New Alzheimer’s Protein – AICD
Larry H. Bernstein, MD, FCAP, Curator
LPBI
SfN 2015 Recap: The Role of Synapses, Neural Networks in Alzheimer’s
Stephanie Guzowski, Editor, Drug Discovery & Development
Cognition and behavior rely on communication between individual neurons and extensive interactions between neural networks. But when synaptic dysfunction occurs, the results can be dire, leading to neurodegenerative symptoms in Alzheimer’s disease.
“The brain is the seed of our personal identity,” said Valina Dawson, Ph.D., director of neurogeneration and stem cell programs at Johns Hopkins University in Baltimore, Maryland. “It allows us to interact with our world but when things go wrong in the brain, it’s disastrous for the individual as well as the family.
“Our ability to treat these diseases is limited at the moment. We need new insight into what goes wrong.”
A lesser-known protein
Researchers, for years, have targeted amyloid beta (Aβ) in attempts to halt the progression of Alzheimer’s disease, and have recently, shown increased interest in the protein, tau.
But Paula Pousinha, Ph.D., at the French National Centre for Scientific Research, has focused her research on a lesser-known protein fragment: amyloid precursor protein intracellular domain (AICD). AICD is a fragment of amyloid precursor protein (APP), which is formed at the same time as Aβ in the brain. New evidence suggests that in addition to Aβ, AICD also disrupts communication between neurons during the progression of Alzheimer’s disease. Pousinha presented thesepublished findings at this year’s Society for Neuroscience (SfN) conference, which took place from October 17 to 21 in Chicago.
“Although AICD has been known for more than 10 years, it has been poorly studied,” said Pousinha.
Crtl 1-Venus. Fusion of a fluorescent protein to small link proteins in the PNN allows tracking of PNN dynamics over time. Credit: S.F. Palida et al.
Pousinha’s research team demonstrated that overexpressing AICD levels with AAV vector in rats’ brains “perturbs neuronal communication in the hippocampus,” a key structure necessary in forming memories and an area earliest affected in Alzheimer’s disease.“In normal animals, if we apply to these neurons a high-frequency stimulation, afterward the neurons are stronger,” said Pousinha. “Neurons where we overexpressed AICD failed to have this potentization.”
Pousinha doesn’t negate the importance of Aβ in the development of neurodegenerative diseases. “Our study doesn’t exclude the pathological effects of Aβ,” she said. “We believe that Alzheimer’s disease is much more complex and has more than one candidate that has implications.
“It’s very important for the scientific community to understand the role of all these APP fragments of neuroinflammation — different pieces of the puzzle of how we can stop the disease progression.”
How do memories persist in the brain long term?
New research, also presented at this year’s SfN, has implications for understanding memory to develop treatments for Alzheimer’s disease and dementias. Sakina Palida, a graduate student at the University of California, San Diego found that localized modifications in the perineuronal net (PNN) at synapses could be a mechanism by which information is stably encoded and preserved in the brain over time.
“We still don’t understand how we stably encode and store memories in our brains for up to our entire lifetimes,” said Palida. The prevailing idea on how memories are maintained over time generally focus on postsynaptic proteins, said Palida. “But the problem with looking at intracellular synaptic proteins is that the majority turn over rapidly, of hours to at most a few days. So they’re very unstable.”
So, Palida and her team identified PNN as an ideal substrate for long-term memory. “Kind of like how you carve into stone — stone is a stable substrate — you retain the information regardless of what comes and goes over it.” They demonstrated that individual PNN proteins are highly stable, and that the PNN is locally degraded when synapses are strengthened.
Cord Blood Cells As a Potential Treatment for Alzheimer’s Disease
Jared Ehrhart from the University of South Florida, who also serves as the Director of Research and Development at Saneron CCEL Therapeutics Inc, and his coworkers have shown that cells from umbilical cord blood can not only improve the health of mice that have an experimental form of Alzheimer’s disease (AD), but these can also be administered intravenously, which is safer and easier than other more invasive procedures.
Laboratory mice can be engineered to harbor mutations that can cause a neurodegenerative disease that greatly resembles human AD. One such mouse is the PSAPP mouse that harbors two mutations that are known to cause an inherited, early-onset form of AD in humans. By placing both mutations in the same mouse, the animal forms the characteristic protein plaques more rapidly and shows significant AD symptoms and brain pathology.
Ehrhart used PSAPP mice to test the ability of human umbilical cord blood to ameliorate the symptoms of AD. He injected one million Human Umbilical Cord Blood Cells (HUCBCs) into the tail veins of PSAPP mice and 2.2 million into the tail veins of Sprague-Dawley rats. Then he harvested their tissues at 24 hours, 7 days, and 30 days after injection. Then Ehrhart and his team used a variety of techniques to detect the presence of the HUCBCs.
Interestingly, the HUCBCs were able to cross the blood-brain barrier and take up residence in the brain. The cells remained in the brain and survived there for up to 30 days and did not promote the growth of any tumors.
Several studies have shown that the administration of HUCBCs to mice with a laboratory form of AD can improve the cognitive abilities of those mice (see Darlington D, et al., Cell Transplant. 2015;24(11):2237-50; Banik A, et al., Behav Brain Res. 2015 Sep 15;291:46-59; Darlington D, et al., Stem Cells Dev. 2013 Feb 1;22(3):412-21). However, in such cases it is essential to establish that the administered cells actually found their way to the site of damage and exerted a regenerative response.
Even though Ehrhart and his troop found that the intravenously administered HUCBCs were widely distributed throughout the bodies of the animals, they persisted in the central nervous system for up to one month after they were injected. In the words of this publication, which appeared in Cell Transplantation, the HUCBCs were “broadly detected in both in the brain and several peripheral organs, including the liver, kidneys, and bone marrow.”. The fact that such a minimally invasive procedure like intravenous injection can effectively introduce these cells into the bodies of the PSAPP mice and still produce a significant therapeutic effect is a significant discovery.
Ehrhart and his colleagues concluded that HUCBCs might provide therapeutic effects by modulating the inflammation that tends to accompany the onset of AD. Furthermore, these cells do not need to be delivered by means of an invasive procedure like intracerebroventricular injection. Furthermore, even though HUCBCs were detected in other organs, their numbers in those places was not excessive and the ability of the HUCBCs to cross the blood-brain barrier suggests that these cells might serve as safe, effective therapeutic agents for AD patients some day.
Crtl1-Venus Neurons. Tracking PNN dynamics in live cells, in mouse brain tissue. (Credit: S.F. Palida et al.)
And the team also demonstrated that mice lacking enzymes that degrade the PNN have deficient long-term, but not short-term, memory. “Which is a really exciting new result,” said Palida.
To track the PNN in live animals, Palida and her team fused a fluorescent protein to a small link protein in the PNN to allow tracking of PNN dynamics in real time. They also monitored PNN degradation in live cells after stimulating neurons with brain-derived neurotrophic factor (BDNF), a chemical secreted in the nervous system to enhance signaling — and observed localized degradation of the PNN at some newly formed synapses.
What’s next? “We’re currently making transgenic animals to express this protein, which would allow us to monitor PNN dynamics simultaneously with synaptic dynamics in a live animal brain, and really investigate this hypothesis further,” said Palida.
TOPICS ANIMAL STUDIES NEUROSCIENCE EXCLUSIVE RESEARCH EXCHANGE
Increased APP intracellular domain (AICD) production perturbs synaptic signal integration via increased NMDAR function
*Paula A Pousinha1 Pubmed Elisabeth Raymond1 Pubmed Xavier Mouska1 Pubmed Michael Willem2 Pubmed Hélène Marie1 Pubmed
http://sfn15.hubbian.com/id_8702
Alzheimer’s disease (AD) is a neurodegenerative disease that begins as mild short-term memory deficits and culminates in total loss of cognition and executive functions. The main culprit of the disease, resulting from Amyloid-Precursor Protein (APP) processing, has been thought to be amyloid-b peptide (Ab). However, despite the genetic and cell biological evidence that supports the amyloid cascade hypothesis, it is becoming clear that AD etiology is complex and that Ab alone is unable to account for all aspects of AD [Pimplikar et al. J Neurosci.30: 14946. 2010]. Gamma-secretase not only liberates Ab, but also its C-terminal intracellular counterpart called APP intracellular domain (AICD) [Passer. et al. JAlzheimers Dis.2: 289-301. 2000], which is known to also accumulate in AD patient’s brain [Ghosal et al. PNAS.106:18367. 2009], but surprisingly little is known about its functions in the hippocampus. To address this crucial issue, we increased AICD production in vivo in adult CA1 pyramidal neurons, mimicking the human pathological condition. Different ex-vivo electrophysiological and pharmacological approaches, including double- patch of neighbor neurons were used. We clearly demonstrate that in vivo AICD production increases synaptic NMDA receptor currents. This causes a frequency-dependent disruption of synaptic signal integration, leading to impaired long-term potentiation, which we were able to rescue by different pharmacological approaches. Our results provide convincing and entirely novel evidence that increased in vivo production of AICD is enough, per se, to cause synaptic dysfunction in CA1 hippocampal neurons.
Multiple low-dose infusions of human umbilical cord blood cells improve cognitive impairments and reduce amyloid-β-associated neuropathology in Alzheimer mice.
Darlington D1, Deng J, Giunta B, Hou H, Sanberg CD, Kuzmin-Nichols N, Zhou HD, Mori T, Ehrhart J, Sanberg PR, Tan J.
Stem Cells Dev. 2013 Feb 1;22(3):412-21. doi: 10.1089/scd.2012.0345. Epub 2012 Sep 5.
Alzheimer’s disease (AD) is the most common progressive age-related dementia in the elderly and the fourth major cause of disability and mortality in that population. The disease is pathologically characterized by deposition of β-amyloid plaques neurofibrillary tangles in the brain. Current strategies for the treatment of AD are symptomatic only. As such, they are less than efficacious in terms of significantly slowing or halting the underlying pathophysiological progression of the disease. Modulation by cell therapy may be new promising disease-modifying therapy. Recently, we showed reduction in amyloid-β (Aβ) levels/β-amyloid plaques and associated astrocytosis following low-dose infusions of mononuclear human umbilical cord blood cells (HUCBCs). Our current study extended our previous findings by examining cognition via (1) the rotarod test, (2) a 2-day version of the radial-arm water maze test, and (3) a subsequent observation in an open pool platform test to characterize the effects of monthly peripheral HUCBC infusion (1×10(6) cells/μL) into the transgenic PSAPP mouse model of cerebral amyloidosis (bearing mutant human APP and presenilin-1 transgenes) from 6 to 12 months of age. We show that HUCBC therapy correlates with decreased (1) cognitive impairment, (2) Aβ levels/β-amyloid plaques, (3) amyloidogenic APP processing, and (4) reactive microgliosis after a treatment of 6 or 10 months. As such, this report lays the groundwork for an HUCBC therapy as potentially novel alternative to oppose AD at the disease-modifying level.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549624/bin/fig-2.jpg
Alzheimer’s disease (ad) is the most common progressive age-related dementia, and is pathologically characterized by the deposition of amyloid-β peptide (Aβ) as amyloid plaques in the brain parenchyma and neurofibrillary tangles (NFTs) within neurons. As a result of the atrophy that occurs in both cortical and subcortical regions, patients suffer cognitive and emotional dysregulation leading eventually to an inability to perform acts of daily living independently and safely. In fact, AD has emerged as a national and international pandemic. According to the World Alzheimer Report 2010, dementia patients account for 35.6 million in worldwide, and are expected to increase to 65.7 million by 2030 and 115.4 million by 2050. Currently, the number of AD patients is around 1% of the world’s gross domestic product. Therefore, it is becoming increasingly evident that a more effective treatment or prophylaxes are needed in the near future. This is because Aβ plaques are potent activators of both microglia and astrocytes—central nervous system (CNS) resident immuno-competent cells that respond to cerebral amyloidosis by chronic, pro-inflammatory activation, also known as “inflammaging” (see review [1]). While it was once thought that activation of microglia and astrocytes in AD brains was an epiphenomenon and not a pathoetiological contributor to AD, more recent studies implicate this Aβ-mediated inflammatory cascade as an etiological perpetrator of AD. For example, therapeutic strategies aimed at manipulating this inflammatory cascade, including Aβ immunization, non-steroidal anti-inflammatory drugs, and modulation of microglial activation, are all able to reduce AD-like pathology and improve cognitive impairments in AD transgenic mouse models [2] and, in some cases, reduce AD pathology in humans [3].
While it is true that no model fully recapitulates AD, transgenic animal models pose novel insights into the pathophysiology of Aβ toxicity. This is especially so with regards to the effects of various Aβ species and the probable pathogenic role of Aβ oligomers [4]. In the PSAPP mouse model of cerebral amyloidosis (bearing mutant human APPsw and presenilin-1 transgenes), there are large numbers of compact Aβ plaques in the hippocampus and cerebral cortex. These mice demonstrate greatly accelerated β-amyloid deposition compared with Tg APPsw mice that is apparent as early as 16 weeks of age [5]. Concurrently, they show increased levels of both Aβ1–40 and Aβ1–42 in their parenchyma and a reduced performance of spatial working memory in the period preceding overt Aβ deposition [5]. Such findings support a critical role of Aβ1–42 in the pathogenesis of AD and suggest a neurotoxic effect of soluble forms of Aβ as well [6].
Human umbilical cord blood cells (HUCBCs) have a unique immunomodulatory potential. Therapeutic benefits derived from HUCBC treatment have been suggested to arise from modulation of peripheral inflammatory processes, which in turn affects inflammation in the brain parenchyma, and the mobilization of adult stem cells from the bone marrow (BM) [7–11]. Indeed, in the animal model of stroke, HUCBCs have been shown to promote a strong anti-inflammatory T helper 2 (Th2) response [7], as opposed to the deleterious proinflammatory T helper cell type 1 (Th1) response. Interestingly, this observation was seen in conjunction with reduced infarct volume and very importantly with rescue of neurological deficits [7,12–14].
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HUCBC studies done in vitro have shown that these cells secrete soluble factors that have salutary effects [16,58]. Cultured HUCBC supernatants, for example, stimulate survival of neural cells and peripheral blood mononuclear cells cultured under conditions designed to induce cell stress and limit protein synthesis [12]. Moreover, HUCBCs have the capacity to stimulate generation of a vast amount of cytokines and neurotrophic factors that modify inflammatory responses, including IL-11, CSF-1, NGF, and thrombopoietin [7,22,23]. It has been reported that HUCBC entry into the brain is not required to promote neuroprotection [59]. According to the report just outlined, recovery following brain injury is mediated through peripheral anti-inflammatory responses resulting in brain recovery [9]. This is in accord with our results that indicated more of a peripheral, HUCBC-mediated CNS affect, since the cells were not detected in the mouse brain for any significant amount of time.
On the other hand, it should be noted that it has been shown that after irradiation, peripheral macrophages are able to penetrate the brain and mitigate cerebral amyloidosis in AD mice, implying that hematogenously derived macrophages are efficient at phagocytosing and clearing Aβ deposits [18]. Nevertheless, earlier reports have shown that Aβ can also be phagocytosed or cleared by brain-resident microglia [58,60,61].
In the current experimental paradigm, we did not detect the presence of brain-infiltrating macrophages. Specifically, we stained for CD45 (a marker for both macrophages and microglia), and observed that in and around Aβ plaques there were process-bearing cells that morphologically resembled microglia. Further, vascular “cuffing” that would suggest the presence of infiltrating macrophages that are frequently observed in other CNS inflammatory conditions, such as experimental autoimmune encephalomyelitis [62], was not detected. Also, given the difficulties inherent to distinguishing macrophages from microglia, and the ease of peripheral macrophages to engraft into the brain, as well as changes of microglial phenotype after brain injury [63], it remains possible that peripheral macrophages contribute to decreased cerebral amyloidosis after treatment with HUCBCs.
In this report, we have demonstrated that HUCBC infusion decreases Aβ/β-amyloid pathology in the brain parenchyma, reduces brain inflammation evidenced by reduction of activated microglia, and improves cognitive impairments associated with the AD-like pathology in PSAPP mice. These HUCBC-imparted beneficial effects, which correlate with increased brain-to-blood efflux of Aβ and a shift from proinflammatory Th1 to anti-inflammatory Th2 cytokines both in the brain and in the periphery, are similar to what we observed in previous studies after Aβ immunization [64–66]. When taken together, our results provide the basis for a novel immunomodulatory strategy for AD using HUCBCs. While the exact mechanism of efficacy of multiple low-dose HUCBC infusions in AD patients is currently being elucidated, further studies investigating which HUCBC secreted factors are capable of modulating neuroinflammation, reducing AD-like pathology, and rescuing cognitive impairments will need to be explored.
GEN News Highlights Nov 13, 2015 Alzheimer’s Drug Candidate Also Reverses Effects of Aging
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Scientists at the Salk Institute say they have found that an experimental drug candidate aimed at combating Alzheimer’s disease has a host of unexpected anti-aging effects in animals.
The Salk team expanded upon their previous development of a drug candidate, called J147, which takes a different tack by targeting Alzheimer’s major risk factor: old age. In the new work, the team showed that J147 worked well in a mouse model of aging not typically used in Alzheimer’s research. When these mice were treated with J147, they had better memory and cognition, healthier blood vessels in the brain and other improved physiological features.
The team’s study (“A comprehensive multiomics approach toward understanding the relationship between aging and dementia”) is published in Aging.
“Initially, the impetus was to test this drug in a novel animal model that was more similar to 99 percent of Alzheimer’s cases,” says Antonio Currais, Ph.D., the lead author and a member of the Schubert Cellular Neurobiology Laboratory at Salk. “We did not predict we’d see this sort of anti-aging effect, but J147 made old mice look like they were young, based upon a number of physiological parameters.”
“While most drugs developed in the past 20 years target the amyloid plaque deposits in the brain (which are a hallmark of the disease), none have proven effective in the clinic,” says David Schubert, Ph.D., senior author of the study.
Several years ago, Dr. Schubert and his colleagues began to approach the treatment of the disease from a new angle. Rather than target amyloid, the lab decided to zero in old age. Using cell-based screens against old age-associated brain toxicities, they synthesized J147.
Previously, the team found that J147 could prevent and even reverse memory loss and Alzheimer’s pathology in mice that have a version of the inherited form of Alzheimer’s, the most commonly used mouse model. However, this form of the disease comprises only about 1% of Alzheimer’s cases. For everyone else, old age is the primary risk factor, according to Dr. Schubert. The team wanted to explore the effects of the drug candidate on a breed of mice that age rapidly and experience a version of dementia that more closely resembles the age-related human disorder.
In this latest work, the researchers used a comprehensive set of assays to measure the expression of all genes in the brain, as well as over 500 small molecules involved with metabolism in the brains and blood of three groups of the rapidly aging mice. The three groups of rapidly aging mice included one set that was young, one set that was old, and one set that was old but fed J147 as they aged.
The old mice that received J147 performed better on memory and other tests for cognition and also displayed more robust motor movements. The mice treated with J147 also had fewer pathological signs of Alzheimer’s in their brains. Importantly, because of the large amount of data collected on the three groups of mice, it was possible to demonstrate that many aspects of gene expression and metabolism in the old mice fed J147 were very similar to those of the young animals. These included markers for increased energy metabolism, reduced brain inflammation and reduced levels of oxidized fatty acids in the brain.
Another notable effect was that J147 prevented the leakage of blood from the microvessels in the brains of old mice. “Damaged blood vessels are a common feature of aging in general, and in Alzheimer’s, it is frequently much worse,” points out Dr. Currais.
While these studies represent a new and exciting approach to Alzheimer’s drug discovery and animal testing in the context of aging, the only way to demonstrate the clinical relevance of the work is to move J147 into clinical trials for Alzheimer’s disease, note the researchers.
“If proven safe and effective for Alzheimer’s, the apparent anti-aging effect of J147 would be a welcome benefit,” adds Dr. Schubert. The team aims to begin human trials next year.
Curry Derivative J147 Beats Aricept for Alzheimer’s
LA JOLLA, CA—A drug developed by scientists at the Salk Institute for Biological Studies, known as J147, reverses memory deficits and slows Alzheimer’s disease in aged mice following short-term treatment.
J147 was developed at Salk in the laboratory of David Schubert, a professor in the Cellular Neurobiology Laboratory. He said,
“It’s been known for a long time that people in India don’t get very much Alzheimer’s relative to what happens in the United States and the rest of the world.
“One of the curiosities about the diet in India is that they eat a lot of curry. A major spice in curry is turmeric. A major component of turmeric is curcumin.
“Curcumin has been around for a while. It is an FDA-Approved drug for cancer. A friend of mine in Los Angeles, Greg Cole, found that if you give curcumin to very similar mice to what this study’s author has been using, they get they get a little better, the (Alzheimer’s) plaques go away.
“The problem with curcumin is that it is not a great drug, in the sense that it gets degraded very rapidly. It’s availability is quite low in the bloodstream and the brain.
“We decided to make a better version of this. We did a lot of medicinal chemistry. We came up with J147.”
Lead study author Marguerite Prior, a research associate in Salk’s Cellular Neurobiology Laboratory, added,
“J147 is an exciting new compound because it really has strong potential to be an Alzheimer’s disease therapeutic by slowing disease progression and reversing memory deficits following short-term treatment.”
Because of its broad ability to protect nerve cells, the researchers believe that J147 may also be effective for treating other neurological disorders, such as Parkinson’s disease, Huntington’s disease and amyotrophic lateral sclerosis (ALS), as well as vascular dementia from stroke, although their study did not directly explore the drug’s efficacy as a therapy for those diseases.
The findings, published in the journal Alzheimer’s Research and Therapy, may pave the way to a new treatment for Alzheimer’s disease in humans.
Despite years of research, scientists are still seeking the first disease-modifying drugs for Alzheimer’s. Current FDA-approved medications, including Aricept®, Razadyne® and Exelon® (generic donepezil, galantamine and rivastigmine), offer only fleeting short-term benefits for Alzheimer’s patients, but they do nothing to slow the steady, irreversible decline of brain function that erases a person’s memory and ability to think clearly.
Professor Schubert and his colleagues bucked the trend within the pharmaceutical industry, which has focused on the biological pathways involved in the formation of amyloid plaques, the dense deposits of protein that characterize the disease. Instead, the Salk team used living neurons grown in laboratory dishes to test whether their new synthetic compounds, which are based upon natural products derived from plants, were effective at protecting brain cells against several pathologies associated with brain aging. From the test results of each chemical iteration of the lead compound, they were able to alter their chemical structures to make them much more potent. Although J147 appears to be safe in mice, the next step will require clinical trials to determine whether the compound will prove safe and effective in humans.
“Alzheimer’s disease research has traditionally focused on a single target, the amyloid pathway,” says Schubert, “but unfortunately drugs that have been developed through this pathway have not been successful in clinical trials. Our approach is based on the pathologies associated with old age-the greatest risk factor for Alzheimer’s and other neurodegenerative diseases-rather than only the specificities of the disease.”
Salk scientists developed J147, a synthetic drug shown to improve memory and prevent brain damage in mice with Alzheimer’s disease.Images: Courtesy of the Salk Institute for Biological Studies
To test the efficacy of J147 in a much more rigorous preclinical Alzheimer’s model, the Salk team treated mice using a therapeutic strategy that they say more accurately reflects the human symptomatic stage of Alzheimer’s. Administered in the food of 20-month-old genetically engineered mice, at a stage when Alzheimer’s pathology is advanced, J147 rescued severe memory loss, reduced soluble levels of amyloid, and increased neurotrophic factors essential for memory, after only three months of treatment.
In a different experiment, the scientists tested J147 directly against Aricept (generic donepezil), the most widely prescribed Alzheimer’s drug, and found that it performed as well or better in several memory tests.
“In addition to yielding an exceptionally promising therapeutic, both the strategy of using mice with existing disease and the drug discovery process based upon aging are what make the study interesting and exciting,” says Schubert, “because it more closely resembles what happens in humans, who have advanced pathology when diagnosis occurs and treatment begins.” Most studies test drugs before pathology is present, which is preventive rather than therapeutic and may be the reason drugs don’t transfer from animal studies to humans.
Prior and her colleagues say that several cellular processes known to be associated with Alzheimer’s pathology are affected by J147, including an increase in a protein called brain-derived neurotrophic factor (BDNF), which protects neurons from toxic insults, helps new neurons grow and connect with other brain cells, and is involved in memory formation. Postmortem studies show lower than normal levels of BDNF in the brains of people with Alzheimer’s.
The Salk researchers say that J147, with its memory enhancing and neuroprotective properties, along with its safety and availability as an oral medication, would make an “ideal candidate” for Alzheimer’s disease clinical trials. They are currently seeking funding for such a trial.
Other researchers on the study were Richard Dargusch, Jennifer L. Ehren and Chandra Chiruta, of the Salk Institute.The work was supported by the Alzheimer’s Drug Discovery Foundation, the Bundy Foundation, the Fritz Burns Foundation, the George E. Hewitt Foundation, the Alzheimer’s Association, and the National Institutes of Health.
Genomics and Proteomics|Proteomics Reagents|Protein and Protein Interaction Assays
AMSBIO announces that Belgian researchers have cited use of BioPORTER Protein Delivery Reagent to introduce Tau seeds into HEK293 cells. BioPORTER Protein Delivery Reagent is a unique lipid formulation that allows direct translocation of proteins into living cells.
Neurodegenerative tauopathies, including Alzheimer disease and frontotemporal dementias, are characterized by neurofibrillary tangles (NFT) composed of intracellular hyperphosphorylated Tau aggregates. Predominantly expressed in neurons, Tau is a microtubule (MT)-binding protein that stabilizes and promotes the assembly of MTs, and the Tau-MT interactions are negatively regulated by phosphorylation of Tau. A naturally unfolded soluble protein under normal conditions, Tau acquires highly ordered ß-pleated sheet structures as it assembles into insoluble hyperphosphorylated paired helical filaments as well as less frequent straight filaments that constitute NFTs in Alzheimer disease and related tauopathies. Significant correlation of total NFT burden with cognitive decline has been observed in Alzheimer disease patients.
In the Belgian research prion-like seeding and propagation of Tau-pathology was demonstrated experimentally and may underlie the stereotyped progression of neurodegenerative Tauopathies. The researchers analyzed the repercussions of prion-like spreading of Tau-pathology via neuronal connections on neuronal network function in TauP301S transgenic mice.
BioPORTER Protein Delivery Reagent provided the researchers with a quick and easy method to study protein function without the need for cloning and DNA transfection. The reagent lipid captures proteins and transports them inside the target cells. The delivered proteins retain their structure and function while leaving the transduced cells unharmed. The reagent is especially useful when studying protein function in cells that are difficult to transfect using traditional DNA transfection reagents. http://www.amsbio.com/BioPORTER-protein-delivery-transfectiom-reagent.aspx
AMSBIO LLC, (617) 945-5033, http://www.amsbio.com
Neurotrophic factors are a family of proteins that are responsible for the growth and survival of nerve cells during development, and for the maintenance of adult nerve cells. Animal studies and test tube (in vitro Latin phrase for ‘in glass’; in a test tube or other artificial environment, as opposed to inside a living organism.”>in vitro)models
Organisms that scientists use to reproduce features of a disease of interest in an organism and then study it. For example, inserting the gene for HD into a mouse means that it will produce the altered HD protein in the brain. This creates an HD mouse model. The consistent use of these models allows researchers to test ideas about biology in a reproducible way, without the expense and ethical problems of performing these tests in humans.”>models have shown that certain neurotrophic factors are capable of making damaged nerve cells regenerate. Because of this capability, these factors represent exciting possibilities for reversing a number of devastating brain disorders, including Alzheimer’s disease
A neurodegenerative disease that causes progressive memory loss and severe dementia in advanced cases. Alzheimer’s disease is associated with certain abnormalities in brain tissue, involving a particular protein, beta-amyloid.”>Alzheimer’s disease, Parkinson’s disease
A neurodegenerative disorder that primarily affects one’s ability to perform smooth movements. The disease is associated with a loss of dopamine-producing nerve cells in the substantia nigra region of the brain.”>Parkinson’s disease, Lou Gehrig’s disease, and Huntington’s disease
A hereditary neurological disorder characterized by movement, cognitive, and psychiatric symptoms.”>Huntington’s Disease (HD). (For more information on how HD relates to Alzheimer’s and Parkinson’s, click here.) Currently, scientists are looking for ways to harness neurotrophic factors and somehow induce the damaged nerve cells to regenerate in order to improve the symptoms
Changes in the body or its functions, experienced by the patient and indicative of disease.”>symptoms of people with neurological having to do with nerve cells and/or the nervous system, particularly the brain”>neurological disorders.
One neurotrophic factor is a protein in the nervous system that promotes the growth of nerve cells.”>neurotrophic factor that is particularly relevant to HD is brain-derived neurotrophic factor (BDNF)
A protein that causes certain types of nerve cells to survive and grow. BDNF is primarily located in the central nervous system, where it acts on cells in the brain and the eye. In the peripheral nervous system, BDNF promotes the growth of sensory and motor neurons.”>Brain-derived neurotrophic factor (BDNF)
.BDNF
An abbreviation of brain-derived neurotrophic factor, which is a protein that causes certain types of nerve cells to survive and grow. BDNF is primarily located in the central nervous system, where it acts on cells in the brain and the eye. In the peripheral nervous system, BDNF promotes the growth of sensory and motor neurons.”>BDNF levels are decreased in the brains of HD patients, which might be partly responsible for the degenerative when a part of the body stops working well, and begins to decline in function”>degenerative processes of HD. Researchers have recently discovered a link between BDNF An abbreviation of brain-derived neurotrophic factor, which is a protein that causes certain types of nerve cells to survive and grow. BDNF is primarily located in the central nervous system, where it acts on cells in the brain and the eye. In the peripheral nervous system, BDNF promotes the growth of sensory and motor neurons.”>BDNF , mutant huntingtin
The altered form of the huntingtin protein caused by having the HD gene.”>mutant huntingtin , and excitotoxicity
Excessive stimulation of a nerve cell by a neurotransmitter, which poisons the nerve cell and degrades it.”>excitotoxicity, a process by which brain cells die after stimulation. The mutant huntingtin protein A key protein in Huntington’s disease. It exists in all humans but has a chemically different form in people with HD. Please note that although Huntingt<strong>o</strong>n’s disease is spelled with an o, the correct spelling of the protein involved is huntingt<strong>i</strong>n with an i.”>huntingtin protein invariably leads to the death of nerve cells in the striatum part of the brain that is involved in controlling movement. It is made up of the caudate and the putamen. Also referred to as the corpus striatum.”>striatum, the region of the brain needed for movements; however, how mutant huntingtin the altered form of the huntingtin protein caused by having the HD gene.”>mutant huntingtin does this damage is unclear. One possibility is that mutant huntingtin
The altered form of the huntingtin protein caused by having the HD gene.”>mutant huntingtin lowers levels of BDNF
An abbreviation of brain-derived neurotrophic factor, which is a protein that causes certain types of nerve cells to survive and grow. BDNF is primarily located in the central nervous system, where it acts on cells in the brain and the eye. In the peripheral nervous system, BDNF promotes the growth of sensory and motor neurons.”>BDNF, making nerve cells more susceptible to injury and death. Therefore, therapeutic approaches aimed at increasing BDNF
An abbreviation of brain-derived neurotrophic factor, which is a protein that causes certain types of nerve cells to survive and grow. BDNF is primarily located in the central nervous system, where it acts on cells in the brain and the eye. In the peripheral nervous system, BDNF promotes the growth of sensory and motor neurons.”>BDNF production may be able to counteract the effects ofmutant huntingtin
The altered form of the huntingtin protein caused by having the HD gene.”>mutant huntingtin and prevent a significant amount of the neurodegeneration
The deterioration or loss of function of nerve cells. Neurodegenerative diseases include HD, Alzheimer’s, Parkinson’s and many more. <em>Adj.</em>neurodegenerative.”>neurodegeneration that would otherwise occur in HD. (For more information on huntingtin protein
A key protein in Huntington’s disease. It exists in all humans but has a chemically different form in people with HD. Please note that although Huntingt<strong>o</strong>n’s disease is spelled with an o, the correct spelling of the protein involved is huntingt<strong>i</strong>n with an i.”>huntingtin protein
, click here.)
http://ghr.nlm.nih.gov/gene/BDNF
What is the official name of the BDNF gene?
The official name of this gene is “brain-derived neurotrophic factor.”
BDNF is the gene’s official symbol. The BDNF gene is also known by other names, listed below.
Read more about gene names and symbols on the About page.
What is the normal function of the BDNF gene?
The BDNF gene provides instructions for making a protein found in the brain and spinal cord called brain-derived neurotrophic factor. This protein promotes the survival of nerve cells (neurons) by playing a role in the growth, maturation (differentiation), and maintenance of these cells. In the brain, the BDNF protein is active at the connections between nerve cells (synapses), where cell-to-cell communication occurs. The synapses can change and adapt over time in response to experience, a characteristic called synaptic plasticity. The BDNF protein helps regulate synaptic plasticity, which is important for learning and memory.
The BDNF protein is found in regions of the brain that control eating, drinking, and body weight; the protein likely contributes to the management of these functions.
Does the BDNF gene share characteristics with other genes?
The BDNF gene belongs to a family of genes called endogenous ligands (endogenous ligands).
A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? in the Handbook.
Brain-derived Neurotrophic Factor
DEVIN K. BINDERa,* and HELEN E. SCHARFMANb
The BDNF gene (in humans mapped to chromosome 11p) has four 5′ exons (exons I-IV) that are associated with distinct promoters, and one 3′ exon (exon V) that encodes the mature BDNF protein (Metsis et al., 1993; Timmusk et al., 1993). Eight distinct mRNAs are transcribed, with transcripts containing exons I-III expressed predominantly in brain and exon IV found in lung and heart (Timmusk et al., 1993).
BDNF shares about 50% amino acid identity with NGF, NT-3 and NT-4/5. Each neurotrophin consists of a noncovalently-1 linked homodimer and contains (1) a signal peptide following the initiation codon; and (2) a pro-region containing an N-linked glycosylation site. Initially produced as proneurotrophins, prohormone convertases such as furin cleave the proneurotrophins (M.W. ~30kDa) to the mature neurotrophin (M.W. ~14kDa) (Chao and Bothwell, 2002). Proneurotrophins have altered binding characteristics and distinct biologic activity in comparison with mature neurotrophins (Lee et al., 2001a,b). Neurotrophins also share a distinctive three-dimensional structure containing two pairs of antiparallel β-strands and cysteine residues in a cystine knot motif.
Each neurotrophin binds one or more of the tropomyosin-related kinase (trk) receptors, members of the family of receptor tyrosine kinases (Patapoutian and Reichardt, 2001). Ligand-induced receptor dimerization results in kinase activation; subsequent receptor autophosphorylation on multiple tyrosine residues creates specific binding sites for intracellular target proteins, which bind to the activated receptor via SH2 domains (Barbacid, 1994; Patapoutian and Reichardt, 2001). These include PLC-γ1 (phospholipase C), p85 (the noncatalytic subunit of PI-3 kinase) and Shc (SH2-containing sequence); activation of these target proteins can then lead to a variety of intracellular signalling cascades such as the Ras-MAP (mitogen-activated protein) kinase cascade and phosphorylation of cyclic AMP-response element binding protein (CREB) (Patapoutian and Reichardt, 2001; Segal, 2003).
TrkA binds NGF (with low-affinity binding by NT-3 in some systems); trkB binds BDNF and NT-4/5 with lower-affinity binding by NT-3; and trkC binds NT-3 (Barbacid, 1994). Trk receptors exist in both a full-length (trkB.FL) form as well as truncated (trkB.T1. trkB.T2) forms lacking the kinase domain (Eide et al., 1996; Fryer et al., 1997). Although most functions attributed to BDNF are associated with full-length trkB, several roles have been suggested for truncated receptors, including growth and development (Fryer et al., 1997; Yacoubian and Lo, 2000; Luikart et al., 2003) and negative modulation of trkB receptor expression and function (Eide et al., 1996; Haapasalo et al., 2001; Haapasalo et al., 2002). Expression of truncated trk receptors on astrocytes is upregulated following injury (Frisen et al.,1993) and may modulate neuronal vulnerability (Saarelainen et al., 2000a,b) and sequestration of BDNF in astrocytes (Biffo et al., 1995;Roback et al., 1995; Alderson et al., 2000). Recent studies have shown that BDNF activates glial calcium signalling by truncated trk receptors (Climent et al., 2000: Rose et al., 2003).
In addition, all of the neurotrophins bind to the p75 receptor, designated p75NTR. p75NTR, related to proteins of the tumor necrosis factor (TNFR) superfamily, has a glycosylated extracellular region involved in ligand binding, a transmembrane region, and a short cytoplasmic sequence lacking intrinsic catalytic activity (Chao and Hempstead, 1995; Dechant and Barde, 2002). Neurotrophin binding to p75NTR is linked to several intracellular signal transduction pathways, including nuclear factor-κB (NF-κB), Jun kinase and sphingo-myelin hydrolysis (Dechant and Barde, 2002). P75NTR signalling mediates biologic actions distinct from those of the trk receptors, notably the initiation of programmed cell death (apoptosis) (Casaccia-Bonnefil et al., 1996; Frade et al., 1996; Roux et al., 1999; Dechant and Barde, 2002). It has also been suggested that p75 may serve to determine neurotrophin binding specificity (Esposito et al., 2001; Lee et al., 2001a,b;Zaccaro et al., 2001).
BDNF GENE REGULATION
A multitude of stimuli have been described that alter BDNF gene expression in both physiologic and pathologic states (Lindholm et al., 1994). For example, light stimulation increases BDNF mRNA in visual cortex (Castrén et al., 1992), osmotic stimulation increases BDNF mRNA in the hypothalamus (Castrén et al., 1995; Dias et al., 2003), and whisker stimulation increases BDNF mRNA expression in somatosensory barrel cortex (Rocamora et al., 1996). Electrical stimuli that induce long-term potentiation (LTP) in the hippocampus, a cellular model of learning and memory, increase BDNF and NGF expression (Patterson et al., 1992; Castrén et al., 1993; Bramham et al., 1996). Even physical exercise has been shown to increase NGF and BDNF expression in hippocampus (Neeper et al., 1995). Interestingly, BDNF levels vary across the estrous cycle, which correlate with its effects on neural excitability (Scharfman et al., 2003).
Distinct BDNF 5′ exons are differentially regulated by stimuli such as neural activity. For example, exons I-III, but not exon IV, increase after kainic acid-induced seizures (Timmusk et al., 1993) or other stimuli that increase activity (Lauterborn et al., 1996; Tao et al., 2002). Protein synthesis is required for the effects of activity on exons I and II, but not III and IV, raising the possibility that the latter act as immediate early genes (Lauterborn et al., 1996; Castrén et al., 1998). The transcription factor CaRF activates transcription of exon III under the control of a calcium response element. CaRE1 (Tao et al., 2002). CREB, which can be stimulated by diverse stimuli ranging from activity to chronic antidepressant treatment (Nibuya et al., 1995,1996; Shieh et al., 1998; Tao et al., 1998; Shieh and Ghosh, 1999), also modulates exon III transcription. Recent evidence also indicates that neural activity triggers calcium-dependent phosphorylation and release of methyl-CpG binding protein 2 (MeCP2) from BDNF promoter III to derepress transcription (Chen et al., 2003).
BDNF and trkB mRNA have a widespread distribution in the central nervous system (Merlio et al., 1993;Conner et al., 1997). BDNF and trkB protein immunoreactivity is also widespread (Conner et al., 1997; Yanet al., 1997a,b; Drake et al., 1999), Like BDNF mRNA, constitutive BDNF protein expression is particularly high in the hippocampus, where the mossy fibre axons of dentate granule cells display BDNF immunoreactivity (Conner et al., 1997).
Unlike the classical target-derived trophic factor model in which neurotrophins—such as NGF—are retrogradely transported, there is now abundant evidence that BDNF is also anterogradely transported in brain. First, BDNF protein is localized to nerve terminals (Conner et al., 1997), and pathway transection or axonal transport inhibition abrogates this terminal expression (Altar et al., 1997; Conner et al., 1997; Altar and DiStefano, 1998). Second, higher-resolution studies have shown that BDNF is associated with dense-core vesicles (Fawcett et al., 1997; Altar and DiStefano, 1998), which are the primary site for neuropeptide storage and release from nerve terminals. Third, further functional studies have supported the anterograde transport hypothesis (Fawcett et al., 1998, 2000). Fourth, pro-BDNF is shuttled from the trans-Golgi network into secretory granules, where it is cleaved by prohormone convertase 1 (PC1) (Farhadi et al., 2000).
In addition, emerging evidence suggests that both BDNF and trk receptors may undergo regulated intracellular transport. For example, seizures lead to redistribution of BDNF mRNA from hippocampal CA3 cell bodies to their apical dendrites (Bregola et al., 2000; Simonato et al., 2002). Trk signalling is now thought to include retrograde transport of intact neurotrophin-trk complexes to the neuronal cell body (Miller and Kaplan, 2001; Ginty and Segal, 2002).
Recent evidence indicates that neurotrophins are released acutely following neuronal depolarization (Griesbeck et al., 1999; Mowla et al., 1999; Goggi et al., 2003). In fact, direct activity-dependent pre- to post-synaptic transneuronal transfer of BDNF has recently been demonstrated using fluorescently-labelled BDNF (Kohara et al., 2001). The released form of BDNF is thought to be proBDNF (Mowla et al., 2001), raising the possibility of postsecretory proteolytic processing by membrane-associated or extracellular proteases in the modulation of BDNF action (Lee et al., 2001a,b).
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Experimental Drug Targeting Alzheimer’s Disease Shows Anti-aging Effects
Salk scientists Antonio Currais, David Schubert and team found a molecule that slows the clock on key aspects of aging in animals. Credit: Salk Institute
Salk Institute researchers have found that an experimental drug candidate aimed at combating Alzheimer’s disease has a host of unexpected anti-aging effects in animals.
The Salk team expanded upon their previous development of a drug candidate, called J147, which takes a different tack by targeting Alzheimer’s major risk factor–old age. In the new work, the team showed that the drug candidate worked well in a mouse model of aging not typically used in Alzheimer’s research. When these mice were treated with J147, they had better memory and cognition, healthier blood vessels in the brain and other improved physiological features, as detailed November 12, 2015 in the journal Aging.
“Initially, the impetus was to test this drug in a novel animal model that was more similar to 99 percent of Alzheimer’s cases,” said Antonio Currais, the lead author and a member of Professor David Schubert’s Cellular Neurobiology Laboratory at Salk. “We did not predict we’d see this sort of anti-aging effect, but J147 made old mice look like they were young, based upon a number of physiological parameters.”
Alzheimer’s disease is a progressive brain disorder, recently ranked as the third leading cause of death in the United States and affecting more than five million Americans. It is also the most common cause of dementia in older adults, according to the National Institutes of Health.
“While most drugs developed in the past 20 years target the amyloid plaque deposits in the brain (which are a hallmark of the disease), none have proven effective in the clinic,” said Schubert, senior author of the study.
Several years ago, Schubert and his colleagues began to approach the treatment of the disease from a new angle. Rather than target amyloid, the lab decided to zero in on the major risk factor for the disease–old age. Using cell-based screens against old age-associated brain toxicities, they synthesized J147.
Previously, the team found that J147 could prevent and even reverse memory loss and Alzheimer’s pathology in mice that have a version of the inherited form of Alzheimer’s, the most commonly used mouse model. However, this form of the disease comprises only about 1 percent of Alzheimer’s cases. For everyone else, old age is the primary risk factor, said Schubert. The team wanted to explore the effects of the drug candidate on a breed of mice that age rapidly and experience a version of dementia that more closely resembles the age-related human disorder.
In this latest work, the researchers used a comprehensive set of assaid to measure the expression of all genes in the brain, as well as over 500 small molecules involved with metabolism in the brains and blood of three groups of the rapidly aging mice. The three groups of rapidly aging mice included one set that was young, one set that was old and one set that was old but fed J147 as they aged.
The old mice that received J147 performed better on memory and other tests for cognition and also displayed more robust motor movements. The mice treated with J147 also had fewer pathological signs of Alzheimer’s in their brains. Importantly, because of the large amount of data collected on the three groups of mice, it was possible to demonstrate that many aspects of gene expression and metabolism in the old mice fed J147 were very similar to those of the young animals. These included markers for increased energy metabolism, reduced brain inflammation and reduced levels of oxidized fatty acids in the brain.
Another notable effect was that J147 prevented the leakage of blood from the microvessels in the brains of old mice. “Damaged blood vessels are a common feature of aging in general, and in Alzheimer’s, it is frequently much worse,” said Currais.
Currais and Schubert note that while these studies represent a new and exciting approach to Alzheimer’s drug discovery and animal testing in the context of aging, the only way to demonstrate the clinical relevance of the work is to move J147 into human clinical trials for Alzheimer’s disease.
“If proven safe and effective for Alzheimer’s, the apparent anti-aging effect of J147 would be a welcome benefit,” adds Schubert. The team aims to begin human trials next year.
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