Cell Signaling Pathways – A Case Study Approach

Slides:



Advertisements
Similar presentations
Cancer and the Cell Cycle : An overview Ken Wu. Disclaimer This tutorial is a simple and conceptual guide to the cancer module and the cell cycle If there.
Advertisements

Lecture 2, Oct 11 Important points from 10/7:
Chapter 15: Signal transduction Know the terminology: Enzyme-linked receptor, G-protein linked receptor, nuclear hormone receptor, G-protein, adaptor protein,
Cell signaling: responding to the outside world Cells interact with their environment by interpreting extracellular signals via proteins that span their.
UNIT FIVE CHAPTER 9. CELL COMMUNICATION CHAPTER 9.
Lecture 23 Signal Transduction 2
Signal Pathways in Eukaryotic Cells Overview. Lipid Soluble Hormones.
Cell Signaling Lecture 10.
Chap. 16 Signaling Pathways That Control Gene Expression
Ligand Receptor Cortisol Receptor is located in the cytosol Retinoid Receptors are in the nucleus Target gene in the nucleus Regulation of Transcription.
Signal Transduction II Transduction Proteins & Second Messengers.
Cytoplasmic Signaling Circuitry Programs Many of the Traits of Cancer
Signal Transduction Biochemistry – February 23, 2005 Chapter 12 – parts 12.3, 12.4.
Mitogen-Activated Protein Kinase Pathway. Mitogen- a compound that encourages a cell to commence division, triggering mitosis Cell division requires the.
Signal Response and Amplification
Cell Communication Chapter 9. Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in.
Cell Signaling II Signal Transduction pathways
CHAPTER 13 Insulin Signaling. Figure 13.1 – General mechanism of signal transduction across a membrane Steps involved: 1. Release of primary messenger.
 Regulation of Cell Number and Cancer Cells Special Limited Edition Packet Tuesday, November 10,
Cell Signaling. I. OVERVIEW Soluble chemical signals sent from one cell to another are essential for communication The cellular recipient of the signal.
Specialized signaling pathways 1: RTK associated pathways
Chapter 15- Cell Communication Part I- General signaling strategies
Introduction to Signaling Networks Biophysics 702, February 2012 Jonathan P Butchar.
Extracellular Environment. Extracellular Environment.
Pharmacology-1 PHL 351 Abdelkader Ashour, Ph.D..
Negative regulation of cell cycle by intracellular signals Checkpoint p53 detects DNA damage & activates p21 p21 inhibits cdk2-cyclinA Intracellular Regulation.
1 Lecture 11: Signal transduction and cell cycle regulation Textbook of Receptor Pharmacology, 3rd edition.
Date of download: 7/5/2016 Copyright © 2016 McGraw-Hill Education. All rights reserved. Insulin signaling pathways. The insulin signaling pathways provide.
Cellular Signaling Section 2-3. Discussion Points: What happened? How did you recognize where to go? How does this model cell communication? What effect.
An Introduction to Medicinal Chemistry 3/e PROTEINS AS DRUG TARGETS:
Lung Cancer Tumour Markers
How do you think cells communicate?
Model for regulation of the Ras p21 product and for the GTPase-activating protein (GAP) as a downstream effector and regulator of ras activity. Ras is.
Biomembrane and Cell signalling BCH 452(V) Cell To Cell Comunication
Briefly explain the location of the cellular receptor and the mechanism of action of steroid hormones. Distinguish between synaptic, paracrine, and endocrine.
Chapter 11 Cell Communication.
Cellular Communication
3.D.3 Signal Transduction Signal transduction pathways link signal reception with cellular response.
Cell Signaling.
Targeting signal transduction
OVERVIEW: Signals for cell surface receptors (hydrophilic):
Overview of Cellular Signaling Mechanisms
Cell Communication Part II
Sustaining Proliferative Signaling and Evading Growth Suppressors
Cell Communication Chapter 11 11/17/ :51 PM
Sustaining Proliferative Signaling and Evading Growth Suppressors
Chap. 16 Problem 1 Cytokine receptors and RTKs both form functional dimers on binding of ligand. Ligand binding activates cytosolic kinase domains which.
You have identified a novel cytoplasmic protein
Cell Communication REVIEW.
Signal Transduction Through the Epidermal Growth Factor Receptor
دکتر مجیری داروساز متخصص فارماکولوژی
In multicellular organisms
Development of PI3K/AKT/mTOR Pathway Inhibitors and Their Application in Personalized Therapy for Non–Small-Cell Lung Cancer  Vassiliki Papadimitrakopoulou,
Endocrinology Introduction Lecture 3.
MCB Exam 2 Review 11/3/2018.
Roles for KRAS in Pancreatic Tumor Development and Progression
The RAS/MAPK Axis Gets Stressed Out
Chapter 11 Cell Communication.
Signal Transduction Through the Epidermal Growth Factor Receptor
AKT/PKB Signaling: Navigating Downstream
11.2 Cell Communication.
Platelet-derived growth factor (PDGF) signalling pathway.
Apoptosis: Current Biology
Phases of the Cell Cycle
Phases of the Cell Cycle
RAS activation RAS activation (A) RAS is bound to GDP in the inactive state. Signal transduction can lead to the activation of RAS, via a GEF (GDP/GTP.
Brief Review – Growth Factors and Receptors
Characterization of the MM.1 human multiple myeloma (MM) cell lines
Successful targeting of ErbB2 receptors—is PTEN the key?
Presentation transcript:

Cell Signaling Pathways – A Case Study Approach By L. Emtage, L. Bradbury, N. Coleman, D. Davenport, A. Dunning and J. Grew

Signaling: An overview Receptor Cell Membrane This slide can be used to review the basic mechanisms of signal transduction, including common mechanisms of activation and inhibition such as binding, recruitment to substrate, and phosphorylation. Relay Molecules = signaling proteins Output : effectors Slide adapted from NESI 2012

The Receptor Tyrosine Kinase (RTK) – MAP Kinase pathway Signal RTK Plasma membrane Ras Ras Sos (Ras GEF) (G protein) Grb2 (adapter) GTP GDP MAPKKK This is the core of the RTK-MAPK signaling pathway. All signaling molecules in the core MAPK signaling pathway are positive regulators of their downstream targets. Each component of the pathway sequentially activates the next, as follows: 1. Signaling is typically initiated when ligand binds to the extracellular ligand-binding domain of two RTK sub-units, bringing them together so that the RTKs are close enough to phosphorylate each other on tyrosine residues. 2. Grb2 is an adaptor protein that binds both to phosphotyrosines on the RTK and to Sos, a guanine nucleotide exchange factor (GEF). 3. Once Sos is brought to the membrane, it causes the small G protein Ras to dissociate from GDP and bind to GTP, thereby activating Ras. 4. G proteins, such as Ras, are described as a molecular switches because they are self-inactivating. G proteins contain a GTPase domain that will eventually hydrolyze the bound GTP to GDP, deactivating themselves. They are therefore prone to gain-of-function mutations, because any loss-of-function mutation in the GTPase domain will cause the G protein to be constitutively active once it is turned on.. 5. GTP-bound Ras will bind to MAPKKK, activating it. Activated MAPKKK phosphorylates MAPKK. 6. Phosphorylation of MAPKK activates it, causing it to phosphorylate MAPK. 7. A significant proportion of phosphorylated, activated MAPK enters the nucleus, where it phosphorylates transcription factors, modulating gene expression. The activation of the three kinases, MAPKKK, MAPKK and MAPK is an example of a phosphorylation cascade. P MAPKK P MAPK

Optional Clicker Questions: 1. In the MAP kinase pathway, phosphorylation serves to: Turn off the pathway Inhibit the next component in the pathway Activate the next component in the pathway Prevent further phosphorylation of downstream components. Correct answer: C This question checks that the students understand that, in the MAPK cascade, phosphorylation is activating. Since this point is central to understanding the case study, it is an opportunity to go back over the logic of the pathway if a significant proportion of the students miss the question.

Optional Clicker Questions: 2. G proteins are described as molecular switches because: G proteins can be turned on and off by Sos. G proteins can activate or inhibit downstream components. G proteins can activate different downstream components depending on whether they are bound to GDP or GTP. G proteins have inherent GTPase activity and will turn themselves off by hydrolyzing GTP to GDP. Correct answer: D This question checks that the students understand that G proteins deactivation is like a timer switch and will turn off on its own after a period of time. This is an opportunity to go back over the logic of the pathway if a significant proportion of the students miss the question.

Optional Clicker Questions: 3. If a MAPKKK is lost due to homozygous mutation in the MAPKKK gene: The pathway will function normally. MAPK can still be activated if enough ligand is present. MAPK cannot be activated regardless of the presence of ligand. The pathway will be always active. Correct answer: C This question checks that the students have an abstract understanding of the logic of the pathway; each activation is dependent on the previous.

The Receptor Tyrosine Kinase (RTK) – cell survival pathway BAD PI3 Kinase RTK Signal Plasma membrane PIP3 P PDK1 Bcl2 Apoptosis Akt PIP3 This is the core of the RTK-cell survival signaling pathway. Activation of the RTK-survival pathway is required to promote cell survival (prevent apoptosis), through inhibition of BAD, an inhibitor of Bcl2. The signal is transduced as follows: 1. Signaling is initiated when ligand binds to two RTK sub-units, and the RTKs phosphorylate each other on tyrosine residues. 2. Phosphoinositde 3-kinase (PI3K) binds, directly or indirectly, to phosphorylated RTK, bringing it in proximity to its substrate. 3. PI3K phosphorylates the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2), which becomes PIP3. 4. PIP3 recruits PIP3-dependent kinase PDK1 to the membrane. 5. PIP3 also recruits Akt to the membrane, where it is phosphorylated by PDK1. Once activated, Akt diffuses away. 6. Akt is a kinase with many downstream targets, including the protein BAD. Phosphorylation inactivates BAD, preventing it from binding to Bcl2. 7. Unbound Bcl2 is able to inhibit apoptosis (by binding to factors that promote release of cytochrome c from the mitochondria).

Optional Clicker Questions: 4. Akt….. prevents apoptosis (promotes cell survival) by inhibiting an inhibitor of Bcl2. is a kinase that activates Bcl2 by phosphorylation. promotes apoptosis but is inhibited by PDK1 phosphorylation. is a phosphatase, and inhibits apoptosis by dephosphorylating PDK1 targets. Correct answer: A If many students miss this question, this is a good point at which to go over the general principle that inhibition of an inhibitor results in activation. The students will need to be able to understand this logic when they do the take-home assignment on the beta-catenin signaling pathway.

Optional Clicker Questions: 5. If all Akt activity is lost due to homozygous mutation in the AKT gene: The pathway will function normally to inhibit apoptosis. The pathway can still be activated if enough ligand is present. The pathway can never be activated regardless of the presence of ligand, and the cell will undergo apoptosis. The pathway will be always active, and the cell will not undergo apoptosis even under appropriate conditions (the absence of the ligand). Correct answer: C This question asks the students to apply the logic assessed in the previous question to a manipulation of the pathway. If Akt is no longer present to phosphorylate Bad, Bad will sequester Bcl2, resulting in apoptosis due to loss of Bcl2’s pro-survival activity.

Example: SCF and Kit activate MITF in melanoblasts RAF (MAPKKK) MEK (MAPKK) ERK (MAPK) Sos (Ras GEF) Grb2 (adapter) Kit SCF Plasma membrane (G protein) Ras GTP GDP MITF CBP Example: SCF and Kit activate MITF in melanoblasts This slide accompanies the interleaving exercise on the importance of differential gene expression.

Case Study: Tiger Syndrome Instructions: Read the text carefully Think-Collaborate-Share (work in groups of approx. 4) Write or draw your group’s answer down (to be collected) You have 20 minutes to complete the activity

Case Study: Tiger Syndrome P Raf (MAPKKK) MEK (MAPKK) ERK (MAPK) Sos (Ras GEF) Grb2 (adapter) RTK Signal Plasma membrane (G protein) Ras GTP GDP Case Study: Tiger Syndrome

Case Study: Tiger Syndrome How do you think the T266K mutation in Sos might alter its activity? b) How does this affect the upstream components of the MAP kinase pathway? And the downstream components?

Case Study: Tiger Syndrome P Raf (MAPKKK) MEK (MAPKK) ERK (MAPK) Sos (Ras GEF) Grb2 (adapter) RTK Signal Plasma membrane (G protein) Ras GTP GDP Case Study: Tiger Syndrome

Case Study: Tiger Syndrome c) The other five individuals do not have mutations in RAF or Sos. Which components of the pathway would you sequence next? Why?

✕ Drug Case Study: Tiger Syndrome Signal Plasma membrane RTK Ras Raf (MAPKKK) MEK (MAPKK) ERK (MAPK) Sos (Ras GEF) Grb2 (adapter) RTK Signal Plasma membrane (G protein) Ras GTP GDP Case Study: Tiger Syndrome ✕ Drug