Cell Signaling and Signal Transduction Quiz
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Questions and Answers

What is a key characteristic of mutated Ras protein?

  • It is constitutively active due to slow hydrolysis of GTP (correct)
  • It prevents membrane association of RAS
  • It hydrolyzes bound GTP very quickly
  • It binds GTP more effectively than normal Ras

    • Which approach is suggested as the most favorable current method for targeting RAS?

  • Searching for synthetic lethal interactors
  • Blocking RAS membrane association
  • Direct inhibitors of RAS
  • Targeting RAS downstream effector signaling (correct)

    • What recent development has sparked hope for RAS-targeting therapies?

  • Breakthroughs in RAS structural biology
  • Renewed interest in developing RAS-inhibitory molecules (correct)
  • Ability to enhance GTP binding in RAS
  • Identification of effective pharmacological inhibitors

    • Which of the following is NOT mentioned as a potential approach to target RAS?

    <p>Increasing GTP hydrolysis rate</p> Signup and view all the answers

    What is a widely held perception regarding RAS proteins?

    <p>They are considered undruggable</p> Signup and view all the answers

    What type of mutations are classified as oncogenes?

    <p>Gain of function mutations</p> Signup and view all the answers

    What is the role of the SH2 domain?

    <p>To recognize phosphotyrosine and nearby residues</p> Signup and view all the answers

    Which of the following pathways does Ras primarily activate?

    <p>Ras/MAP kinase pathway</p> Signup and view all the answers

    Approximately what percentage of human cancers contain mutant versions of RAS genes?

    <p>30%</p> Signup and view all the answers

    How does Ras mediate signaling for most receptor tyrosine kinases (RTKs)?

    <p>As a small GTPase anchored to the plasma membrane</p> Signup and view all the answers

    What does Raf do in the MAP kinase signaling cascade?

    <p>Activates Mek</p> Signup and view all the answers

    Which of these statements best describes the overall signal transduction system mediated by Ras?

    <p>It is highly conserved from yeast to humans.</p> Signup and view all the answers

    What is one of the main roles of Ras proteins in the cell?

    <p>Regulating cell division and differentiation</p> Signup and view all the answers

    What is the first step in the MAP kinase signaling cascade initiated by Ras?

    <p>Recruitment of Raf to the membrane</p> Signup and view all the answers

    Which of the following proteins does MAP kinase (Erk) phosphorylate?

    <p>A variety of downstream proteins including gene regulatory proteins</p> Signup and view all the answers

    What type of cells were used in the experiments to analyze the effects of oncogenic DNA?

    <p>3T3 mouse fibroblasts</p> Signup and view all the answers

    What was the outcome of introducing fragmented DNA from cancer cells into 3T3 mouse fibroblasts?

    <p>Occasional colonies of abnormally proliferating cells</p> Signup and view all the answers

    What characteristic of 3T3 cells made them suitable for studying the effects of oncogenic DNA?

    <p>Their capacity to proliferate indefinitely</p> Signup and view all the answers

    What was the primary goal of introducing cancer cell DNA into the 3T3 fibroblasts?

    <p>To induce uncontrolled cell growth in non-cancer cells</p> Signup and view all the answers

    What was concluded about the colonies that formed as a result of the experiments?

    <p>They were clones from a single cell incorporating oncogenic DNA.</p> Signup and view all the answers

    What is the primary function of KRAS in cancer?

    <p>To encode a key signaling protein</p> Signup and view all the answers

    What is AMG 510 primarily classified as?

    <p>A KRAS(G12C) inhibitor</p> Signup and view all the answers

    What effect did AMG 510 have in preclinical analyses?

    <p>It led to the regression of KRAS(G12C) tumors</p> Signup and view all the answers

    What significant effect did AMG 510 have on the tumor microenvironment?

    <p>It resulted in a pro-inflammatory tumor microenvironment</p> Signup and view all the answers

    What type of tumors did cured mice reject in the studies?

    <p>Isogenic KRAS(G12D) tumors</p> Signup and view all the answers

    What was the significance of the FDA approval for adagrasib?

    <p>It provided accelerated approval for a RAS GTPase family inhibitor</p> Signup and view all the answers

    How do scaffolding proteins influence signaling pathways?

    <p>By enhancing mutual interactions in a spatial orientation</p> Signup and view all the answers

    Which of the following is NOT a characteristic of some scaffolding proteins?

    <p>They can regulate the activity of transcription factors</p> Signup and view all the answers

    What is a key function of Rho family GTPases?

    <p>Controlling actin and microtubules</p> Signup and view all the answers

    What inhibits Rho family GTPases from interacting with its GEF at the plasma membrane?

    <p>Guanine nucleotide dissociation inhibitor (GDI)</p> Signup and view all the answers

    Which of the following pathways do GPCRs and RTKs predominantly activate?

    <p>Overlapping signaling pathways</p> Signup and view all the answers

    What role does the SRC homology domain play in signaling?

    <p>Mediating protein-protein interactions</p> Signup and view all the answers

    Which mutation type is primarily associated with oncogenes?

    <p>Gain of function mutation</p> Signup and view all the answers

    What is the primary function of SRC in cellular processes?

    <p>Signal transduction</p> Signup and view all the answers

    What do the SH2 and SH3 domains of SRC primarily facilitate?

    <p>Protein-protein interactions</p> Signup and view all the answers

    What is the result of a gain-of-function mutation in a proto-oncogene?

    <p>Promotes cell growth</p> Signup and view all the answers

    What is the relationship between c-src and v-src?

    <p>c-src is a proto-oncogene; v-src is its oncogenic counterpart.</p> Signup and view all the answers

    How does phosphorylation at Tyr527 affect c-Src's activity?

    <p>Inhibits its tyrosine kinase activity</p> Signup and view all the answers

    What type of virus was pivotal in the discovery of oncogenes?

    <p>Retrovirus</p> Signup and view all the answers

    What was discovered about the DNA incorporated by retroviruses like RSV?

    <p>It often includes passenger genes from the host.</p> Signup and view all the answers

    What kind of kinases are SRC and c-Src classified as?

    <p>Non-receptor kinases</p> Signup and view all the answers

    What is the designation given to the mutated version of a proto-oncogene?

    <p>Oncogene</p> Signup and view all the answers

    What role did Peyton Rous play in the study of oncogenes?

    <p>He characterized the Rous Sarcoma Virus.</p> Signup and view all the answers

    Study Notes

    Cell Signaling and Signal Transduction

    • Cell signaling is a communication process between cells
    • Signaling molecules are synthesized and released, travel to the target cell, bind to a receptor, resulting in a conformational change in the receptor
    • The receptor initiates intracellular pathways resulting in changes in cellular function, metabolism, gene expression, shape, and movement
    • Signal transduction pathways involve phosphorylation and dephosphorylation events, which cause changes in protein activity, often enabling or inhibiting ligand binding
    • GTP-binding proteins act as molecular switches, activating or inactivating target proteins
    • Enzyme-coupled receptors are transmembrane proteins with an intrinsic kinase activity or an associated kinase; they are activated by ligand binding, and initiate intracellular signaling cascades
    • RTKs (Receptor Tyrosine Kinases) are the most common enzyme-coupled receptors, and are important in many cellular processes
    • Phosphorylation is a key mechanism for signal transduction
    • Tyrosine phosphorylation is a critical step in activating downstream signaling pathways
    • Phosphorylated tyrosine residues serve as docking sites for signaling proteins, which then relay the signal
    • SH2 and PTB domains are common protein domains involved in binding to phosphorylated tyrosines
    • Signal transduction pathways, specifically the RAS-MAP kinase pathway, activate downstream proteins leading to cellular changes
    • Some components of the pathway have been linked to cancer
    • The pathway is highly conserved from yeast to humans

    Oncogenes

    • Oncogenes are genes whose mutations frequently contribute to cancer
    • Proto-oncogenes are normal genes that can mutate into oncogenes through gain-of-function mutations
    • These mutations cause them to promote uncontrolled cell growth
    • Oncogenes often encode proteins, including tyrosine kinases, that play important roles in cell growth or cell cycle
    • Oncogenes were discovered through studies of retroviruses that cause cancers in animals (like Rous Sarcoma Virus)
    • They identified mutated proto-oncogenes that transformed cells even in mammalian hosts

    Other Signal Transduction Pathways

    • GPCRs and RTKs activate overlapping signaling pathways, leading to convergence, divergence, and cross-talk. The different signaling pathways can lead to similar or very distinct responses by the cell.
    • Rho family GTPases couple cell surface receptors and regulate actin and microtubules which in turn, regulate cell shape, motility, adhesion, cell cycle progression, gene transcription, and membrane transport
    • Scaffolding proteins that facilitate specific signaling pathways and interactions exist in a variety of cell types

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    Cell Signaling and Signal Transduction (Chapter 15.2 PDF)

    Description

    Test your knowledge on cell signaling processes and signal transduction pathways. This quiz covers the mechanisms involved in cellular communication, including receptor activation and intracellular signaling cascades. Dive into the world of molecular switches and enzyme-coupled receptors to enhance your understanding.

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