel Prize for Chemistry in 1949 for his contributions to chemical thermodynamics.

The next Nobel Prize given for work in thermodynamics went to Lars Onsager of Yale University in 1968 for contributions to the thermodynamics of irreversible processes. Classical thermodynamics deals with systems at equilibrium, in which the chemical reactions are said to be reversible, but many chemical systems, for example, the most complex of all, living organisms, are far from equilibrium and their reactions are said to be irreversible. Onsager developed his so-called reciprocal relations in 1931, describing the flow of matter and energy in such systems, but the importance of his work was not recognized until the end of the 1940s. A further step forward in the development of non-equilibrium thermodynamics was taken by Ilya Prigogine in Bruxelles, whose theory of dissipative structures was awarded the Nobel Prize for Chemistry in 1977.

3.3 Chemical Change

The chief method to get information about the mechanism of chemical reactions is chemical kinetics, i.e. measurements of the rate of the reaction as a function of reactant concentrations as well as its dependence on temperature, pressure and reaction medium. Important work in this area had been done already in the 1880s by two of the early Laureates, van’t Hoff and Arrhenius, who showed that it is not enough for molecules to collide for a reaction to take place. Only molecules with sufficient kinetic energy in the collision do, in fact, react, and Arrhenius derived an equation in 1889 allowing the calculation of this activation energy from the temperature dependence of the reaction rate. With the advent of quantum mechanics in the 1920s (see Section 3.4), Eyring developed his transition-state theory in 1935 which showed that the activation entropy is also important. Strangely, Eyring never received a Nobel Prize (see Section 1.2).

In 1956 Sir Cyril Norman Hinshelwood of Oxford and Nikolay Nikolaevich Semenov from Moscow shared the Nobel Prize for Chemistry “for their researches into the mechanism of chemical reactions”.  A limit in investigating reaction rates is set by the speed with which the reaction can be initiated. If this is done by rapid mixing of the reactants, the time limit is about one thousandth of a second (millisecond). In the 1950s Manfred Eigen from Göttingen developed chemical relaxation methods that allow measurements in times as short as a thousandth or a millionth of a millisecond (microseconds or nanoseconds). The methods involve disturbing an equilibrium by rapid changes in temperature or pressure and then follow the passage to a new equilibrium. Another way to initiate some reactions rapidly is flash photolysis, i.e. by short light flashes, a method developed by Ronald G.W. Norrish at Cambridge and George Porter (Lord Porter since 1990) in London. Eigen received one-half and Norrish and Porter shared the other half of the Nobel Prize for Chemistry in 1967. The milli- to picosecond time scales gave important information on chemical reactions. However, it was not until it was possible to generate femtosecond laser pulses (10-15 s) that it became possible to reveal when chemical bonds are broken and formed. Ahmed Zewail (born 1946 in Egypt) at California Institute of Technology received the Nobel Prize for Chemistry in 1999 for his development of “femtochemistry” and in particular for being the first to experimentally demonstrate a transition state during a chemical reaction. His experiments relate back to 1889 when Arrhenius (Nobel Prize, 1903) made the important prediction that there must exist intermediates (transition states) in the transformation from reactants to products.

Henry Taube of Stanford University was awarded the Nobel Prize for Chemistry in 1983 “for his work on the mechanism of electron transfer reactions, especially in metal complexes”. Even if Taube’s work was on inorganic reactions, electron transfer is important in many catalytic processes used in industry and also in biological systems, for example, in respiration and photosynthesis.

3.4 Theoretical Chemistry and Chemical Bonding

Quantum mechanics, developed in the 1920s, offered a tool towards a more basic understanding of chemical bonds. In 1927 Walter Heitler and Fritz London showed that it is possible to solve exactly the relevant equations for the hydrogen molecule ion, i.e. two hydrogen nuclei sharing a single electron, and thereby calculate the attractive force between the nuclei. A pioneer in developing such methods was Linus Pauling at California Institute of Technology, who was awarded the Nobel Prize for Chemistry in 1954 “for his research into the nature of the chemical bond …” Pauling’s valence-bond (VB) method is rigorously described in his 1935 book Introduction to Quantum Mechanics (written together with E. Bright Wilson, Jr., at Harvard). A few years later (1939) he published an extensive non-mathematical treatment in The Nature of the Chemical Bond, a book which is one of the most read and influential in the entire history of chemistry. Pauling was not only a theoretician, but he also carried out extensive investigations of chemical structure by X-ray diffraction (see Section 3.5). On the basis of results with small peptides, which are building blocks of proteins, he suggested the α-helix as an important structural element. Pauling was awarded the Nobel Peace Prize for 1962, and he is the only person to date to have won two unshared Nobel Prizes.

α-helix   Pauling’s α-helix

α-carbon atoms are black, other carbon atoms grey, nitrogen atoms blue, oxygen atoms red and hydrogen atoms white; R designates amino-acid side chains. The dotted red lines are hydrogen bonds between amide and carbonyl groups in the peptide bonds.

Pauling’s VB method cannot give an adequate description of chemical bonding in many complicated molecules, and a more comprehensive treatment, the molecular-orbital (MO) method, was introduced already in 1927 by Robert S. Mulliken from Chicago and later developed further. MO theory considers, in quantum-mechanical terms, the interaction between all atomic nuclei and electrons in a molecule. Mulliken also showed that a combination of MO calculations with experimental (spectroscopic) results provides a powerful tool for describing bonding in large molecules. Mulliken received the Nobel Prize for Chemistry in 1966.

Theoretical chemistry has also contributed significantly to our understanding of chemical reaction mechanisms. In 1981 the Nobel Prize for Chemistry was shared between Kenichi Fukui in Kyoto and Roald Hoffmann of Cornell University “for their theories, developed independently, concerning the course of chemical reactions”. Fukui introduced in 1952 the frontier-orbital theory, according to which the occupied MO with the highest energy and the unoccupied one with the lowest energy have a dominant influence on the reactivity of a molecule. Hoffmann formulated in 1965, together with Robert B. Woodward (see Section 3.8), rules based on the conservation of orbital symmetry, for the reactivity and stereochemistry in chemical reactions.
3.5 Chemical Structure

The most commonly used method to determine the structure of molecules in three dimensions is X-ray crystallography. The diffraction of X-rays was discovered by Max von Laue in 1912, and this gave him the Nobel Prize for Physics in 1914. Its use for the determination of crystal structure was developed by Sir William Bragg and his son, Sir Lawrence Bragg, and they shared the Nobel Prize for Physics in 1915. The first Nobel Prize for Chemistry for the use of X-ray diffraction went to Petrus (Peter) Debye, then of Berlin, in 1936. Debye did not study crystals, however, but gases, which give less distinct diffraction patterns.

Many Nobel Prizes have been awarded for the determination of the structure of biological macromolecules (proteins and nucleic acids). Proteins are long chains of amino-acids, as shown by Emil Fischer (see Section 2), and the first step in the determination of their structure is to determine the order (sequence) of these building blocks. An ingenious method for this tedious task was developed by Frederick Sanger of Cambridge, and he reported the amino-acid sequence for a protein, insulin, in 1955. For this achievement he was awarded the Nobel Prize for Chemistry in 1958. Sanger later received part of a second Nobel Prize for Chemistry for a method to determine the nucleotide sequence in nucleic acids (see Section 3.12), and he is the only scientist so far who has won two Nobel Prizes for Chemistry.

The first protein crystal structures were reported by Max Perutz and Sir John Kendrew in 1960, and these two investigators shared the Nobel Prize for Chemistry in 1962. Perutz had started studying the oxygen-carrying blood pigment, hemoglobin, with Sir Lawrence Bragg in Cambridge already in 1937, and ten years later he was joined by Kendrew, who looked at crystals of the related muscle pigment, myoglobin. These proteins are both rich in Pauling’s α-helix (see Section 3.4), and this made it possible to discern the main features of the structures at the relatively low resolution first used. The same year that Perutz and Kendrew won their prize, the Nobel Prize for Physiology or Medicine went to Francis Crick, James Watson and Maurice Wilkins “for their discoveries concerning the molecular structure of nucleic acids … .” Two years later (1964) Dorothy Crowfoot Hodgkin received the Nobel Prize for Chemistry for determining the crystal structures of penicillin and vitamin B12.

Crystallographic electron microscopy was developed by Sir Aaron Klug in Cambridge, who was awarded the Nobel Prize for Chemistry in 1982. Attempts to prepare crystals of membrane proteins for structural studies were unsuccessful, but in 1982 Hartmut Michel managed to crystallize a photosynthetic reaction center after a painstaking series of experiments. He then proceeded to determine the three-dimensional structure of this protein complex in collaboration with Johann Deisenhofer and Robert Huber, and this was published in 1985. Deisenhofer, Huber and Michel shared the Nobel Prize for Chemistry in 1988. Michel has later also crystallized and determined the structure of the terminal enzyme in respiration, and his two structures have allowed detailed studies of electron transfer (cf. Sections 3.3 and 3.4) and its coupling to proton pumping, key features of the chemiosmotic mechanism for which Peter Mitchell had already received the Nobel Prize for Chemistry in 1978 (see Section 3.12). Functional and structural studies on the enzyme ATP synthase, connected to this proton pumping mechanism, was awarded one-half of the Nobel Prize for Chemistry in 1997, shared between Paul D. Boyer and John Walker (see Section 3.12).

3.6 Inorganic and Nuclear Chemistry

Much of the progress in inorganic chemistry during the 20th century has been associated with investigations of coordination compounds, i.e., a central metal ion surrounded by a number of coordinating groups, called ligands. In 1893 Alfred Werner in Zürich presented his coordination theory, and in 1905 he summarized his investigations in this new field in a book (Neuere Anschauungen auf dem Gebiete der anorganischen Chemie), which appeared in no less than five editions from 1905-1923. . Werner showed that a structure for compounds in which a metal ion binds several other molecules (ligands), all the ligand molecules are bound directly to the metal ion. Werner was awarded the Nobel Prize for Chemistry in 1913. Taube’s investigations of electron transfer, awarded in 1983 (see Section 3.3), were mainly carried out with coordination compounds, and vitamin B12 as well as the proteins hemoglobin and myoglobin, investigated by the Laureates Hodgkin, Perutz and Kendrew (see Section 3.5), also belong to this category.

Much inorganic chemistry in the early 1900s was a consequence of the discovery of radioactivity in 1896, for which Henri Becquerel from Paris was awarded the Nobel Prize for Physics in 1903, together with Pierre and Marie Curie. In 1911 Marie Curie received the Nobel Prize for Chemistry for her discovery of the elements radium and polonium and for the isolation of radium and studies of its compounds, and this made her the first investigator to be awarded two Nobel Prizes. The prize in 1921 went to Frederick Soddy of Oxford for his work on the chemistry of radioactive substances and on the origin of isotopes. In 1934 Frédéric Joliot and his wife Irène Joliot-Curie, the daughter of the Curies, discovered artificial radioactivity, i.e., new radioactive elements produced by the bombardment of non-radioactive elements with a-particles or neutrons. They were awarded the Nobel Prize for Chemistry in 1935 for “their synthesis of new radioactive elements”.

Many elements are mixtures of non-radioactive isotopes (see Section 3.1), and in 1934 Harold Urey of Columbia University had been given the Nobel Prize for Chemistry for his isolation of heavy hydrogen (deuterium). Urey had also separated uranium isotopes, and his work was an important basis for the investigations by Otto Hahn from Berlin. In attempts to make transuranium elements, i.e., elements with a higher atomic number than 92 (uranium), by radiating uranium atoms with neutrons, Hahn discovered that one of the products was barium, a lighter element. Lise Meitner, at the time a refugee from Nazism in Sweden, who had earlier worked with Hahn and taken the initiative for the uranium bombardment experiments, provided the explanation, namely, that the uranium atom was cleaved and that barium was one of the products. Hahn was awarded the Nobel Prize for Chemistry in 1944 “for his discovery of the fission of heavy nuclei”, and it can be wondered why Meitner was not included. Hahn’s original intention with his experiments was later achieved by Edwin M. McMillan and Glenn T. Seaborg of Berkeley, who were given the Nobel Prize for Chemistry in 1951 for “discoveries in the chemistry of transuranium elements”.

The use of stable as well as radioactive isotopes have important applications, not only in chemistry, but also in fields as far apart as biology, geology and archeology. In 1943 George de Hevesy from Stockholm received the Nobel Prize for Chemistry for his work on the use of isotopes as tracers, involving studies in inorganic chemistry and geochemistry as well as on the metabolism in living organisms. The prize in 1960 was given to Willard F. Libby of the University of California, Los Angeles (UCLA), for his method to determine the age of various objects (of geological or archeological origin) by measurements of the radioactive isotope carbon-14.

3.7 General Organic Chemistry

Contributions in organic chemistry have led to more Nobel Prizes for Chemistry than work in any other of the traditional branches of chemistry. Like the first prize in this area, that to Emil Fischer in 1902 (see Section 2), most of them have, however, been awarded for advances in the chemistry of natural products and will be treated separately (Section 3.9). Another large group, preparative organic chemistry, has also been given its own section (Section 3.8), and here only the prizes for more general contributions to organic chemistry will be discussed.

In 1969 the Nobel Prize for Chemistry went to Sir Derek H. R. Barton from London, and Odd Hassel from Oslo for developing the concept of conformation, i.e. the spatial arrangement of atoms in molecules, which differ only by the orientation of chemical groups by rotation around a single bond. This stereochemical concept rests on the original suggestion by van’t Hoff of the tetrahedral arrangement of the four valences of the carbon atom (see Section 2), and most organic molecules exist in two or more stable conformations.

The Nobel Prize for Chemistry in 1975 to Sir John Warcup Cornforth of the University of Sussex and Vladimir Prelog of ETH in Zürich was also based on research in stereochemistry. Not only can a compound have more than one geometric form, but chemical reactions can also have specificity in their stereochemistry, thereby forming a product with a particular three-dimensional arrangement of the atoms. This is especially true of reactions in living organisms, and Cornforth has mainly studied enzyme-catalyzed reactions, so his work borders onto biochemistry (Section 3.12). One of Prelog’s main contributions concerns chiral molecules, i.e. molecules that have two forms differing from one another as the right hand does from the left. Stereochemically specific reactions have great practical importance, as many drugs, for example, are active only in one particular geometric form.

Organometallic compounds constitute a group of organic molecules containing one or more carbon-metal bond, and they are thus the organic counterpart to Werner’s inorganic coordination. In 1952 Ernst Otto Fischer and Sir Geoffrey Wilkinson independently described a completely new group of organometallic molecules, called sandwich compounds in which compounds a metal ion is bound not to a single carbon atom but is “sandwiched” between two aromatic organic molecules. Fischer and Wilkinson shared the Nobel Prize for Chemistry in 1973.

3.8 Preparative Organic Chemistry

One of the chief goals of the organic chemist is to be able to synthesize increasingly complex compounds of carbon in combination with various other elements. The first Nobel Prize for Chemistry recognizing pioneering work in preparative organic chemistry was that to Victor Grignard from Nancy and Paul Sabatier from Toulouse in 1912. Grignard had discovered that organic halides can form compounds with magnesium. Sabatier was given the prize for developing a method to hydrogenate organic compounds in the presence of metallic catalysts. The prize in 1950 was presented to Otto Diels from Kiel and Kurt Alder from Cologne “for their discovery and development of the diene synthesis”, developed in 1928, by which organic compounds containing two double bonds (“dienes”) can effect the syntheses of many cyclic organic substances.

The German organic chemist Hans Fischer from Munich had already done significant work on the structure of hemin, the organic pigment in hemoglobin, when he synthesized it from simpler organic molecules in 1928. He also contributed much to the elucidation of the structure of chlorophyll, and for these important achievements he was awarded the Nobel Prize for Chemistry in 1930 (cf. Section 3.5). He finished his determination of the structure of chlorophyll in 1935, and by the time of his death he had almost completed its synthesis as well.

Robert Burns Woodward from Harvard is rightly considered the founder of the most advanced, modern art of organic synthesis. He designed methods for the total synthesis of a large number of complicated natural products, for example, cholesterol, chlorophyll and vitamin B12. He received the Nobel Prize for Chemistry in 1965, and he would probably have received a second chemistry prize in 1981 for his part in the formulation of the Woodward-Hoffmann rules (see Section 3.4), had it not been for his early death.

The Nobel Prize for Chemistry in 1984 was given to Robert Bruce Merrifield of Rockefeller University “for his development of methodology for chemical synthesis on a solid matrix”. Specifically, the synthesis of large peptides and small proteins.

3.9 Chemistry of Natural Product

The synthesis of complex organic molecules must be based on detailed knowledge of their structure. Early work on plant pigments was carried out by Richard Willstätter, a student of Adolf von Baeyer from Munich (see Section 2). Willstätter showed a structural relatedness between chlorophyll and hemin, and he demonstrated that chlorophyll contains magnesium as an integral component. He also carried out pioneering investigations on other plant pigments, such as the carotenoids, and he was awarded the Nobel Prize for Chemistry in 1915 for these achievements. Willstätter’s work laid the ground for the synthetic accomplishments of Hans Fischer (see Section 3.8). In addition, Willstätter contributed to the understanding of enzyme reactions.

The prizes for 1927 and 1928 were both presented to Heinrich Otto Wieland from Munich and Adolf Windaus from Göttingen, respectively, at the Nobel ceremony in 1928. These two chemists had done closely related work on the structure of steroids. The award to Wieland was primarily for his investigations of bile acids, whereas Windaus was recognized mainly for his work on cholesterol and his demonstration of the steroid nature of vitamin D. Wieland had already in 1912, before his prize-winning work, formulated a theory for biological oxidation, according to which removal of hydrogen (dehydrogenation) rather than reaction with oxygen is the dominating process.

Investigations on vitamins were recognized in 1937 and 1938 with the prizes to Sir Norman Haworth from Birmingham and Paul Karrer from Zürich and to Richard Kuhn from Heidelberg. Haworth did outstanding work in carbohydrate chemistry, establishing the ring structure of glucose. He was the first chemist to synthesize vitamin C, and this is the basis for the present large-scale production of this nutrient. Haworth shared the prize with Karrer, who determined the structure of carotene and of vitamin A. Kuhn also worked on carotenoids, and he published the structure of vitamin B2 at the same time as Karrer. He also isolated vitamin B6. In 1939 the Nobel Prize for Chemistry was shared between Adolf Butenandt from Berlin and Leopold Ruzicka (1887-1976) of ETH, Zurich. Butenandt was recognized “for his work on sex hormones”, having isolated estrone, progesterone and androsterone. Ruzicka synthesized androsterone and also testosterone.

The awards for outstanding work in natural-product chemistry continued after World War II. In 1947 Sir Robert Robinson from Oxford received the prize for his studies on plant substances, particularly alkaloids, such as morphine. Robinson also synthesized steroid hormones, and he elucidated the structure of penicillin. Many hormones are of a polypeptide nature, and in 1955 Vincent du Vigneaud of Cornell University was given the prize for his synthesis of two such hormones, vasopressin and oxytocin. Finally, in this area, Alexander R. Todd (Lord Todd since 1962) was recognized in 1957 “for his work on nucleotides and nucleotide co-enzymes”. Todd had synthesized ATP (adenosine triphosphate) and ADP (adenosine diphosphate), the main energy carriers in living cells, and he determined the structure of vitamin B12 (cf. Section 3.5) and of FAD (flavin-adenine dinucleotide).

3.10 Analytical Chemistry and Separation Science

A prize in analytical chemistry was given to Jaroslav Heyrovsky from Prague in 1959 for his development of polarographic methods of analysis. In these a dropping mercury electrode is employed to determine current-voltage curves for electrolytes. A given ion reacts at a specific voltage, and the current is a measure of the concentration of this ion.

The analysis of macromolecular constituents in living organisms requires specialized methods of separation. Ultracentrifugation wad developed by The Svedberg from Uppsala a few years before he was awarded the Nobel Prize for Chemistry in 1926 “for his work on disperse systems” (see Section 3.11). Svedberg’s student, Arne Tiselius, studied the migration of protein molecules in an electric field, and with this method, named electrophoresis, he demonstrated the complex nature of blood proteins. Tiselius also refined adsorption analysis, a method first used by the Russian botanist, Michail Tswett, for the separation of plant pigments and named chromatography by him. In 1948 Tiselius was given the prize for these achievements. A few years later (1952) Archer J.P. Martin from London and Richard L.M. Synge from Bucksburn (Scotland) shared the prize “for their invention of partition chromatography”, and this method was a major tool in many biochemical investigations later awarded with Nobel Prizes (see Section 3.12).

3.11 Polymers and Colloids

The Svedberg who received the Nobel Prize for Chemistry in 1926, also investigated gold sols. He used Zsigmond’s ultramicroscope to study the Brownian movement of colloidal particles, so named after the Scottish botanist Robert Brown, and confirmed a theory developed by Albert Einstein in 1905 and, independently, by M. Smoluchowski. His greatest achievement was, however, the construction of the ultracentrifuge, with which he studied not only the particle size distribution in gold sols but also determined the molecular weight of proteins, for example, hemoglobin. In the same year as Svedberg got the prize the Nobel Prize for Physics was awarded to Jean Baptiste Perrin of Sorbonne for developing equilibrium sedimentation in colloidal solutions, a method which Svedberg later perfected in his ultracentrifuge. Svedberg’s investigations with the ultracentrifuge and Tiselius’s electrophoresis studies (see Section 3.10) were instrumental in establishing that protein molecules have a unique size and structure, and this was a prerequisite for Sanger’s determination of their amino-acid sequence and the crystallographic work of Kendrew and Perutz (see Section 3.5).

3.12 Biochemistry

The second Nobel Prize for discoveries in biochemistry came in 1929, when Sir Arthur Harden from London and Hans von Euler-Chelpin from Stockholm shared the prize for investigations of sugar fermentation, which formed a direct continuation of Buchner’s work awarded in 1907. With his young co-worker, William John Young, Harden had shown in 1906 that fermentation requires a dialysable substance, called co-zymase, which is not destroyed by heat. Harden and Young also demonstrated that the process stops before all sugar (glucose) has been used up, but it starts again on addition of inorganic phosphate, and they suggested that hexose phosphates are formed in the early steps of fermentation. von Euler had done important work on the structure of co-zymase, shown to be nicotinamide adenine dinucleotide (NAD, earlier called DPN). As the number of Laureates can be three, it may seem appropriate for Young to have been included in the award, but Euler’s discovery was published together with Karl Myrbäck, and the number of Laureates is limited to three.

The next biochemical Nobel Prize was given in 1946 for work in the protein field. James B. Sumner of Cornell University received half the prize “for his discovery that enzymes can be crystallized” and John H. Northrop together with Wendell M. Stanley, both of the Rockefeller Institute, shared the other half “for their preparation of enzymes and virus proteins in a pure form”. Sumner had in 1926 crystalized an enzyme, urease, from jack beans and suggested that the crystals were the pure protein. His claim was, however, greeted with great scepticism, and the crystals were suggested to be inorganic salts with the enzyme adsorbed or occluded. Just a few years after Sumner’s discovery Northrop, however, managed to crystalize three digestive enzymes, pepsin, trypsin and chymotrypsin, and by painstaking experiments shown them to be pure proteins. Stanley started his attempt to purify virus proteins in the 1930s, but not until 1945 did he get virus crystals, and this then made it possible to show that viruses are complexes of protein and nucleic acid. The pioneering studies of these three investigators form the basis for the enormous number of new crystal structures of biological macromolecules, which have been published in the second half of the 20th century (cf. Section 3.5).

Several Nobel Prizes for Chemistry have been awarded for work in photosynthesis and respiration, the two main processes in the energy metabolism of living organisms (cf. Section 3.5). In 1961 Melvin Calvin of Berkeley received the prize for elucidating the carbon dioxide assimilation in plants. With the aid of carbon-14 (cf. Section 3.6) Calvin had shown that carbon dioxide is fixed in a cyclic process involving several enzymes. Peter Mitchell of the Glynn Research Laboratories in England was awarded in 1978 for his formulation of the chemiosmotic theory. According to this theory, electron transfer (cf. Sections 3.3 and 3.4) in the membrane-bound enzyme complexes in both respiration and photosynthesis, is coupled to proton translocation across the membranes, and the electrochemical gradient thus created is used to drive the synthesis of ATP (adenosine triphosphate), the energy storage molecule in all living cells. Paul D. Boyer of UCLA and John C. Walker of the MRC Laboratory in Cambridge shared one-half of the 1997 prize for their elucidation of the mechanism of ATP synthesis; the other half of the prize went to Jens C. Skou in Aarhus for the first discovery of an ion-transporting enzyme. Walker had determined the crystal structure of ATP synthase, and this structure confirmed a mechanism earlier proposed by Boyer, mainly on the basis of isotopic studies.

Luis F. Leloir from Buenos Aires was awarded in 1970 “for the discovery of sugar nucleotides and their role in the biosynthesis of carbohydrates”. In particular, Leloir had elucidated the biosynthesis of glycogen, the chief sugar reserve in animals and many microorganisms. Two years later the prize went with one half to Christian B. Anfinsen of NIH and the other half shared by Stanford Moore and William H. Stein, both from Rockefeller University, for fundamental work in protein chemistry. Anfinsen had shown, with the enzyme ribonuclease, that the information for a protein assuming a specific three-dimensional structure is inherent in its amino-acid sequence, and this discovery was the starting point for studies of the mechanism of protein folding, one of the major areas of present-day biochemical research. Moore and Stein had determined the amino-acid sequence of ribonuclease, but they received the prize for discovering anomalous properties of functional groups in the enzyme’s active site, which is a result of the protein fold.

Naturally a number of Nobel Prizes for Chemistry have been given for work in the nucleic acid field. In 1980 Paul Berg of Stanford received one half of the prize for studies of recombinant DNA, i.e. a molecule containing parts of DNA from different species, and the other half was shared by Walter Gilbert from Harvard and Frederick Sanger (see Section 3.5) for developing methods for the determination of the base sequences of nucleic acids. Berg’s work provides the basis of genetic engineering, which has led to the large biotechnology industry. Base sequence determinations are essential steps in recombinant-DNA technology, which is the rationale for Gilbert and Sanger sharing the prize with Berg.

Sidney Altman of Yale and Thomas R. Cech of the University of Colorado shared the prize in 1989 “for their discovery of the catalytic properties of RNA”. The central dogma of molecular biology is: DNA –> RNA –> enzyme. The discovery that not only enzymes but also RNA possesses catalytic properties have led to new ideas about the origin of life. The 1993 prize was shared by Kary B. Mullis from La Jolla and Michael Smith from Vancouver, who both have given important contributions to DNA technology. Mullis developed the PCR (“polymerase chain reaction”) technique, which makes it possible to replicate millions of times a specific DNA segment in a complicated genetic material. Smith’s work forms the basis for site-directed mutagenesis, a technique by which it is possible to change a specific amino-acid in a protein and thereby illuminate its functional role.

  1. Concluding Remarks

The first eighty years of Nobel Prizes for Chemistry outlines the development of modern chemistry. The prizes cover a broad spectrum of the basic chemical sciences, from theoretical chemistry to biochemistry, and also a number of contributions to applied chemistry. Organic chemistry dominates with no less than 25 awards. This is not surprising, since the special valence properties of carbon result in an almost infinite variation in the structure of organic compounds. Also, a large number of the prizes in organic chemistry were given for investigations of the chemistry of natural products of increasing complexity, and have lead to pharmaceutical development .

As many as 11 prizes have been awarded for biochemical discoveries. The first biochemical prize was already given in 1907 (Buchner), but only three awards in this area came in the first half of the century, illustrating the explosive growth of biochemistry in recent decades (8 prizes in 1970-1997). At the other end of the chemical spectrum, physical chemistry, including chemical thermodynamics and kinetics, dominates with 14 prizes, but there have also been 6 prizes in theoretical chemistry. Chemical structure is a large area with 8 prizes, including awards for methodological developments as well as for the determination of the structure of large biological molecules or molecular complexes. Industrial chemistry was first recognized in 1931 (Bergius, Bosch), but many more recent prizes for basic contributions lie close to industrial applications.

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Summary and Perspectives: Impairments in Pathological States: Endocrine Disorders, Stress Hypermetabolism and Cancer

Summary and Perspectives: Impairments in Pathological States: Endocrine Disorders, Stress Hypermetabolism and Cancer

Author and Curator: Larry H. Bernstein, MD, FCAP

Article ID #160: Summary and Perspectives: Impairments in Pathological States: Endocrine Disorders, Stress Hypermetabolism and Cancer. Published on 11/9/2014

WordCloud Image Produced by Adam Tubman

This summary is the last of a series on the impact of transcriptomics, proteomics, and metabolomics on disease investigation, and the sorting and integration of genomic signatures and metabolic signatures to explain phenotypic relationships in variability and individuality of response to disease expression and how this leads to  pharmaceutical discovery and personalized medicine.  We have unquestionably better tools at our disposal than has ever existed in the history of mankind, and an enormous knowledge-base that has to be accessed.  I shall conclude here these discussions with the powerful contribution to and current knowledge pertaining to biochemistry, metabolism, protein-interactions, signaling, and the application of the -OMICS to diseases and drug discovery at this time.

The Ever-Transcendent Cell

Deriving physiologic first principles By John S. Torday | The Scientist Nov 1, 2014
http://www.the-scientist.com/?articles.view/articleNo/41282/title/The-Ever-Transcendent-Cell/

Both the developmental and phylogenetic histories of an organism describe the evolution of physiology—the complex of metabolic pathways that govern the function of an organism as a whole. The necessity of establishing and maintaining homeostatic mechanisms began at the cellular level, with the very first cells, and homeostasis provides the underlying selection pressure fueling evolution.

While the events leading to the formation of the first functioning cell are debatable, a critical one was certainly the formation of simple lipid-enclosed vesicles, which provided a protected space for the evolution of metabolic pathways. Protocells evolved from a common ancestor that experienced environmental stresses early in the history of cellular development, such as acidic ocean conditions and low atmospheric oxygen levels, which shaped the evolution of metabolism.

The reduction of evolution to cell biology may answer the perennially unresolved question of why organisms return to their unicellular origins during the life cycle.

As primitive protocells evolved to form prokaryotes and, much later, eukaryotes, changes to the cell membrane occurred that were critical to the maintenance of chemiosmosis, the generation of bioenergy through the partitioning of ions. The incorporation of cholesterol into the plasma membrane surrounding primitive eukaryotic cells marked the beginning of their differentiation from prokaryotes. Cholesterol imparted more fluidity to eukaryotic cell membranes, enhancing functionality by increasing motility and endocytosis. Membrane deformability also allowed for increased gas exchange.

Acidification of the oceans by atmospheric carbon dioxide generated high intracellular calcium ion concentrations in primitive aquatic eukaryotes, which had to be lowered to prevent toxic effects, namely the aggregation of nucleotides, proteins, and lipids. The early cells achieved this by the evolution of calcium channels composed of cholesterol embedded within the cell’s plasma membrane, and of internal membranes, such as that of the endoplasmic reticulum, peroxisomes, and other cytoplasmic organelles, which hosted intracellular chemiosmosis and helped regulate calcium.

As eukaryotes thrived, they experienced increasingly competitive pressure for metabolic efficiency. Engulfed bacteria, assimilated as mitochondria, provided more bioenergy. As the evolution of eukaryotic organisms progressed, metabolic cooperation evolved, perhaps to enable competition with biofilm-forming, quorum-sensing prokaryotes. The subsequent appearance of multicellular eukaryotes expressing cellular growth factors and their respective receptors facilitated cell-cell signaling, forming the basis for an explosion of multicellular eukaryote evolution, culminating in the metazoans.

Casting a cellular perspective on evolution highlights the integration of genotype and phenotype. Starting from the protocell membrane, the functional homolog for all complex metazoan organs, it offers a way of experimentally determining the role of genes that fostered evolution based on the ontogeny and phylogeny of cellular processes that can be traced back, in some cases, to our last universal common ancestor.  ….

As eukaryotes thrived, they experienced increasingly competitive pressure for metabolic efficiency. Engulfed bacteria, assimilated as mitochondria, provided more bioenergy. As the evolution of eukaryotic organisms progressed, metabolic cooperation evolved, perhaps to enable competition with biofilm-forming, quorum-sensing prokaryotes. The subsequent appearance of multicellular eukaryotes expressing cellular growth factors and their respective receptors facilitated cell-cell signaling, forming the basis for an explosion of multicellular eukaryote evolution, culminating in the metazoans.

Casting a cellular perspective on evolution highlights the integration of genotype and phenotype. Starting from the protocell membrane, the functional homolog for all complex metazoan organs, it offers a way of experimentally determining the role of genes that fostered evolution based on the ontogeny and phylogeny of cellular processes that can be traced back, in some cases, to our last universal common ancestor.

Given that the unicellular toolkit is complete with all the traits necessary for forming multicellular organisms (Science, 301:361-63, 2003), it is distinctly possible that metazoans are merely permutations of the unicellular body plan. That scenario would clarify a lot of puzzling biology: molecular commonalities between the skin, lung, gut, and brain that affect physiology and pathophysiology exist because the cell membranes of unicellular organisms perform the equivalents of these tissue functions, and the existence of pleiotropy—one gene affecting many phenotypes—may be a consequence of the common unicellular source for all complex biologic traits.  …

The cell-molecular homeostatic model for evolution and stability addresses how the external environment generates homeostasis developmentally at the cellular level. It also determines homeostatic set points in adaptation to the environment through specific effectors, such as growth factors and their receptors, second messengers, inflammatory mediators, crossover mutations, and gene duplications. This is a highly mechanistic, heritable, plastic process that lends itself to understanding evolution at the cellular, tissue, organ, system, and population levels, mediated by physiologically linked mechanisms throughout, without having to invoke random, chance mechanisms to bridge different scales of evolutionary change. In other words, it is an integrated mechanism that can often be traced all the way back to its unicellular origins.

The switch from swim bladder to lung as vertebrates moved from water to land is proof of principle that stress-induced evolution in metazoans can be understood from changes at the cellular level.

http://www.the-scientist.com/Nov2014/TE_21.jpg

A MECHANISTIC BASIS FOR LUNG DEVELOPMENT: Stress from periodic atmospheric hypoxia (1) during vertebrate adaptation to land enhances positive selection of the stretch-regulated parathyroid hormone-related protein (PTHrP) in the pituitary and adrenal glands. In the pituitary (2), PTHrP signaling upregulates the release of adrenocorticotropic hormone (ACTH) (3), which stimulates the release of glucocorticoids (GC) by the adrenal gland (4). In the adrenal gland, PTHrP signaling also stimulates glucocorticoid production of adrenaline (5), which in turn affects the secretion of lung surfactant, the distension of alveoli, and the perfusion of alveolar capillaries (6). PTHrP signaling integrates the inflation and deflation of the alveoli with surfactant production and capillary perfusion.  THE SCIENTIST STAFF

From a cell-cell signaling perspective, two critical duplications in genes coding for cell-surface receptors occurred during this period of water-to-land transition—in the stretch-regulated parathyroid hormone-related protein (PTHrP) receptor gene and the β adrenergic (βA) receptor gene. These gene duplications can be disassembled by following their effects on vertebrate physiology backwards over phylogeny. PTHrP signaling is necessary for traits specifically relevant to land adaptation: calcification of bone, skin barrier formation, and the inflation and distention of lung alveoli. Microvascular shear stress in PTHrP-expressing organs such as bone, skin, kidney, and lung would have favored duplication of the PTHrP receptor, since sheer stress generates radical oxygen species (ROS) known to have this effect and PTHrP is a potent vasodilator, acting as an epistatic balancing selection for this constraint.

Positive selection for PTHrP signaling also evolved in the pituitary and adrenal cortex (see figure on this page), stimulating the secretion of ACTH and corticoids, respectively, in response to the stress of land adaptation. This cascade amplified adrenaline production by the adrenal medulla, since corticoids passing through it enzymatically stimulate adrenaline synthesis. Positive selection for this functional trait may have resulted from hypoxic stress that arose during global episodes of atmospheric hypoxia over geologic time. Since hypoxia is the most potent physiologic stressor, such transient oxygen deficiencies would have been acutely alleviated by increasing adrenaline levels, which would have stimulated alveolar surfactant production, increasing gas exchange by facilitating the distension of the alveoli. Over time, increased alveolar distension would have generated more alveoli by stimulating PTHrP secretion, impelling evolution of the alveolar bed of the lung.

This scenario similarly explains βA receptor gene duplication, since increased density of the βA receptor within the alveolar walls was necessary for relieving another constraint during the evolution of the lung in adaptation to land: the bottleneck created by the existence of a common mechanism for blood pressure control in both the lung alveoli and the systemic blood pressure. The pulmonary vasculature was constrained by its ability to withstand the swings in pressure caused by the systemic perfusion necessary to sustain all the other vital organs. PTHrP is a potent vasodilator, subserving the blood pressure constraint, but eventually the βA receptors evolved to coordinate blood pressure in both the lung and the periphery.

Gut Microbiome Heritability

Analyzing data from a large twin study, researchers have homed in on how host genetics can shape the gut microbiome.
By Tracy Vence | The Scientist Nov 6, 2014

Previous research suggested host genetic variation can influence microbial phenotype, but an analysis of data from a large twin study published in Cell today (November 6) solidifies the connection between human genotype and the composition of the gut microbiome. Studying more than 1,000 fecal samples from 416 monozygotic and dizygotic twin pairs, Cornell University’s Ruth Ley and her colleagues have homed in on one bacterial taxon, the family Christensenellaceae, as the most highly heritable group of microbes in the human gut. The researchers also found that Christensenellaceae—which was first described just two years ago—is central to a network of co-occurring heritable microbes that is associated with lean body mass index (BMI).  …

Of particular interest was the family Christensenellaceae, which was the most heritable taxon among those identified in the team’s analysis of fecal samples obtained from the TwinsUK study population.

While microbiologists had previously detected 16S rRNA sequences belonging to Christensenellaceae in the human microbiome, the family wasn’t named until 2012. “People hadn’t looked into it, partly because it didn’t have a name . . . it sort of flew under the radar,” said Ley.

Ley and her colleagues discovered that Christensenellaceae appears to be the hub in a network of co-occurring heritable taxa, which—among TwinsUK participants—was associated with low BMI. The researchers also found that Christensenellaceae had been found at greater abundance in low-BMI twins in older studies.

To interrogate the effects of Christensenellaceae on host metabolic phenotype, the Ley’s team introduced lean and obese human fecal samples into germ-free mice. They found animals that received lean fecal samples containing more Christensenellaceae showed reduced weight gain compared with their counterparts. And treatment of mice that had obesity-associated microbiomes with one member of the Christensenellaceae family, Christensenella minuta, led to reduced weight gain.   …

Ley and her colleagues are now focusing on the host alleles underlying the heritability of the gut microbiome. “We’re running a genome-wide association analysis to try to find genes—particular variants of genes—that might associate with higher levels of these highly heritable microbiota.  . . . Hopefully that will point us to possible reasons they’re heritable,” she said. “The genes will guide us toward understanding how these relationships are maintained between host genotype and microbiome composition.”

J.K. Goodrich et al., “Human genetics shape the gut microbiome,” Cell,  http://dx.doi.org:/10.1016/j.cell.2014.09.053, 2014.

Light-Operated Drugs

Scientists create a photosensitive pharmaceutical to target a glutamate receptor.
By Ruth Williams | The Scentist Nov 1, 2014
http://www.the-scientist.com/?articles.view/articleNo/41279/title/Light-Operated-Drugs/

light operated drugs MO1

light operated drugs MO1

http://www.the-scientist.com/Nov2014/MO1.jpg

The desire for temporal and spatial control of medications to minimize side effects and maximize benefits has inspired the development of light-controllable drugs, or optopharmacology. Early versions of such drugs have manipulated ion channels or protein-protein interactions, “but never, to my knowledge, G protein–coupled receptors [GPCRs], which are one of the most important pharmacological targets,” says Pau Gorostiza of the Institute for Bioengineering of Catalonia, in Barcelona.

Gorostiza has taken the first step toward filling that gap, creating a photosensitive inhibitor of the metabotropic glutamate 5 (mGlu5) receptor—a GPCR expressed in neurons and implicated in a number of neurological and psychiatric disorders. The new mGlu5 inhibitor—called alloswitch-1—is based on a known mGlu receptor inhibitor, but the simple addition of a light-responsive appendage, as had been done for other photosensitive drugs, wasn’t an option. The binding site on mGlu5 is “extremely tight,” explains Gorostiza, and would not accommodate a differently shaped molecule. Instead, alloswitch-1 has an intrinsic light-responsive element.

In a human cell line, the drug was active under dim light conditions, switched off by exposure to violet light, and switched back on by green light. When Gorostiza’s team administered alloswitch-1 to tadpoles, switching between violet and green light made the animals stop and start swimming, respectively.

The fact that alloswitch-1 is constitutively active and switched off by light is not ideal, says Gorostiza. “If you are thinking of therapy, then in principle you would prefer the opposite,” an “on” switch. Indeed, tweaks are required before alloswitch-1 could be a useful drug or research tool, says Stefan Herlitze, who studies ion channels at Ruhr-Universität Bochum in Germany. But, he adds, “as a proof of principle it is great.” (Nat Chem Biol, http://dx.doi.org:/10.1038/nchembio.1612, 2014)

Enhanced Enhancers

The recent discovery of super-enhancers may offer new drug targets for a range of diseases.
By Eric Olson | The Scientist Nov 1, 2014
http://www.the-scientist.com/?articles.view/articleNo/41281/title/Enhanced-Enhancers/

To understand disease processes, scientists often focus on unraveling how gene expression in disease-associated cells is altered. Increases or decreases in transcription—as dictated by a regulatory stretch of DNA called an enhancer, which serves as a binding site for transcription factors and associated proteins—can produce an aberrant composition of proteins, metabolites, and signaling molecules that drives pathologic states. Identifying the root causes of these changes may lead to new therapeutic approaches for many different diseases.

Although few therapies for human diseases aim to alter gene expression, the outstanding examples—including antiestrogens for hormone-positive breast cancer, antiandrogens for prostate cancer, and PPAR-γ agonists for type 2 diabetes—demonstrate the benefits that can be achieved through targeting gene-control mechanisms.  Now, thanks to recent papers from laboratories at MIT, Harvard, and the National Institutes of Health, researchers have a new, much bigger transcriptional target: large DNA regions known as super-enhancers or stretch-enhancers. Already, work on super-enhancers is providing insights into how gene-expression programs are established and maintained, and how they may go awry in disease.  Such research promises to open new avenues for discovering medicines for diseases where novel approaches are sorely needed.

Super-enhancers cover stretches of DNA that are 10- to 100-fold longer and about 10-fold less abundant in the genome than typical enhancer regions (Cell, 153:307-19, 2013). They also appear to bind a large percentage of the transcriptional machinery compared to typical enhancers, allowing them to better establish and enforce cell-type specific transcriptional programs (Cell, 153:320-34, 2013).

Super-enhancers are closely associated with genes that dictate cell identity, including those for cell-type–specific master regulatory transcription factors. This observation led to the intriguing hypothesis that cells with a pathologic identity, such as cancer cells, have an altered gene expression program driven by the loss, gain, or altered function of super-enhancers.

Sure enough, by mapping the genome-wide location of super-enhancers in several cancer cell lines and from patients’ tumor cells, we and others have demonstrated that genes located near super-enhancers are involved in processes that underlie tumorigenesis, such as cell proliferation, signaling, and apoptosis.

Super-enhancers cover stretches of DNA that are 10- to 100-fold longer and about 10-fold less abundant in the genome than typical enhancer regions.

Genome-wide association studies (GWAS) have found that disease- and trait-associated genetic variants often occur in greater numbers in super-enhancers (compared to typical enhancers) in cell types involved in the disease or trait of interest (Cell, 155:934-47, 2013). For example, an enrichment of fasting glucose–associated single nucleotide polymorphisms (SNPs) was found in the stretch-enhancers of pancreatic islet cells (PNAS, 110:17921-26, 2013). Given that some 90 percent of reported disease-associated SNPs are located in noncoding regions, super-enhancer maps may be extremely valuable in assigning functional significance to GWAS variants and identifying target pathways.

Because only 1 to 2 percent of active genes are physically linked to a super-enhancer, mapping the locations of super-enhancers can be used to pinpoint the small number of genes that may drive the biology of that cell. Differential super-enhancer maps that compare normal cells to diseased cells can be used to unravel the gene-control circuitry and identify new molecular targets, in much the same way that somatic mutations in tumor cells can point to oncogenic drivers in cancer. This approach is especially attractive in diseases for which an incomplete understanding of the pathogenic mechanisms has been a barrier to discovering effective new therapies.

Another therapeutic approach could be to disrupt the formation or function of super-enhancers by interfering with their associated protein components. This strategy could make it possible to downregulate multiple disease-associated genes through a single molecular intervention. A group of Boston-area researchers recently published support for this concept when they described inhibited expression of cancer-specific genes, leading to a decrease in cancer cell growth, by using a small molecule inhibitor to knock down a super-enhancer component called BRD4 (Cancer Cell, 24:777-90, 2013).  More recently, another group showed that expression of the RUNX1 transcription factor, involved in a form of T-cell leukemia, can be diminished by treating cells with an inhibitor of a transcriptional kinase that is present at the RUNX1 super-enhancer (Nature, 511:616-20, 2014).

Fungal effector Ecp6 outcompetes host immune receptor for chitin binding through intrachain LysM dimerization 
Andrea Sánchez-Vallet, et al.   eLife 2013;2:e00790 http://elifesciences.org/content/2/e00790#sthash.LnqVMJ9p.dpuf

LysM effector

LysM effector

http://img.scoop.it/ZniCRKQSvJOG18fHbb4p0Tl72eJkfbmt4t8yenImKBVvK0kTmF0xjctABnaLJIm9

While host immune receptors

  • detect pathogen-associated molecular patterns to activate immunity,
  • pathogens attempt to deregulate host immunity through secreted effectors.

Fungi employ LysM effectors to prevent

  • recognition of cell wall-derived chitin by host immune receptors

Structural analysis of the LysM effector Ecp6 of

  • the fungal tomato pathogen Cladosporium fulvum reveals
  • a novel mechanism for chitin binding,
  • mediated by intrachain LysM dimerization,

leading to a chitin-binding groove that is deeply buried in the effector protein.

This composite binding site involves

  • two of the three LysMs of Ecp6 and
  • mediates chitin binding with ultra-high (pM) affinity.

The remaining singular LysM domain of Ecp6 binds chitin with

  • low micromolar affinity but can nevertheless still perturb chitin-triggered immunity.

Conceivably, the perturbation by this LysM domain is not established through chitin sequestration but possibly through interference with the host immune receptor complex.

Mutated Genes in Schizophrenia Map to Brain Networks
From www.nih.gov –  Sep 3, 2013

Previous studies have shown that many people with schizophrenia have de novo, or new, genetic mutations. These misspellings in a gene’s DNA sequence

  • occur spontaneously and so aren’t shared by their close relatives.

Dr. Mary-Claire King of the University of Washington in Seattle and colleagues set out to

  • identify spontaneous genetic mutations in people with schizophrenia and
  • to assess where and when in the brain these misspelled genes are turned on, or expressed.

The study was funded in part by NIH’s National Institute of Mental Health (NIMH). The results were published in the August 1, 2013, issue of Cell.

The researchers sequenced the exomes (protein-coding DNA regions) of 399 people—105 with schizophrenia plus their unaffected parents and siblings. Gene variations
that were found in a person with schizophrenia but not in either parent were considered spontaneous.

The likelihood of having a spontaneous mutation was associated with

  • the age of the father in both affected and unaffected siblings.

Significantly more mutations were found in people

  • whose fathers were 33-45 years at the time of conception compared to 19-28 years.

Among people with schizophrenia, the scientists identified

  • 54 genes with spontaneous mutations
  • predicted to cause damage to the function of the protein they encode.

The researchers used newly available database resources that show

  • where in the brain and when during development genes are expressed.

The genes form an interconnected expression network with many more connections than

  • that of the genes with spontaneous damaging mutations in unaffected siblings.

The spontaneously mutated genes in people with schizophrenia

  • were expressed in the prefrontal cortex, a region in the front of the brain.

The genes are known to be involved in important pathways in brain development. Fifty of these genes were active

  • mainly during the period of fetal development.

“Processes critical for the brain’s development can be revealed by the mutations that disrupt them,” King says. “Mutations can lead to loss of integrity of a whole pathway,
not just of a single gene.”

These findings support the concept that schizophrenia may result, in part, from

  • disruptions in development in the prefrontal cortex during fetal development.

James E. Darnell’s “Reflections”

A brief history of the discovery of RNA and its role in transcription — peppered with career advice
By Joseph P. Tiano

James Darnell begins his Journal of Biological Chemistry “Reflections” article by saying, “graduate students these days

  • have to swim in a sea virtually turgid with the daily avalanche of new information and
  • may be momentarily too overwhelmed to listen to the aging.

I firmly believe how we learned what we know can provide useful guidance for how and what a newcomer will learn.” Considering his remarkable discoveries in

  • RNA processing and eukaryotic transcriptional regulation

spanning 60 years of research, Darnell’s advice should be cherished. In his second year at medical school at Washington University School of Medicine in St. Louis, while
studying streptococcal disease in Robert J. Glaser’s laboratory, Darnell realized he “loved doing the experiments” and had his first “career advancement event.”
He and technician Barbara Pesch discovered that in vivo penicillin treatment killed streptococci only in the exponential growth phase and not in the stationary phase. These
results were published in the Journal of Clinical Investigation and earned Darnell an interview with Harry Eagle at the National Institutes of Health.

Darnell arrived at the NIH in 1956, shortly after Eagle  shifted his research interest to developing his minimal essential cell culture medium, still used. Eagle, then studying cell metabolism, suggested that Darnell take up a side project on poliovirus replication in mammalian cells in collaboration with Robert I. DeMars. DeMars’ Ph.D.
adviser was also James  Watson’s mentor, so Darnell met Watson, who invited him to give a talk at Harvard University, which led to an assistant professor position
at the MIT under Salvador Luria. A take-home message is to embrace side projects, because you never know where they may lead: this project helped to shape
his career.

Darnell arrived in Boston in 1961. Following the discovery of DNA’s structure in 1953, the world of molecular biology was turning to RNA in an effort to understand how
proteins are made. Darnell’s background in virology (it was discovered in 1960 that viruses used RNA to replicate) was ideal for the aim of his first independent lab:
exploring mRNA in animal cells grown in culture. While at MIT, he developed a new technique for purifying RNA along with making other observations

  • suggesting that nonribosomal cytoplasmic RNA may be involved in protein synthesis.

When Darnell moved to Albert Einstein College of Medicine for full professorship in 1964,  it was hypothesized that heterogenous nuclear RNA was a precursor to mRNA.
At Einstein, Darnell discovered RNA processing of pre-tRNAs and demonstrated for the first time

  • that a specific nuclear RNA could represent a possible specific mRNA precursor.

In 1967 Darnell took a position at Columbia University, and it was there that he discovered (simultaneously with two other labs) that

  • mRNA contained a polyadenosine tail.

The three groups all published their results together in the Proceedings of the National Academy of Sciences in 1971. Shortly afterward, Darnell made his final career move
four short miles down the street to Rockefeller University in 1974.

Over the next 35-plus years at Rockefeller, Darnell never strayed from his original research question: How do mammalian cells make and control the making of different
mRNAs? His work was instrumental in the collaborative discovery of

  • splicing in the late 1970s and
  • in identifying and cloning many transcriptional activators.

Perhaps his greatest contribution during this time, with the help of Ernest Knight, was

  • the discovery and cloning of the signal transducers and activators of transcription (STAT) proteins.

And with George Stark, Andy Wilks and John Krowlewski, he described

  • cytokine signaling via the JAK-STAT pathway.

Darnell closes his “Reflections” with perhaps his best advice: Do not get too wrapped up in your own work, because “we are all needed and we are all in this together.”

Darnell Reflections - James_Darnell

Darnell Reflections – James_Darnell

http://www.asbmb.org/assets/0/366/418/428/85528/85529/85530/8758cb87-84ff-42d6-8aea-96fda4031a1b.jpg

Recent findings on presenilins and signal peptide peptidase

By Dinu-Valantin Bălănescu

γ-secretase and SPP

γ-secretase and SPP

Fig. 1 from the minireview shows a schematic depiction of γ-secretase and SPP

http://www.asbmb.org/assets/0/366/418/428/85528/85529/85530/c2de032a-daad-41e5-ba19-87a17bd26362.png

GxGD proteases are a family of intramembranous enzymes capable of hydrolyzing

  • the transmembrane domain of some integral membrane proteins.

The GxGD family is one of the three families of

  • intramembrane-cleaving proteases discovered so far (along with the rhomboid and site-2 protease) and
  • includes the γ-secretase and the signal peptide peptidase.

Although only recently discovered, a number of functions in human pathology and in numerous other biological processes

  • have been attributed to γ-secretase and SPP.

Taisuke Tomita and Takeshi Iwatsubo of the University of Tokyo highlighted the latest findings on the structure and function of γ-secretase and SPP
in a recent minireview in The Journal of Biological Chemistry.

  • γ-secretase is involved in cleaving the amyloid-β precursor protein, thus producing amyloid-β peptide,

the main component of senile plaques in Alzheimer’s disease patients’ brains. The complete structure of mammalian γ-secretase is not yet known; however,
Tomita and Iwatsubo note that biochemical analyses have revealed it to be a multisubunit protein complex.

  • Its catalytic subunit is presenilin, an aspartyl protease.

In vitro and in vivo functional and chemical biology analyses have revealed that

  • presenilin is a modulator and mandatory component of the γ-secretase–mediated cleavage of APP.

Genetic studies have identified three other components required for γ-secretase activity:

  1. nicastrin,
  2. anterior pharynx defective 1 and
  3. presenilin enhancer 2.

By coexpression of presenilin with the other three components, the authors managed to

  • reconstitute γ-secretase activity.

Tomita and Iwatsubo determined using the substituted cysteine accessibility method and by topological analyses, that

  • the catalytic aspartates are located at the center of the nine transmembrane domains of presenilin,
  • by revealing the exact location of the enzyme’s catalytic site.

The minireview also describes in detail the formerly enigmatic mechanism of γ-secretase mediated cleavage.

SPP, an enzyme that cleaves remnant signal peptides in the membrane

  • during the biogenesis of membrane proteins and
  • signal peptides from major histocompatibility complex type I,
  • also is involved in the maturation of proteins of the hepatitis C virus and GB virus B.

Bioinformatics methods have revealed in fruit flies and mammals four SPP-like proteins,

  • two of which are involved in immunological processes.

By using γ-secretase inhibitors and modulators, it has been confirmed

  • that SPP shares a similar GxGD active site and proteolytic activity with γ-secretase.

Upon purification of the human SPP protein with the baculovirus/Sf9 cell system,

  • single-particle analysis revealed further structural and functional details.

HLA targeting efficiency correlates with human T-cell response magnitude and with mortality from influenza A infection

From www.pnas.org –  Sep 3, 2013 4:24 PM

Experimental and computational evidence suggests that

  • HLAs preferentially bind conserved regions of viral proteins, a concept we term “targeting efficiency,” and that
  • this preference may provide improved clearance of infection in several viral systems.

To test this hypothesis, T-cell responses to A/H1N1 (2009) were measured from peripheral blood mononuclear cells obtained from a household cohort study
performed during the 2009–2010 influenza season. We found that HLA targeting efficiency scores significantly correlated with

  • IFN-γ enzyme-linked immunosorbent spot responses (P = 0.042, multiple regression).

A further population-based analysis found that the carriage frequencies of the alleles with the lowest targeting efficiencies, A*24,

  • were associated with pH1N1 mortality (r = 0.37, P = 0.031) and
  • are common in certain indigenous populations in which increased pH1N1 morbidity has been reported.

HLA efficiency scores and HLA use are associated with CD8 T-cell magnitude in humans after influenza infection.
The computational tools used in this study may be useful predictors of potential morbidity and

  • identify immunologic differences of new variant influenza strains
  • more accurately than evolutionary sequence comparisons.

Population-based studies of the relative frequency of these alleles in severe vs. mild influenza cases

  • might advance clinical practices for severe H1N1 infections among genetically susceptible populations.

Metabolomics in drug target discovery

J D Rabinowitz et al.

Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ.
Cold Spring Harbor Symposia on Quantitative Biology 11/2011; 76:235-46.
http://dx.doi.org:/10.1101/sqb.2011.76.010694 

Most diseases result in metabolic changes. In many cases, these changes play a causative role in disease progression. By identifying pathological metabolic changes,

  • metabolomics can point to potential new sites for therapeutic intervention.

Particularly promising enzymatic targets are those that

  • carry increased flux in the disease state.

Definitive assessment of flux requires the use of isotope tracers. Here we present techniques for

  • finding new drug targets using metabolomics and isotope tracers.

The utility of these methods is exemplified in the study of three different viral pathogens. For influenza A and herpes simplex virus,

  • metabolomic analysis of infected versus mock-infected cells revealed
  • dramatic concentration changes around the current antiviral target enzymes.

Similar analysis of human-cytomegalovirus-infected cells, however, found the greatest changes

  • in a region of metabolism unrelated to the current antiviral target.

Instead, it pointed to the tricarboxylic acid (TCA) cycle and

  • its efflux to feed fatty acid biosynthesis as a potential preferred target.

Isotope tracer studies revealed that cytomegalovirus greatly increases flux through

  • the key fatty acid metabolic enzyme acetyl-coenzyme A carboxylase.
  • Inhibition of this enzyme blocks human cytomegalovirus replication.

Examples where metabolomics has contributed to identification of anticancer drug targets are also discussed. Eventual proof of the value of

  • metabolomics as a drug target discovery strategy will be
  • successful clinical development of therapeutics hitting these new targets.

 Related References

Use of metabolic pathway flux information in targeted cancer drug design. Drug Discovery Today: Therapeutic Strategies 1:435-443, 2004.

Detection of resistance to imatinib by metabolic profiling: clinical and drug development implications. Am J Pharmacogenomics. 2005;5(5):293-302. Review. PMID: 16196499

Medicinal chemistry, metabolic profiling and drug target discovery: a role for metabolic profiling in reverse pharmacology and chemical genetics.
Mini Rev Med Chem.  2005 Jan;5(1):13-20. Review. PMID: 15638788 [PubMed – indexed for MEDLINE] Related citations

Development of Tracer-Based Metabolomics and its Implications for the Pharmaceutical Industry. Int J Pharm Med 2007; 21 (3): 217-224.

Use of metabolic pathway flux information in anticancer drug design. Ernst Schering Found Symp Proc. 2007;(4):189-203. Review. PMID: 18811058

Pharmacological targeting of glucagon and glucagon-like peptide 1 receptors has different effects on energy state and glucose homeostasis in diet-induced obese mice. J Pharmacol Exp Ther. 2011 Jul;338(1):70-81. http://dx.doi.org:/10.1124/jpet.111.179986. PMID: 21471191

Single valproic acid treatment inhibits glycogen and RNA ribose turnover while disrupting glucose-derived cholesterol synthesis in liver as revealed by the
[U-C(6)]-d-glucose tracer in mice. Metabolomics. 2009 Sep;5(3):336-345. PMID: 19718458

Metabolic Pathways as Targets for Drug Screening, Metabolomics, Dr Ute Roessner (Ed.), ISBN: 978-953-51-0046-1, InTech, Available from: http://www.intechopen.com/books/metabolomics/metabolic-pathways-as-targets-for-drug-screening

Iron regulates glucose homeostasis in liver and muscle via AMP-activated protein kinase in mice. FASEB J. 2013 Jul;27(7):2845-54.
http://dx.doi.org:/10.1096/fj.12-216929. PMID: 23515442

Metabolomics and systems pharmacology: why and how to model the human metabolic network for drug discovery

Drug Discov. Today 19 (2014), 171–182     http://dx.doi.org:/10.1016/j.drudis.2013.07.014

Highlights

  • We now have metabolic network models; the metabolome is represented by their nodes.
  • Metabolite levels are sensitive to changes in enzyme activities.
  • Drugs hitchhike on metabolite transporters to get into and out of cells.
  • The consensus network Recon2 represents the present state of the art, and has predictive power.
  • Constraint-based modelling relates network structure to metabolic fluxes.

Metabolism represents the ‘sharp end’ of systems biology, because changes in metabolite concentrations are

  • necessarily amplified relative to changes in the transcriptome, proteome and enzyme activities, which can be modulated by drugs.

To understand such behaviour, we therefore need (and increasingly have) reliable consensus (community) models of

  • the human metabolic network that include the important transporters.

Small molecule ‘drug’ transporters are in fact metabolite transporters, because

  • drugs bear structural similarities to metabolites known from the network reconstructions and
  • from measurements of the metabolome.

Recon2 represents the present state-of-the-art human metabolic network reconstruction; it can predict inter alia:

(i) the effects of inborn errors of metabolism;

(ii) which metabolites are exometabolites, and

(iii) how metabolism varies between tissues and cellular compartments.

However, even these qualitative network models are not yet complete. As our understanding improves

  • so do we recognise more clearly the need for a systems (poly)pharmacology.

Introduction – a systems biology approach to drug discovery

It is clearly not news that the productivity of the pharmaceutical industry has declined significantly during recent years

  • following an ‘inverse Moore’s Law’, Eroom’s Law, or
  • that many commentators, consider that the main cause of this is
  • because of an excessive focus on individual molecular target discovery rather than a more sensible strategy
  • based on a systems-level approach (Fig. 1).
drug discovery science

drug discovery science

Figure 1.

The change in drug discovery strategy from ‘classical’ function-first approaches (in which the assay of drug function was at the tissue or organism level),
with mechanistic studies potentially coming later, to more-recent target-based approaches where initial assays usually involve assessing the interactions
of drugs with specified (and often cloned, recombinant) proteins in vitro. In the latter cases, effects in vivo are assessed later, with concomitantly high levels of attrition.

Arguably the two chief hallmarks of the systems biology approach are:

(i) that we seek to make mathematical models of our systems iteratively or in parallel with well-designed ‘wet’ experiments, and
(ii) that we do not necessarily start with a hypothesis but measure as many things as possible (the ’omes) and

  • let the data tell us the hypothesis that best fits and describes them.

Although metabolism was once seen as something of a Cinderella subject,

  • there are fundamental reasons to do with the organisation of biochemical networks as
  • to why the metabol(om)ic level – now in fact seen as the ‘apogee’ of the ’omics trilogy –
  •  is indeed likely to be far more discriminating than are
  • changes in the transcriptome or proteome.

The next two subsections deal with these points and Fig. 2 summarises the paper in the form of a Mind Map.

metabolomics and systems pharmacology

metabolomics and systems pharmacology

http://ars.els-cdn.com/content/image/1-s2.0-S1359644613002481-gr2.jpg

Metabolic Disease Drug Discovery— “Hitting the Target” Is Easier Said Than Done

David E. Moller, et al.   http://dx.doi.org:/10.1016/j.cmet.2011.10.012

Despite the advent of new drug classes, the global epidemic of cardiometabolic disease has not abated. Continuing

  • unmet medical needs remain a major driver for new research.

Drug discovery approaches in this field have mirrored industry trends, leading to a recent

  • increase in the number of molecules entering development.

However, worrisome trends and newer hurdles are also apparent. The history of two newer drug classes—

  1. glucagon-like peptide-1 receptor agonists and
  2. dipeptidyl peptidase-4 inhibitors—

illustrates both progress and challenges. Future success requires that researchers learn from these experiences and

  • continue to explore and apply new technology platforms and research paradigms.

The global epidemic of obesity and diabetes continues to progress relentlessly. The International Diabetes Federation predicts an even greater diabetes burden (>430 million people afflicted) by 2030, which will disproportionately affect developing nations (International Diabetes Federation, 2011). Yet

  • existing drug classes for diabetes, obesity, and comorbid cardiovascular (CV) conditions have substantial limitations.

Currently available prescription drugs for treatment of hyperglycemia in patients with type 2 diabetes (Table 1) have notable shortcomings. In general,

Therefore, clinicians must often use combination therapy, adding additional agents over time. Ultimately many patients will need to use insulin—a therapeutic class first introduced in 1922. Most existing agents also have

  • issues around safety and tolerability as well as dosing convenience (which can impact patient compliance).

Pharmacometabolomics, also known as pharmacometabonomics, is a field which stems from metabolomics,

  • the quantification and analysis of metabolites produced by the body.

It refers to the direct measurement of metabolites in an individual’s bodily fluids, in order to

  • predict or evaluate the metabolism of pharmaceutical compounds, and
  • to better understand the pharmacokinetic profile of a drug.

Alternatively, pharmacometabolomics can be applied to measure metabolite levels

  • following the administration of a pharmaceutical compound, in order to
  • monitor the effects of the compound on certain metabolic pathways(pharmacodynamics).

This provides detailed mapping of drug effects on metabolism and

  • the pathways that are implicated in mechanism of variation of response to treatment.

In addition, the metabolic profile of an individual at baseline (metabotype) provides information about

  • how individuals respond to treatment and highlights heterogeneity within a disease state.

All three approaches require the quantification of metabolites found

relationship between -OMICS

relationship between -OMICS

http://upload.wikimedia.org/wikipedia/commons/thumb/e/eb/OMICS.png/350px-OMICS.png

Pharmacometabolomics is thought to provide information that

Looking at the characteristics of an individual down through these different levels of detail, there is an

  • increasingly more accurate prediction of a person’s ability to respond to a pharmaceutical compound.
  1. the genome, made up of 25 000 genes, can indicate possible errors in drug metabolism;
  2. the transcriptome, made up of 85,000 transcripts, can provide information about which genes important in metabolism are being actively transcribed;
  3. and the proteome, >10,000,000 members, depicts which proteins are active in the body to carry out these functions.

Pharmacometabolomics complements the omics with

  • direct measurement of the products of all of these reactions, but with perhaps a relatively
  • smaller number of members: that was initially projected to be approximately 2200 metabolites,

but could be a larger number when gut derived metabolites and xenobiotics are added to the list. Overall, the goal of pharmacometabolomics is

  • to more closely predict or assess the response of an individual to a pharmaceutical compound,
  • permitting continued treatment with the right drug or dosage
  • depending on the variations in their metabolism and ability to respond to treatment.

Pharmacometabolomic analyses, through the use of a metabolomics approach,

  • can provide a comprehensive and detailed metabolic profile or “metabolic fingerprint” for an individual patient.

Such metabolic profiles can provide a complete overview of individual metabolite or pathway alterations,

This approach can then be applied to the prediction of response to a pharmaceutical compound

  • by patients with a particular metabolic profile.

Pharmacometabolomic analyses of drug response are

Pharmacogenetics focuses on the identification of genetic variations (e.g. single-nucleotide polymorphisms)

  • within patients that may contribute to altered drug responses and overall outcome of a certain treatment.

The results of pharmacometabolomics analyses can act to “inform” or “direct”

  • pharmacogenetic analyses by correlating aberrant metabolite concentrations or metabolic pathways to potential alterations at the genetic level.

This concept has been established with two seminal publications from studies of antidepressants serotonin reuptake inhibitors

  • where metabolic signatures were able to define a pathway implicated in response to the antidepressant and
  • that lead to identification of genetic variants within a key gene
  • within the highlighted pathway as being implicated in variation in response.

These genetic variants were not identified through genetic analysis alone and hence

  • illustrated how metabolomics can guide and inform genetic data.

en.wikipedia.org/wiki/Pharmacometabolomics

Benznidazole Biotransformation and Multiple Targets in Trypanosoma cruzi Revealed by Metabolomics

Andrea Trochine, Darren J. Creek, Paula Faral-Tello, Michael P. Barrett, Carlos Robello
Published: May 22, 2014   http://dx.doi.org:/10.1371/journal.pntd.0002844

The first line treatment for Chagas disease, a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi,

  • involves administration of benznidazole (Bzn).

Bzn is a 2-nitroimidazole pro-drug which requires nitroreduction to become active. We used a

  • non-targeted MS-based metabolomics approach to study the metabolic response of T. cruzi to Bzn.

Parasites treated with Bzn were minimally altered compared to untreated trypanosomes, although the redox active thiols

  1. trypanothione,
  2. homotrypanothione and
  3. cysteine

were significantly diminished in abundance post-treatment. In addition, multiple Bzn-derived metabolites were detected after treatment.

These metabolites included reduction products, fragments and covalent adducts of reduced Bzn

  • linked to each of the major low molecular weight thiols:
  1. trypanothione,
  2. glutathione,
  3. g-glutamylcysteine,
  4. glutathionylspermidine,
  5. cysteine and
  6. ovothiol A.

Bzn products known to be generated in vitro by the unusual trypanosomal nitroreductase, TcNTRI,

  • were found within the parasites,
  • but low molecular weight adducts of glyoxal, a proposed toxic end-product of NTRI Bzn metabolism, were not detected.

Our data is indicative of a major role of the

  • thiol binding capacity of Bzn reduction products
  • in the mechanism of Bzn toxicity against T. cruzi.

 

 

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Summary to Metabolomics

Summary to Metabolomics

Author and Curator: Larry H. Bernstein, MD, FCAP 

This concludes a long step-by-step journey into rediscovering biological processes from the genome as a framework to the remodeled and reconstituted cell through a number of posttranscription and posttranslation processes that modify the proteome and determine the metabolome.  The remodeling process continues over a lifetime. The process requires a balance between nutrient intake, energy utilization for work in the lean body mass, energy reserves, endocrine, paracrine and autocrine mechanisms, and autophagy.  It is true when we look at this in its full scope – What a creature is man?

http://masspec.scripps.edu/metabo_science/recommended_readings.php
 Recommended Readings and Historical Perspectives

Metabolomics is the scientific study of chemical processes involving metabolites. Specifically, metabolomics is the “systematic study of the unique chemical fingerprints that specific cellular processes leave behind”, the study of their small-molecule metabolite profiles.[1] The metabolome represents the collection of all metabolites in a biological cell, tissue, organ or organism, which are the end products of cellular processes.[2] mRNA gene expression data and proteomic analyses reveal the set of gene products being produced in the cell, data that represents one aspect of cellular function. Conversely, metabolic profiling can give an instantaneous snapshot of the physiology of that cell. One of the challenges of systems biology and functional genomics is to integrate proteomic, transcriptomic, and metabolomic information to provide a better understanding of cellular biology.

The term “metabolic profile” was introduced by Horning, et al. in 1971 after they demonstrated that gas chromatography-mass spectrometry (GC-MS) could be used to measure compounds present in human urine and tissue extracts. The Horning group, along with that of Linus Pauling and Arthur B. Robinson led the development of GC-MS methods to monitor the metabolites present in urine through the 1970s.

Concurrently, NMR spectroscopy, which was discovered in the 1940s, was also undergoing rapid advances. In 1974, Seeley et al. demonstrated the utility of using NMR to detect metabolites in unmodified biological samples.This first study on muscle highlighted the value of NMR in that it was determined that 90% of cellular ATP is complexed with magnesium. As sensitivity has improved with the evolution of higher magnetic field strengths and magic angle spinning, NMR continues to be a leading analytical tool to investigate metabolism. Efforts to utilize NMR for metabolomics have been influenced by the laboratory of Dr. Jeremy Nicholson at Birkbeck College, University of London and later at Imperial College London. In 1984, Nicholson showed 1H NMR spectroscopy could potentially be used to diagnose diabetes mellitus, and later pioneered the application of pattern recognition methods to NMR spectroscopic data.

In 2005, the first metabolomics web database, METLIN, for characterizing human metabolites was developed in the Siuzdak laboratory at The Scripps Research Institute and contained over 10,000 metabolites and tandem mass spectral data. As of September 2012, METLIN contains over 60,000 metabolites as well as the largest repository of tandem mass spectrometry data in metabolomics.

On 23 January 2007, the Human Metabolome Project, led by Dr. David Wishart of the University of Alberta, Canada, completed the first draft of the human metabolome, consisting of a database of approximately 2500 metabolites, 1200 drugs and 3500 food components. Similar projects have been underway in several plant species, most notably Medicago truncatula and Arabidopsis thaliana for several years.

As late as mid-2010, metabolomics was still considered an “emerging field”. Further, it was noted that further progress in the field depended in large part, through addressing otherwise “irresolvable technical challenges”, by technical evolution of mass spectrometry instrumentation.

Metabolome refers to the complete set of small-molecule metabolites (such as metabolic intermediates, hormones and other signaling molecules, and secondary metabolites) to be found within a biological sample, such as a single organism. The word was coined in analogy with transcriptomics and proteomics; like the transcriptome and the proteome, the metabolome is dynamic, changing from second to second. Although the metabolome can be defined readily enough, it is not currently possible to analyse the entire range of metabolites by a single analytical method. The first metabolite database(called METLIN) for searching m/z values from mass spectrometry data was developed by scientists at The Scripps Research Institute in 2005. In January 2007, scientists at the University of Alberta and the University of Calgary completed the first draft of the human metabolome. They catalogued approximately 2500 metabolites, 1200 drugs and 3500 food components that can be found in the human body, as reported in the literature. This information, available at the Human Metabolome Database (www.hmdb.ca) and based on analysis of information available in the current scientific literature, is far from complete.

Each type of cell and tissue has a unique metabolic ‘fingerprint’ that can elucidate organ or tissue-specific information, while the study of biofluids can give more generalized though less specialized information. Commonly used biofluids are urine and plasma, as they can be obtained non-invasively or relatively non-invasively, respectively. The ease of collection facilitates high temporal resolution, and because they are always at dynamic equilibrium with the body, they can describe the host as a whole.

Metabolites are the intermediates and products of metabolism. Within the context of metabolomics, a metabolite is usually defined as any molecule less than 1 kDa in size.
A primary metabolite is directly involved in the normal growth, development, and reproduction. A secondary metabolite is not directly involved in those processes.  By contrast, in human-based metabolomics, it is more common to describe metabolites as being either endogenous (produced by the host organism) or exogenous. Metabolites of foreign substances such as drugs are termed xenometabolites. The metabolome forms a large network of metabolic reactions, where outputs from one enzymatic chemical reaction are inputs to other chemical reactions.

Metabonomics is defined as “the quantitative measurement of the dynamic multiparametric metabolic response of living systems to pathophysiological stimuli or genetic modification”. The word origin is from the Greek μεταβολή meaning change and nomos meaning a rule set or set of laws. This approach was pioneered by Jeremy Nicholson at Imperial College London and has been used in toxicology, disease diagnosis and a number of other fields. Historically, the metabonomics approach was one of the first methods to apply the scope of systems biology to studies of metabolism.

There is a growing consensus that ‘metabolomics’ places a greater emphasis on metabolic profiling at a cellular or organ level and is primarily concerned with normal endogenous metabolism. ‘Metabonomics’ extends metabolic profiling to include information about perturbations of metabolism caused by environmental factors (including diet and toxins), disease processes, and the involvement of extragenomic influences, such as gut microflora. This is not a trivial difference; metabolomic studies should, by definition, exclude metabolic contributions from extragenomic sources, because these are external to the system being studied.

Toxicity assessment/toxicology. Metabolic profiling (especially of urine or blood plasma samples) detects the physiological changes caused by toxic insult of a chemical (or mixture of chemicals).

Functional genomics. Metabolomics can be an excellent tool for determining the phenotype caused by a genetic manipulation, such as gene deletion or insertion. Sometimes this can be a sufficient goal in itself—for instance, to detect any phenotypic changes in a genetically-modified plant intended for human or animal consumption. More exciting is the prospect of predicting the function of unknown genes by comparison with the metabolic perturbations caused by deletion/insertion of known genes.

Nutrigenomics is a generalised term which links genomics, transcriptomics, proteomics and metabolomics to human nutrition. In general a metabolome in a given body fluid is influenced by endogenous factors such as age, sex, body composition and genetics as well as underlying pathologies. The large bowel microflora are also a very significant potential confounder of metabolic profiles and could be classified as either an endogenous or exogenous factor. The main exogenous factors are diet and drugs. Diet can then be broken down to nutrients and non- nutrients.

http://en.wikipedia.org/wiki/Metabolomics

Jose Eduardo des Salles Roselino

The problem with genomics was it was set as explanation for everything. In fact, when something is genetic in nature the genomic reasoning works fine. However, this means whenever an inborn error is found and only in this case the genomic knowledge afterwards may indicate what is wrong and not the completely way to put biology upside down by reading everything in the DNA genetic as well as non-genetic problems.

Coordination of the transcriptome and metabolome by the circadian clock PNAS 2012

Coordination of the transcriptome and metabolome by the circadian clock PNAS 2012

analysis of metabolomic data and differential metabolic regulation for fetal lungs, and maternal blood plasma

conformational changes leading to substrate efflux.img

conformational changes leading to substrate efflux.img

The cellular response is defined by a network of chemogenomic response signatures.

The cellular response is defined by a network of chemogenomic response signatures.

Dynamic Construct of the –Omics

Dynamic Construct of the –Omics

 genome cartoon

genome cartoon

central dogma phenotype

central dogma phenotype

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Summary of Cell Structure, Anatomic Correlates of Metabolic Function

Author and Curator: Larry H. Bernstein, MD, FCAP  

 

This chapter has been concerned with the subcellular ultrastructure of organelles, and importantly, their function.  There is no waste in the cell structure. The nucleus has the instructions necessary to carry out the cell’s functions.  In the Eukaryotic cell there is significant differentiation so that the cells are regulated for the needs that they uniquely carry out.  When there is disregulation, it leads to remodeling or to cell death.

Here I shall note some highlights of this chapter.

  1. In every aspect of cell function, proteins are involved embedded in the structure, for most efficient functioning.
  2. Metabolic regulation is dependent on pathways that are also linkages of proteins.
  3. Energy utilization is dependent on enzymatic reactions, often involving essential metal ions of high valence numbers, which facilitates covalent and anion binding, and has an essential role in allostericity.

Mitochondria

Mitochondria,_mammalian_lung

Mitochondria,_mammalian_lung

http://en.wikipedia.org/wiki/File:Mitochondria,_mammalian_lung_-_TEM.jpg

Mitochondria range from 0.5 to 1.0 micrometer (μm) in diameter. These structures are sometimes described as “cellular power plants” because they generate most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy. In addition to supplying cellular energy, mitochondria are involved in other tasks such as signaling, cellular differentiation, cell death, as well as the control of the cell cycle and cell growth. Mitochondria have been implicated in several human diseases, including mitochondrial disorders and cardiac dysfunction.

The number of mitochondria in a cell can vary widely by organism, tissue, and cell type. For instance, red blood cells have no mitochondria, whereas liver cells can have more than 2000. The organelle is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, the intermembrane space, the inner membrane, and the cristae and matrix. Mitochondrial proteins vary depending on the tissue and the species. The mitochondrial proteome is thought to be dynamically regulated. Although most of a cell’s DNA is contained in the cell nucleus, the mitochondrion has its own independent genome. Further, its DNA shows substantial similarity to bacterial genomes.

In 1913 particles from extracts of guinea-pig liver were linked to respiration by Otto Heinrich Warburg, which he called “grana”. Warburg and Heinrich Otto Wieland, who had also postulated a similar particle mechanism, disagreed on the chemical nature of the respiration. It was not until 1925 when David Keilin discovered cytochromes that the respiratory chain was described.  In 1939, experiments using minced muscle cells demonstrated that one oxygen atom can form two adenosine triphosphate molecules, and, in 1941, the concept of phosphate bonds being a form of energy in cellular metabolism was developed by Fritz Albert Lipmann. In the following years, the mechanism behind cellular respiration was further elaborated, although its link to the mitochondria was not known. The introduction of tissue fractionation by Albert Claude allowed mitochondria to be isolated from other cell fractions and biochemical analysis to be conducted on them alone. In 1946, he concluded that cytochrome oxidase and other enzymes responsible for the respiratory chain were isolated to the mitchondria.

The first high-resolution micrographs appeared in 1952, replacing the Janus Green stains as the preferred way of visualising the mitochondria. This led to a more detailed analysis of the structure of the mitochondria, including confirmation that they were surrounded by a membrane. It also showed a second membrane inside the mitochondria that folded up in ridges dividing up the inner chamber and that the size and shape of the mitochondria varied from cell to cell.  In 1967, it was discovered that mitochondria contained ribosomes. In 1968, methods were developed for mapping the mitochondrial genes, with the genetic and physical map of yeast mitochondria being completed in 1976.

A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins. The two membranes have different properties. Because of this double-membraned organization, there are five distinct parts to a mitochondrion. They are:

  1. the outer mitochondrial membrane,
  2. the intermembrane space (the space between the outer and inner membranes),
  3. the inner mitochondrial membrane,
  4. the cristae space (formed by infoldings of the inner membrane), and
  5. the matrix (space within the inner membrane).

Mitochondria stripped of their outer membrane are called mitoplasts.

Mitochondrion_structure_drawing

Mitochondrion_structure_drawing

http://upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Mitochondrion_structure_drawing.svg/500px-Mitochondrion_structure_drawing.svg.png

Mitochondrion ultrastructure (interactive diagram) A mitochondrion has a double membrane; the inner one contains its chemiosmotic apparatus and has deep grooves which increase its surface area. While commonly depicted as an “orange sausage with a blob inside of it” (like it is here), mitochondria can take many shapes and their intermembrane space is quite thin.

The intermembrane space is the space between the outer membrane and the inner membrane. It is also known as perimitochondrial space. Because the outer membrane is freely permeable to small molecules, the concentrations of small molecules such as ions and sugars in the intermembrane space is the same as the cytosol. However, large proteins must have a specific signaling sequence to be transported across the outer membrane, so the protein composition of this space is different from the protein composition of the cytosol. One protein that is localized to the intermembrane space in this way is cytochrome c.

The inner mitochondrial membrane contains proteins with five types of functions:

  1. Those that perform the redox reactions of oxidative phosphorylation
  2. ATP synthase, which generates ATP in the matrix
  3. Specific transport proteins that regulate metabolite passage into and out of the matrix
  4. Protein import machinery.
  5. Mitochondria fusion and fission protein.

It contains more than 151 different polypeptides, and has a very high protein-to-phospholipid ratio (more than 3:1 by weight, which is about 1 protein for 15 phospholipids). The inner membrane is home to around 1/5 of the total protein in a mitochondrion. In addition, the inner membrane is rich in an unusual phospholipid, cardiolipin. This phospholipid was originally discovered in cow hearts in 1942, and is usually characteristic of mitochondrial and bacterial plasma membranes. Cardiolipin contains four fatty acids rather than two, and may help to make the inner membrane impermeable. Unlike the outer membrane, the inner membrane doesn’t contain porins, and is highly impermeable to all molecules. Almost all ions and molecules require special membrane transporters to enter or exit the matrix. Proteins are ferried into the matrix via the translocase of the inner membrane (TIM) complex or via Oxa1. In addition, there is a membrane potential across the inner membrane, formed by the action of the enzymes of the electron transport chain.

The inner mitochondrial membrane is compartmentalized into numerous cristae, which expand the surface area of the inner mitochondrial membrane, enhancing its ability to produce ATP. For typical liver mitochondria, the area of the inner membrane is about five times as large as the outer membrane. This ratio is variable and mitochondria from cells that have a greater demand for ATP, such as muscle cells, contain even more cristae. These folds are studded with small round bodies known as F1 particles or oxysomes. These are not simple random folds but rather invaginations of the inner membrane, which can affect overall chemiosmotic function. One recent mathematical modeling study has suggested that the optical properties of the cristae in filamentous mitochondria may affect the generation and propagation of light within the tissue.

Mitochondrion

Mitochondrion

http://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/MitochondrionCAM.jpg/250px-MitochondrionCAM.jpg

The matrix is the space enclosed by the inner membrane. It contains about 2/3 of the total protein in a mitochondrion. The matrix is important in thThe MAM is enriched in enzymes involved in lipid biosynthesis, such as phosphatidylserine synthase on the ER face and phosphatidylserine decarboxylase on the mitochondrial face.[28][29] Because mitochondria are dynamic organelles constantly undergoing fission and fusion events, they require a constant and well-regulated supply of phospholipids for membrane integrity.[30][31] But mitochondria are not only a destination for the phospholipids they finish synthesis of; rather, this organelle also plays a role in inter-organelle trafficking of the intermediates and products of phospholipid biosynthetic pathways, ceramide and cholesterol metabolism, and glycosphingolipid anabolisme production of ATP with the aid of the ATP synthase contained in the inner membrane. The matrix contains a highly concentrated mixture of hundreds of enzymes, special mitochondrial ribosomes, tRNA, and several copies of the mitochondrial DNA genome. Of the enzymes, the major functions include oxidation of pyruvate and fatty acids, and the citric acid cycle.

Purified MAM from subcellular fractionation has shown to be enriched in enzymes involved in phospholipid exchange, in addition to channels associated with Ca2+ signaling. The mitochondria-associated ER membrane (MAM) is another structural element that is increasingly recognized for its critical role in cellular physiology and homeostasis. Once considered a technical snag in cell fractionation techniques, the alleged ER vesicle contaminants that invariably appeared in the mitochondrial fraction have been re-identified as membranous structures derived from the MAM—the interface between mitochondria and the ER. Physical coupling between these two organelles had previously been observed in electron micrographs and has more recently been probed with fluorescence microscopy. Such studies estimate that at the MAM, which may comprise up to 20% of the mitochondrial outer membrane, the ER and mitochondria are separated by a mere 10–25 nm and held together by protein tethering complexes.

Such trafficking capacity depends on the MAM, which has been shown to facilitate transfer of lipid intermediates between organelles. In contrast to the standard vesicular mechanism of lipid transfer, evidence indicates that the physical proximity of the ER and mitochondrial membranes at the MAM allows for lipid flipping between opposed bilayers. Despite this unusual and seemingly energetically unfavorable mechanism, such transport does not require ATP. Instead, in yeast, it has been shown to be dependent on a multiprotein tethering structure termed the ER-mitochondria encounter structure, or ERMES, although it remains unclear whether this structure directly mediates lipid transfer or is required to keep the membranes in sufficiently close proximity to lower the energy barrier for lipid flipping.

A critical role for the ER in calcium signaling was acknowledged before such a role for the mitochondria was widely accepted, in part because the low affinity of Ca2+ channels localized to the outer mitochondrial membrane seemed to fly in the face of this organelle’s purported responsiveness to changes in intracellular Ca2+ flux. But the presence of the MAM resolves this apparent contradiction: the close physical association between the two organelles results in Ca2+ microdomains at contact points that facilitate efficient Ca2+ transmission from the ER to the mitochondria. Transmission occurs in response to so-called “Ca2+ puffs” generated by spontaneous clustering and activation of IP3R, a canonical ER membrane Ca2+ channel.

The properties of the Ca2+ pump SERCA and the channel IP3R present on the ER membrane facilitate feedback regulation coordinated by MAM function. In particular, clearance of Ca2+ by the MAM allows for spatio-temporal patterning of Ca2+ signaling because Ca2+ alters IP3R activity in a biphasic manner. SERCA is likewise affected by mitochondrial feedback: uptake of Ca2+ by the MAM stimulates ATP production, thus providing energy that enables SERCA to reload the ER with Ca2+ for continued Ca2+ efflux at the MAM. Thus, the MAM is not a passive buffer for Ca2+ puffs; rather it helps modulate further Ca2+ signaling through feedback loops that affect ER dynamics.

Regulating ER release of Ca2+ at the MAM is especially critical because only a certain window of Ca2+ uptake sustains the mitochondria, and consequently the cell, at homeostasis. Sufficient intraorganelle Ca2+ signaling is required to stimulate metabolism by activating dehydrogenase enzymes critical to flux through the citric acid cycle. However, once Ca2+ signaling in the mitochondria passes a certain threshold, it stimulates the intrinsic pathway of apoptosis in part by collapsing the mitochondrial membrane potential required for metabolism.  Studies examining the role of pro- and anti-apoptotic factors support this model; for example, the anti-apoptotic factor Bcl-2 has been shown to interact with IP3Rs to reduce Ca2+ filling of the ER, leading to reduced efflux at the MAM and preventing collapse of the mitochondrial membrane potential post-apoptotic stimuli. Given the need for such fine regulation of Ca2+ signaling, it is perhaps unsurprising that dysregulated mitochondrial Ca2+ has been implicated in several neurodegenerative diseases, while the catalogue of tumor suppressors includes a few that are enriched at the MAM.

…more

http://en.wikipedia.org/wiki/Mitochondrion

Lysosome and Apoptosis

Role of autophagy in cancer

R Mathew, V Karantza-Wadsworth & E White

Nature Reviews Cancer 7, 961-967 (Dec 2007) |  http://dx.doi.org:/10.1038/nrc2254

Autophagy is a cellular degradation pathway for the clearance of damaged or superfluous proteins and organelles. The recycling of these intracellular constituents also serves as an alternative energy source during periods of metabolic stress to maintain homeostasis and viability. In tumour cells with defects in apoptosis, autophagy allows prolonged survival. Paradoxically, autophagy defects are associated with increased tumorigenesis, but the mechanism behind this has not been determined. Recent evidence suggests that autophagy provides a protective function to limit tumour necrosis and inflammation, and to mitigate genome damage in tumour cells in response to metabolic stress.

Sustained Activation of mTORC1 in Skeletal Muscle Inhibits Constitutive and Starvation-Induced Autophagy and Causes a Severe, Late-Onset Myopathy

P Castets, S Lin, N Rion, S Di Fulvio, et al.
cell-metabolism 7 May, 2013; 17(5): p731–744   http://dx.doi.org/10.1016/j.cmet.2013.03.015

  • mTORC1 inhibition is required for constitutive and starvation-induced autophagy
  • Sustained activation of mTORC1 causes a severe myopathy due to autophagy impairment
  • TSC1 depletion is sufficient to activate mTORC1 irrespective of other stimuli
  • mTORC1 inactivation is sufficient to trigger LC3 lipidation

Autophagy is a catabolic process that ensures homeostatic cell clearance and is deregulated in a growing number of myopathological conditions. Although FoxO3 was shown to promote the expression of autophagy-related genes in skeletal muscle, the mechanisms triggering autophagy are unclear. We show that TSC1-deficient mice (TSCmKO), characterized by sustained activation of mTORC1, develop a late-onset myopathy related to impaired autophagy. In young TSCmKO mice,

  • constitutive and starvation-induced autophagy is blocked at the induction steps via
  • mTORC1-mediated inhibition of Ulk1, despite FoxO3 activation.

Rapamycin is sufficient to restore autophagy in TSCmKO mice and

  • improves the muscle phenotype of old mutant mice.

Inversely, abrogation of mTORC1 signaling by

  • depletion of raptor induces autophagy regardless of FoxO inhibition.

Thus, mTORC1 is the dominant regulator of autophagy induction in skeletal muscle and

  • ensures a tight coordination of metabolic pathways.

These findings may open interesting avenues for therapeutic strategies directed toward autophagy-related muscle diseases.

Histone deacetylases 1 and 2 regulate autophagy flux and skeletal muscle homeostasis in mice

Viviana Moresi, et al.   PNAS Jan 31, 2012; 109(5): 1649-1654
http://dx.doi.org:/10.1073/pnas.1121159109
http://www.pnas.org/content/109/5/1649/F6.medium.gif

HDAC1 activates FoxO and is both sufficient and required for skeletal muscle atrophy

Beharry, PB. Sandesara, BM. Roberts, et al.
J. Cell Sci. Apr 2014 127 (7) 1441-1453   http://dx.doi.org:/10.1242/​jcs.136390

The Forkhead box O (FoxO) transcription factors are activated, and necessary for the muscle atrophy, in several pathophysiological conditions, including muscle disuse and cancer cachexia. However, the mechanisms that lead to FoxO activation are not well defined. Recent data from our laboratory and others indicate that

  • the activity of FoxO is repressed under basal conditions via reversible lysine acetylation,
  • which becomes compromised during catabolic conditions.

Therefore, we aimed to determine how histone deacetylase (HDAC) proteins contribute to

  • activation of FoxO and induction of the muscle atrophy program.

Through the use of various pharmacological inhibitors to block HDAC activity, we demonstrate that

  • class I HDACs are key regulators of FoxO and the muscle-atrophy program
  • during both nutrient deprivation and skeletal muscle disuse.

Furthermore, we demonstrate, through the use of wild-type and dominant-negative HDAC1 expression plasmids,

  • that HDAC1 is sufficient to activate FoxO and induce muscle fiber atrophy in vivo and
  • is necessary for the atrophy of muscle fibers that is associated with muscle disuse.

The ability of HDAC1 to cause muscle atrophy required its deacetylase activity and

  • was linked to the induction of several atrophy genes by HDAC1,
  • including atrogin-1, which required deacetylation of FoxO3a.

Moreover, pharmacological inhibition of class I HDACs during muscle disuse, using MS-275,

  • significantly attenuated both disuse muscle fiber atrophy and contractile dysfunction.

Together, these data solidify the importance of class I HDACs in the muscle atrophy program and

  • indicate that class I HDAC inhibitors are feasible countermeasures to impede muscle atrophy and weakness.

Autophagy and thyroid carcinogenesis: genetic and epigenetic links
F Morani, R Titone, L Pagano, et al.  Endocr Relat Cancer Feb 1, 2014 21 R13-R29
http://dx.doi.org:/10.1530/ERC-13-0271

Autophagy is a vesicular process for the lysosomal degradation of protein aggregates and

  • of damaged or redundant organelles.

Autophagy plays an important role in cell homeostasis, and there is evidence that

  • this process is dysregulated in cancer cells.

Recent in vitro preclinical studies have indicated that autophagy is

  • involved in the cytotoxic response to chemotherapeutics in thyroid cancer cells.

Indeed, several oncogenes and oncosuppressor genes implicated in thyroid carcinogenesis

  • also play a role in the regulation of autophagy.

In addition, some epigenetic modulators involved in thyroid carcinogenesis also influence autophagy. In this review, we highlight the genetic and epigenetic factors that

  • mechanistically link thyroid carcinogenesis and autophagy, thus substantiating the rationale for
  • an autophagy-targeted therapy of aggressive and radio-chemo-resistant thyroid cancers.

Read Full Post »

Functional Correlates of Signaling Pathways

Author and Curator: Larry H. Bernstein, MD, FCAP

 

We here move on to a number of specific, key published work on signaling, and look at the possible therapeutic applications to disease states.

Scripps Research Professor Wolfram Ruf and colleagues have identified a key connection between

  • the signaling pathways and the immune system spiraling out of control involving
  • the coagulation system and vascular endothelium that,
  • if disrupted may be a target for sepsis. (Science Daily, Feb 29, 2008).

It may be caused by a bacterial infection that enters the bloodstream, but

  • we now recognize the same cascade not triggered by bacterial invasion.

The acute respiratory distress syndrome (ARDS) has been defined as

  • a severe form of acute lung injury featuring
  • pulmonary inflammation and increased capillary leak.

ARDS is associated with a high mortality rate and accounts for 100,000 deaths annually in the United States. ARDS may arise in a number of clinical situations, especially in patients with sepsis. A well-described pathophysiological model of ARDS is one form of

  • the acute lung inflammation mediated by
  1. neutrophils,
  2. cytokines, and
  3. oxidant stress.

Neutrophils are major effect cells at the frontier of

  • innate immune responses, and they play
  • a critical role in host defense against invading microorganisms.

The tissue injury appears to be related to

  • proteases and toxic reactive oxygen radicals
  • released from activated neutrophils.

In addition, neutrophils can produce cytokines and chemokines that

enhance the acute inflammatory response.

Neutrophil accumulation in the lung plays a pivotal role in the pathogenesis of acute lung injury during sepsis. Directed movement of neutrophils is

  • mediated by a group of chemoattractants,
  • especially CXC chemokines.

Local lung production of CXC chemokines is intensified during experimental sepsis induced by cecal ligation and puncture (CLP).

Sepsis, Multi-organ Dysfunction Syndrome, and Septic Shock: A Conundrum of Signaling Pathways Cascading Out of Control

http://pharmaceuticalintelligence.com/2012/10/13/sepsis-multi-organ-dysfunction-syndrome-and-septic-shock-a-conundrum-of-signaling-pathways-cascading-out-of-control/

Integrins and extracellular matrix in mechanotransduction

ligand binding of integrins

ligand binding of integrins

Integrins are a family of cell surface receptors which

mediate cell–matrix and cell–cell adhesions.

Among other functions they provide an important

mechanical link between the cells external and intracellular environments while

the adhesions that they form also have critical roles in cellular signal-transduction.

Cell–matrix contacts occur at zones in the cell surface where

adhesion receptors cluster and when activated

the receptors bind to ligands in the extracellular matrix.

The extracellular matrix surrounds the cells of tissues and forms the

structural support of tissue which is particularly important in connective tissues.

Cells attach to the extracellular matrix through

specific cell-surface receptors and molecules

including integrins and transmembrane proteoglycans.

The integrin family of αβ heterodimeric receptors act as

cell adhesion molecules

connecting the ECM to the actin cytoskeleton.

The actin cytoskeleton is involved in the regulation of

1.cell motility,

2.cell polarity,

3.cell growth, and

4.cell survival.

The combination of αβ subunits determines

binding specificity and

signaling properties.

Both α and β integrin subunits contain two separate tails, which

penetrate the plasma membrane and possess small cytoplasmic domains which facilitate

the signaling functions of the receptor.

There is some evidence that the β subunit is the principal site for

binding of cytoskeletal and signaling molecules,

whereas the α subunit has a regulatory role. The integrin tails

link the ECM to the actin cytoskeleton within the cell and with cytoplasmic proteins,

such as talin, tensin, and filamin. The extracellular domains of integrin receptors bind the ECM ligands.

binding of integrins depends on ECM divalent cations ch19

binding of integrins depends on ECM divalent cations ch19

integrin coupled to F-actin via linker

integrin coupled to F-actin via linker

http://www.nature.com/nrm/journal/vaop/ncurrent/images/nrm3896-f4.jpg

Schematic of the ‘focal adhesion clutch’ on stiff (a) versus soft (b) extracellular matrix (ECM). In all cases, integrins are coupled to F-actin via linker proteins (for example, talin and vinculin). The linker proteins move backwards (as indicated by the small arrows) as F-actin also moves backwards, under pushing forces from actin polymerization and/or pulling forces from myosin II activity. This mechanism transfers force from actin to integrins, which pull on the ECM. A stiff ECM (a) resists this force so that the bound integrins remain immobile. A compliant matrix (b) deforms under this force (as indicated by the compressed ECM labelled as deformed matrix) so that the bound integrins can also move backwards. Their movement reduces the net loading rate on all the force-bearing elements, which results in altered cellular responses

The ECM is a complex mixture of matrix molecules, including –

  • glycoproteins, collagens, laminins, glycosaminoglycans, proteoglycans,
  • and nonmatrix proteins, – including growth factors

The integrin receptor formed from the binding of α and β subunits is

  • shaped like a globular head supported by two rod-like legs (Figure 1).

Most of the contact between the two subunits occurs in the head region, with

  • the intracellular tails of the subunits forming the legs of the receptor.

Integrin recognition of ligands is not constitutive but

  • is regulated by alteration of integrin affinity for ligand binding.

For integrin binding to ligands to occur

  • the integrin must be primed and activated, both of which involve
  • conformational changes to the receptor.

Linking integrin conformation to function

Figure  Integrin binding to extracellular matrix (ECM). Conformational changes to integrin structure and clustering of subunits which allow enhanced function of the receptor.

Integrins work alongside other proteins such as

cadherins,

immunoglobulin superfamily

cell adhesion molecules,

selectins, and

syndecans

to mediate

cell–cell and

cell–matrix interactions and communication.

Activation of adhesion receptors triggers the formation of matrix contacts in which

bound matrix components,

adhesion receptors,

and associated intracellular cytoskeletal and signaling molecules

form large functional, localized multiprotein complexes.

Cell–matrix contacts are important in a variety of different cell and

tissue properties including

1.embryonic development,

2.inflammatory responses,

3.wound healing,

4.and adult tissue homeostasis.

Integrin extracellular binding activity is regulated from inside the cell and binding to the ECM induces signals that are transmitted into the cell. This bidirectional signaling requires

dynamic,

spatially, and

temporally regulated formation and

disassembly of multiprotein complexes that

form around the short cytoplasmic tails of integrins.

Ligand binding to integrin family members leads to clustering of integrin molecules in the plasma membrane and recruitment of actin filaments and intracellular signaling molecules to the cytoplasmic domain of the integrins. This forms focal adhesion complexes which are able to maintain

not only adhesion to the ECM

but are involved in complex signaling pathways

which include establishing

1.cell polarity,

2.directed cell migration, and

3.maintaining cell growth and survival.

Initial activation through integrin adhesion to matrix recruits up to around 50 diverse signaling molecules

to assemble the focal adhesion complex

which is capable of responding to environmental stimuli efficiently.

Mapping of the integrin

adhesome binding and signaling interactions

a network of 156 components linked together which can be modified by 690 interactions.

Genetic programming occurs with the binding of integrins to the ECM

Signal transduction pathway activation arising from integrin-ECM binding results in

  • changes in gene expression of cells and
  • leads to alterations in cell and tissue function.

Various different effects can arise depending on the

1.cell type,

2.matrix composition, and

3.integrins activated

It has been suggested that integrin-type I collagen interaction is necessary for

  • the phosphorylation and activation of osteoblast-specific transcription factors
  • present in committed osteoprogenitor cells.

During mechanical loading/stimulation of chondrocytes there is an

  1. influx of ions across the cell membrane resulting from
  2. activation of mechanosensitive ion channels
  3. which can be inhibited by subunit-specific anti-integrin blocking antibodies or RGD peptides.

Using these strategies it was identified that

  • α5β1 integrin is a major mechanoreceptor in articular chondrocyte
  • responses to mechanical loading/stimulation.

Osteoarthritic chondrocytes show a depolarization response to 0.33 Hz stimulation

  • in contrast to the hyperpolarization response of normal chondrocytes.

The mechanotransduction pathway in chondrocytes derived from normal and osteoarthritic cartilage

  • both involve recognition of the mechanical stimulus
  • by integrin receptors resulting in
  • the activation of integrin signaling pathways
  • leading to the generation of a cytokine loop.

Normal and osteoarthritic chondrocytes show differences

  • at multiple stages of the mechanotransduction cascade.
Signaling pathways activated in chondrocytes

Signaling pathways activated in chondrocytes

http://dx.doi.org/10.1016/j.matbio.2014.08.007

Chondrocyte integrins are important mediators of cell–matrix interactions in cartilage

  • by regulating the response of the cells to signals from the ECM that
  1. control cell proliferation,
  2. survival,
  3. differentiation,
  4. matrix remodeling.

Integrins participate in development and maintenance of the tissue but also

  • in pathological processes related to matrix destruction, where
  • they likely play a role in the progression of OA.

Cellular adaptation to mechanical stress: role of integrins, Rho, cytoskeletal tension and mechanosensitive ion channels

Cells exhibited four types of mechanical responses:

(1) an immediate viscoelastic response;

(2) early adaptive behavior characterized by pulse-to-pulse attenuation in response to oscillatory forces;

(3) later adaptive cell stiffening with sustained (>15 second) static stresses; and

(4) a large-scale repositioning response with prolonged (>1 minute) stress.

Importantly, these adaptation responses differed biochemically.

The immediate and early responses were affected by

chemically dissipating cytoskeletal prestress (isometric tension), whereas

the later adaptive response was not.

The repositioning response was prevented by

inhibiting tension through interference with Rho signaling,

similar to the case of the immediate and early responses, but it was also prevented by

blocking mechanosensitive ion channels or

by inhibiting Src tyrosine kinases.

All adaptive responses were suppressed by cooling cells to 4°C to slow biochemical remodeling. Thus, cells use multiple mechanisms to sense and respond to static and dynamic changes in the level of mechanical stress applied to integrins.

Microtubule-Stimulated ADP Release, ATP Binding, and Force Generation In Transport Kinesins

All three classes of molecular motor proteins are now known to be

  • large protein families with diverse cellular functions.

Both the kinesin family and the myosin family have been defined and their proteins grouped into subfamilies. Finally, the elusive cytoplasmic version of dynein was identified and a multigene family of flagellar and cytoplasmic dyneins defined. Members of a given motor protein family share

  • significant homology in their motor domains with the defining member,
  • kinesin, dynein or myosin; but they also contain
  • unique protein domains that are specialized for interaction with different cargoes.

This large number of motor proteins may reflect

  • the number of cellular functions that require force generation or movement,
  • ranging from mitosis to morphogenesis to transport of vesicles.

Kinesins are a large family of microtubule (MT)-based motors that play important roles in many cellular activities including

mitosis,

motility, and

intracellular transport

Their involvement in a range of pathological processes

  • also highlights their significance as therapeutic targets and
  • the importance of understanding the molecular basis of their function

They are defined by their motor domains that contain both

  • the microtubule (MT) and
  • ATP binding sites.

Three ATP binding motifs—

  1. the P-loop,
  2. switch I,
  3. switch II–

are highly conserved among

  1. kinesins,
  2. myosin motors, and
  • small GTPases.

They share a conserved mode of MT binding such that

  • MT binding,
  • ATP binding, and
  • hydrolysis

are functionally coupled for efficient MT-based work.

The interior of a cell is a hive of activity, filled with

  • proteins and other items moving from one location to another.

A network of filaments called microtubules forms tracks

  • along which so-called motor proteins carry these items.

Kinesins are one group of motor proteins, and a typical kinesin protein has

  • one end (called the ‘motor domain’) that can attach itself to the microtubules.

The other end links to the cargo being carried, and a ‘neck’ connects the two. When two of these proteins work together,

  • flexible regions of the neck allow the two motor domains to move past one another,
  • which enable the kinesin to essentially walk along a microtubule in a stepwise manner.

Although the two kinesins have been thought to move along the microtubule tracks in different ways, Atherton et al. find that the core mechanism used by their motor domains is the same.

When a motor domain binds to the microtubule, its shape changes,

  • first stimulating release of the breakdown products of ATP from the previous cycle.

This release makes room for a new ATP molecule to bind. The structural changes caused by ATP binding

  • produce larger changes in the flexible neck region that
  • enable individual motor domains within a kinesin pair to
  • co-ordinate their movement and move in a consistent direction.

The major and largely invariant point of contact between kinesin motor domains and the MT is helix-α4,

  • which lies at the tubulin intradimer interface.

The conformational changes in functionally important regions of each motor domain are described,

  • starting with the nucleotide-binding site,
  • from which all other conformational changes emanate.

The nucleotide-binding site (Figure 2) has three major elements:

(1) the P-loop (brown) is visible in all our reconstructions;

(2) loop9 (yellow, contains switch I) undergoes major conformational changes through the ATPase cycle; and

(3) loop11 (red, contains switch II) that connects strand-β7 to helix-α4, the conformation and flexibility of which is

  • determined by MT binding and motor nucleotide state.

Movement and extension of helix-α6 controls neck linker docking

the N-terminus of helix-α6 is closely associated with elements of the nucleotide binding site suggesting that

  • its conformation alters in response to different nucleotide states.

Further,

  • because the orientation of helix-α6 with respect to helix-α4 controls neck linker docking and
  • because helix-α4 is held against the MT during the ATPase cycle,
    • conformational changes in helix-α6 control movement of the neck linker.

Mechanical amplification and force generation involves conformational changes across the motor domain

A key conformational change in the motor domain following Mg-ATP binding is

  • peeling of the central β-sheet from the C-terminus of helix-α4 increasing their separation;
  • this is required to accommodate rotation of helix-α6 and consequent neck linker docking

ATP binding draws loop11 and loop9 closer together; causing

(1) tilting of most of the motor domain not contacting the MT towards the nucleotide-binding site,

(2) rotation, translation, and extension of helix-α6 which we propose contributes to force generation, and

(3) allows neck linker docking and biases movement of the 2nd head towards the MT plus end.

In both motors, microtubule binding promotes

ordered conformations of conserved loops that

stimulate ADP release,

enhance microtubule affinity and

prime the catalytic site for ATP binding.

ATP binding causes only small shifts of these nucleotide-coordinating loops but induces

large conformational changes elsewhere that

allow force generation and

neck linker docking towards the microtubule plus end.

The study presents evidence provide evidence for a conserved ATP-driven

mechanism for kinesins and

reveals the critical mechanistic contribution of the microtubule interface.

Phosphorylation at endothelial cell–cell junctions: Implications for VE-cadherin function

This review summarizes the role of VE-cadherin phosphorylation in the regulation of endothelial cell–cell junctions and highlights how this affects vascular permeability and leukocyte extravasation.

The vascular endothelium is the inner lining of blood vessels and

forms a physical barrier between the vessel lumen and surrounding tissue;

controlling the extravasation of fluids,

plasma proteins and leukocytes.

Changes in the permeability of the endothelium are tightly regulated. Under basal physiological conditions, there is a continuous transfer of substances across the capillary beds. In addition the endothelium can mediate inducible,

transient hyperpermeability

in response to stimulation with inflammatory mediators,

which takes place primarily in post-capillary venules

However, when severe, inflammation may result in dysfunction of the endothelial barrier

  • in various parts of the vascular tree, including large veins, arterioles and capillaries.

Dysregulated permeability is observed in various pathological conditions, such as

  • tumor-induced angiogenesis,
  • cerebrovascular accident and
  • atherosclerosis.

Two fundamentally different pathways regulate endothelial permeability,

  1. the transcellular and
  2. paracellular pathways.

Solutes and cells can pass through the body of endothelial cells via the transcellular pathway, which includes

  • vesicular transport systems,
  • fenestrae, and
  • biochemical transporters.

The paracellular route is controlled by

  • the coordinated opening and closing of endothelial junctions and
  • thereby regulates traffic across the intercellular spaces between endothelial cells.

Endothelial cells are connected by

tight, gap and

adherens junctions,

of which the latter, and particularly the adherens junction component,

vascular endothelial (VE)-cadherin,

are of central importance for the initiation and stabilization of cell–cell contacts.

Although multiple adhesion molecules are localized at endothelial junctions,

  • blocking the adhesive function of VE-cadherin using antibodies
  • is sufficient to disrupt endothelial junctions and
  • to increase endothelial monolayer permeability both in vitro and in vivo.

Like other cadherins, VE-cadherin mediates adhesion via

  • homophilic, calcium-dependent interactions.

This cell–cell adhesion

is strengthened by binding of cytoplasmic proteins, the catenins,

to the C-terminus of VE-cadherin.

VE-cadherin can directly bind

  • β-catenin and plakoglobin, which
  • both associate with the actin binding protein α-catenin.

Initially, α-catenin was thought to directly anchor cadherins to the actin cytoskeleton, but recently it became clear that

  • α-catenin cannot bind to both β-catenin and actin simultaneously.

Numerous lines of evidence indicate that p120-catenin

  • promotes VE-cadherin surface expression and stability at the plasma membrane.

Different models are proposed that describe how

  • p120-catenin regulates cadherin membrane dynamics, including the hypothesis
  • that p120-catenin functions as a ‘cap’ that prevents the interaction of VE-cadherin
  • with the endocytic membrane trafficking machinery.

In addition, p120-catenin might regulate VE-cadherin internalization

  • through interactions with small GTPases.

Cytoplasmic p120-catenin, which is not bound to VE-cadherin, has been shown to

decrease RhoA activity,

elevate active Rac1 and Cdc42, and thereby is thought

to regulate actin cytoskeleton organization and membrane trafficking.

The intact cadherin-catenin complex is required for proper functioning of the adherens junction.

Several mechanisms may be involved in the

  • regulation of the organization and function of the cadherin–catenin complex, including
  1. endocytosis of the complex,
  2. VE-cadherin cleavage and
  3. actin cytoskeleton reorganization.

The remainder of this review primarily focuses on the

role of tyrosine phosphorylation in the control of VE-cadherin-mediated cell–cell adhesion.

Regulation of the adhesive function of VE-cadherin by tyrosine phosphorylation

It is a widely accepted concept that tyrosine phosphorylation of

  • components of the VE–cadherin-catenin complex
  • Correlates with the weakening of cell–cell adhesion.

A general idea has emerged that

tyrosine phosphorylation of the VE-cadherin complex

leads to the uncoupling of VE-cadherin from the actin cytoskeleton

through dissociation of catenins from the cadherin.

However, tyrosine phosphorylation of VE-cadherin

  • is required for efficient transmigration of leukocytes.

This suggests that VE-cadherin-mediated cell–cell contacts

1.are not just pushed open by the migrating leukocytes, but play

2.a more active role in the transmigration process.

A schematic overview of leukocyte adhesion-induced signals leading to VE-cadherin phosphorylation

Regulation of the integrity of endothelial cell–cell contacts by phosphorylation of VE-cadherin.

Regulation of the integrity of endothelial cell–cell contacts by phosphorylation of VE-cadherin

Regulation of the integrity of endothelial cell–cell contacts by phosphorylation of VE-cadherin

N-glycosylation status of E-cadherin controls cytoskeletal dynamics through the organization of distinct β-catenin- and γ-catenin-containing AJs

N-glycosylation of E-cadherin has been shown to inhibit cell–cell adhesion.

Specifically, our recent studies have provided evidence that

  • the reduction of E-cadherin N-glycosylation
  • promoted the recruitment of stabilizing components,
  • vinculin and serine/ threonine protein phosphatase 2A (PP2A), to adherens junctions (AJs)
  • and enhanced the association of AJs with the actin cytoskeleton.

Here, we examined the details of how

N-glycosylation of E-cadherin affected the molecular organization of AJs and their cytoskeletal interactions.

Using the hypoglycosylated E-cadherin variant, V13, we show that

V13/β-catenin complexes preferentially interacted with PP2A and with the microtubule motor protein dynein.

This correlated with dephosphorylation of the microtubule-associated protein tau, suggesting that

increased association of PP2A with V13-containing AJs promoted their tethering to microtubules.

These studies provide the first mechanistic insights into how N-glycosylation of E-cadherin drives changes in AJ composition through

  • the assembly of distinct β-catenin- and γ-catenin-containing scaffolds that impact the interaction with different cytoskeletal components

Cytoskeletal Basis of Ion Channel Function in Cardiac Muscle

MacKinnon. Fig 1  Ion channels exhibit three basic properties

MacKinnon. Fig 1 Ion channels exhibit three basic properties

In order to contract and accommodate the repetitive morphological changes induced by the cardiac cycle, cardiomyocytes

depend on their highly evolved and specialized cytoskeletal apparatus.

Defects in components of the cytoskeleton, in the long term,

affect the ability of the cell to compensate at both functional and structural levels.

In addition to the structural remodeling,

the myocardium becomes increasingly susceptible to altered electrical activity leading to arrhythmogenesis.

The development of arrhythmias secondary to structural remodeling defects has been noted, although the detailed molecular mechanisms are still elusive.

subjects with severe left ventricular chamber dilation such as in DCM can have left bundle branch block (LBBB), while right bundle branch block (RBBB) is more characteristic of right ventricular failure.  LBBB and RBBB have both been repeatedly associated with AV block in heart failure.

The impact of volume overload on structural and electro-cardiographic alterations has been noted in cardiomyopathy patients treated with left ventricular assist device (LVAD) therapy, which puts the heart at mechanical rest.

In LVAD-treated subjects,

QRS- and both QT- and QTc duration decreased,

suggesting that QRS- and QT-duration are significantly influenced by mechanical load and

that the shortening of the action potential duration contributes to the improved contractile performance after LVAD support.

An early postoperative period study after cardiac unloading therapy in 17 HF patients showed that in the first two weeks after LVAD implantation,

HF was associated with a relatively high incidence of ventricular arrhythmias associated with QTc interval prolongation.

In addition, a recent retrospective study of 100 adult patients with advanced HF, treated with an axial-flow HeartMate LVAD suggested that

  • the rate of new-onset monomorphic ventricular tachycardia (MVT) was increased in LVAD treated patients compared to patients given only medical treatment,

The myocardium is exposed to severe and continuous biomechanical stress during each contraction-relaxation cycle. When fiber tension remains uncompensated or simply unbalanced,

it may represent a trigger for arrhythmogenesis caused by cytoskeletal stretching,

which ultimately leads to altered ion channel localization, and subsequent action potential and conduction alterations.

Cytoskeletal proteins not only provide the backbone of the cellular structure, but they also

maintain the shape and flexibility of the different sub-cellular compartments, including the

1.plasma membrane,

2.the double lipid layer, which defines the boundaries of the cell and where

ion channels are mainly localized.

The interaction between the sarcomere, which is the basic for the passive force during diastole and for the restoring force during systole.

Sarcomeric Proteins and Ion Channels

besides fiber stretch associated with mechanical and hemodynamic impairment, cytoskeletal alterations due to primary genetic defects or indirectly to alterations in response to cellular injury can potentially

1.affect ion channel anchoring, and trafficking, as well as

2.functional regulation by second messenger pathways,

3.causing an imbalance in cardiac ionic homeostasis that will trigger arrhythmogenesis.

Intense investigation of

the sarcomeric actin network,

the Z-line structure, and

chaperone molecules docking in the plasma membrane,

has shed new light on the molecular basis of

  • cytoskeletal interactions in regulating ion channels

Actin disruption using cytochalasin D, an agent that interferes with actin polymerization, increased Na+ channel activity in 90% of excised patches tested within 2 min, which indicated that

the integrity of the filamentous actin (F-actin) network was essential for the maintenance of normal Na+ channel function

These data were the first to support a role for the cytoskeleton in cardiac arrhythmias.

Molecular interactions between the cytoskeleton and ion channels

The figure illustrates the interactions between the ion channels on the sarcolemma, and the sarcomere in cardiac myocytes. Note that the Z-line is connected to the cardiac T-tubules. The diagram illustrates the complex protein-protein interactions that occur between structural components of the cytoskeleton and ion channels. The cytoskeleton is involved in regulating the metabolism of ion channels, modifying their expression, localization, and electrical properties.

sarcomere structure

sarcomere structure

It is important to be aware of the enormous variety of clinical presentations that derive from distinct variants in the same pool of genetic factors. Knowledge of these variants could facilitate tailoring the therapy of choice for each patient. In particular,

the recent findings of structural and functional links between

the cytoskeleton and ion channels

could expand the therapeutic interventions in

arrhythmia management in structurally abnormal myocardium, where aberrant binding

between cytoskeletal proteins can directly or indirectly alter ion channel function.

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Introduction to Protein Synthesis and Degradation

Curator: Larry H. Bernstein, MD, FCAP

Updated 8/31/2019

 

Introduction to Protein Synthesis and Degradation

This chapter I made to follow signaling, rather than to precede it. I had already written much of the content before reorganizing the contents. The previous chapters on carbohydrate and on lipid metabolism have already provided much material on proteins and protein function, which was persuasive of the need to introduce signaling, which entails a substantial introduction to conformational changes in proteins that direct the trafficking of metabolic pathways, but more subtly uncovers an important role for microRNAs, not divorced from transcription, but involved in a non-transcriptional role.  This is where the classic model of molecular biology lacked any integration with emerging metabolic concepts concerning regulation. Consequently, the science was bereft of understanding the ties between the multiple convergence of transcripts, the selective inhibition of transcriptions, and the relative balance of aerobic and anaerobic metabolism, the weight of the pentose phosphate shunt, and the utilization of available energy source for synthetic and catabolic adaptive responses.

The first subchapter serves to introduce the importance of transcription in translational science.  The several subtitles that follow are intended to lay out the scope of the transcriptional activity, and also to direct attention toward the huge role of proteomics in the cell construct.  As we have already seen, proteins engage with carbohydrates and with lipids in important structural and signaling processes.  They are integrasl to the composition of the cytoskeleton, and also to the extracellular matrix.  Many proteins are actually enzymes, carrying out the transformation of some substrate, a derivative of the food we ingest.  They have a catalytic site, and they function with a cofactor – either a multivalent metal or a nucleotide.

The amino acids that go into protein synthesis include “indispensable” nutrients that are not made for use, but must be derived from animal protein, although the need is partially satisfied by plant sources. The essential amino acids are classified into well established groups. There are 20 amino acids commonly found in proteins.  They are classified into the following groups based on the chemical and/or structural properties of their side chains :

  1. Aliphatic Amino Acids
  2. Cyclic Amino Acid
  3. AAs with Hydroxyl or Sulfur-containing side chains
  4. Aromatic Amino Acids
  5. Basic Amino Acids
  6. Acidic Amino Acids and their Amides

Examples include:

Alanine                  aliphatic hydrophobic neutral
Arginine                 polar hydrophilic charged (+)
Cysteine                polar hydrophobic neutral
Glutamine             polar hydrophilic neutral
Histidine                aromatic polar hydrophilic charged (+)
Lysine                   polar hydrophilic charged (+)
Methionine            hydrophobic neutral
Serine                   polar hydrophilic neutral
Tyrosine                aromatic polar hydrophobic

Transcribe and Translate a Gene

  1. For each RNA base there is a corresponding DNA base
  2. Cells use the two-step process of transcription and translation to read each gene and produce the string of amino acids that makes up a protein.
  3. mRNA is produced in the nucleus, and is transferred to the ribosome
  4. mRNA uses uracil instead of thymine
  5. the ribosome reads the RNA sequence and makes protein
  6. There is a sequence combination to fit each amino acid to a three letter RNA code
  7. The ribosome starts at AUG (start), and it reads each codon three letters at a time
  8. Stop codons are UAA, UAG and UGA

 

protein synthesis

protein synthesis

http://learn.genetics.utah.edu/content/molecules/transcribe/images/TandT.png

mcell-transcription-translation

mcell-transcription-translation

http://www.vcbio.science.ru.nl/images/cellcycle/mcell-transcription-translation_eng_zoom.gif

transcription_translation

transcription_translation

 

http://www.biologycorner.com/resources/transcription_translation.JPG

 

What about the purine inosine?

Inosine triphosphate pyrophosphatase – Pyrophosphatase that hydrolyzes the non-canonical purine nucleotides inosine triphosphate (ITP), deoxyinosine triphosphate (dITP) as well as 2′-deoxy-N-6-hydroxylaminopurine triposphate (dHAPTP) and xanthosine 5′-triphosphate (XTP) to their respective monophosphate derivatives. The enzyme does not distinguish between the deoxy- and ribose forms. Probably excludes non-canonical purines from RNA and DNA precursor pools, thus preventing their incorporation into RNA and DNA and avoiding chromosomal lesions.

Gastroenterology. 2011 Apr;140(4):1314-21.  http://dx.doi.org:/10.1053/j.gastro.2010.12.038. Epub 2011 Jan 1.

Inosine triphosphate protects against ribavirin-induced adenosine triphosphate loss by adenylosuccinate synthase function.

Hitomi Y1, Cirulli ET, Fellay J, McHutchison JG, Thompson AJ, Gumbs CE, Shianna KV, Urban TJ, Goldstein DB.

Genetic variation of inosine triphosphatase (ITPA) causing an accumulation of inosine triphosphate (ITP) has been shown to protect patients against ribavirin (RBV)-induced anemia during treatment for chronic hepatitis C infection by genome-wide association study (GWAS). However, the biologic mechanism by which this occurs is unknown.

Although ITP is not used directly by human erythrocyte ATPase, it can be used for ATP biosynthesis via ADSS in place of guanosine triphosphate (GTP). With RBV challenge, erythrocyte ATP reduction was more severe in the wild-type ITPA genotype than in the hemolysis protective ITPA genotype. This difference also remains after inhibiting adenosine uptake using nitrobenzylmercaptopurine riboside (NBMPR).

ITP confers protection against RBV-induced ATP reduction by substituting for erythrocyte GTP, which is depleted by RBV, in the biosynthesis of ATP. Because patients with excess ITP appear largely protected against anemia, these results confirm that RBV-induced anemia is due primarily to the effect of the drug on GTP and consequently ATP levels in erythrocytes.

Ther Drug Monit. 2012 Aug;34(4):477-80.  http://dx.doi.org:/10.1097/FTD.0b013e31825c2703.

Determination of inosine triphosphate pyrophosphatase phenotype in human red blood cells using HPLC.

Citterio-Quentin A1, Salvi JP, Boulieu R.

Thiopurine drugs, widely used in cancer chemotherapy, inflammatory bowel disease, and autoimmune hepatitis, are responsible for common adverse events. Only some of these may be explained by genetic polymorphism of thiopurine S-methyltransferase. Recent articles have reported that inosine triphosphate pyrophosphatase (ITPase) deficiency was associated with adverse drug reactions toward thiopurine drug therapy. Here, we report a weak anion exchange high-performance liquid chromatography method to determine ITPase activity in red blood cells and to investigate the relationship with the occurrence of adverse events during azathioprine therapy.

The chromatographic method reported allows the analysis of IMP, inosine diphosphate, and ITP in a single run in <12.5 minutes. The method was linear in the range 5-1500 μmole/L of IMP. Intraassay and interassay precisions were <5% for red blood cell lysates supplemented with 50, 500, and 1000 μmole/L IMP. Km and Vmax evaluated by Lineweaver-Burk plot were 677.4 μmole/L and 19.6 μmole·L·min, respectively. The frequency distribution of ITPase from 73 patients was investigated.

The method described is useful to determine the ITPase phenotype from patients on thiopurine therapy and to investigate the potential relation between ITPase deficiency and the occurrence of adverse events.

 

System wide analyses have underestimated protein abundances and the importance of transcription in mammals

Jingyi Jessica Li1, 2, Peter J Bickel1 and Mark D Biggin3

PeerJ 2:e270; http://dx.doi.org:/10.7717/peerj.270

Using individual measurements for 61 housekeeping proteins to rescale whole proteome data from Schwanhausser et al. (2011), we find that the median protein detected is expressed at 170,000 molecules per cell and that our corrected protein abundance estimates show a higher correlation with mRNA abundances than do the uncorrected protein data. In addition, we estimated the impact of further errors in mRNA and protein abundances using direct experimental measurements of these errors. The resulting analysis suggests that mRNA levels explain at least 56% of the differences in protein abundance for the 4,212 genes detected by Schwanhausser et al. (2011), though because one major source of error could not be estimated the true percent contribution should be higher.We also employed a second, independent strategy to determine the contribution of mRNA levels to protein expression.We show that the variance in translation rates directly measured by ribosome profiling is only 12% of that inferred by Schwanhausser et al. (2011), and that the measured and inferred translation rates correlate poorly (R2 D 0.13). Based on this, our second strategy suggests that mRNA levels explain 81% of the variance in protein levels. We also determined the percent contributions of transcription, RNA degradation, translation and protein degradation to the variance in protein abundances using both of our strategies. While the magnitudes of the two estimates vary, they both suggest that transcription plays a more important role than the earlier studies implied and translation a much smaller role. Finally, the above estimates only apply to those genes whose mRNA and protein expression was detected. Based on a detailed analysis by Hebenstreit et al. (2012), we estimat that approximately 40% of genes in a given cell within a population express no mRNA. Since there can be no translation in the ab-sence of mRNA, we argue that differences in translation rates can play no role in determining the expression levels for the 40% of genes that are non-expressed.

 

Related studies that reveal issues that are not part of this chapter:

  1. Ubiquitylation in relationship to tissue remodeling
  2. Post-translational modification of proteins
    1. Glycosylation
    2. Phosphorylation
    3. Methylation
    4. Nitrosylation
    5. Sulfation – sulfotransferases
      cell-matrix communication
    6. Acetylation and histone deacetylation (HDAC)
      Connecting Protein Phosphatase to 1α (PP1α)
      Acetylation complexes (such as CBP/p300 and PCAF)
      Sirtuins
      Rel/NF-kB Signal Transduction
      Homologous Recombination Pathway of Double-Strand DNA Repair
    7. Glycination
    8. cyclin dependent kinases (CDKs)
    9. lyase
    10. transferase

 

This year, the Lasker award for basic medical research went to Kazutoshi Mori (Kyoto University) and Peter Walter (University of California, San Francisco) for their “discoveries concerning the unfolded protein response (UPR) — an intracellular quality control system that

detects harmful misfolded proteins in the endoplasmic reticulum and signals the nucleus to carry out corrective measures.”

About UPR: Approximately a third of cellular proteins pass through the Endoplasmic Reticulum (ER) which performs stringent quality control of these proteins. All proteins need to assume the proper 3-dimensional shape in order to function properly in the harsh cellular environment. Related to this is the fact that cells are under constant stress and have to make rapid, real time decisions about survival or death.

A major indicator of stress is the accumulation of unfolded proteins within the Endoplasmic Reticulum (ER), which triggers a transcriptional cascade in order to increase the folding capacity of the ER. If the metabolic burden is too great and homeostasis cannot be achieved, the response shifts from

damage control to the induction of pro-apoptotic pathways that would ultimately cause cell death.

This response to unfolded proteins or the UPR is conserved among all eukaryotes, and dysfunction in this pathway underlies many human diseases, including Alzheimer’s, Parkinson’s, Diabetes and Cancer.

 

The discovery of a new class of human proteins with previously unidentified activities

In a landmark study conducted by scientists at the Scripps Research Institute, The Hong Kong University of Science and Technology, aTyr Pharma and their collaborators, a new class of human proteins has been discovered. These proteins [nearly 250], called Physiocrines belong to the aminoacyl tRNA synthetase gene family and carry out novel, diverse and distinct biological functions.

The aminoacyl tRNA synthetase gene family codes for a group of 20 ubiquitous enzymes almost all of which are part of the protein synthesis machinery. Using recombinant protein purification, deep sequencing technique, mass spectroscopy and cell based assays, the team made this discovery. The finding is significant, also because it highlights the alternate use of a gene family whose protein product normally performs catalytic activities for non-catalytic regulation of basic and complex physiological processes spanning metabolism, vascularization, stem cell biology and immunology

 

Muscle maintenance and regeneration – key player identified

Muscle tissue suffers from atrophy with age and its regenerative capacity also declines over time. Most molecules discovered thus far to boost tissue regeneration are also implicated in cancers.  During a quest to find safer alternatives that can regenerate tissue, scientists reported that the hormone Oxytocin is required for proper muscle tissue regeneration and homeostasis and that its levels decline with age.

Oxytocin could be an alternative to hormone replacement therapy as a way to combat aging and other organ related degeneration.

Oxytocin is an age-specific circulating hormone that is necessary for muscle maintenance and regeneration (June 2014)

 

Proc Natl Acad Sci U S A. 2014 Sep 30;111(39):14289-94.   http://dx.doi.org:/10.1073/pnas.1407640111. Epub 2014 Sep 15.

Role of forkhead box protein A3 in age-associated metabolic decline.

Ma X1, Xu L1, Gavrilova O2, Mueller E3.

Aging is associated with increased adiposity and diminished thermogenesis, but the critical transcription factors influencing these metabolic changes late in life are poorly understood. We recently demonstrated that the winged helix factor forkhead box protein A3 (Foxa3) regulates the expansion of visceral adipose tissue in high-fat diet regimens; however, whether Foxa3 also contributes to the increase in adiposity and the decrease in brown fat activity observed during the normal aging process is currently unknown. Here we report that during aging, levels of Foxa3 are significantly and selectively up-regulated in brown and inguinal white fat depots, and that midage Foxa3-null mice have increased white fat browning and thermogenic capacity, decreased adipose tissue expansion, improved insulin sensitivity, and increased longevity. Foxa3 gain-of-function and loss-of-function studies in inguinal adipose depots demonstrated a cell-autonomous function for Foxa3 in white fat tissue browning. Furthermore, our analysis revealed that the mechanisms of Foxa3 modulation of brown fat gene programs involve the suppression of peroxisome proliferator activated receptor γ coactivtor 1 α (PGC1α) levels through interference with cAMP responsive element binding protein 1-mediated transcriptional regulation of the PGC1α promoter.

 

Asymmetric mRNA localization contributes to fidelity and sensitivity of spatially localized systems

RJ Weatheritt, TJ Gibson & MM Babu
Nature Structural & Molecular Biology 24 Aug, 2014; 21: 833–839 http://dx.do.orgi:/10.1038/nsmb.2876

Although many proteins are localized after translation, asymmetric protein distribution is also achieved by translation after mRNA localization. Why are certain mRNA transported to a distal location and translated on-site? Here we undertake a systematic, genome-scale study of asymmetrically distributed protein and mRNA in mammalian cells. Our findings suggest that asymmetric protein distribution by mRNA localization enhances interaction fidelity and signaling sensitivity. Proteins synthesized at distal locations frequently contain intrinsically disordered segments. These regions are generally rich in assembly-promoting modules and are often regulated by post-translational modifications. Such proteins are tightly regulated but display distinct temporal dynamics upon stimulation with growth factors. Thus, proteins synthesized on-site may rapidly alter proteome composition and act as dynamically regulated scaffolds to promote the formation of reversible cellular assemblies. Our observations are consistent across multiple mammalian species, cell types and developmental stages, suggesting that localized translation is a recurring feature of cell signaling and regulation.

 

An overview of the potential advantages conferred by distal-site protein synthesis, inferred from our analysis.

 

An overview of the potential advantages conferred by distal-site protein synthesis

An overview of the potential advantages conferred by distal-site protein synthesis

 

Turquoise and red filled circle represents off-target and correct interaction partners, respectively. Wavy lines represent a disordered region within a distal site synthesis protein. Grey and red line in graphs represents profiles of t…

http://www.nature.com/nsmb/journal/v21/n9/carousel/nsmb.2876-F5.jpg

 

Tweaking transcriptional programming for high quality recombinant protein production

Since overexpression of recombinant proteins in E. coli often leads to the formation of inclusion bodies, producing properly folded, soluble proteins is undoubtedly the most important end goal in a protein expression campaign. Various approaches have been devised to bypass the insolubility issues during E. coli expression and in a recent report a group of researchers discuss reprogramming the E. coli proteostasis [protein homeostasis] network to achieve high yields of soluble, functional protein. The premise of their studies is that the basal E. coli proteostasis network is insufficient, and often unable, to fold overexpressed proteins, thus clogging the folding machinery.

By overexpressing a mutant, negative-feedback deficient heat shock transcription factor [σ32 I54N] before and during overexpression of the protein of interest, reprogramming can be achieved, resulting in high yields of soluble and functional recombinant target protein. The authors explain that this method is better than simply co-expressing/over-expressing chaperones, co-chaperones, foldases or other components of the proteostasis network because reprogramming readies the folding machinery and up regulates the essential folding components beforehand thus  maintaining system capability of the folding machinery.

The Heat-Shock Response Transcriptional Program Enables High-Yield and High-Quality Recombinant Protein Production in Escherichia coli (July 2014)

 

 Unfolded proteins collapse when exposed to heat and crowded environments

Proteins are important molecules in our body and they fulfil a broad range of functions. For instance as enzymes they help to release energy from food and as muscle proteins they assist with motion. As antibodies they are involved in immune defence and as hormone receptors in signal transduction in cells. Until only recently it was assumed that all proteins take on a clearly defined three-dimensional structure – i.e. they fold in order to be able to assume these functions. Surprisingly, it has been shown that many important proteins occur as unfolded coils. Researchers seek to establish how these disordered proteins are capable at all of assuming highly complex functions.

Ben Schuler’s research group from the Institute of Biochemistry of the University of Zurich has now established that an increase in temperature leads to folded proteins collapsing and becoming smaller. Other environmental factors can trigger the same effect.

Measurements using the “molecular ruler”

“The fact that unfolded proteins shrink at higher temperatures is an indication that cell water does indeed play an important role as to the spatial organisation eventually adopted by the molecules”, comments Schuler with regard to the impact of temperature on protein structure. For their studies the biophysicists use what is known as single-molecule spectroscopy. Small colour probes in the protein enable the observation of changes with an accuracy of more than one millionth of a millimetre. With this “molecular yardstick” it is possible to measure how molecular forces impact protein structure.

With computer simulations the researchers have mimicked the behaviour of disordered proteins.
(Courtesy of Jose EDS Roselino, PhD.

 

MLKL compromises plasma membrane integrity

Necroptosis is implicated in many diseases and understanding this process is essential in the search for new therapies. While mixed lineage kinase domain-like (MLKL) protein has been known to be a critical component of necroptosis induction, how MLKL transduces the death signal was not clear. In a recent finding, scientists demonstrated that the full four-helical bundle domain (4HBD) in the N-terminal region of MLKL is required and sufficient to induce its oligomerization and trigger cell death.

They also found a patch of positively charged amino acids on the surface of the 4HBD that bound to phosphatidylinositol phosphates (PIPs) and allowed the recruitment of MLKL to the plasma membrane that resulted in the formation of pores consisting of MLKL proteins, due to which cells absorbed excess water causing them to explode. Detailed knowledge about how MLKL proteins create pores offers possibilities for the development of new therapeutic interventions for tolerating or preventing cell death.

MLKL compromises plasma membrane integrity by binding to phosphatidylinositol phosphates (May 2014)

 

Mitochondrial and ER proteins implicated in dementia

Mitochondria and the endoplasmic reticulum (ER) form tight structural associations that facilitate a number of cellular functions. However, the molecular mechanisms of these interactions aren’t properly understood.

A group of researchers showed that the ER protein VAPB interacted with mitochondrial protein PTPIP51 to regulate ER-mitochondria associations and that TDP-43, a protein implicated in dementia, disturbs this interaction to regulate cellular Ca2+ homeostasis. These studies point to a new pathogenic mechanism for TDP-43 and may also provide a potential new target for the development of new treatments for devastating neurological conditions like dementia.

ER-mitochondria associations are regulated by the VAPB-PTPIP51 interaction and are disrupted by ALS/FTD-associated TDP-43. Nature (June 2014)

 

A novel strategy to improve membrane protein expression in Yeast

Membrane proteins play indispensable roles in the physiology of an organism. However, recombinant production of membrane proteins is one of the biggest hurdles facing protein biochemists today. A group of scientists in Belgium showed that,

by increasing the intracellular membrane production by interfering with a key enzymatic step of lipid synthesis,

enhanced expression of recombinant membrane proteins in yeast is achieved.

Specifically, they engineered the oleotrophic yeast, Yarrowia lipolytica, by

deleting the phosphatidic acid phosphatase, PAH1 gene,

which led to massive proliferation of endoplasmic reticulum (ER) membranes.

For all 8 tested representatives of different integral membrane protein families, they obtained enhanced protein accumulation.

 

An unconventional method to boost recombinant protein levels

MazF is an mRNA interferase enzyme in E.coli that functions as and degrades cellular mRNA in a targeted fashion, at the “ACA” sequence. This degradation of cellular mRNA causes a precipitous drop in cellular protein synthesis. A group of scientists at the Robert Wood Johnson Medical School in New Jersey, exploited the degeneracy of the genetic code to modify all “ACA” triplets within their gene of interest in a way that the corresponding amino acid (Threonine) remained unchanged. Consequently, induction of MazF toxin caused degradation of E.coli cellular mRNA but the recombinant gene transcription and protein synthesis continued, causing significant accumulation of high quality target protein. This expression system enables unparalleled signal to noise ratios that could dramatically simplify structural and functional studies of difficult-to-purify, biologically important proteins.

 

Tandem fusions and bacterial strain evolution for enhanced functional membrane protein production

Membrane protein production remains a significant challenge in its characterization and structure determination. Despite the fact that there are a variety of host cell types, E.coli remains the popular choice for producing recombinant membrane proteins. A group of scientists in Netherlands devised a robust strategy to increase the probability of functional membrane protein overexpression in E.coli.

By fusing Green Fluorescent Protein (GFP) and the Erythromycin Resistance protein (ErmC) to the C-terminus of a target membrane protein they wer e able to track the folding state of their target protein while using Erythromycin to select for increased expression. By increasing erythromycin concentration in the growth media and testing different membrane targets, they were able to identify four evolved E.coli strains, all of which carried a mutation in the hns gene, whose product is implicated in genome organization and transcriptional silencing. Through their experiments the group showed that partial removal of the transcriptional silencing mechanism was related to production of proteins that were essential for functional overexpression of membrane proteins.

 

The role of an anti-apoptotic factor in recombinant protein production

In a recent study, scientists at the Johns Hopkins University and Frederick National Laboratory for Cancer Research examined an alternative method of utilizing the benefits of anti-apoptotic gene expression to enhance the transient expression of biotherapeutics, specifically, through the co-transfection of Bcl-xL along with the product-coding target gene.

Chinese Hamster Ovary(CHO) cells were co-transfected with the product-coding gene and a vector containing Bcl-xL, using Polyethylenimine (PEI) reagent. They found that the cells co-transfected with Bcl-xL demonstrated reduced apoptosis, increased specific productivity, and an overall increase in product yield.

B-cell lymphoma-extra-large (Bcl-xL) is a mitochondrial transmembrane protein and a member of the Bcl-2 family of proteins which are known to act as either pro- or anti-apoptotic proteins. Bcl-xL itself acts as an anti-apoptotic molecule by preventing the release of mitochondrial contents such as cytochrome c, which would lead to caspase activation. Higher levels of Bcl-xL push a cell toward survival mode by making the membranes pores less permeable and leaky.

Introduction to Protein Synthesis and Degradation Updated 8/31/2019

N-Terminal Degradation of Proteins: The N-End Rule and N-degrons

In both prokaryotes and eukaryotes mitochondria and chloroplasts, the ribosomal synthesis of proteins is initiated with the addition of the N-formyl methionine residue.  However in eukaryotic cytosolic ribosomes, the N terminal was assumed to be devoid of the N-formyl group.  The unformylated N-terminal methionine residues of eukaryotes is then  often N-acetylated (Ac) and creates specific degradation signals, the Ac N-end rule.  These N-end rule pathways are proteolytic systems which recognize these N-degrons resulting in proteosomal degradation or autophagy.  In prokaryotes this system is stimulated by certain amino acid deficiencies and in eukaryotes is dependent on the Psh1 E3 ligase.

Two papers in the journal Science describe this N-degron in more detail.

Structured Abstract
INTRODUCTION

In both bacteria and eukaryotic mitochondria and chloroplasts, the ribosomal synthesis of proteins is initiated with the N-terminal (Nt) formyl-methionine (fMet) residue. Nt-fMet is produced pretranslationally by formyltransferases, which use 10-formyltetrahydrofolate as a cosubstrate. By contrast, proteins synthesized by cytosolic ribosomes of eukaryotes were always presumed to bear unformylated N-terminal Met (Nt-Met). The unformylated Nt-Met residue of eukaryotic proteins is often cotranslationally Nt-acetylated, a modification that creates specific degradation signals, Ac/N-degrons, which are targeted by the Ac/N-end rule pathway. The N-end rule pathways are a set of proteolytic systems whose unifying feature is their ability to recognize proteins containing N-degrons, thereby causing the degradation of these proteins by the proteasome or autophagy in eukaryotes and by the proteasome-like ClpAP protease in bacteria. The main determinant of an N‑degron is a destabilizing Nt-residue of a protein. Studies over the past three decades have shown that all 20 amino acids of the genetic code can act, in cognate sequence contexts, as destabilizing Nt‑residues. The previously known eukaryotic N-end rule pathways are the Arg/N-end rule pathway, the Ac/N-end rule pathway, and the Pro/N-end rule pathway. Regulated degradation of proteins and their natural fragments by the N-end rule pathways has been shown to mediate a broad range of biological processes.

RATIONALE

The chemical similarity of the formyl and acetyl groups and their identical locations in, respectively, Nt‑formylated and Nt-acetylated proteins led us to suggest, and later to show, that the Nt-fMet residues of nascent bacterial proteins can act as bacterial N-degrons, termed fMet/N-degrons. Here we wished to determine whether Nt-formylated proteins might also form in the cytosol of a eukaryote such as the yeast Saccharomyces cerevisiae and to determine the metabolic fates of Nt-formylated proteins if they could be produced outside mitochondria. Our approaches included molecular genetic techniques, mass spectrometric analyses of proteins’ N termini, and affinity-purified antibodies that selectively recognized Nt-formylated reporter proteins.

RESULTS

We discovered that the yeast formyltransferase Fmt1, which is imported from the cytosol into the mitochondria inner matrix, can generate Nt-formylated proteins in the cytosol, because the translocation of Fmt1 into mitochondria is not as efficacious, even under unstressful conditions, as had previously been assumed. We also found that Nt‑formylated proteins are greatly up-regulated in stationary phase or upon starvation for specific amino acids. The massive increase of Nt-formylated proteins strictly requires the Gcn2 kinase, which phosphorylates Fmt1 and mediates its retention in the cytosol. Notably, the ability of Gcn2 to retain a large fraction of Fmt1 in the cytosol of nutritionally stressed cells is confined to Fmt1, inasmuch as the Gcn2 kinase does not have such an effect, under the same conditions, on other examined nuclear DNA–encoded mitochondrial matrix proteins. The Gcn2-Fmt1 protein localization circuit is a previously unknown signal transduction pathway. A down-regulation of cytosolic Nt‑formylation was found to increase the sensitivity of cells to undernutrition stresses, to a prolonged cold stress, and to a toxic compound. We also discovered that the Nt-fMet residues of Nt‑formylated cytosolic proteins act as eukaryotic fMet/N-degrons and identified the Psh1 E3 ubiquitin ligase as the recognition component (fMet/N-recognin) of the previously unknown eukaryotic fMet/N-end rule pathway, which destroys Nt‑formylated proteins.

CONCLUSION

The Nt-formylation of proteins, a long-known pretranslational protein modification, is mediated by formyltransferases. Nt-formylation was thought to be confined to bacteria and bacteria-descended eukaryotic organelles but was found here to also occur at the start of translation by the cytosolic ribosomes of a eukaryote. The levels of Nt‑formylated eukaryotic proteins are greatly increased upon specific stresses, including undernutrition, and appear to be important for adaptation to these stresses. We also discovered that Nt-formylated cytosolic proteins are selectively destroyed by the eukaryotic fMet/N-end rule pathway, mediated by the Psh1 E3 ubiquitin ligase. This previously unknown proteolytic system is likely to be universal among eukaryotes, given strongly conserved mechanisms that mediate Nt‑formylation and degron recognition.

The eukaryotic fMet/N-end rule pathway.

(Top) Under undernutrition conditions, the Gcn2 kinase augments the cytosolic localization of the Fmt1 formyltransferase, and possibly also its enzymatic activity. Consequently, Fmt1 up-regulates the cytosolic fMet–tRNAi (initiator transfer RNA), and thereby increases the levels of cytosolic Nt-formylated proteins, which are required for the adaptation of cells to specific stressors. (Bottom) The Psh1 E3 ubiquitin ligase targets the N-terminal fMet-residues of eukaryotic cytosolic proteins, such as Cse4, Pgd1, and Rps22a, for the polyubiquitylation-mediated, proteasome-dependent degradation.

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The eukaryotic fMet/N-end rule pathway.

(Top) Under undernutrition conditions, the Gcn2 kinase augments the cytosolic localization of the Fmt1 formyltransferase, and possibly also its enzymatic activity. Consequently, Fmt1 up-regulates the cytosolic fMet–tRNAi (initiator transfer RNA), and thereby increases the levels of cytosolic Nt-formylated proteins, which are required for the adaptation of cells to specific stressors. (Bottom) The Psh1 E3 ubiquitin ligase targets the N-terminal fMet-residues of eukaryotic cytosolic proteins, such as Cse4, Pgd1, and Rps22a, for the polyubiquitylation-mediated, proteasome-dependent degradation.

 

A glycine-specific N-degron pathway mediates the quality control of protein N-myristoylation. Richard T. Timms1,2Zhiqian Zhang1,2David Y. Rhee3J. Wade Harper3Itay Koren1,2,*,Stephen J. Elledge1,2

Science  05 Jul 2019: Vol. 365, Issue 6448

The second paper describes a glycine specific N-degron pathway in humans.  Specifically the authors set up a screen to identify specific N-terminal degron motifs in the human.  Findings included an expanded repertoire for the UBR E3 ligases to include substrates with arginine and lysine following an intact initiator methionine and a glycine at the extreme N-terminus, which is a potent degron.

Glycine N-degron regulation revealed

For more than 30 years, N-terminal sequences have been known to influence protein stability, but additional features of these N-end rule, or N-degron, pathways continue to be uncovered. Timms et al. used a global protein stability (GPS) technology to take a broader look at these pathways in human cells. Unexpectedly, glycine exposed at the N terminus could act as a potent degron; proteins bearing N-terminal glycine were targeted for proteasomal degradation by two Cullin-RING E3 ubiquitin ligases through the substrate adaptors ZYG11B and ZER1. This pathway may be important, for example, to degrade proteins that fail to localize properly to cellular membranes and to destroy protein fragments generated during cell death.

Science, this issue p. eaaw4912

Structured Abstract

INTRODUCTION

The ubiquitin-proteasome system is the major route through which the cell achieves selective protein degradation. The E3 ubiquitin ligases are the major determinants of specificity in this system, which is thought to be achieved through their selective recognition of specific degron motifs in substrate proteins. However, our ability to identify these degrons and match them to their cognate E3 ligase remains a major challenge.

RATIONALE

It has long been known that the stability of proteins is influenced by their N-terminal residue, and a large body of work over the past three decades has characterized a collection of N-end rule pathways that target proteins for degradation through N-terminal degron motifs. Recently, we developed Global Protein Stability (GPS)–peptidome technology and used it to delineate a suite of degrons that lie at the extreme C terminus of proteins. We adapted this approach to examine the stability of the human N terminome, allowing us to reevaluate our understanding of N-degron pathways in an unbiased manner.

RESULTS

Stability profiling of the human N terminome identified two major findings: an expanded repertoire for UBR family E3 ligases to include substrates that begin with arginine and lysine following an intact initiator methionine and, more notably, that glycine positioned at the extreme N terminus can act as a potent degron. We established human embryonic kidney 293T reporter cell lines in which unstable peptides that bear N-terminal glycine degrons were fused to green fluorescent protein, and we performed CRISPR screens to identify the degradative machinery involved. These screens identified two Cul2 Cullin-RING E3 ligase complexes, defined by the related substrate adaptors ZYG11B and ZER1, that act redundantly to target substrates bearing N-terminal glycine degrons for proteasomal degradation. Moreover, through the saturation mutagenesis of example substrates, we defined the composition of preferred N-terminal glycine degrons specifically recognized by ZYG11B and ZER1.

We found that preferred glycine degrons are depleted from the native N termini of metazoan proteomes, suggesting that proteins have evolved to avoid degradation through this pathway, but are strongly enriched at annotated caspase cleavage sites. Stability profiling of N-terminal peptides lying downstream of all known caspase cleavages sites confirmed that Cul2ZYG11Band Cul2ZER1 could make a substantial contribution to the removal of proteolytic cleavage products during apoptosis. Last, we identified a role for ZYG11B and ZER1 in the quality control of N-myristoylated proteins. N-myristoylation is an important posttranslational modification that occurs exclusively on N-terminal glycine. By profiling the stability of the human N-terminome in the absence of the N-myristoyltransferases NMT1 and NMT2, we found that a failure to undergo N-myristoylation exposes N-terminal glycine degrons that are otherwise obscured. Thus, conditional exposure of glycine degrons to ZYG11B and ZER1 permits the selective proteasomal degradation of aberrant proteins that have escaped N-terminal myristoylation.

CONCLUSION

These data demonstrate that an additional N-degron pathway centered on N-terminal glycine regulates the stability of metazoan proteomes. Cul2ZYG11B– and Cul2ZER1-mediated protein degradation through N-terminal glycine degrons may be particularly important in the clearance of proteolytic fragments generated by caspase cleavage during apoptosis and in the quality control of protein N-myristoylation.

The glycine N-degron pathway.

Stability profiling of the human N-terminome revealed that N-terminal glycine acts as a potent degron. CRISPR screening revealed two Cul2 complexes, defined by the related substrate adaptors ZYG11B and ZER1, that recognize N-terminal glycine degrons. This pathway may be particularly important for the degradation of caspase cleavage products during apoptosis and the removal of proteins that fail to undergo N-myristoylation.

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The glycine N-degron pathway.

Stability profiling of the human N-terminome revealed that N-terminal glycine acts as a potent degron. CRISPR screening revealed two Cul2 complexes, defined by the related substrate adaptors ZYG11B and ZER1, that recognize N-terminal glycine degrons. This pathway may be particularly important for the degradation of caspase cleavage products during apoptosis and the removal of proteins that fail to undergo N-myristoylation.

 

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Summary of Signaling and Signaling Pathways

Summary of Signaling and Signaling Pathways

Author and Curator: Larry H Bernstein, MD, FCAP

In the imtroduction to this series of discussions I pointed out JEDS Rosalino’s observation about the construction of a complex molecule of acetyl coenzyme A, and the amount of genetic coding that had to go into it.  Furthermore, he observes –  Millions of years later, or as soon as, the information of interaction leading to activity and regulation could be found in RNA, proteins like reverse transcriptase move this information to a more stable form (DNA). In this way it is easier to understand the use of CoA to make two carbon molecules more reactive.

acetylCoA

acetylCoA

In the tutorial that follows we find support for the view that mechanisms and examples from the current literature, which give insight into the developments in cell metabolism, are achieving a separation from inconsistent views introduced by the classical model of molecular biology and genomics, toward a more functional cellular dynamics that is not dependent on the classic view.  The classical view fits a rigid framework that is to genomics and metabolomics as Mendelian genetics if to multidimentional, multifactorial genetics.  The inherent difficulty lies in two places:

  1. Interactions between differently weighted determinants
  2. A large part of the genome is concerned with regulatory function, not expression of the code

The goal of the tutorial was to achieve an understanding of how cell signaling occurs in a cell.  Completion of the tutorial would provide

  1. a basic understanding signal transduction and
  2. the role of phosphorylation in signal transduction.
Regulation of the integrity of endothelial cell–cell contacts by phosphorylation of VE-cadherin

Regulation of the integrity of endothelial cell–cell contacts by phosphorylation of VE-cadherin

In addition – detailed knowledge of –

  1. the role of Tyrosine kinases and
  2. G protein-coupled receptors in cell signaling.
serine

serine

threonine

threonine

protein kinase

protein kinase

We are constantly receiving and interpreting signals from our environment, which can come

  • in the form of light, heat, odors, touch or sound.

The cells of our bodies are also

  • constantly receiving signals from other cells.

These signals are important to

  • keep cells alive and functioning as well as
  • to stimulate important events such as
  • cell division and differentiation.

Signals are most often chemicals that can be found

  • in the extracellular fluid around cells.

These chemicals can come

  • from distant locations in the body (endocrine signaling by hormones), from
  • nearby cells (paracrine signaling) or can even
  • be secreted by the same cell (autocrine signaling).

Notch-mediated juxtacrine signal between adjacent cells. 220px-Notchccr

Signaling molecules may trigger any number of cellular responses, including

  • changing the metabolism of the cell receiving the signal or
  • result in a change in gene expression (transcription) within the nucleus of the cell or both.
controlling the output of ribosomes.

controlling the output of ribosomes.

To which I would now add..

  • result in either an inhibitory or a stimulatory effect

The three stages of cell signaling are:

Cell signaling can be divided into 3 stages:

Reception: A cell detects a signaling molecule from the outside of the cell.

Transduction: When the signaling molecule binds the receptor it changes the receptor protein in some way. This change initiates the process of transduction. Signal transduction is usually a pathway of several steps. Each relay molecule in the signal transduction pathway changes the next molecule in the pathway.

Response: Finally, the signal triggers a specific cellular response.

signal transduction

signal transduction

http://www.hartnell.edu/tutorials/biology/images/signaltransduction_simple.jpg

The initiation is depicted as follows:

Signal Transduction – ligand binds to surface receptor

Membrane receptors function by binding the signal molecule (ligand) and causing the production of a second signal (also known as a second messenger) that then causes a cellular response. These types of receptors transmit information from the extracellular environment to the inside of the cell.

  • by changing shape or
  • by joining with another protein
  • once a specific ligand binds to it.

Examples of membrane receptors include

  • G Protein-Coupled Receptors and
Understanding these receptors and identifying their ligands and the resulting signal transduction pathways represent a major conceptual advance.

Understanding these receptors and identifying their ligands and the resulting signal transduction pathways represent a major conceptual advance.

  • Receptor Tyrosine Kinases.
intracellular signaling

intracellular signaling

http://www.hartnell.edu/tutorials/biology/images/membrane_receptor_tk.jpg

Intracellular receptors are found inside the cell, either in the cytopolasm or in the nucleus of the target cell (the cell receiving the signal).

Note that though change in gene expression is stated, the change in gene expression does not here imply a change in the genetic information – such as – mutation.  That does not have to be the case in the normal homeostatic case.

This point is the differentiating case between what JEDS Roselino has referred as

  1. a fast, adaptive reaction, that is the feature of protein molecules, and distinguishes this interaction from
  2. a one-to-one transcription of the genetic code.

The rate of transcription can be controlled, or it can be blocked.  This is in large part in response to the metabolites in the immediate interstitium.

This might only be

  • a change in the rate of a transcription or a suppression of expression through RNA.
  • Or through a conformational change in an enzyme
 Swinging domains in HECT E3 enzymes

Swinging domains in HECT E3 enzymes

Since signaling systems need to be

  • responsive to small concentrations of chemical signals and act quickly,
  • cells often use a multi-step pathway that transmits the signal quickly,
  • while amplifying the signal to numerous molecules at each step.

Signal transduction pathways are shown (simplified):

Signal Transduction

Signal Transduction

Signal transduction occurs when an

  1. extracellular signaling molecule activates a specific receptor located on the cell surface or inside the cell.
  2. In turn, this receptor triggers a biochemical chain of events inside the cell, creating a response.
  3. Depending on the cell, the response alters the cell’s metabolism, shape, gene expression, or ability to divide.
  4. The signal can be amplified at any step. Thus, one signaling molecule can cause many responses.

In 1970, Martin Rodbell examined the effects of glucagon on a rat’s liver cell membrane receptor. He noted that guanosine triphosphate disassociated glucagon from this receptor and stimulated the G-protein, which strongly influenced the cell’s metabolism. Thus, he deduced that the G-protein is a transducer that accepts glucagon molecules and affects the cell. For this, he shared the 1994 Nobel Prize in Physiology or Medicine with Alfred G. Gilman.

Guanosine monophosphate structure

Guanosine monophosphate structure

In 2007, a total of 48,377 scientific papers—including 11,211 e-review papers—were published on the subject. The term first appeared in a paper’s title in 1979. Widespread use of the term has been traced to a 1980 review article by Rodbell: Research papers focusing on signal transduction first appeared in large numbers in the late 1980s and early 1990s.

Signal transduction involves the binding of extracellular signaling molecules and ligands to cell-surface receptors that trigger events inside the cell. The combination of messenger with receptor causes a change in the conformation of the receptor, known as receptor activation.

This activation is always the initial step (the cause) leading to the cell’s ultimate responses (effect) to the messenger. Despite the myriad of these ultimate responses, they are all directly due to changes in particular cell proteins. Intracellular signaling cascades can be started through cell-substratum interactions; examples are the integrin that binds ligands in the extracellular matrix and steroids.

Integrin

Integrin

Most steroid hormones have receptors within the cytoplasm and act by stimulating the binding of their receptors to the promoter region of steroid-responsive genes.

steroid hormone receptor

steroid hormone receptor

Various environmental stimuli exist that initiate signal transmission processes in multicellular organisms; examples include photons hitting cells in the retina of the eye, and odorants binding to odorant receptors in the nasal epithelium. Certain microbial molecules, such as viral nucleotides and protein antigens, can elicit an immune system response against invading pathogens mediated by signal transduction processes. This may occur independent of signal transduction stimulation by other molecules, as is the case for the toll-like receptor. It may occur with help from stimulatory molecules located at the cell surface of other cells, as with T-cell receptor signaling. Receptors can be roughly divided into two major classes: intracellular receptors and extracellular receptors.

Signal transduction cascades amplify the signal output

Signal transduction cascades amplify the signal output

Signal transduction cascades amplify the signal output

G protein-coupled receptors (GPCRs) are a family of integral transmembrane proteins that possess seven transmembrane domains and are linked to a heterotrimeric G protein. Many receptors are in this family, including adrenergic receptors and chemokine receptors.

Arrestin binding to active GPCR kinase (GRK)-phosphorylated GPCRs blocks G protein coupling

signal transduction pathways

signal transduction pathways

Arrestin binding to active GPCR kinase (GRK)-phosphorylated GPCRs blocks G protein coupling

Arrestin binding to active GPCR kinase (GRK)-phosphorylated GPCRs blocks G protein coupling

Signal transduction by a GPCR begins with an inactive G protein coupled to the receptor; it exists as a heterotrimer consisting of Gα, Gβ, and Gγ. Once the GPCR recognizes a ligand, the conformation of the receptor changes to activate the G protein, causing Gα to bind a molecule of GTP and dissociate from the other two G-protein subunits.

The dissociation exposes sites on the subunits that can interact with other molecules. The activated G protein subunits detach from the receptor and initiate signaling from many downstream effector proteins such as phospholipases and ion channels, the latter permitting the release of second messenger molecules.

Receptor tyrosine kinases (RTKs) are transmembrane proteins with an intracellular kinase domain and an extracellular domain that binds ligands; examples include growth factor receptors such as the insulin receptor.

 insulin receptor and and insulin receptor signaling pathway (IRS)

insulin receptor and and insulin receptor signaling pathway (IRS)

To perform signal transduction, RTKs need to form dimers in the plasma membrane; the dimer is stabilized by ligands binding to the receptor.

RTKs

RTKs

The interaction between the cytoplasmic domains stimulates the autophosphorylation of tyrosines within the domains of the RTKs, causing conformational changes.

Allosteric_Regulation.svg

Subsequent to this, the receptors’ kinase domains are activated, initiating phosphorylation signaling cascades of downstream cytoplasmic molecules that facilitate various cellular processes such as cell differentiation and metabolism.

Signal-Transduction-Pathway

Signal-Transduction-Pathway

As is the case with GPCRs, proteins that bind GTP play a major role in signal transduction from the activated RTK into the cell. In this case, the G proteins are

  • members of the Ras, Rho, and Raf families, referred to collectively as small G proteins.

They act as molecular switches usually

  • tethered to membranes by isoprenyl groups linked to their carboxyl ends.

Upon activation, they assign proteins to specific membrane subdomains where they participate in signaling. Activated RTKs in turn activate

  • small G proteins that activate guanine nucleotide exchange factors such as SOS1.

Once activated, these exchange factors can activate more small G proteins, thus

  • amplifying the receptor’s initial signal.

The mutation of certain RTK genes, as with that of GPCRs, can result in the expression of receptors that exist in a constitutively activate state; such mutated genes may act as oncogenes.

Integrin

 

Integrin

Integrin

Integrin-mediated signal transduction

An overview of integrin-mediated signal transduction, adapted from Hehlgens et al. (2007).

Integrins are produced by a wide variety of cells; they play a role in

  • cell attachment to other cells and the extracellular matrix and
  • in the transduction of signals from extracellular matrix components such as fibronectin and collagen.

Ligand binding to the extracellular domain of integrins

  • changes the protein’s conformation,
  • clustering it at the cell membrane to
  • initiate signal transduction.

Integrins lack kinase activity; hence, integrin-mediated signal transduction is achieved through a variety of intracellular protein kinases and adaptor molecules, the main coordinator being integrin-linked kinase.

As shown in the picture, cooperative integrin-RTK signaling determines the

  1. timing of cellular survival,
  2. apoptosis,
  3. proliferation, and
  4. differentiation.
integrin-mediated signal transduction

integrin-mediated signal transduction

Integrin signaling

Integrin signaling

ion channel

A ligand-gated ion channel, upon binding with a ligand, changes conformation

  • to open a channel in the cell membrane
  • through which ions relaying signals can pass.

An example of this mechanism is found in the receiving cell of a neural synapse. The influx of ions that occurs in response to the opening of these channels

  1. induces action potentials, such as those that travel along nerves,
  2. by depolarizing the membrane of post-synaptic cells,
  3. resulting in the opening of voltage-gated ion channels.
RyR and Ca+ release from SR

RyR and Ca+ release from SR

An example of an ion allowed into the cell during a ligand-gated ion channel opening is Ca2+;

  • it acts as a second messenger
  • initiating signal transduction cascades and
  • altering the physiology of the responding cell.

This results in amplification of the synapse response between synaptic cells

  • by remodelling the dendritic spines involved in the synapse.

In eukaryotic cells, most intracellular proteins activated by a ligand/receptor interaction possess an enzymatic activity; examples include tyrosine kinase and phosphatases. Some of them create second messengers such as cyclic AMP and IP3,

cAMP

cAMP

Inositol_1,4,5-trisphosphate.svg

Inositol_1,4,5-trisphosphate.svg

  • the latter controlling the release of intracellular calcium stores into the cytoplasm.

Many adaptor proteins and enzymes activated as part of signal transduction possess specialized protein domains that bind to specific secondary messenger molecules. For example,

  • calcium ions bind to the EF hand domains of calmodulin,
  • allowing it to bind and activate calmodulin-dependent kinase.
calcium movement and RyR2 receptor

calcium movement and RyR2 receptor

PIP3 and other phosphoinositides do the same thing to the Pleckstrin homology domains of proteins such as the kinase protein AKT.

Signals can be generated within organelles, such as chloroplasts and mitochondria, modulating the nuclear
gene expression in a process called retrograde signaling.

Recently, integrative genomics approaches, in which correlation analysis has been applied on transcript and metabolite profiling data of Arabidopsis thaliana, revealed the identification of metabolites which are putatively acting as mediators of nuclear gene expression.

http://fpls.com/unraveling_retrograde_signaling_pathways:_finding_candidate_signaling_molecules_via_metabolomics_and_systems_biology_driven_approaches

Related articles

  1. Systems Biology Approach Reveals Genome to Phenome Correlation in Type 2 Diabetes (plosone.org)
  2. Gene Expression and Thiopurine Metabolite Profiling in Inflammatory Bowel Disease – Novel Clues to Drug Targets and Disease Mechanisms? (plosone.org)
  3. Activation of the Jasmonic Acid Plant Defence Pathway Alters the Composition of Rhizosphere

Nutrients 2014, 6, 3245-3258; http://dx.doi.org:/10.3390/nu6083245

Omega-3 (ω-3) fatty acids are one of the two main families of long chain polyunsaturated fatty acids (PUFA). The main omega-3 fatty acids in the mammalian body are

  • α-linolenic acid (ALA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

Central nervous tissues of vertebrates are characterized by a high concentration of omega-3 fatty acids. Moreover, in the human brain,

  • DHA is considered as the main structural omega-3 fatty acid, which comprises about 40% of the PUFAs in total.

DHA deficiency may be the cause of many disorders such as depression, inability to concentrate, excessive mood swings, anxiety, cardiovascular disease, type 2 diabetes, dry skin and so on.

On the other hand,

  • zinc is the most abundant trace metal in the human brain.

There are many scientific studies linking zinc, especially

  • excess amounts of free zinc, to cellular death.

Neurodegenerative diseases, such as Alzheimer’s disease, are characterized by altered zinc metabolism. Both animal model studies and human cell culture studies have shown a possible link between

  • omega-3 fatty acids, zinc transporter levels and
  • free zinc availability at cellular levels.

Many other studies have also suggested a possible

  • omega-3 and zinc effect on neurodegeneration and cellular death.

Therefore, in this review, we will examine

  • the effect of omega-3 fatty acids on zinc transporters and
  • the importance of free zinc for human neuronal cells.

Moreover, we will evaluate the collective understanding of

  • mechanism(s) for the interaction of these elements in neuronal research and their
  • significance for the diagnosis and treatment of neurodegeneration.

Epidemiological studies have linked high intake of fish and shellfish as part of the daily diet to

  • reduction of the incidence and/or severity of Alzheimer’s disease (AD) and senile mental decline in

Omega-3 fatty acids are one of the two main families of a broader group of fatty acids referred to as polyunsaturated fatty acids (PUFAs). The other main family of PUFAs encompasses the omega-6 fatty acids. In general, PUFAs are essential in many biochemical events, especially in early post-natal development processes such as

  • cellular differentiation,
  • photoreceptor membrane biogenesis and
  • active synaptogenesis.

Despite the significance of these

two families, mammals cannot synthesize PUFA de novo, so they must be ingested from dietary sources. Though belonging to the same family, both

  • omega-3 and omega-6 fatty acids are metabolically and functionally distinct and have
  • opposing physiological effects. In the human body,
  • high concentrations of omega-6 fatty acids are known to increase the formation of prostaglandins and
  • thereby increase inflammatory processes [10].

the reverse process can be seen with increased omega-3 fatty acids in the body.

Many other factors, such as

  1. thromboxane A2 (TXA2),
  2. leukotriene
  3. B4 (LTB4),
  4. IL-1,
  5. IL-6,
  6. tumor necrosis factor (TNF) and
  7. C-reactive protein,

which are implicated in various health conditions, have been shown to be increased with high omega-6 fatty acids but decreased with omega-3 fatty acids in the human body.

Dietary fatty acids have been identified as protective factors in coronary heart disease, and PUFA levels are known to play a critical role in

  • immune responses,
  • gene expression and
  • intercellular communications.

omega-3 fatty acids are known to be vital in

  • the prevention of fatal ventricular arrhythmias, and
  • are also known to reduce thrombus formation propensity by decreasing platelet aggregation, blood viscosity and fibrinogen levels

.Since omega-3 fatty acids are prevalent in the nervous system, it seems logical that a deficiency may result in neuronal problems, and this is indeed what has been identified and reported.

The main

In another study conducted with individuals of 65 years of age or older (n = 6158), it was found that

  • only high fish consumption, but
  • not dietary omega-3 acid intake,
  • had a protective effect on cognitive decline

In 2005, based on a meta-analysis of the available epidemiology and preclinical studies, clinical trials were conducted to assess the effects of omega-3 fatty acids on cognitive protection. Four of the trials completed have shown

a protective effect of omega-3 fatty acids only among those with mild cognitive impairment conditions.

A  trial of subjects with mild memory complaints demonstrated

  • an improvement with 900 mg of DHA.

We review key findings on

  • the effect of the omega-3 fatty acid DHA on zinc transporters and the
  • importance of free zinc to human neuronal cells.

DHA is the most abundant fatty acid in neural membranes, imparting appropriate

  • fluidity and other properties,

and is thus considered as the most important fatty acid in neuronal studies. DHA is well conserved throughout the mammalian species despite their dietary differences. It is mainly concentrated

  • in membrane phospholipids at synapses and
  • in retinal photoreceptors and
  • also in the testis and sperm.

In adult rats’ brain, DHA comprises approximately

  • 17% of the total fatty acid weight, and
  • in the retina it is as high as 33%.

DHA is believed to have played a major role in the evolution of the modern human –

  • in particular the well-developed brain.

Premature babies fed on DHA-rich formula show improvements in vocabulary and motor performance.

Analysis of human cadaver brains have shown that

  • people with AD have less DHA in their frontal lobe
  • and hippocampus compared with unaffected individuals

Furthermore, studies in mice have increased support for the

  • protective role of omega-3 fatty acids.

Mice administrated with a dietary intake of DHA showed

  • an increase in DHA levels in the hippocampus.

Errors in memory were decreased in these mice and they demonstrated

  • reduced peroxide and free radical levels,
  • suggesting a role in antioxidant defense.

Another study conducted with a Tg2576 mouse model of AD demonstrated that dietary

  • DHA supplementation had a protective effect against reduction in
  • drebrin (actin associated protein), elevated oxidation, and to some extent, apoptosis via
  • decreased caspase activity.

 

Zinc

Zinc is a trace element, which is indispensable for life, and it is the second most abundant trace element in the body. It is known to be related to

  • growth,
  • development,
  • differentiation,
  • immune response,
  • receptor activity,
  • DNA synthesis,
  • gene expression,
  • neuro-transmission,
  • enzymatic catalysis,
  • hormonal storage and release,
  • tissue repair,
  • memory,
  • the visual process

and many other cellular functions. Moreover, the indispensability of zinc to the body can be discussed in many other aspects,  as

  • a component of over 300 different enzymes
  • an integral component of a metallothioneins
  • a gene regulatory protein.

Approximately 3% of all proteins contain

  • zinc binding motifs .

The broad biological functionality of zinc is thought to be due to its stable chemical and physical properties. Zinc is considered to have three different functions in enzymes;

  1. catalytic,
  2. coactive and

Indeed, it is the only metal found in all six different subclasses

of enzymes. The essential nature of zinc to the human body can be clearly displayed by studying the wide range of pathological effects of zinc deficiency. Anorexia, embryonic and post-natal growth retardation, alopecia, skin lesions, difficulties in wound healing, increased hemorrhage tendency and severe reproductive abnormalities, emotional instability, irritability and depression are just some of the detrimental effects of zinc deficiency.

Proper development and function of the central nervous system (CNS) is highly dependent on zinc levels. In the mammalian organs, zinc is mainly concentrated in the brain at around 150 μm. However, free zinc in the mammalian brain is calculated to be around 10 to 20 nm and the rest exists in either protein-, enzyme- or nucleotide bound form. The brain and zinc relationship is thought to be mediated

  • through glutamate receptors, and
  • it inhibits excitatory and inhibitory receptors.

Vesicular localization of zinc in pre-synaptic terminals is a characteristic feature of brain-localized zinc, and

  • its release is dependent on neural activity.

Retardation of the growth and development of CNS tissues have been linked to low zinc levels. Peripheral neuropathy, spina bifida, hydrocephalus, anencephalus, epilepsy and Pick’s disease have been linked to zinc deficiency. However, the body cannot tolerate excessive amounts of zinc.

The relationship between zinc and neurodegeneration, specifically AD, has been interpreted in several ways. One study has proposed that β-amyloid has a greater propensity to

  • form insoluble amyloid in the presence of
  • high physiological levels of zinc.

Insoluble amyloid is thought to

  • aggregate to form plaques,

which is a main pathological feature of AD. Further studies have shown that

  • chelation of zinc ions can deform and disaggregate plaques.

In AD, the most prominent injuries are found in

  • hippocampal pyramidal neurons, acetylcholine-containing neurons in the basal forebrain, and in
  • somatostatin-containing neurons in the forebrain.

All of these neurons are known to favor

  • rapid and direct entry of zinc in high concentration
  • leaving neurons frequently exposed to high dosages of zinc.

This is thought to promote neuronal cell damage through oxidative stress and mitochondrial dysfunction. Excessive levels of zinc are also capable of

  • inhibiting Ca2+ and Na+ voltage gated channels
  • and up-regulating the cellular levels of reactive oxygen species (ROS).

High levels of zinc are found in Alzheimer’s brains indicating a possible zinc related neurodegeneration. A study conducted with mouse neuronal cells has shown that even a 24-h exposure to high levels of zinc (40 μm) is sufficient to degenerate cells.

If the human diet is deficient in zinc, the body

  • efficiently conserves zinc at the tissue level by compensating other cellular mechanisms

to delay the dietary deficiency effects of zinc. These include reduction of cellular growth rate and zinc excretion levels, and

  • redistribution of available zinc to more zinc dependent cells or organs.

A novel method of measuring metallothionein (MT) levels was introduced as a biomarker for the

  • assessment of the zinc status of individuals and populations.

In humans, erythrocyte metallothionein (E-MT) levels may be considered as an indicator of zinc depletion and repletion, as E-MT levels are sensitive to dietary zinc intake. It should be noted here that MT plays an important role in zinc homeostasis by acting

  • as a target for zinc ion binding and thus
  • assisting in the trafficking of zinc ions through the cell,
  • which may be similar to that of zinc transporters

Zinc Transporters

Deficient or excess amounts of zinc in the body can be catastrophic to the integrity of cellular biochemical and biological systems. The gastrointestinal system controls the absorption, excretion and the distribution of zinc, although the hydrophilic and high-charge molecular characteristics of zinc are not favorable for passive diffusion across the cell membranes. Zinc movement is known to occur

  • via intermembrane proteins and zinc transporter (ZnT) proteins

These transporters are mainly categorized under two metal transporter families; Zip (ZRT, IRT like proteins) and CDF/ZnT (Cation Diffusion Facilitator), also known as SLC (Solute Linked Carrier) gene families: Zip (SLC-39) and ZnT (SLC-30). More than 20 zinc transporters have been identified and characterized over the last two decades (14 Zips and 8 ZnTs).

Members of the SLC39 family have been identified as the putative facilitators of zinc influx into the cytosol, either from the extracellular environment or from intracellular compartments (Figure 1).

The identification of this transporter family was a result of gene sequencing of known Zip1 protein transporters in plants, yeast and human cells. In contrast to the SLC39 family, the SLC30 family facilitates the opposite process, namely zinc efflux from the cytosol to the extracellular environment or into luminal compartments such as secretory granules, endosomes and synaptic vesicles; thus decreasing intracellular zinc availability (Figure 1). ZnT3 is the most important in the brain where

  • it is responsible for the transport of zinc into the synaptic vesicles of
  • glutamatergic neurons in the hippocampus and neocortex,

Figure 1: Subcellular localization and direction of transport of the zinc transporter families, ZnT and ZIP. Arrows show the direction of zinc mobilization for the ZnT (green) and ZIP (red) proteins. A net gain in cytosolic zinc is achieved by the transportation of zinc from the extracellular region and organelles such as the endoplasmic reticulum (ER) and Golgi apparatus by the ZIP transporters. Cytosolic zinc is mobilized into early secretory compartments such as the ER and Golgi apparatus by the ZnT transporters. Figures were produced using Servier Medical Art, http://www.servier.com/.   http://www.hindawi.com/journals/jnme/2012/173712.fig.001.jpg

Figure 2: Early zinc signaling (EZS) and late zinc signaling (LZS). EZS involves transcription-independent mechanisms where an extracellular stimulus directly induces an increase in zinc levels within several minutes by releasing zinc from intracellular stores (e.g., endoplasmic reticulum). LSZ is induced several hours after an external stimulus and is dependent on transcriptional changes in zinc transporter expression. Components of this figure were produced using Servier Medical Art, http://www.servier.com/ and adapted from Fukada et al. [30].

omega-3 fatty acids in the mammalian body are

  1. α-linolenic acid (ALA),
  2. docosahexenoic acid (DHA) and
  3. eicosapentaenoic acid (EPA).

In general, seafood is rich in omega-3 fatty acids, more specifically DHA and EPA (Table 1). Thus far, there are nine separate epidemiological studies that suggest a possible link between

  • increased fish consumption and reduced risk of AD
  • and eight out of ten studies have reported a link between higher blood omega-3 levels

DHA and Zinc Homeostasis

Many studies have identified possible associations between DHA levels, zinc homeostasis, neuroprotection and neurodegeneration. Dietary DHA deficiency resulted in

  • increased zinc levels in the hippocampus and
  • elevated expression of the putative zinc transporter, ZnT3, in the rat brain.

Altered zinc metabolism in neuronal cells has been linked to neurodegenerative conditions such as AD. A study conducted with transgenic mice has shown a significant link between ZnT3 transporter levels and cerebral amyloid plaque pathology. When the ZnT3 transporter was silenced in transgenic mice expressing cerebral amyloid plaque pathology,

  • a significant reduction in plaque load
  • and the presence of insoluble amyloid were observed.

In addition to the decrease in plaque load, ZnT3 silenced mice also exhibited a significant

  • reduction in free zinc availability in the hippocampus
  • and cerebral cortex.

Collectively, the findings from this study are very interesting and indicate a clear connection between

  • zinc availability and amyloid plaque formation,

thus indicating a possible link to AD.

DHA supplementation has also been reported to limit the following:

  1. amyloid presence,
  2. synaptic marker loss,
  3. hyper-phosphorylation of Tau,
  4. oxidative damage and
  5. cognitive deficits in transgenic mouse model of AD.

In addition, studies by Stoltenberg, Flinn and colleagues report on the modulation of zinc and the effect in transgenic mouse models of AD. Given that all of these are classic pathological features of AD, and considering the limiting nature of DHA in these processes, it can be argued that DHA is a key candidate in preventing or even curing this debilitating disease.

In order to better understand the possible links and pathways of zinc and DHA with neurodegeneration, we designed a study that incorporates all three of these aspects, to study their effects at the cellular level. In this study, we were able to demonstrate a possible link between omega-3 fatty acid (DHA) concentration, zinc availability and zinc transporter expression levels in cultured human neuronal cells.

When treated with DHA over 48 h, ZnT3 levels were markedly reduced in the human neuroblastoma M17 cell line. Moreover, in the same study, we were able to propose a possible

  • neuroprotective mechanism of DHA,

which we believe is exerted through

  • a reduction in cellular zinc levels (through altering zinc transporter expression levels)
  • that in turn inhibits apoptosis.

DHA supplemented M17 cells also showed a marked depletion of zinc uptake (up to 30%), and

  • free zinc levels in the cytosol were significantly low compared to the control

This reduction in free zinc availability was specific to DHA; cells treated with EPA had no significant change in free zinc levels (unpublished data). Moreover, DHA-repleted cells had

  • low levels of active caspase-3 and
  • high Bcl-2 levels compared to the control treatment.

These findings are consistent with previous published data and further strengthen the possible

  • correlation between zinc, DHA and neurodegeneration.

On the other hand, recent studies using ZnT3 knockout (ZnT3KO) mice have shown the importance of

  • ZnT3 in memory and AD pathology.

For example, Sindreu and colleagues have used ZnT3KO mice to establish the important role of

  • ZnT3 in zinc homeostasis that modulates presynaptic MAPK signaling
  • required for hippocampus-dependent memory

Results from these studies indicate a possible zinc-transporter-expression-level-dependent mechanism for DHA neuroprotection.

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Complex Models of Signaling: Therapeutic Implications

Complex Models of Signaling: Therapeutic Implications

Curator: Larry H. Bernstein, MD, FCAP

Updated 6/24/2019

Fishy Business: Effect of Omega-3 Fatty Acids on Zinc Transporters and Free Zinc Availability in Human Neuronal Cells

Damitha De Mel and Cenk Suphioglu *

NeuroAllergy Research Laboratory (NARL), School of Life and Environmental Sciences, Faculty of Science, Engineering and Built Environment, Waurn Ponds, Victoria, Australia.

Nutrients 2014, 6, 3245-3258; http://dx.doi.org:/10.3390/nu6083245

Omega-3 (ω-3) fatty acids are one of the two main families of long chain polyunsaturated fatty acids (PUFA). The main omega-3 fatty acids in the mammalian body are

  • α-linolenic acid (ALA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

Central nervous tissues of vertebrates are characterized by a high concentration of omega-3 fatty acids. Moreover, in the human brain,

  • DHA is considered as the main structural omega-3 fatty acid, which comprises about 40% of the PUFAs in total.

DHA deficiency may be the cause of many disorders such as depression, inability to concentrate, excessive mood swings, anxiety, cardiovascular disease, type 2 diabetes, dry skin and so on.

On the other hand,

  • zinc is the most abundant trace metal in the human brain.

There are many scientific studies linking zinc, especially

  • excess amounts of free zinc, to cellular death.

Neurodegenerative diseases, such as Alzheimer’s disease, are characterized by altered zinc metabolism. Both animal model studies and human cell culture studies have shown a possible link between

  • omega-3 fatty acids, zinc transporter levels and
  • free zinc availability at cellular levels.

Many other studies have also suggested a possible

  • omega-3 and zinc effect on neurodegeneration and cellular death.

Therefore, in this review, we will examine

  • the effect of omega-3 fatty acids on zinc transporters and
  • the importance of free zinc for human neuronal cells.

Moreover, we will evaluate the collective understanding of

  • mechanism(s) for the interaction of these elements in neuronal research and their
  • significance for the diagnosis and treatment of neurodegeneration.

Epidemiological studies have linked high intake of fish and shellfish as part of the daily diet to

  • reduction of the incidence and/or severity of Alzheimer’s disease (AD) and senile mental decline in

Omega-3 fatty acids are one of the two main families of a broader group of fatty acids referred to as polyunsaturated fatty acids (PUFAs). The other main family of PUFAs encompasses the omega-6 fatty acids. In general, PUFAs are essential in many biochemical events, especially in early post-natal development processes such as

  • cellular differentiation,
  • photoreceptor membrane biogenesis and
  • active synaptogenesis.

Despite the significance of these

two families, mammals cannot synthesize PUFA de novo, so they must be ingested from dietary sources. Though belonging to the same family, both

  • omega-3 and omega-6 fatty acids are metabolically and functionally distinct and have
  • opposing physiological effects. In the human body,
  • high concentrations of omega-6 fatty acids are known to increase the formation of prostaglandins and
  • thereby increase inflammatory processes [10].

the reverse process can be seen with increased omega-3 fatty acids in the body.

Many other factors, such as

  1. thromboxane A2 (TXA2),
  2. leukotriene
  3. B4 (LTB4),
  4. IL-1,
  5. IL-6,
  6. tumor necrosis factor (TNF) and
  7. C-reactive protein,

which are implicated in various health conditions, have been shown to be increased with high omega-6 fatty acids but decreased with omega-3 fatty acids in the human body.

Dietary fatty acids have been identified as protective factors in coronary heart disease, and PUFA levels are known to play a critical role in

  • immune responses,
  • gene expression and
  • intercellular communications.

omega-3 fatty acids are known to be vital in

  • the prevention of fatal ventricular arrhythmias, and
  • are also known to reduce thrombus formation propensity by decreasing platelet aggregation, blood viscosity and fibrinogen levels

.Since omega-3 fatty acids are prevalent in the nervous system, it seems logical that a deficiency may result in neuronal problems, and this is indeed what has been identified and reported.

The main omega-3 fatty acids in the mammalian body are

  1. α-linolenic acid (ALA),
  2. docosahexenoic acid (DHA) and
  3. eicosapentaenoic acid (EPA).

In general, seafood is rich in omega-3 fatty acids, more specifically DHA and EPA (Table 1). Thus far, there are nine separate epidemiological studies that suggest a possible link between

  • increased fish consumption and reduced risk of AD
  • and eight out of ten studies have reported a link between higher blood omega-3 levels

Table 1. Total percentage of omega-3 fatty acids in common foods and supplements.

Food/Supplement EPA DHA ALA Total %
Fish
SalmonSardine

Anchovy

Halibut

Herring

Mackerel

Tuna

Fresh Bluefin

XX

X

X

X

X

X

X

XX

X

X

X

X

X

X

>50%>50%

>50%

>50%

>50%

>50%

>50%

>50%

Oils/Supplements
Fish oil capsulesCod liver oils

Salmon oil

Sardine oil

XX

X

X

XX

X

X

>50%>50%

>50%

>50%

Black currant oilCanola oil Mustard seed oils

Soybean oil

Walnut oil

Wheat germ oil

XX

X

X

X

X

10%–50%10%–50%

10%–50%

10%–50%

10%–50%

10%–50%

Seeds and other foods
Flaxseeds/LinseedsSpinach

Wheat germ Human milk

Peanut butter

Soybeans

Olive oil

Walnuts

XX

X

X

X

X

X

X

>50%>50%

10%–50%

10%–50%

<10%

<10%

<10%

<10%

 

Table adopted from Maclean C.H. et al. [18].

In another study conducted with individuals of 65 years of age or older (n = 6158), it was found that

  • only high fish consumption, but
  • not dietary omega-3 acid intake,
  • had a protective effect on cognitive decline

In 2005, based on a meta-analysis of the available epidemiology and preclinical studies, clinical trials were conducted to assess the effects of omega-3 fatty acids on cognitive protection. Four of the trials completed have shown

a protective effect of omega-3 fatty acids only among those with mild cognitive impairment conditions.

A  trial of subjects with mild memory complaints demonstrated

  • an improvement with 900 mg of DHA.

We review key findings on

  • the effect of the omega-3 fatty acid DHA on zinc transporters and the
  • importance of free zinc to human neuronal cells.

DHA is the most abundant fatty acid in neural membranes, imparting appropriate

  • fluidity and other properties,

and is thus considered as the most important fatty acid in neuronal studies. DHA is well conserved throughout the mammalian species despite their dietary differences. It is mainly concentrated

  • in membrane phospholipids at synapses and
  • in retinal photoreceptors and
  • also in the testis and sperm.

In adult rats’ brain, DHA comprises approximately

  • 17% of the total fatty acid weight, and
  • in the retina it is as high as 33%.

DHA is believed to have played a major role in the evolution of the modern human –

  • in particular the well-developed brain.

Premature babies fed on DHA-rich formula show improvements in vocabulary and motor performance.

Analysis of human cadaver brains have shown that

  • people with AD have less DHA in their frontal lobe
  • and hippocampus compared with unaffected individuals

Furthermore, studies in mice have increased support for the

  • protective role of omega-3 fatty acids.

Mice administrated with a dietary intake of DHA showed

  • an increase in DHA levels in the hippocampus.

Errors in memory were decreased in these mice and they demonstrated

  • reduced peroxide and free radical levels,
  • suggesting a role in antioxidant defense.

Another study conducted with a Tg2576 mouse model of AD demonstrated that dietary

  • DHA supplementation had a protective effect against reduction in
  • drebrin (actin associated protein), elevated oxidation, and to some extent, apoptosis via
  • decreased caspase activity.

 

Zinc

Zinc is a trace element, which is indispensable for life, and it is the second most abundant trace element in the body. It is known to be related to

  • growth,
  • development,
  • differentiation,
  • immune response,
  • receptor activity,
  • DNA synthesis,
  • gene expression,
  • neuro-transmission,
  • enzymatic catalysis,
  • hormonal storage and release,
  • tissue repair,
  • memory,
  • the visual process

and many other cellular functions. Moreover, the indispensability of zinc to the body can be discussed in many other aspects,  as

  • a component of over 300 different enzymes
  • an integral component of a metallothioneins
  • a gene regulatory protein.

Approximately 3% of all proteins contain

  • zinc binding motifs .

The broad biological functionality of zinc is thought to be due to its stable chemical and physical properties. Zinc is considered to have three different functions in enzymes;

  1. catalytic,
  2. coactive and

Indeed, it is the only metal found in all six different subclasses

of enzymes. The essential nature of zinc to the human body can be clearly displayed by studying the wide range of pathological effects of zinc deficiency. Anorexia, embryonic and post-natal growth retardation, alopecia, skin lesions, difficulties in wound healing, increased hemorrhage tendency and severe reproductive abnormalities, emotional instability, irritability and depression are just some of the detrimental effects of zinc deficiency.

Proper development and function of the central nervous system (CNS) is highly dependent on zinc levels. In the mammalian organs, zinc is mainly concentrated in the brain at around 150 μm. However, free zinc in the mammalian brain is calculated to be around 10 to 20 nm and the rest exists in either protein-, enzyme- or nucleotide bound form. The brain and zinc relationship is thought to be mediated

  • through glutamate receptors, and
  • it inhibits excitatory and inhibitory receptors.

Vesicular localization of zinc in pre-synaptic terminals is a characteristic feature of brain-localized zinc, and

  • its release is dependent on neural activity.

Retardation of the growth and development of CNS tissues have been linked to low zinc levels. Peripheral neuropathy, spina bifida, hydrocephalus, anencephalus, epilepsy and Pick’s disease have been linked to zinc deficiency. However, the body cannot tolerate excessive amounts of zinc.

The relationship between zinc and neurodegeneration, specifically AD, has been interpreted in several ways. One study has proposed that β-amyloid has a greater propensity to

  • form insoluble amyloid in the presence of
  • high physiological levels of zinc.

Insoluble amyloid is thought to

  • aggregate to form plaques,

which is a main pathological feature of AD. Further studies have shown that

  • chelation of zinc ions can deform and disaggregate plaques.

In AD, the most prominent injuries are found in

  • hippocampal pyramidal neurons, acetylcholine-containing neurons in the basal forebrain, and in
  • somatostatin-containing neurons in the forebrain.

All of these neurons are known to favor

  • rapid and direct entry of zinc in high concentration
  • leaving neurons frequently exposed to high dosages of zinc.

This is thought to promote neuronal cell damage through oxidative stress and mitochondrial dysfunction. Excessive levels of zinc are also capable of

  • inhibiting Ca2+ and Na+ voltage gated channels
  • and up-regulating the cellular levels of reactive oxygen species (ROS).

High levels of zinc are found in Alzheimer’s brains indicating a possible zinc related neurodegeneration. A study conducted with mouse neuronal cells has shown that even a 24-h exposure to high levels of zinc (40 μm) is sufficient to degenerate cells.

If the human diet is deficient in zinc, the body

  • efficiently conserves zinc at the tissue level by compensating other cellular mechanisms

to delay the dietary deficiency effects of zinc. These include reduction of cellular growth rate and zinc excretion levels, and

  • redistribution of available zinc to more zinc dependent cells or organs.

A novel method of measuring metallothionein (MT) levels was introduced as a biomarker for the

  • assessment of the zinc status of individuals and populations.

In humans, erythrocyte metallothionein (E-MT) levels may be considered as an indicator of zinc depletion and repletion, as E-MT levels are sensitive to dietary zinc intake. It should be noted here that MT plays an important role in zinc homeostasis by acting

  • as a target for zinc ion binding and thus
  • assisting in the trafficking of zinc ions through the cell,
  • which may be similar to that of zinc transporters

Zinc Transporters

Deficient or excess amounts of zinc in the body can be catastrophic to the integrity of cellular biochemical and biological systems. The gastrointestinal system controls the absorption, excretion and the distribution of zinc, although the hydrophilic and high-charge molecular characteristics of zinc are not favorable for passive diffusion across the cell membranes. Zinc movement is known to occur

  • via intermembrane proteins and zinc transporter (ZnT) proteins

These transporters are mainly categorized under two metal transporter families; Zip (ZRT, IRT like proteins) and CDF/ZnT (Cation Diffusion Facilitator), also known as SLC (Solute Linked Carrier) gene families: Zip (SLC-39) and ZnT (SLC-30). More than 20 zinc transporters have been identified and characterized over the last two decades (14 Zips and 8 ZnTs).

Members of the SLC39 family have been identified as the putative facilitators of zinc influx into the cytosol, either from the extracellular environment or from intracellular compartments (Figure 1).

The identification of this transporter family was a result of gene sequencing of known Zip1 protein transporters in plants, yeast and human cells. In contrast to the SLC39 family, the SLC30 family facilitates the opposite process, namely zinc efflux from the cytosol to the extracellular environment or into luminal compartments such as secretory granules, endosomes and synaptic vesicles; thus decreasing intracellular zinc availability (Figure 1). ZnT3 is the most important in the brain where

  • it is responsible for the transport of zinc into the synaptic vesicles of
  • glutamatergic neurons in the hippocampus and neocortex,

 

Figure 1. Putative cellular localization of some of the different human zinc transporters (i.e., Zip1- Zip4 and ZnT1- ZnT7). Arrows indicate the direction of zinc passage by the appropriate putative zinc transporters in a generalized human cell. Although there are fourteen Zips and eight ZnTs known so far, only the main zinc transporters are illustrated in this figure for clarity and brevity.

Figure 1: Subcellular localization and direction of transport of the zinc transporter families, ZnT and ZIP. Arrows show the direction of zinc mobilization for the ZnT (green) and ZIP (red) proteins. A net gain in cytosolic zinc is achieved by the transportation of zinc from the extracellular region and organelles such as the endoplasmic reticulum (ER) and Golgi apparatus by the ZIP transporters. Cytosolic zinc is mobilized into early secretory compartments such as the ER and Golgi apparatus by the ZnT transporters. Figures were produced using Servier Medical Art, http://www.servier.com/.   http://www.hindawi.com/journals/jnme/2012/173712.fig.001.jpg

zinc transporters

zinc transporters

 

 

Early zinc signaling (EZS) and late zinc signaling (LZS)

Early zinc signaling (EZS) and late zinc signaling (LZS)

http://www.hindawi.com/journals/jnme/2012/floats/173712/thumbnails/173712.fig.002_th.jpg

 

Figure 2: Early zinc signaling (EZS) and late zinc signaling (LZS). EZS involves transcription-independent mechanisms where an extracellular stimulus directly induces an increase in zinc levels within several minutes by releasing zinc from intracellular stores (e.g., endoplasmic reticulum). LSZ is induced several hours after an external stimulus and is dependent on transcriptional changes in zinc transporter expression. Components of this figure were produced using Servier Medical Art, http://www.servier.com/ and adapted from Fukada et al. [30].

 

DHA and Zinc Homeostasis

Many studies have identified possible associations between DHA levels, zinc homeostasis, neuroprotection and neurodegeneration. Dietary DHA deficiency resulted in

  • increased zinc levels in the hippocampus and
  • elevated expression of the putative zinc transporter, ZnT3, in the rat brain.

Altered zinc metabolism in neuronal cells has been linked to neurodegenerative conditions such as AD. A study conducted with transgenic mice has shown a significant link between ZnT3 transporter levels and cerebral amyloid plaque pathology. When the ZnT3 transporter was silenced in transgenic mice expressing cerebral amyloid plaque pathology,

  • a significant reduction in plaque load
  • and the presence of insoluble amyloid were observed.

In addition to the decrease in plaque load, ZnT3 silenced mice also exhibited a significant

  • reduction in free zinc availability in the hippocampus
  • and cerebral cortex.

Collectively, the findings from this study are very interesting and indicate a clear connection between

  • zinc availability and amyloid plaque formation,

thus indicating a possible link to AD.

DHA supplementation has also been reported to limit the following:

  1. amyloid presence,
  2. synaptic marker loss,
  3. hyper-phosphorylation of Tau,
  4. oxidative damage and
  5. cognitive deficits in transgenic mouse model of AD.

In addition, studies by Stoltenberg, Flinn and colleagues report on the modulation of zinc and the effect in transgenic mouse models of AD. Given that all of these are classic pathological features of AD, and considering the limiting nature of DHA in these processes, it can be argued that DHA is a key candidate in preventing or even curing this debilitating disease.

In order to better understand the possible links and pathways of zinc and DHA with neurodegeneration, we designed a study that incorporates all three of these aspects, to study their effects at the cellular level. In this study, we were able to demonstrate a possible link between omega-3 fatty acid (DHA) concentration, zinc availability and zinc transporter expression levels in cultured human neuronal cells.

When treated with DHA over 48 h, ZnT3 levels were markedly reduced in the human neuroblastoma M17 cell line. Moreover, in the same study, we were able to propose a possible

  • neuroprotective mechanism of DHA,

which we believe is exerted through

  • a reduction in cellular zinc levels (through altering zinc transporter expression levels)
  • that in turn inhibits apoptosis.

DHA supplemented M17 cells also showed a marked depletion of zinc uptake (up to 30%), and

  • free zinc levels in the cytosol were significantly low compared to the control

This reduction in free zinc availability was specific to DHA; cells treated with EPA had no significant change in free zinc levels (unpublished data). Moreover, DHA-repleted cells had

  • low levels of active caspase-3 and
  • high Bcl-2 levels compared to the control treatment.

These findings are consistent with previous published data and further strengthen the possible

  • correlation between zinc, DHA and neurodegeneration.

On the other hand, recent studies using ZnT3 knockout (ZnT3KO) mice have shown the importance of

  • ZnT3 in memory and AD pathology.

For example, Sindreu and colleagues have used ZnT3KO mice to establish the important role of

  • ZnT3 in zinc homeostasis that modulates presynaptic MAPK signaling
  • required for hippocampus-dependent memory

Results from these studies indicate a possible zinc-transporter-expression-level-dependent mechanism for DHA neuroprotection.

Collectively from these studies, the following possible mechanism can be proposed (Figure 2).

possible benefits of DHA in neuroprotection through reduction of ZnT3 transporter

possible benefits of DHA in neuroprotection through reduction of ZnT3 transporter

 

Figure 2. Proposed neuroprotection mechanism of docosahexaenoic acid (DHA) in reference to synaptic zinc. Schematic diagram showing possible benefits of DHA in neuroprotection through reduction of ZnT3 transporter expression levels in human neuronal cells, which results in a reduction of zinc flux and thus lowering zinc concentrations in neuronal synaptic vesicles, and therefore contributing to a lower incidence of neurodegenerative diseases (ND), such as Alzheimer’s disease (AD).

More recent data from our research group have also shown a link between the expression levels of histone H3 and H4 proteins in human neuronal cells in relation to DHA and zinc. Following DHA treatment, both H3 and H4 levels were up-regulated. In contrast, zinc treatment resulted in a down-regulation of histone levels. Both zinc and DHA have shown opposing effects on histone post-translational modifications, indicating a possible distinctive epigenetic pattern. Upon treatment with zinc, M17 cells displayed an increase in histone deacetylase (HDACs) and a reduction in histone acetylation. Conversely, with DHA treatment, HDAC levels were significantly reduced and the acetylation of histones was up-regulated. These findings also support a possible interaction between DHA and zinc availability.

Conclusions

It is possible to safely claim that there is more than one potential pathway by which DHA and zinc interact at a cellular level, at least in cultured human neuronal cells. Significance and importance of both DHA and zinc in neuronal survival is attested by the presence of these multiple mechanisms.
Most of these reported studies were conducted using human neuroblastoma cells, or similar cell types, due to the lack of live mature human neuronal cells. Thus, the results may differ from results achieved under actual human physiological conditions due to the structural and functional differences between these cells and mature human neurons. Therefore, an alternative approach that can mimic the human neuronal cells more effectively would be advantageous.

Sphingosine-1-phosphate signaling as a therapeutic target          

E Giannoudaki, DJ Swan, JA Kirby, S Ali

Applied Immunobiology and Transplantation Research Group, Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK

Cell Health and Cytoskeleton 2012; 4: 63–72

S1P is a 379Da member of the lysophospholipid family. It is the direct metabolite of sphingosine through the action of two sphingosine kinases, SphK1 and SphK2. The main metabolic pathway starts with the hydrolysis of sphingomyelin, a membrane sphingolipid, into ceramide by the enzyme sphingomyelinase and the subsequent production of sphingosine by ceramidase (Figure 1). Ceramide can also be produced de novo in the endoplasmic reticulum (ER) from serine and palmitoyl coenzyme A through multiple intermediates. S1P production is regulated by various S1P-specific and general lipid phosphatases, as well as S1P lyase, which irreversibly degrades S1P into phosphoethanolamine and hexadecanal. The balance between intracellular S1P and its metabolite ceramide can determine cellular fate. Ceramide promotes apoptosis, while S1P suppresses cell death and promotes cell survival. This creates an S1P ceramide “rheostat” inside the cells. S1P lyase expression in tissue is higher than it is in erythrocytes and platelets, the main “suppliers” of S1P in blood. This causes a tissue–blood gradient of S1P, which is important in many S1P-mediated responses, like the lymphocyte egress from lymphoid organs.

S1P signaling overview

S1P is produced inside cells; however, it can also be found extracellularly, in a variety of different tissues. It is abundant in the blood, at concentrations of 0.4–1.5 μM, where it is mainly secreted by erythrocytes and platelets. Blood S1P can be found separately, but mainly it exists in complexes with high-density lipoprotein (HDL) (∼60%).  Many of the cardioprotective effects of HDL are hypothesized to involve S1P. Before 1996, S1P was thought to act mainly intracellularly as a second messenger. However, the identification of several GPCRs that bind S1P led to the initiation of many studies on

  • extracellular S1P signaling through those receptors.

There are five receptors that have been identified currently. These can be coupled with different G-proteins. Assuming that each receptor coupling with a G protein has a slightly different function, one can recognize the complexity of S1P receptor signaling.

S1P as a second messenger

S1P is involved in many cellular processes through its GPCR signaling; studies demonstrate that S1P also acts at an intracellular level. Intracellular S1P plays a role in maintaining the balance of cell survival signal toward apoptotic signals, creating a

  • cell “rheostat” between S1P and its precursor ceramide.

Important evidence that S1P can act intracellularly as a second messenger came from yeast (Saccharomyces cerevisiae) and plant (Arabidopsis thaliana) cells. Yeast cells do not express any S1P receptors, although they can be affected by S1P during heat-shock responses. Similarly, Arabidopsis has only one GPCR-like protein, termed “GCR1,” which does not bind S1P, although S1P regulates stomata closure during drought.

Sphingosine-1-phosphate

Sphingosine-1-phosphate

In mammals, the sphingosine kinases have been found to localize in different cell compartments, being responsible for the accumulation of S1P in those compartments to give intracellular signals. In mitochondria, for instance,

  • S1P was recently found to interact with prohibitin 2,

a conserved protein that maintains mitochondria assembly and function. According to the same study,

SphK2 is the major producer of S1P in mitochondria and the knockout of its gene can cause

  • disruption of mitochondrial respiration and cytochrome c oxidase function.

SphK2 is also present in the nucleus of many cells and has been implicated to cause cell cycle arrest, and it causes S1P accumulation in the nucleus. It seems that nuclear S1P is affiliated with the histone deacetylases HDAC1 and HDAC2,

  • inhibiting their activity, thus having an indirect effect in epigenetic regulation of gene expression.

In the ER, SphK2 has been identified to translocate during stress, and promote apoptosis. It seems that S1P has specific targets in the ER that cause apoptosis, probably through calcium mobilization signals.

Sphingosine 1-phosphate (S1P) is a small bioactive lipid molecule that is involved in several processes both intracellularly and extracellularly. It acts intracellularly

  • to promote the survival and growth of the cell,

through its interaction with molecules in different compartments of the cell.

It can also exist at high concentrations extracellularly, in the blood plasma and lymph. This causes an S1P gradient important for cell migration. S1P signals through five G protein-coupled receptors, S1PR1–S1PR5, whose expression varies in different types of cells and tissue. S1P signaling can be involved in physiological and pathophysiological conditions of the cardiovascular, nervous, and immune systems and diseases such as ischemia/reperfusion injury, autoimmunity, and cancer. In this review, we discuss how it can be used to discover novel therapeutic targets.

The involvement of S1P signaling in disease

In a mouse model of myocardial ischemia-reperfusion injury (IRI), S1P and its carrier, HDL, can help protect myocardial tissue and decrease the infarct size. It seems they reduce cardiomyocyte apoptosis and neutrophil recruitment to the ischemic tissue and may decrease leukocyte adhesion to the endothelium. This effect appears to be S1PR3 mediated, since in S1PR3 knockout mice it is alleviated.

Ischemia activates SphK1, which is then translocated to the plasma membrane. This leads to an increase of intracellular S1P, helping to promote cardiomyocyte survival against apoptosis, induced by ceramide. SphK1 knockout mice cannot be preconditioned against IRI, whereas SphK1 gene induction in the heart protects it from IRI. Interestingly, a recent study shows SphK2 may also play a role, since its knockout reduces the cardioprotective effects of preconditioning. Further, administration of S1P or sphingosine during reperfusion results in better recovery and attenuation of damage to cardiomyocytes. As with preconditioning, SphK1 deficiency also affects post-conditioning of mouse hearts after ischemia reperfusion (IR).

S1P does not only protect the heart from IRI. During intestinal IR, multiple organs can be damaged, including the lungs. S1P treatment of mice during intestinal IR seems to have a protective effect on lung injury, probably due to suppression of iNOS-induced nitric oxide generation. In renal IRI, SphK1 seems to be important, since its deficiency increased the damage in kidney tissue, whereas the lentiviral overexpression of the SphK1 gene protected from injury. Another study suggests that, after IRI, apoptotic renal cells release S1P, which recruits macrophages through S1PR3 activation and might contribute to kidney regeneration and restoration of renal epithelium. However, SphK2 is negatively implicated in hepatic IRI, its inhibition helping protect hepatocytes and restoring mitochondrial function.

Further studies are implicating S1P signaling or sphingosine kinases in several kinds of cancer as well as autoimmune diseases.

Figure 2 FTY720-P causes retention of T cells in the lymph nodes.

Notes: C57BL/6 mice were injected with BALB/c splenocytes in the footpad to create an allogenic response then treated with FTY720-P or vehicle every day on days 2 to 5. On day 6, the popliteal lymph nodes were removed. Popliteal node-derived cells were mixed with BALB/c splenocytes in interferon gamma (IFN-γ) cultured enzyme-linked immunosorbent spot reactions. Bars represent the mean number of IFN-γ spot-forming cells per 1000 popliteal node-derived cells, from six mice treated with vehicle and seven with FTY720-P. **P , 0.01.  (not shown)

Fingolimod (INN, trade name Gilenya, Novartis) is an immunomodulating drug, approved for treating multiple sclerosis. It has reduced the rate of relapses in relapsing-remitting multiple sclerosis by over half. Fingolimod is a sphingosine-1-phosphate receptor modulator, which sequesters lymphocytes in lymph nodes, preventing them from contributing to an autoimmune reaction.

Fingolimod3Dan

Fingolimod3Dan

 

http://upload.wikimedia.org/wikipedia/commons/thumb/4/48/Fingolimod3Dan.gif/200px-Fingolimod3Dan.gif

The S1P antagonist FTY720 has been approved by the US Food and Drug Administration to be used as a drug against multiple sclerosis (MS). FTY720 is in fact a prodrug, since it is phosphorylated in vivo by SphK2 into FTY720-P, an S1P structural analog, which can activate S1PR1, 3, 4, and 5. FTY720-P binding to S1PR1 causes internalization of the receptor, as does S1P – but instead of recycling it back to the cell surface, it promotes its ubiquitination and degradation at the proteasome. This has a direct effect on lymphocyte trafficking through the lymph nodes, since it relies on S1PR1 signaling and S1P gradient (Figure 2). In MS, it stops migrating lymphocytes into the brain, but it may also have direct effects on the CNS through neuroprotection. FTY720 can pass the blood–brain barrier and it could be phosphorylated by local sphingosine kinases to act through S1PR1 and S1PR3 receptors that are mainly expressed in the CNS. In MS lesions, astrocytes upregulate those two receptors and it has been shown that FTY720-P treatment in vitro inhibits astrocyte production of inflammatory cytokines. A recent study confirms the importance of S1PR3 signaling on activated astrocytes, as well as SphK1, that are upregulated and promote the secretion of the potentially neuroprotective cytokine CXCL-1.

There are several studies implicating the intracellular S1P ceramide rheostat to cancer cell survival or apoptosis and resistance to chemotherapy or irradiation in vitro. Studies with SphK1 inhibition in pancreatic, prostate cancers, and leukemia, show increased ceramide/S1P ratio and induction of apoptosis. However, S1P receptor signaling plays conflicting roles in cancer cell migration and metastasis.

Modulation of S1P signaling: therapeutic potential

S1P signaling can be involved in many pathophysiological conditions. This means that we could look for therapeutic targets in all the molecules taking part in S1P signaling and production, most importantly the S1P receptors and the sphingosine kinases. S1P agonists and antagonists could also be used to modulate S1P signaling during pathological conditions.

S1P can have direct effects on the cardiovascular system. During IRI, intracellular S1P can protect the cardiomyocytes and promote their survival. Pre- or post-conditioning of the heart with S1P could be used as a treatment, but upregulation of sphingosine kinases could also increase intracellular S1P bioavailability. S1P could also have effects on endothelial cells and neutrophil trafficking. Vascular endothelial cells mainly express S1PR1 and S1PR3; only a few types express S1PR2. S1PR1 and S1PR3 activation on these cells has been shown to enhance their chemotactic migration, probably through direct phosphorylation of S1PR1 by Akt, in a phosphatidylinositol 3-kinase and Rac1-dependent signaling pathway. Moreover, it stimulates endothelial cell proliferation through an ERK pathway. S1PR2 activation, however, inhibits endothelial cell migration, morphogenesis, and angiogenesis, most likely through Rho-dependent inhibition of Rac signaling pathway, as Inoki et al showed in mouse cells with the use of S1PR1 and S1PR3 specific antagonists.

Regarding permeability of the vascular endothelium and endothelial barrier integrity, S1P receptors can have different effects. S1PR1 activation enhances endothelial barrier integrity by stimulation of cellular adhesion and upregulation of adhesion molecules. However, S1PR2 and S1PR3 have been shown to have barrier-disrupting effects in vitro, and vascular permeability increasing effects in vivo. All the effects S1P can have on vascular endothelium and smooth muscle cells suggest that activation of S1PR2, not S1PR1 and S1PR3, signaling, perhaps with the use of S1PR2 specific agonists, could be used therapeutically to inhibit angiogenesis and disrupt vasculature, suppressing tumor growth and progression.

An important aspect of S1P signaling that is being already therapeutically targeted, but could be further investigated, is immune cell trafficking. Attempts have already been made to regulate lymphocyte cell migration with the use of the drug FTY720, whose phosphorylated form can inhibit the cells S1PR1-dependent egress from the lymph nodes, causing lymphopenia. FTY720 is used as an immunosuppressant for MS but is also being investigated for other autoimmune conditions and for transplantation. Unfortunately, Phase II and III clinical trials for the prevention of kidney graft rejection have not shown an advantage over standard therapies. Moreover, FTY720 can have some adverse cardiac effects, such as bradycardia. However, there are other S1PR1 antagonists that could be considered instead, including KRP-203, AUY954, and SEW2871. KRP-203 in particular has been shown to prolong rat skin and heart allograft survival and attenuate chronic rejection without causing bradycardia, especially when combined with other immunomodulators.

There are studies that argue S1P pretreatment has a negative effect on neutrophil chemotaxis toward the chemokine CXCL-8 (interleukin-8) or the potent chemoattractant formyl-methionyl-leucyl-phenylalanine. S1P pretreatment might also inhibit trans-endothelial migration of neutrophils, without affecting their adhesion to the endothelium. S1P effects on neutrophil migration toward CXCL-8 might be the result of S1PRs cross-linking with the CXCL-8 receptors in neutrophils, CXCR-1 and CXCR-2. Indeed, there is evidence suggesting S1PR4 and S1PR3 form heterodimers with CXCR-1 in neutrophils. Another indication that S1P plays a role in neutrophil trafficking is a recent paper on S1P lyase deficiency, a deficiency that impairs neutrophil migration from blood to tissue in knockout mice.

S1P lyase and S1PRs in neutrophils may be new therapeutic targets against IRI and inflammatory conditions in general. Consistent with these results, another study has shown that inhibition of S1P lyase can have a protective effect on the heart after IRI and this effect is alleviated when pretreated with an S1PR1 and S1PR3 antagonist. Inhibition was achieved with a US Food and Drug Administration-approved food additive, 2-acetyl-4-tetrahydroxybutylimidazole, providing a possible new drug perspective. Another S1P lyase inhibitor, LX2931, a synthetic analog of 2-acetyl-4-tetrahydroxybutylimidazole, has been shown to cause peripheral lymphopenia when administered in mice, providing a potential treatment for autoimmune diseases and prevention of graft rejection in transplantation. This molecule is currently under Phase II clinical trials in rheumatoid arthritis patients.

S1P signaling research has the potential to discover novel therapeutic targets. S1P signaling is involved in many physiological and pathological processes. However, the complexity of S1P signaling makes it necessary to consider every possible pathway, either through its GPCRs, or intracellularly, with S1P as a second messenger. Where the activation of one S1P receptor may lead to the desired outcome, the simultaneous activation of another S1P receptor may lead to the opposite outcome. Thus, if we are to target a specific signaling pathway, we might need specific agonists for S1P receptors to activate one S1P receptor pathway, while, at the same time, we might need to inhibit another through S1P receptor antagonists.

Evidence of sphingolipid signaling in cancer

Biologically active lipids are important cellular signaling molecules and play a role in cell communication and cancer cell proliferation, and cancer stem cell biology.  A recent study in ovarian cancer cell lines shows that exogenous sphingosine 1 phosphate (SIP1) or overexpression of the sphingosine kinase (SPHK1) increases ovarian cancer cell proliferation, invasion and contributes to cancer stem cell like phenotype.  The diabetes drug metformin was shown to be an inhibitor of SPHK1 and reduce ovarian cancer tumor growth.

 2019 Apr;17(4):870-881. doi: 10.1158/1541-7786.MCR-18-0409. Epub 2019 Jan 17.

SPHK1 Is a Novel Target of Metformin in Ovarian Cancer.

Abstract

The role of phospholipid signaling in ovarian cancer is poorly understood. Sphingosine-1-phosphate (S1P) is a bioactive metabolite of sphingosine that has been associated with tumor progression through enhanced cell proliferation and motility. Similarly, sphingosine kinases (SPHK), which catalyze the formation of S1P and thus regulate the sphingolipid rheostat, have been reported to promote tumor growth in a variety of cancers. The findings reported here show that exogenous S1P or overexpression of SPHK1 increased proliferation, migration, invasion, and stem-like phenotypes in ovarian cancer cell lines. Likewise, overexpression of SPHK1 markedly enhanced tumor growth in a xenograft model of ovarian cancer, which was associated with elevation of key markers of proliferation and stemness. The diabetes drug, metformin, has been shown to have anticancer effects. Here, we found that ovarian cancer patients taking metformin had significantly reduced serum S1P levels, a finding that was recapitulated when ovarian cancer cells were treated with metformin and analyzed by lipidomics. These findings suggested that in cancer the sphingolipid rheostat may be a novel metabolic target of metformin. In support of this, metformin blocked hypoxia-induced SPHK1, which was associated with inhibited nuclear translocation and transcriptional activity of hypoxia-inducible factors (HIF1α and HIF2α). Further, ovarian cancer cells with high SPHK1 were found to be highly sensitive to the cytotoxic effects of metformin, whereas ovarian cancer cells with low SPHK1 were resistant. Together, the findings reported here show that hypoxia-induced SPHK1 expression and downstream S1P signaling promote ovarian cancer progression and that tumors with high expression of SPHK1 or S1P levels might have increased sensitivity to the cytotoxic effects of metformin. IMPLICATIONS: Metformin targets sphingolipid metabolism through inhibiting SPHK1, thereby impeding ovarian cancer cell migration, proliferation, and self-renewal.

Nrf2:INrf2(Keap1) Signaling in Oxidative Stress

James W. Kaspar, Suresh K. Niture, and Anil K. Jaiswal*

Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD

Free Radic Biol Med. 2009 Nov 1; 47(9): 1304–1309. http://dx.doi.org:/10.1016/j.freeradbiomed.2009.07.035

Nrf2:INrf2(Keap1) are cellular sensors of chemical and radiation induced oxidative and electrophilic stress. Nrf2 is a nuclear transcription factor that

  • controls the expression and coordinated induction of a battery of defensive genes encoding detoxifying enzymes and antioxidant proteins.

This is a mechanism of critical importance for cellular protection and cell survival. Nrf2 is retained in the cytoplasm by an inhibitor INrf2. INrf2 functions as an adapter for

  • Cul3/Rbx1 mediated degradation of Nrf2.
  • In response to oxidative/electrophilic stress,
  • Nrf2 is switched on and then off by distinct

early and delayed mechanisms.

Oxidative/electrophilic modification of INrf2cysteine151 and/or PKC phosphorylation of Nrf2serine40 results in the escape or release of Nrf2 from INrf2. Nrf2 is stabilized and translocates to the nucleus, forms heterodimers with unknown proteins, and binds antioxidant response element (ARE) that leads to coordinated activation of gene expression. It takes less than fifteen minutes from the time of exposure

  • to switch on nuclear import of Nrf2.

This is followed by activation of a delayed mechanism that controls

  • switching off of Nrf2 activation of gene expression.

GSK3β phosphorylates Fyn at unknown threonine residue(s) leading to

  • nuclear localization of Fyn.

Fyn phosphorylates Nrf2tyrosine568 resulting in

  • nuclear export of Nrf2,
  • binding with INrf2 and
  • degradation of Nrf2.

The switching on and off of Nrf2 protects cells against free radical damage, prevents apoptosis and promotes cell survival.

NPRA-mediated suppression of AngII-induced ROS production contributes to the antiproliferative effects of B-type natriuretic peptide in VSMC

Pan Gao, De-Hui Qian, Wei Li,  Lan Huang
Mol Cell Biochem (2009) 324:165–172

http://dx.doi.org/10.1007/s11010-008-9995-y

Excessive proliferation of vascular smooth cells (VSMCs) plays a critical role in the pathogenesis of diverse vascular disorders, and inhibition of VSMCs proliferation has been proved to be beneficial to these diseases.

In this study, we investigated the antiproliferative effect of

  • B-type natriuretic peptide (BNP), a natriuretic peptide with potent antioxidant capacity,

on rat aortic VSMCs, and the possible mechanisms involved. The results indicate that

  • BNP potently inhibited Angiotensin II (AngII)-induced VSMCs proliferation,

as evaluated by [3H]-thymidine incorporation assay. Consistently, BNP significantly decreased

  • AngII-induced intracellular reactive oxygen species (ROS)
  • and NAD(P)H oxidase activity.

8-Br-cGMP, a cGMP analog,

  • mimicked these effects.

To confirm its mechanism, siRNA of natriuretic peptide receptor-A(NRPA) strategy technology was used

  • to block cGMP production in VSMCs, and
  • siNPRA attenuated the inhibitory effects of BNP in VSMCs.

Taken together, these results indicate that

  • BNP was capable of inhibiting VSMCs proliferation by
  • NPRA/cGMP pathway,

which might be associated with

  • the suppression of ROS production.

These results might be related, at least partly, to the anti-oxidant property of BNP.

Cellular prion protein is required for neuritogenesis: fine-tuning of multiple signaling pathways involved in focal adhesions and actin cytoskeleton dynamics

A Alleaume-Butaux, C Dakowski, M Pietri, S Mouillet-Richard, Jean-Marie Launay, O Kellermann, B Schneider

1INSERM, UMR-S 747, 2Paris Descartes University, Sorbonne Paris, 3Public Hospital of Paris, Department of Biochemistry, Paris, France; 4Pharma Research Department, Hoffmann La Roche Ltd, Basel, Switzerland

Cell Health and Cytoskeleton 2013; 5: 1–12

Neuritogenesis is a complex morphological phenomena accompanying neuronal differentiation. Neuritogenesis relies on the initial breakage of the rather spherical symmetry of neuroblasts and the formation of buds emerging from the postmitotic neuronal soma. Buds then evolve into neurites, which later convert into an axon or dendrites. At the distal tip of neurites, the growth cone integrates extracellular signals and guides the neurite to its target. The acquisition of neuronal polarity depends on deep modifications of the neuroblast cytoskeleton characterized by the remodeling and activation of focal adhesions (FAs) and localized destabilization of the actin network in the neuronal sphere.Actin instability in unpolarized neurons allows neurite sprouting, ie, the protrusion of microtubules, and subsequent neurite outgrowth. Once the neurite is formed, actin microfilaments recover their stability and exert a sheathed action on neurites, a dynamic process necessary for the maintenance and integrity of neurites.

A combination of extrinsic and intrinsic cues pilots the architectural and functional changes in FAs and the actin network along neuritogenesis. This process includes neurotrophic factors (nerve growth factor, brain derived neurotrophic factor, neurotrophin, ciliary neurotrophic factor, glial derived neurotrophic factor) and their receptors, protein components of the extracellular matrix (ECM) (laminin, vitronectin, fibronectin), plasma membrane integrins and neural cell adhesion molecules (NCAM), and intracellular molecular protagonists such as small G proteins (RhoA, Rac, Cdc42) and their downstream targets.

Neuritogenesis is a dynamic phenomenon associated with neuronal differentiation that allows a rather spherical neuronal stem cell to develop dendrites and axon, a prerequisite for the integration and transmission of signals. The acquisition of neuronal polarity occurs in three steps:

(1) neurite sprouting, which consists of the formation of buds emerging from the postmitotic neuronal soma;

(2) neurite outgrowth, which represents the conversion of buds into neurites, their elongation and evolution into axon or dendrites; and

(3) the stability and plasticity of neuronal polarity.

In neuronal stem cells, remodeling and activation of focal adhesions (FAs) associated with deep modifications of the actin cytoskeleton is a prerequisite for neurite sprouting and subsequent neurite outgrowth. A multiple set of growth factors and interactors located in the extracellular matrix and the plasma membrane orchestrate neuritogenesis

  • by acting on intracellular signaling effectors,
  • notably small G proteins such as RhoA, Rac, and Cdc42,
  • which are involved in actin turnover and the dynamics of FAs.

The cellular prion protein (PrPC), a glycosylphosphatidylinositol

  • (GPI)-anchored membrane protein

mainly known for its role in a group of fatal

  • neurodegenerative diseases,

has emerged as a central player in neuritogenesis.

Here, we review the contribution of PrPC to neuronal polarization and detail the current knowledge on the

  • signaling pathways fine-tuned by PrPC
  • to promote neurite sprouting, outgrowth, and maintenance.

We emphasize that PrPC-dependent neurite sprouting is a process in which PrPC

  • governs the dynamics of FAs and the actin cytoskeleton
  • via β1 integrin signaling.

The presence of PrPC is necessary to render neuronal stem cells

  • competent to respond to neuronal inducers and
  • to develop neurites.

In differentiating neurons, PrPC exerts

  • a facilitator role towards neurite elongation.

This function relies on the interaction of PrPC with a set of diverse partners such as

  1. elements of the extracellular matrix,
  2. plasma membrane receptors,
  3. adhesion molecules, and
  4. soluble factors that control actin cytoskeleton turnover through Rho-GTPase signaling.

Once neurons have reached their terminal stage of differentiation and acquired their polarized morphology, PrPC also

  • takes part in the maintenance of neurites.

By acting on tissue nonspecific alkaline phosphatase, or

  • matrix metalloproteinase type 9,

PrPC stabilizes interactions between

  • neurites and the extracellular matrix.

Keywords: prion, neuronal differentiation

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