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Archive for the ‘Cell Biology’ Category


Cholesterol-busting gut bacteria affect people’s cardiac health

Reporter: Irina Robu, PhD

Scientists at Broad Institute of MIT and Harvard University, has discovered a group a gut bacterium that can metabolize enough cholesterol to affect metabolism. Their study in Cell Host and Microbe, found that bacteria in the intestines have lower cholesterol levels in their blood. Cholesterol is a key biological molecule that functions as a structural component of all animal cell membranes and is a precursor of steroid hormones, vitamin D, and bile acids. Two main sources of cholesterol are thought to influence concentrations of this metabolite in serum: endogenous cholesterol synthesized in the liver and exogenous cholesterol derived from dietary components of animal origin.

The study shows a roadmap of how enzymes and microbial genes can manipulate metabolism and impact human health. The concept that bacteria can metabolize cholesterol is been known for a long time, but not enough has been known of which species of bacteria was doing this. However, isolating cholesterol metabolizing bacteria and growing them in the lab proved to be difficult.

The idea that bacteria can metabolize cholesterol isn’t a new one; in the early 1900s, scientists reported the existence of bacteria that could chemically transform cholesterol into a compound called coprostanol. Coprostanol-generating bacteria have been found in the guts of rats, baboons, pigs, and even humans, but the biology of these bacteria was poorly understood.

The scientists genetically engineered bacteria in the lab to produce genetically engineered bacteria in the lab to produce four enzymes of interest. Yet, they focused on one gene named Intestinal Stool Metabolism (IsmA) that could metabolize cholesterol. Furthermore, individuals with the IsmA gene had, on average, cholesterol levels in the blood that were 2.7 mg/dL lower than those without any copies of the IsmA genes in their microbiomes. This is a larger average effect on blood cholesterol than human genes such as HMGCR and PCSK9, which are known to alter a person’s risk of high cholesterol levels and are targeted by some FDA-approved cholesterol drugs.

SOURCE

https://www.broadinstitute.org/news/cholesterol-busting-gut-bacteria-may-affect-people%E2%80%99s-cardiac-health

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Live Conference Coverage AACR 2020 in Real Time: Monday June 22, 2020 Late Day Sessions

 

Reporter: Stephen J. Williams, PhD

 

Follow Live in Real Time using

#AACR20

@pharma_BI

@AACR

 

Register for FREE at https://www.aacr.org/

 

AACR VIRTUAL ANNUAL MEETING II

 

June 22-24: Free Registration for AACR Members, the Cancer Community, and the Public
This virtual meeting will feature more than 120 sessions and 4,000 e-posters, including sessions on cancer health disparities and the impact of COVID-19 on clinical trials

 

This Virtual Meeting is Part II of the AACR Annual Meeting.  Part I was held online in April and was centered only on clinical findings.  This Part II of the virtual meeting will contain all the Sessions and Abstracts pertaining to basic and translational cancer research as well as clinical trial findings.

 

REGISTER NOW

 

 

 

Virtual Educational Session

Prevention Research, Science Policy, Epidemiology, Survivorship

Carcinogens at Home: Science and Pathways to Prevention

Chemicals known to cause cancer are used and released to the environment in large volumes, exposing people where they live, work, play, and go to school. The science establishing an important role for such exposures in the development of cancers continues to strengthen, yet cancer prevention researchers are largely unfamiliar with the data drawn upon in identifying carcinogens and making decisions about their use. Characterizing and reducing harmful exposures and accelerating the devel

Julia Brody, Kathryn Z. Guyton, Polly J. Hoppin, Bill Walsh, Mary H. Ward

DETAILS

Monday, June 22

1:30 PM – 3:30 PM EDT

Virtual Educational Session

Tumor Biology, Molecular and Cellular Biology/Genetics, Clinical Research Excluding Trials

EMT Still Matters: Let’s Explore! – Dedicated to the Memory of Isaiah J. Fidler

During carcinoma progression, initially benign epithelial cells acquire the ability to invade locally and disseminate to distant tissues by activating epithelial-mesenchymal transition (EMT). EMT is a cellular process during which epithelial cells lose their epithelial features and acquire mesenchymal phenotypes and behavior. Growing evidence supports the notion that EMT programs during tumor progression are usually activated to various extents and often partial and reversible, thus pr

Jean-Paul Thiery, Heide L Ford, Jing Yang, Geert Berx

DETAILS

Monday, June 22

1:30 PM – 3:00 PM EDT

Virtual Educational Session

Tumor Biology, Experimental and Molecular Therapeutics, Molecular and Cellular Biology/Genetics

One of These Things Is Not Like the Other: The Many Faces of Senescence in Cancer

Cellular senescence is a stable cell growth arrest that is broadly recognized to act as a barrier against tumorigenesis. Senescent cells acquire a senescence-associated secretory phenotype (SASP), a transcriptional response involving the secretion of inflammatory cytokines, immune modulators, and proteases that can shape the tumor microenvironment. The SASP can initially stimulate tumor immune surveillance and reinforce growth arrest. However, if senescent cells are not removed by the

Clemens A Schmitt, Andrea Alimonti, René Bernards

DETAILS

Monday, June 22

1:30 PM – 3:00 PM EDT

Virtual Educational Session

Clinical Research Excluding Trials, Molecular and Cellular Biology/Genetics

Recent Advances in Applications of Cell-Free DNA

The focus of this educational session will be on recent developments in cell-free DNA (cfDNA) analysis that have the potential to impact the care of cancer patients. Tumors continually shed DNA into the circulation, where it can be detected as circulating tumor DNA (ctDNA). Analysis of ctDNA has become a routine part of care for a subset of patients with advanced malignancies. However, there are a number of exciting potential applications that have promising preliminary data but that h

Michael R Speicher, Maximilian Diehn, Aparna Parikh

DETAILS

Monday, June 22

1:30 PM – 3:30 PM EDT

Virtual Methods Workshop

Clinical Research Excluding Trials, Clinical Trials, Experimental and Molecular Therapeutics, Molecular and Cellular Biology/Genetics

Translating Genetics and Genomics to the Clinic and Population

This session will describe how advances in understanding cancer genomes and in genetic testing technologies are being translated to the clinic. The speakers will illustrate the clinical impact of genomic discoveries for diagnostics and treatment of common tumor types in adults and in children. Cutting-edge technologies for characterization of patient and tumor genomes will be described. New insights into the importance of patient factors for cancer risk and outcome, including predispos

Heather L. Hampel, Gordana Raca, Jaclyn Biegel, Jeffrey M Trent

DETAILS

Monday, June 22

1:30 PM – 3:22 PM EDT

Virtual Educational Session

Regulatory Science and Policy, Drug Development, Epidemiology

Under-representation in Clinical Trials and the Implications for Drug Development

The U.S. Food and Drug Administration relies on data from clinical trials to determine whether medical products are safe and effective. Ideally, patients enrolled in those trials are representative of the population in which the product will be used if approved, including people of different ages, races, ethnic groups, and genders. Unfortunately, with few patients enrolling in clinical trials, many groups are not well-represented in clinical trials. This session will explore challenges

Ajay K. Nooka, Nicole J. Gormley, Kenneth C Anderson, Ruben A. Mesa, Daniel J. George, Yelak Biru, RADM Richardae Araojo, Lola A. Fashoyin-Aje

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Cancer Chemistry

Targeted Protein Degradation: Target Validation Tools and Therapeutic Opportunity

This educational session will cover the exciting emerging field of targeted protein degradation. Key learning topics will include: 1. an introduction to the technology and its relevance to oncology; 2. PROTACS, degraders, and CELMoDs; 3. enzymology and protein-protein interactions in targeted protein degraders; 4. examples of differentiated biology due to degradation vs. inhibition; 5. how to address questions of specificity; and 6. how the field is approaching challenges in optimizing therapies

George Burslem, Mary Matyskiela, Lyn H. Jones, Stewart L Fisher, Andrew J Phillips

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Bioinformatics and Systems Biology, Experimental and Molecular Therapeutics, Drug Development, Molecular and Cellular Biology/Genetics

Obstacles and opportunities for protein degradation drug discovery

Lyn H. Jones
  • PROTACs ubiquitin mediated by E3 ligases;  first discovered by DeShaies and targeted to specific proteins
  • PROTACs used in drug discovery against a host of types of targets including kinases and membrane receptors
  • PROTACs can be modular but lack molecular structural activity relationships
  • can use chemical probes for target validation
  • four requirements: candidate exposure at site of action (for example lipophilicity for candidates needed to cross membranes and accumulate in lysosomes), target engagement (ternary occupancy as measured by FRET), functional pharmacology, relevant phenotype
  • PROTACs hijack the proteosomal degradation system

Proteolysis-targeting chimeras as therapeutics and tools for biological discovery

George Burslem
  • first PROTAC developed to coopt the VHL ubiquitin ligase system which degrades HIF1alpha but now modified for EREalpha
  • in screen for potential PROTACS there were compounds which bound high affinity but no degradation so phenotypic screening very important
  • when look at molecular dynamics can see where PROTAC can add additional protein protein interaction, verifed by site directed mutagenesis
  • able to target bcr-Abl
  • he says this is a rapidly expanding field because of all the new E3 ligase targets being discovered

Expanding the horizons of cereblon modulators

Mary Matyskiela

Translating cellular targeted protein degradation to in vivo models using an enzymology framework

Stewart L Fisher
  • new targeting compounds have an E3 ligase binding domain, a target binding domain and a linker domain
  • in vivo these compounds are very effective; BRD4 degraders good invitro and in vivo with little effect on body weight
  • degraders are essential activators of E3 ligases as these degraders bring targets in close proximity so activates a catalytic cycle of a multistep process (has now high turnover number)
  • in enzymatic pathway the degraders make a productive complex so instead of a kcat think of measuring a kprod or productivity of degraders linked up an E3 ligase
  • the degraders are also affecting the rebound protein synthesis; so Emax never to zero and see a small rebound of protein synthesis

 

Data-Driven Approaches for Choosing Combinatorial Therapies

Drug combinations remain the gold standard for treating cancer, as they significantly outperform single agents. However, due to the enormous size of drug combination space, it is virtually impossible to interrogate all possible combinations. This session will discuss approaches to identify novel combinations using both experimental and computational approaches. Speakers will discuss i) approaches to drug screening in cell lines, the impact of the microenvironment, and attempts to more

Bence Szalai, James E Korkola, Lisa Tucker-Kellogg, Jeffrey W Tyner

DETAILS

Monday, June 22

3:45 PM – 5:21 PM EDT

Virtual Educational Session

Tumor Biology

Cancer Stem Cells and Therapeutic Resistance

Cancer stem cells are a subpopulation of cells with a high capacity for self-renewal, differentiation and resistance to therapy. In this session, we will define cancer stem cells, discuss cellular plasticity, interactions between cancer stem cells and the tumor microenvironment, and mechanisms that contribute to therapeutic resistance.

Robert S Kerbel, Dolores Hambardzumyan, Jennifer S. Yu

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Drug Development, Experimental and Molecular Therapeutics

Molecular Imaging in Cancer Research

This session will cover the fundamentals as well as the major advances made in the field of molecular imaging. Topics covered will include the basics for optical, nuclear, and ultrasound imaging; the pros and cons of each modality; and the recent translational advancements. Learning objectives include the fundamentals of each imaging modality, recent advances in the technology, the processes involved to translate an imaging agent from bench to bedside, and how molecular imaging can gui

Julie Sutcliffe, Summer L Gibbs, Mark D Pagel, Katherine W Ferrara

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Tumor Biology, Immunology, Experimental and Molecular Therapeutics, Drug Development

Tumor Endothelium: The Gatekeepers of Tumor Immune Surveillance

Tumor-associated endothelium is a gatekeeper that coordinates the entry and egress of innate and adaptive immune cells within the tumor microenvironment. This is achieved, in part, via the coordinated expression of chemokines and cell adhesion molecules on the endothelial cell surface that attract and retain circulating leukocytes. Crosstalk between adaptive immune cells and the tumor endothelium is therefore essential for tumor immune surveillance and the success of immune-based thera

Dai Fukumura, Maria M Steele, Wen Jiang, Andrew C Dudley

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Immunology, Experimental and Molecular Therapeutics

Novel Strategies in Cancer Immunotherapy: The Next Generation of Targets for Anticancer Immunotherapy

T-cell immunotherapy in the form of immune checkpoint blockade or cellular T-cell therapies has been tremendously successful in some types of cancer. This success has opened the door to consider what other modalities or types of immune cells can be harnessed for exert antitumor functions. In this session, experts in their respective fields will discuss topics including novel approaches in immunotherapy, including NK cells, macrophage, and viral oncotherapies.

Evanthia Galanis, Kerry S Campbell, Milan G Chheda, Jennifer L Guerriero

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Tumor Biology, Drug Development, Immunology, Clinical Research Excluding Trials

Benign Cells as Drivers of Cancer Progression: Fat and Beyond

Carcinomas develop metastases and resistance to therapy as a result of interaction with tumor microenvironment, composed of various nonmalignant cell types. Understanding the complexity and origins of tumor stromal cells is a prerequisite for development of effective treatments. The link between obesity and cancer progression has revealed the engagement of adipose stromal cells (ASC) and adipocytes from adjacent fat tissue. However, the molecular mechanisms through which they stimulate

Guojun Wu, Matteo Ligorio, Mikhail Kolonin, Maria T Diaz-Meco

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Clinical Research Excluding Trials, Experimental and Molecular Therapeutics, Tumor Biology

Dharma Master Jiantai Symposium on Lung Cancer: Know Thy Organ – Lessons Learned from Lung and Pancreatic Cancer Research

The term “cancer” encompasses hundreds of distinct disease entities involving almost every possible site in the human body. Effectively interrogating cancer, either in animals models or human specimens, requires a deep understanding of the involved organ. This includes both the normal cellular constituents of the affected tissue as well as unique aspects of tissue-specific tumorigenesis. It is critical to “Know Thy Organ” when studying cancer. This session will focus on two of the most

Trudy G Oliver, Hossein Borghaei, Laura Delong Wood, Howard C Crawford

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Methods Workshop

Clinical Trials

Clinical Trial Design: Part 1: Novel Approaches and Methods in Clinical Trial Design

Good clinical trial design has always had to balance the competing interests of effectively and convincingly answering the question with the limitations imposed by scarce resources, complex logistics, and risks and potential benefits to participants. New targeted therapies, immuno-oncology, and novel combination treatments add new challenges on top of the old ones. This session will introduce these concerns and 1) suggest ways to consider what outcomes are relevant, 2) how we can best

Mary W. Redman, Nolan A. Wages, Susan G Hilsenbeck, Karyn A. Goodman

DETAILS

Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Methods Workshop

Tumor Biology, Drug Development

High-Throughput Screens for Drivers of Progression and Resistance

The sequencing of human cancers now provides a landscape of the genetic alterations that occur in human cancer, and increasingly knowledge of somatic genetic alterations is becoming part of the evaluation of cancer patients. In some cases, this information leads directly to the selection of particular therapeutic approaches; however, we still lack the ability to decipher the significance of genetic alterations in many cancers. This session will focus on recent developments that permit the identification of molecular targets in specific cancers. This information, coupled with genomic characterization of cancer, will facilitate the development of new therapeutic agents and provide a path to implement precision cancer medicine to all patients.

William C Hahn, Mark A Dawson, Mariella Filbin, Michael Bassik

DETAILS

Monday, June 22

3:45 PM – 5:15 PM EDT

Defining a cancer dependency map

William C Hahn

Introduction

William C Hahn

Genome-scale CRISPR screens in 3D spheroids identify cancer vulnerabilities

Michael Bassik

Utilizing single-cell RNAseq and CRISPR screens to target cancer stem cells in pediatric brain tumors

Mariella Filbin
  • many gliomas are defined by discreet mutational spectra that also discriminates based on age and site as well (for example many cortical tumors have mainly V600E Braf mutations while thalamus will be FGFR1
  • they did single cell RNAseq on needle biopsy from 7 gliomas which gave about 3500 high quality single cells; obtained full length RNA
  • tumors clustered mainly where the patient it came from but had stromal cell contamination probably so did a deconvolution?  Copy number variation showed which were tumor cells and did principle component analysis
  • it seems they used a human glioma model as training set
  • identified a stem cell like glioma cell so concentrated on the genes altered in these for translational studies
  • developed multiple PDX models from patients
  • PDX transcriptome closest to patient transcriptome but organoid grown in serum free very close while organoids grown in serum very distinct transcriptome
  • developed a CRISPR barcoded library to determine genes for survival genes
  • pulled out BMI1  and EZH2 (polycomb complex proteins) as good targets

Virtual Methods Workshop

Prevention Research, Survivorship, Clinical Research Excluding Trials, Epidemiology

Implementation Science Methods for Cancer Prevention and Control in Diverse Populations: Integration of Implementation Science Methods in Care Settings

Through this Education Session we will use examples from ongoing research to provide an overview of implementation science approaches to cancer prevention and control research. We draw on examples to highlight study design approaches, research methods, and real-world solutions when applying implementation science to achieve health equity. Approaches to defining change in the care setting and measuring sustained changes are also emphasized. Using real examples of patient navigation prog

Graham A Colditz, Sanja Percac-Lima, Nathalie Huguet

DETAILS

Monday, June 22

3:45 PM – 5:30 PM EDT

Virtual Educational Session

Regulatory Science and Policy, Epidemiology

COVID-19 and Cancer: Guidance for Clinical Trial Conduct and Considerations for RWE

This session will consider the use of real-world evidence in the context of oncology clinical trials affected by the COVID-19 pandemic. Key aspects of the FDA’s recent “Guidance on Conduct of Clinical Trials of Medical Products of Medical Products during COVID-19 Public Health Emergency” will be discussed, including telemedicine, accounting for missing data, obtaining laboratory tests and images locally, using remote informed consent procedures, and additional considerations for contin

Wendy Rubinstein, Paul G. Kluetz, Amy P. Abernethy, Jonathan Hirsch, C.K. Wang

 

 

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Important but Unseen Human Embryo Developmental Stages Mimicked in Lab

 

Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

Scientists have created embryo-like structures that mimic a crucial yet not much known stage of human development. The structures, created from stem cells and called gastruloids, are the first to form a 3D assembly that lays out how the body will take shape. The gastruloids developed rudimentary components of a heart and nervous system, but lacked the components to form a brain and other cell types that would make them capable of becoming a viable fetus.

Human embryos take a momentous leap in their third week, when the largely homogeneous ball of cells starts to differentiate and develop specific characteristics of the body parts they will become, a process known as gastrulation. During this process, the embryo elongates and lays down a body plan with a head and tail, often called the head-to-tail axis. But scientists have never seen this process live in action. That is partly because many countries have regulations that stop embryos from being grown in the laboratory for research beyond 14 days.

Over the past years, several research groups have cultured embryonic stem-cell structures that model when cells start to differentiate. The latest model developed at the University of Cambridge, UK and their collaborators in the Netherlands, Showed for the first time what happens when the blueprint for the body’s development is laid out, around 18–21 days after conception. Genetic analysis showed that the cells formed were those that would eventually go on to form muscles in the trunk, vertebrae, heart and other organs.

If everything is done properly, the cells develop into 3D structures on their own — and then spontaneously mimic the gastrulation process. Although they display certain key features of a 21-day-old embryo, the gastruloids reach that stage after just 72 hours and survive for maximum 4 days before collapsing. Scientists will probably use the model to make structures that are even more realistic representations of early development.

The model could help scientists to understand the role of genetics and environmental factors in different disorders. The artificial structures make it possible to avoid ethical concerns about doing research on human embryos. But as the structures become more advanced and life-like, there may be ethical restrictions.

SOURCE

David Cyranoski

References for Original Study

https://www.nature.com/articles/d41586-020-01757-z?utm_source=Nature+Briefing

 

Other References:

https://pubmed.ncbi.nlm.nih.gov/32528178/

https://pubmed.ncbi.nlm.nih.gov/22804578/

https://pubmed.ncbi.nlm.nih.gov/24973948/

https://pubmed.ncbi.nlm.nih.gov/27419872/

https://pubmed.ncbi.nlm.nih.gov/28179190/

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Live Notes, Real Time Conference Coverage 2020 AACR Virtual Meeting April 27, 2020 Minisymposium on Signaling in Cancer 11:45am-1:30 pm

Reporter: Stephen J. Williams, PhD.

SESSION VMS.MCB01.01 – Emerging Signaling Vulnerabilities in Cancer
April 27, 2020, 11:45 AM – 1:30 PM
Virtual Meeting: All Session Times Are U.S. EDT
DESCRIPTION

All session times are U.S. Eastern Daylight Time (EDT). Access to AACR Virtual Annual Meeting I sessions are free with registration. Register now at http://www.aacr.org/virtualam2020

Session Type

Virtual Minisymposium

Track(s)

Molecular and Cellular Biology/Genetics

16 Presentations
11:45 AM – 1:30 PM
– Chairperson

J. Silvio Gutkind. UCSD Moores Cancer Center, La Jolla, CA

11:45 AM – 1:30 PM
– Chairperson

  • in 80’s and 90’s signaling focused on defects and also oncogene addiction.  Now the field is switching to finding vulnerabilities in signaling cascades in cancer

Adrienne D. Cox. University of North Carolina at Chapel Hill, Chapel Hill, NC

11:45 AM – 11:55 AM
– Introduction

J. Silvio Gutkind. UCSD Moores Cancer Center, La Jolla, CA

11:55 AM – 12:05 PM
1085 – Interrogating the RAS interactome identifies EFR3A as a novel enhancer of RAS oncogenesis

Hema Adhikari, Walaa Kattan, John F. Hancock, Christopher M. Counter. Duke University, Durham, NC, University of Texas MD Anderson Cancer Center, Houston, TX

Abstract: Activating mutations in one of the three RAS genes (HRAS, NRAS, and KRAS) are detected in as much as a third of all human cancers. As oncogenic RAS mediates it tumorigenic signaling through protein-protein interactions primarily at the plasma membrane, we sought to document the protein networks engaged by each RAS isoform to identify new vulnerabilities for future therapeutic development. To this end, we determined interactomes of oncogenic HRAS, NRAS, and KRAS by BirA-mediated proximity labeling. This analysis identified roughly ** proteins shared among multiple interactomes, as well as a smaller subset unique to a single RAS oncoprotein. To identify those interactome components promoting RAS oncogenesis, we created and screened sgRNA library targeting the interactomes for genes modifying oncogenic HRAS-, NRAS-, or KRAS-mediated transformation. This analysis identified the protein EFR3A as not only a common component of all three RAS interactomes, but when inactivated, uniformly reduced the growth of cells transformed by any of the three RAS isoforms. EFR3A recruits a complex containing the druggable phosphatidylinositol (Ptdlns) 4 kinase alpha (PI4KA) to the plasma membrane to generate the Ptdlns species PI4P. We show that EFR3A sgRNA reduced multiple RAS effector signaling pathways, suggesting that EFR3A acts at the level of the oncoprotein itself. As lipids play a critical role in the membrane localization of RAS, we tested and found that EFR3A sgRNA reduced not only the occupancy of RAS at the plasma membrane, but also the nanoclustering necessary for signaling. Furthermore, the loss of oncogenic RAS signaling induced by EFR3A sgRNA was rescued by targeting PI4K to the plasma membrane. Taken together, these data support a model whereby EFR3A recruits PI4K to oncogenic RAS to promote plasma membrane localization and nonclustering, and in turn, signaling and transformation. To investigate the therapeutic potential of this new RAS enhancer, we show that EFR3A sgRNA reduced oncogenic KRAS signaling and transformed growth in a panel of pancreatic ductal adenocarcinoma (PDAC) cell lines. Encouraged by these results we are exploring whether genetically inactivating the kinase activity of PI4KA inhibits oncogenic signaling and transformation in PDAC cell lines. If true, pharmacologically targeting PI4K may hold promise as a way to enhance the anti-neoplastic activity of drugs targeting oncogenic RAS or its effectors.

@DukeU

@DukeMedSchool

@MDAndersonNews

  • different isoforms of ras mutations exist differentially in various tumor types e.g. nras vs kras
  • the C terminal end serve as hotspots of mutations and probably isoform specific functions
  • they determined the interactomes of nras and kras and determined how many candidates are ras specific
  • they overlayed results from proteomic and CRSPR screen; EFR3a was a potential target that stuck out
  • using TCGA patients with higher EFR3a had poorer prognosis
  • EFR3a promotes Ras signaling; and required for RAS driven tumor growth (in RAS addicted tumors?)
  • EGFR3a promotes clustering of oncogenic RAS at plasma membrane

 

12:05 PM – 12:10 PM
– Discussion

12:10 PM – 12:20 PM
1086 – Downstream kinase signaling is dictated by specific KRAS mutations; Konstantin Budagyan, Jonathan Chernoff. Drexel University College of Medicine, Philadelphia, PA, Fox Chase Cancer Center, Philadelphia, PA @FoxChaseCancer

Abstract: Oncogenic KRAS mutations are common in colorectal cancer (CRC), found in ~50% of tumors, and are associated with poor prognosis and resistance to therapy. There is substantial diversity of KRAS alleles observed in CRC. Importantly, emerging clinical and experimental analysis of relatively common KRAS mutations at amino acids G12, G13, A146, and Q61 suggest that each mutation differently influences the clinical properties of a disease and response to therapy. For example, KRAS G12 mutations confer resistance to EGFR-targeted therapy, while G13D mutations do not. Although there is clinical evidence to suggest biological differences between mutant KRAS alleles, it is not yet known what drives these differences and whether they can be exploited for allele-specific therapy. We hypothesized that different KRAS mutants elicit variable alterations in downstream signaling pathways. To investigate this hypothesis, we created a novel system by which we can model KRAS mutants in isogenic mouse colon epithelial cell lines. To generate the cell lines, we developed an assay using fluorescent co-selection for CRISPR-driven genome editing. This assay involves simultaneous introduction of single-guide RNAs (sgRNAs) to two different endogenous loci resulting in double-editing events. We first introduced Cas9 and blue fluorescent protein (BFP) into mouse colon epithelial cell line containing heterozygous KRAS G12D mutation. We then used sgRNAs targeting BFP and the mutant G12D KRAS allele along with homology-directed repair (HDR) templates for a GFP gene and a KRAS mutant allele of our choice. Cells that successfully undergo HDR are GFP-positive and contain the desired KRAS mutation. Therefore, selection for GFP-positive cells allows us to identify those with phenotypically silent KRAS edits. Ultimately, this method allows us to toggle between different mutant alleles while preserving the wild-type allele, all in an isogenic background. Using this method, we have generated cell lines with endogenous heterozygous KRAS mutations commonly seen in CRC (G12D, G12V, G12C, G12R, G13D). In order to elucidate cellular signaling pathway differences between the KRAS mutants, we screened the mutated cell lines using a small-molecule library of ~160 protein kinase inhibitors. We found that there are mutation-specific differences in drug sensitivity profiles. These observations suggest that KRAS mutants drive specific cellular signaling pathways, and that further exploration of these pathways may prove to be valuable for identification of novel therapeutic opportunities in CRC.

  • Flourescent coselection of KRAS edits by CRSPR screen in a colorectal cancer line; a cell that is competent to undergo HR can undergo combination multiple KRAS
  • target only mutant allele while leaving wild type intact;
  • it was KRAS editing event in APC  +/- mouse cell line
  • this enabled a screen for kinase inhibitors that decreased tumor growth in isogenic cell lines; PKC alpha and beta 1 inhibitors, also CDK4 inhibitors inhibited cell growth
  • questions about heterogeneity in KRAS clones; they looked at off target guides and looked at effects in screens; then they used top two clones that did not have off target;  questions about 3D culture- they have not done that; Question ? dependency on AKT activity? perhaps the G12E has different downstream effectors

 

12:20 PM – 12:25 PM
– Discussion

12:25 PM – 12:35 PM
1087 – NF1 regulates the RAS-related GTPases, RRAS and RRAS2, independent of RAS activity; Jillian M. Silva, Lizzeth Canche, Frank McCormick. University of California, San Francisco, San Francisco, CA @UCSFMedicine

Abstract: Neurofibromin, which is encoded by the neurofibromatosis type 1 (NF1) gene, is a tumor suppressor that acts as a RAS-GTPase activating protein (RAS-GAP) to stimulate the intrinsic GTPase activity of RAS as well as the closely related RAS subfamily members, RRAS, RRAS2, and MRAS. This results in the conversion of the active GTP-bound form of RAS into the inactive GDP-bound state leading to the downregulation of several RAS downstream effector pathways, most notably MAPK signaling. While the region of NF1 that regulates RAS activity represents only a small fraction of the entire protein, a large extent of the NF1 structural domains and their corresponding mechanistic functions remain uncharacterized despite the fact there is a high frequency of NF1 mutations in several different types of cancer. Thus, we wanted to elucidate the underlying biochemical and signaling functions of NF1 that are unrelated to the regulation of RAS and how loss of these functions contributes to the pathogenesis of cancer. To accomplish this objective, we used CRISPR-Cas9 methods to knockout NF1 in an isogenic “RASless” MEF model system, which is devoid of the major oncogenic RAS isoforms (HRAS, KRAS, and NRAS) and reconstituted with the KRAS4b wild-type or mutant KRASG12C or KRASG12D isoform. Loss of NF1 led to elevated RAS-GTP levels, however, this increase was not as profound as the levels in KRAS-mutated cells or provided a proliferative advantage. Although ablation of NF1 resulted in sustained activation of MAPK signaling, it also unexpectedly, resulted in a robust increase in AKT phosphorylation compared to KRAS-mutated cells. Surprisingly, loss of NF1 in KRAS4b wild-type and KRAS-mutated cells potently suppressed the RAS-related GTPases, RRAS and RRAS2, with modest effects on MRAS, at both the transcript and protein levels. A Clariom™D transcriptome microarray analysis revealed a significant downregulation in the NF-κB target genes, insulin-like growth factor binding protein 2 (IGFBP2), argininosuccinate synthetase 1 (ASS1), and DUSP1, in both the NF1 knockout KRAS4b wild-type and KRAS-mutated cells. Moreover, NF1Null melanoma cells also displayed a potent suppression of RRAS and RRAS2 as well as these NF-κB transcription factors. Since RRAS and RRAS2 both contain the same NF-κB transcription factor binding sites, we hypothesize that IGFBP2, ASS1, and/or DUSP1 may contribute to the NF1-mediated regulation of these RAS-related GTPases. More importantly, this study provides the first evidence of at least one novel RAS-independent function of NF1 to regulate the RAS-related subfamily members, RRAS and RRAS2, in a manner exclusive of its RAS-GTPase activity and this may provide insight into new potential biomarkers and molecular targets for treating patients with mutations in NF1.
  • NF1 and SPRED work together to signal from RTK cKIT through RAS
  • NF1 knockout cells had higher KRAS and had increased cell proliferation
  • NF1 -/-  or SPRED loss had increased ERK phosphorylation and some increase in AKT activity compared to parental cells
  • they used isogenic cell lines devoid of all RAS isoforms and then reconstituted with specific RAS WT or mutants
  • NF1 and SPRED KO both reduce RRAS expression; in an AKT independent mannner
  • NF1 SPRED KO cells have almost no IGFBP2 protein expression and SNAIL so maybe affecting EMT?
  • this effect is independent of its RAS GTPAse activity (noncanonical)

12:35 PM – 12:40 PM
– Discussion

12:40 PM – 12:50 PM
1088 – Elucidating the regulation of delayed-early gene targets of sustained MAPK signaling; Kali J. Dale, Martin McMahon. University of Utah, Salt Lake City, UT, Huntsman Cancer Institute, Salt Lake City, UT

Abstract: RAS and its downstream effector, BRAF, are commonly mutated proto-oncogenes in many types of human cancer. Mutationally activated RAS or BRAF signal through the MEK→ERK MAP kinase (MAPK) pathway to regulate key cancer cell hallmarks such as cell division cycle progression, reduced programmed cell death, and enhanced cell motility. Amongst the list of RAS/RAF-regulated genes are those encoding integrins, alpha-beta heterodimeric transmembrane proteins that regulate cell adhesion to the extracellular matrix. Altered integrin expression has been linked to the acquisition of more aggressive behavior by melanoma, lung, and breast cancer cells leading to diminished survival of cancer patients. We have previously documented the ability of the RAS-activated MAPK pathway to induce the expression of ITGB3 encoding integrin β3 in several different cell types. RAS/RAF-mediated induction of ITGB3 mRNA requires sustained, high-level activation of RAF→MEK→ERK signaling mediated by oncogene activation and is classified as “delayed-early”, in that it is sensitive to the protein synthesis inhibitor cycloheximide. However, to date, the regulatory mechanisms that allow for induced ITGB3 downstream of sustained, high-level activation of MAPK signaling remains obscure. We have identified over 300 DEGs, including those expressing additional cell surface proteins, that display similar regulatory characteristics as ITGB3. We use integrin β3 as a model to test our hypothesis that there is a different mechanism of regulation for delayed-early genes (DEG) compared to the canonical regulation of Immediate-Early genes. There are three regions in the chromatin upstream of the ITGB3 that become more accessible during RAF activation. We are relating the chromatin changes seen during RAF activation to active enhancer histone marks. To elucidate the essential genes of this regulation process, we are employing the use of a genome-wide CRISPR knockout screen. The work presented from this abstract will help elucidate the regulatory properties of oncogenic progression in BRAF mutated cancers that could lead to the identification of biomarkers.

12:50 PM – 12:55 PM
– Discussion

12:55 PM – 1:05 PM
1090 – Regulation of PTEN translation by PI3K signaling maintains pathway homeostasis

Radha Mukherjee, Kiran Gireesan Vanaja, Jacob A. Boyer, Juan Qiu, Xiaoping Chen, Elisa De Stanchina, Sarat Chandarlapaty, Andre Levchenko, Neal Rosen. Memorial Sloan Kettering Cancer Center, New York, NY, Yale University, West Haven, CT, Memorial Sloan Kettering Cancer Center, New York, NY, Memorial Sloan Kettering Cancer Center, New York, NY @sloan_kettering

Abstract: The PI3K pathway is a key regulator of metabolism, cell proliferation and migration and some of its components (e.g. PIK3CA and PTEN) are frequently altered in cancer by genetic events that deregulate its output. However, PI3K signaling is not usually the primary driver of these tumors and inhibitors of components of the pathway have only modest antitumor effects. We now show that both physiologic and oncogenic activation of the PI3K signaling by growth factors and an activating hotspot PIK3CA mutation respectively, cause an increase in the expression of the lipid phosphatase PTEN, thus limiting the duration of the signal and the output of the pathway in tumors. Pharmacologic and physiologic inhibition of the pathway by HER2/PI3K/AKT/mTOR inhibitors and nutrient starvation respectively reduce PTEN, thus buffering the effects of inhibition and contributing to the rebound in pathway activity that occurs in tumors. This regulation is found to be a feature of multiple types of cancer, non-cancer cell line and PDX models thereby highlighting its role as a key conserved feedback loop within the PI3K signaling network, both in vitro and in vivo. Regulation of expression is due to mTOR/4EBP1 dependent control of PTEN translation and is lost when 4EBP1 is knocked out. Translational regulation of PTEN is therefore a major homeostatic regulator of physiologic PI3K signaling and plays a role in reducing the output of oncogenic mutants that deregulate the pathway and the antitumor activity of PI3K pathway inhibitors.

  • mTOR can be a potent regulator of PTEN and therefore a major issue when developing PI3K inhibitors

1:05 PM – 1:10 PM
– Discussion

1:10 PM – 1:20 PM
1091 – BI-3406 and BI 1701963: Potent and selective SOS1::KRAS inhibitors induce regressions in combination with MEK inhibitors or irinotecan

Daniel Gerlach, Michael Gmachl, Juergen Ramharter, Jessica Teh, Szu-Chin Fu, Francesca Trapani, Dirk Kessler, Klaus Rumpel, Dana-Adriana Botesteanu, Peter Ettmayer, Heribert Arnhof, Thomas Gerstberger, Christiane Kofink, Tobias Wunberg, Christopher P. Vellano, Timothy P. Heffernan, Joseph R. Marszalek, Mark Pearson, Darryl B. McConnell, Norbert Kraut, Marco H. Hofmann. Boehringer Ingelheim RCV GmbH & Co KG, Vienna, Austria, The University of Texas MD Anderson Cancer Center, Houston, TX, The University of Texas MD Anderson Cancer Center, Houston, TX, Boehringer Ingelheim RCV GmbH & Co KG, Vienna, Austria

  • there is rational for developing an SOS1 inhibitor (GEF); BI3406 shows better PK and PD as a candidate
  • most sensitive cell lines to inhibitor carry KRAS mutation; NRAS or BRAF mutations are not sensititve
  • KRAS mutation defines sensitivity so they created KRAS mut isogenic cell lines
  • found best to co inhibit SOS and MEK as observed plasticity with only SOS
  • dual combination in lung NSCLC pancreatic showed enhanced efficacy compared to monotherapy
  • SOS1 inhibition plus irinotecan enhances DNA double strand breaks; no increased DNA damage in normal stroma but preferentially in tumor cells
  • these SOS1 had broad activity against KRAS mutant models;
  • phase 1 started in 2019;

@Boehringer

1:20 PM – 1:25 PM
– Discussion

1:25 PM – 1:30 PM
– Closing Remarks

Adrienne D. Cox. University of North Carolina at Chapel Hill, Chapel Hill, NC

Follow on Twitter at:

@pharma_BI

@AACR

@GenomeInstitute

@CureCancerNow

@UCLAJCCC

#AACR20

#AACR2020

#curecancernow

#pharmanews

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Lesson 7 of Cell Signaling 7 Motility: Tubulin and Tutorial Quizes for #TUBiol3373

Stephen J. Williams, Ph.D.

This lesson (lesson 7) will discuss the last type of cytoskeletal structure: microtubules and tubulin.  In addition I want to go over the last quiz answers and also introduce some new poll quizes.

I had given the lecture 7 over Canvas and each of you can download and go over the lecture but I will highlight a few slides in the lecture.

Let’s first review:

Remember that microtubules are the largest of the three cytoskeletal structures:

actin microfilaments < intermediate filaments < microtubules

This is very important to understand as the microtubules, as shown later, shuttle organelles and cellular structures like synaptic vesicles, as well as forming the centrisome and spindle fibers of mitosis.

 

 

 

 

 

 

 

 

 

 

 

 

 

Now remember the quiz question from last time

Remember that actin monomers (the G actin binds ATP)  while tubulin, the protein which makes up the microtubules binds GTP {although it is a little more complex than that as the following diagram shows}

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

See how the growth at the plus end is dependent on tubulin heterodimer GTP while when GDP is only bound to tubulin (both forms) you get a destabilization of the plus end and removal of tubulin dimers (catastrophe) if there is no source of tubulin GTP dimers (alpha tubulin GTP with beta tubulin GTP).

 

 

 

 

Also remember that like actin microfilaments you can have treadmilling (the plus end  continues growing while minus end undergoes catasrophe).  The VIDEO below describes these processes:

 

 

 

Certain SNPs and mutants of tubulin are found and can result in drastic phenotypic changes in microtubule stability and structure. Below is an article where a mutation in tubulin can result in microtubule catastrophe or destabilization of microtubule structures.

 

From: A mutation uncouples the tubulin conformational and GTPase cycles, revealing allosteric control of microtubule dynamics;, E.A. Geyer et al..; elife 2015;4:e10113

Abstract

Microtubule dynamic instability depends on the GTPase activity of the polymerizing αβ-tubulin subunits, which cycle through at least three distinct conformations as they move into and out of microtubules. How this conformational cycle contributes to microtubule growing, shrinking, and switching remains unknown. Here, we report that a buried mutation in αβ-tubulin yields microtubules with dramatically reduced shrinking rate and catastrophe frequency. The mutation causes these effects by suppressing a conformational change that normally occurs in response to GTP hydrolysis in the lattice, without detectably changing the conformation of unpolymerized αβ-tubulin. Thus, the mutation weakens the coupling between the conformational and GTPase cycles of αβ-tubulin. By showing that the mutation predominantly affects post-GTPase conformational and dynamic properties of microtubules, our data reveal that the strength of the allosteric response to GDP in the lattice dictates the frequency of catastrophe and the severity of rapid shrinking.

https://doi.org/10.7554/eLife.10113.001

 

Remember the term allosterism: change in the affinity for binding of a ligand or substrate that is caused by the binding of another ligand away from the active site (for example like 2,3 DPG effect on oxygen binding to hemoglobin

 

Cellular transport of organelles and vesicles: a function of microtubules

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Now the above figure (figure 9 in your Powerpoint) shows the movement of organelles and vesicles in two different types of cells along microtubules.

Note the magenta arrow which goes from the nucleus toward the plus end of the microtubule (at cell membrane) is referred to as anterograde transport and is movement away from center of cell to the periphery.  Retrograde transport is movement of organelles and vesicles from periphery of cell to the center of the cell.

Note that kinesin is involved in anterograde transport while dyenin is involved in retrograde transport

Also refer to the Wiki page which shows a nice cartoon of this walking down a microtubule on the right hand side of the page

https://en.wikipedia.org/wiki/Axonal_transport

 

 

 

 

 

 

 

Cilia; a cellular structure of microtubules (we will talk about cilia later)

for more information on structure of Cillia please see https://www.ncbi.nlm.nih.gov/books/NBK21698/

This is from a posting by Dr. Larry Bernstein of Yale University at https://pharmaceuticalintelligence.com/2015/11/04/cilia-and-tubulin/

 

RESEARCHERS VIDEO AND MEASURE TUBULIN TRANSPORT IN CILIA FOR THE FIRST TIME.

http://health-innovations.org/2015/01/27/researchers-image-and-measure-tubulin-transport-in-cilia/

 

 

https://michellepetersen76.files.wordpress.com/2015/01/uga-researchers-image-and-measure-tubulin-transport-in-cilia-healthinnovations1.png

 

Defective cilia can lead to a host of diseases and conditions in the human body, from rare, inherited bone malformations to blindness, male infertility, kidney disease and obesity. It is known that these tiny cell organelles become deformed and cause these diseases because of a problem related to their assembly, which requires the translocation of vast quantities of the vital cell protein tubulin. What they didn’t know was how tubulin and another cell organelle known as flagella fit into the process.

Now, a new study from University of Georgia shows the mechanism behind tubulin transport and its assembly into cilia, including the first video imagery of the process. The study was published in the Journal of Cell Biology.

Cilia are found throughout the body, so defects in cilia formation affect cells that line airways, brain ventricles or the reproductive track.  One of the main causes of male infertility is the cilia won’t function properly.

The team used total internal reflection fluorescence microscopy to analyze moving protein particles inside the cilia of Chlamydomonas reinhardtii, a green alga widely used as a model for cilia analysis.

The team exploited the natural behaviour of the organism, which is to attach by its cilia to a smooth surface, such as a microscope glass cover. This positions the cilia within the 200-nanometer reach of the total internal reflection fluorescence microscope allowing for the imaging of individual proteins as they move inside the cilia.  A video explaining the process was published along with the study.

Tubulin is transported by this process called intraflagellar transport, or IFT.  Though it has long been suspected in the field and there was indirect evidence to support the theory, this is the first time it has been shown directly, through live imaging, that IFT does function as a tubulin pump.  The team observed that about 400,000 tubulin dimers need to be transported within 60 minutes to assemble a single cilium. Being able to see tubulin moving into cilia allowed for first insights into how this transport is regulated to make sure cilia will have the correct size.

The new findings are expected to have wide implications for a variety of diseases and conditions related to cilia defects in the body.  The team state that they are on the very basic side of this research.  But because more and more diseases are being connected to cilia-related conditions, including obesity and even diabetes, the number of people working on cilia has greatly expanded over the last few years.

 

So here are the answer to last weeks polls

  1. Actin filaments are the SMALLEST of the cytoskeletal structures.  As shown in this lecture it is tubulin that binds GTP.  Actin binds ATP.
  2.  ARP2/3 or actin related proteins 2 and 3 are nucleating proteins that assist in initiating growth of branched chain micofiliment networks.  Formins are associated with unbranched actin formations.
  3.  The answer is GAPs or GTPase activating proteins.  Remember RAS in active state when GTP is bound and when you hydrolyze the GTP to GDP Ras is inactive state

 

 

 

 

 

4.  Okay so I did a type here but the best answer was acetylcholinesterase (AchE) degrading acetylcholine.  Acetylcholinesterase degrades the neurotransmitter acetylcholine into choline and acetate not as I accidentally put into acetylCoA.  The freed choline can then be taken back up into the presynaptic neuron and then, with a new acetyl group (with Coenzyme A) will form acetylcholine.

 

Synthesis of the neurotransmitter acetylcholine

 

 

 

The neuromuscular junction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thanks to all who took the quiz.  Remember it is for your benefit.

 

 

 

 

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Lesson 6 of Cell Signaling & Motility – Cytoskeleton II: #TUBiol3373

Stephen J. Williams, Ph.D.

In this lesson we will go over the biochemical makeup and formation of various actin containing cellular structures involved in cellular motility, structure, as well as the dynamics of muscular contraction.  The lesson had been put on your Canvas and I am emailing you the Google Docs version.  If you are having problems downloading you can download here (I believe maybe the Canvas version had problems with embedding videos properly so that is why I am sending you also by email)

Download Below

cell signaling 6 lesson 2020

After opening the powerpoint (or Google Doc) please review with the following notes which highlight some concepts as well as some reviews and reminders of past lectures.  It may be handy to also have lecture 5 handy if you need to refer to it.  In between some sections there will be polls (really multiple choice quizzes DON’T WORRY you will not be graded on them but they are for your benefit.  There will also be a section under Comments all the way at the end and at the last quiz where you can also ask questions.

Remember you can always email me or Tweet me any questions @StephenJWillia2 using the hashtag #TUBiol3373.

In addition you can also leave comments at the very bottom which can be answered.

Slide 2 of lesson 6 is a refresher of the end of our last lecture, talking about Actin Binding Regulatory Proteins.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The picture above shows a brief review of some of the structures and actin binding proteins involved in helping to form these actin filament structures (like filamin in cross linked structures, profilin which binds the actin monomers [G-actin] and helps with addition of these monomers to the leading plus end.

*** Remember G-actin (Globular Actin) is the monomer and F-actin (filamentious actin) is the polymerized actin strand [filament]

Also remember from the last lecture that G-Actin as monomer has affinity for ATP {Adenosine triphosphate} and these G-Actin-ATP will be able to polymerize to form the F-Actin form.  Also F-actin can then hydrolyze the ATP to ADP and inorganic phosphate.  At this point the actin-ADP unit looses affinity for the remaining F-Actin chain and depolymerization can occur

 

An event referred to as TREADMILLING or when the G actin units are removed from minus end and added to the plus (or growing barbed) end

Also remember that there is a critical concentration of G-Actin-ATP needed for bypassing the lag phase of nucleation before the elongation phase and the rate of addition to the plus end is faster than addition to minus end and greater than the rate of depolymerization at the minus end

Cell Structures That Involve Actin (see links for more information)

  1. filopodia
  2. parallel actin bundles
  3. actin cortex
  4. lamellipodia
  5. stress fibers
  6. microvilli
  7. contractile ring in cytokinesis

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Nucleating proteins Arp (actin related protein and Formins

Arp ====> formation of lamellipodia

Formins ====> formation of stress fibers

Process involving formins starts with a signaling event by activation of a G-protein, the GTP binding protein Rho

Rho is a subfamily member of the Ras superfamily.  The Rho family consists of cdc42, rac1, and RhoA (we will discuss at a later date).  Rho acts like G proteins, as a molecular switch.

Note that just like the Ras member of G-proteins and the Ras GTP/GDP cycle, the Rho activation, deactivation cycle also depends on GEFs [Guanine nucleotide exchange factors] and GAPs [GTPase activating proteins] and also GDIs [guanine nucleotide dissociation inhibitors which we will discuss later but involved in preventing Rho diffusion in the cell, acting as a tether].

Myosin and Motor (muscle) Function; Neuromuscular junctions, the sarcoplasmic reticulum and Ohhh the plethora of signaling events

In this section, from slides 29 to 54, we talk about myosin and the interactions between myosin and actin in formation of the contractile unit of the muscle (skeletal).

We also talk about some familiar signaling events, in particular the neuromuscular junction.

At this junction is a special type of acetylcholine receptor

Remember we talked about two types of acetylcholine receptors:

  1. muscarinic receptors – typical GPCRs that tranduce the signal via Gi or Gq depending on the muscarinic subtype
  2. nicotinic receptors – these are ligand {receptor} operated channels and when activated opens a Na+ channel which leads to depolarization

 

Now the depolarization activates another set of channels, the voltage operated calcium channels so we have two types of ion channels: Receptor {ligand} operated channels and Voltage operated channels.  These are sometimes abbreviated as ROCs and VOCs.

The unit of the myofibril on the contactile unit of the skeletal muscle is the sarcomere and upon the calcium transient, the sarcomere shortens with the two z-disks moving closer to each other as shown in the video in the lecture.

Also briefly review the introduction part on microtubules. We will finish that next week. Note that the microtubule is comprised of the protein tubulin, which is another GTP binding protein.

For other articles and more information please see

Lesson 5 Cell Signaling And Motility: Cytoskeleton & Actin: Curations and Articles of reference as supplemental information: #TUBiol3373

Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Identification of Biomarkers that are Related to the Actin Cytoskeleton

 

 

 

 

 

 

 

 

 

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Bioinformatic Tools for RNASeq: A Curation

Curator: Stephen J. Williams, Ph.D. 

 

Note:  This will be an ongoing curation as new information and tools become available.

RNASeq is a powerful tool for the analysis of the transcriptome profile and has been used to determine the transcriptional changes occurring upon stimuli such as drug treatment or detecting transcript differences between biological sample cohorts such as tumor versus normal tissue.  Unlike its genomic companion, whole genome and whole exome sequencing, which analyzes the primary sequence of the genomic DNA, RNASeq analyzes the mRNA transcripts, thereby more closely resembling the ultimate translated proteome. In addition, RNASeq and transcriptome profiling can determine if splicing variants occur as well as determining the nonexomic sequences, such as miRNA and lncRNA species, all of which have shown pertinence in the etiology of many diseases, including cancer.

However, RNASeq, like other omic technologies, generates enormous big data sets, which requires multiple types of bioinformatic tools in order to correctly analyze the sequence reads, and to visualize and interpret the output data.  This post represents a curation by the RNA-Seq blog of such tools useful for RNASeq studies and lists and reviews published literature using these curated tools.

 

From the RNA-Seq Blog

List of RNA-Seq bioinformatics tools

Posted by: RNA-Seq Blog in Data Analysis, Web Tools September 16, 2015 6,251 Views

from: https://en.wiki2.org/wiki/List_of_RNA-Seq_bioinformatics_tools

A review of some of the literature using some of the aforementioned curated tools are discussed below:

 

A.   Tools Useful for Single Cell RNA-Seq Analysis

 

B.  Tools for RNA-Seq Analysis of the Sliceasome

 

C.  Tools Useful for RNA-Seq read assembly visualization

 

Other articles on RNA and Transcriptomics in this Open Access Journal Include:

NIH to Award Up to $12M to Fund DNA, RNA Sequencing Research: single-cell genomics, sample preparation, transcriptomics and epigenomics, and genome-wide functional analysis.

Single-cell Genomics: Directions in Computational and Systems Biology – Contributions of Prof. Aviv Regev @Broad Institute of MIT and Harvard, Cochair, the Human Cell Atlas Organizing Committee with Sarah Teichmann of the Wellcome Trust Sanger Institute

Complex rearrangements and oncogene amplification revealed by long-read DNA and RNA sequencing of a breast cancer cell line

Single-cell RNA-seq helps in finding intra-tumoral heterogeneity in pancreatic cancer

First challenge to make use of the new NCI Cloud Pilots – Somatic Mutation Challenge – RNA: Best algorithms for detecting all of the abnormal RNA molecules in a cancer cell

Evolution of the Human Cell Genome Biology Field of Gene Expression, Gene Regulation, Gene Regulatory Networks and Application of Machine Learning Algorithms in Large-Scale Biological Data Analysis

 

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

Parkinson’s Disease (PD), characterized by both motor and non-motor system pathology, is a common neurodegenerative disorder affecting about 1% of the population over age 60. Its prevalence presents an increasing social burden as the population ages. Since its introduction in the 1960’s, dopamine (DA)-replacement therapy (e.g., L-DOPA) has remained the gold standard treatment. While improving PD patients’ quality of life, the effects of treatment fade with disease progression and prolonged usage of these medications often (>80%) results in side effects including dyskinesias and motor fluctuations. Since the selective degeneration of A9 mDA neurons (mDANs) in the substantia nigra (SN) is a key pathological feature of the disease and is directly associated with the cardinal motor symptoms, dopaminergic cell transplantation has been proposed as a therapeutic strategy.

 

Researchers showed that mammalian fibroblasts can be converted into embryonic stem cell (ESC)-like induced pluripotent stem cells (iPSCs) by introducing four transcription factors i.e., Oct4, Sox2, Klf4, and c-Myc. This was then accomplished with human somatic cells, reprogramming them into human iPSCs (hiPSCs), offering the possibility of generating patient-specific stem cells. There are several major barriers to implementation of hiPSC-based cell therapy for PD. First, probably due to the limited understanding of the reprogramming process, wide variability exists between the differentiation potential of individual hiPSC lines. Second, the safety of hiPSC-based cell therapy has yet to be fully established. In particular, since any hiPSCs that remain undifferentiated or bear sub-clonal tumorigenic mutations have neoplastic potential, it is critical to eliminate completely such cells from a therapeutic product.

 

In the present study the researchers established human induced pluripotent stem cell (hiPSC)-based autologous cell therapy. Researchers reported a platform of core techniques for the production of mDA progenitors as a safe and effective therapeutic product. First, by combining metabolism-regulating microRNAs with reprogramming factors, a method was developed to more efficiently generate clinical grade iPSCs, as evidenced by genomic integrity and unbiased pluripotent potential. Second, a “spotting”-based in vitro differentiation methodology was established to generate functional and healthy mDA cells in a scalable manner. Third, a chemical method was developed that safely eliminates undifferentiated cells from the final product. Dopaminergic cells thus produced can express high levels of characteristic mDA markers, produce and secrete dopamine, and exhibit electrophysiological features typical of mDA cells. Transplantation of these cells into rodent models of PD robustly restored motor dysfunction and reinnervated host brain, while showing no evidence of tumor formation or redistribution of the implanted cells.

 

Together these results supported the promise of these techniques to provide clinically applicable personalized autologous cell therapy for PD. It was recognized by researchers that this methodology is likely to be more costly in dollars and manpower than techniques using off-the-shelf methods and allogenic cell lines. Nevertheless, the cost for autologous cell therapy may be expected to decrease steadily with technological refinement and automation. Given the significant advantages inherent in a cell source free of ethical concerns and with the potential to obviate the need for immunosuppression, with its attendant costs and dangers, it was proposed that this platform is suitable for the successful implementation of human personalized autologous cell therapy for PD.

 

References:

 

https://www.jci.org/articles/view/130767/pdf?elqTrackId=2fd7d0edee744f9cb6d70a686d7b273b

 

https://www.ncbi.nlm.nih.gov/pubmed/31714896

 

https://www.ncbi.nlm.nih.gov/pubmed/23666606

 

https://www.ncbi.nlm.nih.gov/pubmed/27343168

 

https://www.ncbi.nlm.nih.gov/pubmed/21495962

 

https://www.ncbi.nlm.nih.gov/pubmed/28083784

 

https://www.ncbi.nlm.nih.gov/pubmed/20336395

 

https://www.ncbi.nlm.nih.gov/pubmed/28585381

 

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

Effective humoral immune responses to infection and immunization are defined by high-affinity antibodies generated as a result of B cell differentiation and selection that occurs within germinal centers (GC). Within the GC, B cells undergo affinity maturation, an iterative and competitive process wherein B cells mutate their immunoglobulin genes (somatic hypermutation) and undergo clonal selection by competing for T cell help. Balancing the decision to remain within the GC and continue participating in affinity maturation or to exit the GC as a plasma cell (PC) or memory B cell (MBC) is critical for achieving optimal antibody avidity, antibody quantity, and establishing immunological memory in response to immunization or infection. Humoral immune responses during chronic infections are often dysregulated and characterized by hypergammaglobulinemia, decreased affinity maturation, and delayed development of neutralizing antibodies. Previous studies have suggested that poor antibody quality is in part due to deletion of B cells prior to establishment of the GC response.

 

In fact the impact of chronic infections on B cell fate decisions in the GC remains poorly understood. To address this question, researchers used single-cell transcriptional profiling of virus-specific GC B cells to test the hypothesis that chronic viral infection disrupted GC B cell fate decisions leading to suboptimal humoral immunity. These studies revealed a critical GC differentiation checkpoint that is disrupted by chronic infection, specifically at the point of dark zone re-entry. During chronic viral infection, virus-specific GC B cells were shunted towards terminal plasma cell (PC) or memory B cell (MBC) fates at the expense of continued participation in the GC. Early GC exit was associated with decreased B cell mutational burden and antibody quality. Persisting antigen and inflammation independently drove facets of dysregulation, with a key role for inflammation in directing premature terminal GC B cell differentiation and GC exit. Thus, the present research defines GC defects during chronic viral infection and identify a critical GC checkpoint that is short-circuited, preventing optimal maturation of humoral immunity.

 

Together, these studies identify a key GC B cell differentiation checkpoint that is dysregulated during chronic infection. Further, it was found that the chronic inflammatory environment, rather than persistent antigen, is sufficient to drive altered GC B cell differentiation during chronic infection even against unrelated antigens. However, the data also indicate that inflammatory circuits are likely linked to perception of antigen stimulation. Nevertheless, this study reveals a B cell-intrinsic program of transcriptional skewing in chronic viral infection that results in shunting out of the cyclic GC B cell process and early GC exit with consequences for antibody quality and hypergammaglobulinemia. These findings have implications for vaccination in individuals with pre-existing chronic infections where antibody responses are often ineffective and suggest that modulation of inflammatory pathways may be therapeutically useful to overcome impaired humoral immunity and foster affinity maturation during chronic viral infections.

 

References:

 

https://www.biorxiv.org/content/10.1101/849844v1

 

https://www.ncbi.nlm.nih.gov/pubmed/25656706

 

https://www.ncbi.nlm.nih.gov/pubmed/27653600

 

https://www.ncbi.nlm.nih.gov/pubmed/26912368

 

https://www.ncbi.nlm.nih.gov/pubmed/26799208

 

https://www.ncbi.nlm.nih.gov/pubmed/23001146

 

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

One of the most contagious diseases known to humankind, measles killed an average of 2.6 million people each year before a vaccine was developed, according to the World Health Organization. Widespread vaccination has slashed the death toll. However, lack of access to vaccination and refusal to get vaccinated means measles still infects more than 7 million people and kills more than 100,000 each year worldwide as reported by WHO. The cases are on the rise, tripling in early 2019 and some experience well-known long-term consequences, including brain damage and vision and hearing loss. Previous epidemiological research into immune amnesia suggests that death rates attributed to measles could be even higher, accounting for as much as 50 percent of all childhood mortality.

 

Over the last decade, evidence has mounted that the measles vaccine protects in two ways. It prevents the well-known acute illness with spots and fever and also appears to protect from other infections over the long term by giving general boost to the immune system. The measles virus can impair the body’s immune memory, causing so-called immune amnesia. By protecting against measles infection, the vaccine prevents the body from losing or “forgetting” its immune memory and preserves its resistance to other infections. Researchers showed that the measles virus wipes out 11% to 73% of the different antibodies that protect against viral and bacterial strains a person was previously immune to like from influenza to herpes virus to bacteria that cause pneumonia and skin infections.

 

This study at Harvard Medical School and their collaborators is the first to measure the immune damage caused by the virus and underscores the value of preventing measles infection through vaccination. The discovery that measles depletes people’s antibody repertoires, partially obliterating immune memory to most previously encountered pathogens, supports the immune amnesia hypothesis. It was found that those who survive measles gradually regain their previous immunity to other viruses and bacteria as they get re-exposed to them. But because this process may take months to years, people remain vulnerable in the meantime to serious complications of those infections and thus booster shots of routine vaccines may be required.

 

VirScan detects antiviral and antibacterial antibodies in the blood that result from current or past encounters with viruses and bacteria, giving an overall snapshot of the immune system. Researchers gathered blood samples from unvaccinated children during a 2013 measles outbreak in the Netherlands and used VirScan to measure antibodies before and two months after infection in 77 children who’d contracted the disease. The researchers also compared the measurements to those of 115 uninfected children and adults. Researchers found a striking drop in antibodies from other pathogens in the measles-infected children that clearly suggested a direct effect on the immune system resembling measles-induced immune amnesia.

 

Further tests revealed that severe measles infection reduced people’s overall immunity more than mild infection. This could be particularly problematic for certain categories of children and adults, the researchers said. The present study observed the effects in previously healthy children only. But, measles is known to hit malnourished children much harder, the degree of immune amnesia and its effects could be even more severe in less healthy populations. Inoculation with the MMR (measles, mumps, rubella) vaccine did not impair children’s overall immunity. The results align with decades of research. Ensuring widespread vaccination against measles would not only help prevent the expected 120,000 deaths that will be directly attributed to measles this year alone, but could also avert potentially hundreds of thousands of additional deaths attributable to the lasting damage to the immune system.

 

References:

 

https://hms.harvard.edu/news/inside-immune-amnesia?utm_source=Silverpop

 

https://science.sciencemag.org/content/366/6465/599

 

www.who.int/immunization/newsroom/measles-data-2019/en/

 

https://www.ncbi.nlm.nih.gov/pubmed/20636817

 

https://www.ncbi.nlm.nih.gov/pubmed/27157064

 

https://www.ncbi.nlm.nih.gov/pubmed/30797735

 

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