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What is the primary function of second messengers in signal transduction?

  • To generate energy for the cell
  • To inhibit cell division
  • To activate/inactivate target proteins (correct)
  • To transport molecules across the membrane

    • Which G protein is associated with the activation of phospholipase C (PLC)?

  • Gq (correct)
  • Gi
  • Gs
  • G12/13

    • What is the role of Protein Kinase A (PKA) in cell signaling?

  • To transport calcium ions
  • To degrade glucose
  • To phosphorylate target proteins (correct)
  • To synthesize cAMP

    • What effect does glucagon have on liver cells according to the signal transduction pathway?

    <p>Inhibits glycogen synthesis</p> Signup and view all the answers

    What is the transcription factor that binds to the cAMP response element (CRE)?

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

    Which of the following is a second messenger produced by the activation of phospholipase C?

    <p>IP3</p> Signup and view all the answers

    Which G protein-coupled receptor is involved in excessive cell proliferation and malignancies?

    <p>G12/13</p> Signup and view all the answers

    How does cAMP function in the regulation of blood glucose levels?

    <p>It activates PKA, which phosphorylates CREB.</p> Signup and view all the answers

    What is the typical cytosolic concentration of Ca2+ that is maintained to optimize the 'signal:noise' ratio?

    <p>0.1 mM</p> Signup and view all the answers

    What mechanism does Calcium Induced Calcium Release (CICR) utilize?

    <p>Release of Ca2+ from the endoplasmic reticulum via RyRs</p> Signup and view all the answers

    How does the cortical reaction prevent polyspermy?

    <p>Through the release of calcium granules that inactivate sperm-binding receptors</p> Signup and view all the answers

    Which receptor is activated by sperm binding to initiate calcium release during fertilization?

    <p>IP3 receptor</p> Signup and view all the answers

    What is the consequence of an increase in cytosolic Ca2+ concentration during fertilization?

    <p>Activation of GPCR signaling pathways</p> Signup and view all the answers

    What is the primary role of cAMP in liver cells in response to glucagon or epinephrine?

    <p>It activates protein kinases to enhance glucose production.</p> Signup and view all the answers

    Which enzyme is responsible for the cleavage of phosphatidylinositol bisphosphate (PIP2) into IP3 and DAG?

    <p>Phospholipase C</p> Signup and view all the answers

    What happens to cytosolic cGMP levels when light activates rhodopsin in rod cells?

    <p>cGMP levels decrease significantly.</p> Signup and view all the answers

    Which G protein is activated by light in rod cells?

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

    What is the effect of RGS9 mutations on cGMP activity in patients with bradyopsia?

    <p>Delayed inactivation of transducin.</p> Signup and view all the answers

    Which of the following statements is true regarding G protein-coupled receptors (GPCRs)?

    <p>GPCRs can activate different effector enzymes depending on the type of G protein.</p> Signup and view all the answers

    In which part of the cell do IP3 and DAG act as second messengers?

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

    What is the main effect of increased cAMP in cells that utilize Gs proteins?

    <p>Activation of adenylyl cyclase.</p> Signup and view all the answers

    Which second messenger is specifically associated with the action of phosphatidylinositol-derived pathways?

    <p>Inositol trisphosphate (IP3)</p> Signup and view all the answers

    What physiological process do G12/13 proteins primarily influence?

    <p>Induction of excessive cell proliferation.</p> Signup and view all the answers

    What is the initial effect of alpha 2 adrenergic receptors on cAMP?

    <p>Reduce cAMP levels</p> Signup and view all the answers

    Which second messengers are generated from the breakdown of PIP2?

    <p>IP3 and DAG</p> Signup and view all the answers

    What activates phospholipase C (PLCβ) in the signaling pathway?

    <p>Replacement of GDP with GTP on Gαq</p> Signup and view all the answers

    What does DAG do upon activation in the cell membrane?

    <p>Recruits protein kinase C (PKC)</p> Signup and view all the answers

    What effect does IP3 have in the signaling pathway?

    <p>It binds to calcium channels on the smooth endoplasmic reticulum</p> Signup and view all the answers

    Which of the following ligands does NOT activate phospholipase C (PLCβ)?

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

    What is the result of calcium release into the cytosol?

    <p>Recruitment of PKC to DAG</p> Signup and view all the answers

    Phosphatidylinositol bisphosphate (PIP2) is phosphorylated to produce which compound?

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

    Which of the following is NOT a receptor associated with G protein-coupled receptors as mentioned?

    <p>Histamine receptor type 2</p> Signup and view all the answers

    What is one of the primary functions of protein kinase C (PKC)?

    <p>Promoting cellular growth and differentiation</p> Signup and view all the answers

    Which type of PKC isozyme requires both DAG and Ca2+ for activation?

    <p>Conventional PKC isozymes</p> Signup and view all the answers

    What is the primary role of Ca2+ as an intracellular messenger?

    <p>Promotion of muscle contraction</p> Signup and view all the answers

    Which PKC isozymes are classified as novel or nonclassic?

    <p>δ, ε, η, θ</p> Signup and view all the answers

    What mechanism is NOT involved in maintaining low calcium levels in the cytosol?

    <p>Passive diffusion of Ca2+ into the cell</p> Signup and view all the answers

    Which of the following is a consequence of elevated intracellular Ca2+ levels?

    <p>Exocytosis of neurotransmitters</p> Signup and view all the answers

    What type of diseases are associated with abnormal PKC signaling?

    <p>Multiple diseases including CVD and diabetes</p> Signup and view all the answers

    Which of the following cellular processes does NOT involve Ca2+ signaling?

    <p>DNA replication</p> Signup and view all the answers

    What is the primary factor that contributes to the 'signal:noise' ratio in Ca2+ signaling?

    <p>Low cytosolic concentration of Ca2+</p> Signup and view all the answers

    Which PKC isozyme class does not require either DAG or Ca2+ for activation?

    <p>Atypical PKCs</p> Signup and view all the answers

    In the context of Ca2+ signaling, what specifically triggers muscle contraction?

    <p>Increase in intracellular Ca2+ concentration</p> Signup and view all the answers

    Which G protein is associated with increasing intracellular cAMP levels?

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

    What is the primary action of protein kinase C (PKC) in cell signaling?

    <p>Phosphorylate target proteins</p> Signup and view all the answers

    Which second messenger is formed as a result of phosphatidylinositol bisphosphate (PIP2) cleavage?

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

    What is the role of calcium in the signaling pathways discussed?

    <p>To act as an intracellular messenger activating various processes</p> Signup and view all the answers

    Which cellular process is NOT primarily influenced by G protein-coupled receptor signaling?

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

    How does the activation of phospholipase C affect intracellular signaling?

    <p>It leads to the release of calcium from the endoplasmic reticulum</p> Signup and view all the answers

    Which outcome is primarily associated with elevated intracellular cAMP levels?

    <p>Enhanced glycogen breakdown</p> Signup and view all the answers

    Which transcription factor is activated by phosphorylated cAMP response element binding protein (CREB)?

    <p>p-CREB</p> Signup and view all the answers

    What is the primary reason for maintaining a low cytosolic concentration of Ca2+?

    <p>To optimize the 'signal:noise' ratio in signaling</p> Signup and view all the answers

    How does Calcium Induced Calcium Release (CICR) primarily function?

    <p>Through the activation of calcium-sensitive receptors</p> Signup and view all the answers

    What is the role of IP3 receptors in calcium signaling during fertilization?

    <p>To modulate the effects of extracellular signals on calcium release</p> Signup and view all the answers

    What prevents more than one sperm from fertilizing an egg?

    <p>Activation of the cortical reaction leading to a calcium wave</p> Signup and view all the answers

    What critical process is facilitated by ryanodine receptors (RyRs) in muscle cells?

    <p>Facilitating rapid calcium release for muscle contraction</p> Signup and view all the answers

    What triggers muscle contraction in relation to intracellular calcium levels?

    <p>Increase in intracellular Ca2+</p> Signup and view all the answers

    What is a physiological consequence of elevated intracellular Ca2+ levels?

    <p>Enhanced cell adhesion</p> Signup and view all the answers

    Which of the following diseases is associated with abnormal PKC signaling?

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

    What mechanism maintains low calcium levels in the cytosol?

    <p>Active transport of Ca2+ out of the cell</p> Signup and view all the answers

    Which PKC isozymes require DAG but not Ca2+ for activation?

    <p>Novel PKCs</p> Signup and view all the answers

    What is the most widely used intracellular messenger involved in signaling processes?

    <p>Ca2+</p> Signup and view all the answers

    What role does histamine release play in cell signaling?

    <p>Induction of contraction</p> Signup and view all the answers

    How does the cytosolic concentration of Ca2+ influence the 'signal:noise' ratio?

    <p>Lower levels are critical for optimizing the ratio</p> Signup and view all the answers

    What type of signaling does Protein Kinase C (PKC) mediate?

    <p>Signaling pathways involving several intracellular messengers</p> Signup and view all the answers

    What effect do alpha 2 adrenergic receptors have on cAMP levels?

    <p>Decrease cAMP production</p> Signup and view all the answers

    Which intracellular component is produced when phospholipase C (PLCβ) cleaves PIP2?

    <p>DAG and IP3</p> Signup and view all the answers

    What role does diacylglycerol (DAG) play after it is generated in the signaling pathway?

    <p>It recruits protein kinase C (PKC) to the membrane</p> Signup and view all the answers

    Which receptor is NOT mentioned as relevant in the context of G Protein-Coupled Receptors?

    <p>Nicotinic acetylcholine receptor</p> Signup and view all the answers

    What is the initial event that occurs after a ligand binds to a G protein-coupled receptor (GPCR)?

    <p>Replacement of GDP with GTP on Gαq</p> Signup and view all the answers

    What happens to calcium ions after IP3 diffuses into the cytosol?

    <p>Calcium is released from smooth endoplasmic reticulum (SER)</p> Signup and view all the answers

    Which of the following processes is influenced by protein kinase C (PKC) upon activation?

    <p>Cell growth and differentiation</p> Signup and view all the answers

    What triggers the activation of phospholipase C (PLCβ) in the signaling pathway?

    <p>Binding of ligand to a receptor</p> Signup and view all the answers

    What is a common consequence of calcium being released into the cytosol?

    <p>Recruitment of PKC to DAG</p> Signup and view all the answers

    In the generation of second messengers, what is the first step involving PhosphoInositides (PIP2)?

    <p>Phosphorylation of PI to produce PIP2</p> Signup and view all the answers

    Which enzyme is responsible for the decreasing levels of cGMP in response to light activation in rod cells?

    <p>cGMP phosphodiesterase</p> Signup and view all the answers

    What is the effect of decreasing cGMP levels in rod cells when light is present?

    <p>Closure of Na+ and Ca2+ channels</p> Signup and view all the answers

    Which G protein is primarily associated with the light-activated signaling pathway in rods?

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

    What role does RGS9 play in the signaling process of rod cells?

    <p>Inactivates transducin</p> Signup and view all the answers

    What is the effect of G12/13 proteins on cellular processes?

    <p>Promote excessive cell proliferation</p> Signup and view all the answers

    What is the by-product of phosphatidylinositol bisphosphate (PIP2) cleavage by phospholipase C?

    <p>IP3 and DAG</p> Signup and view all the answers

    How does cAMP production differ between Gs and Gi G proteins?

    <p>Gs increases cAMP; Gi decreases cAMP</p> Signup and view all the answers

    What function does diacylglycerol (DAG) serve in the cell after activation?

    <p>It activates protein kinase C (PKC)</p> Signup and view all the answers

    What defines the role of phospholipase enzymes in cell signaling?

    <p>Cleavage of phospholipids</p> Signup and view all the answers

    Which of the following is true regarding inositol trisphosphate (IP3) function?

    <p>It mobilizes calcium from endoplasmic reticulum</p> Signup and view all the answers

    What primarily prevents more than one sperm from fertilizing an egg during the cortical reaction?

    <p>Release of calcium granules outside the egg</p> Signup and view all the answers

    Which component is essential for facilitating rapid calcium release during muscle contraction?

    <p>Ryanodine receptors</p> Signup and view all the answers

    What is the role of IP3 receptors in the context of calcium signaling?

    <p>Facilitate calcium release from the endoplasmic reticulum</p> Signup and view all the answers

    How is the cytosolic concentration of Ca2+ typically maintained at a low level?

    <p>Active transport by calcium pumps</p> Signup and view all the answers

    What characteristic of calcium signaling optimizes the 'signal:noise' ratio?

    <p>Low cytosolic concentration of Ca2+</p> Signup and view all the answers

    What is the consequence of activating the Gq protein in signal transduction?

    <p>Increased levels of IP3 and DAG</p> Signup and view all the answers

    Which role does p-CREB play in the context of cAMP signaling?

    <p>It promotes the binding to CRE to enhance transcription</p> Signup and view all the answers

    How does the activation of protein kinase C (PKC) influence cellular functions?

    <p>It phosphorylates proteins to regulate their activity</p> Signup and view all the answers

    The signaling pathway initiated by glucagon and epinephrine primarily affects which organ's cells?

    <p>Liver cells</p> Signup and view all the answers

    What mechanisms primarily maintain low calcium levels in the cytosol under resting conditions?

    <p>Calcium sequestration by organelles</p> Signup and view all the answers

    What is the consequence of Gαq activation in the signaling pathway?

    <p>Stimulates phospholipase C (PLCβ)</p> Signup and view all the answers

    Which of the following statements best describes the role of DAG in signal transduction?

    <p>DAG acts as a second messenger to recruit PKC to the membrane</p> Signup and view all the answers

    Which of the following ligands does NOT promote the activation of phospholipase C?

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

    What is a key distinguishing feature of G12/13 protein signaling compared to other G proteins?

    <p>They are primarily involved in cell proliferation and cancer progression</p> Signup and view all the answers

    What is one consequence of increased intracellular calcium levels in a muscle cell?

    <p>Initiation of muscle contraction</p> Signup and view all the answers

    Which statement about IP3 and DAG is true?

    <p>Both act as second messengers following PIP2 cleavage</p> Signup and view all the answers

    What role does DAG play after its formation from PIP2?

    <p>Recruits and activates protein kinase C (PKC)</p> Signup and view all the answers

    Which process is triggered by the binding of IP3 to smooth endoplasmic reticulum receptors?

    <p>Calcium release into the cytosol</p> Signup and view all the answers

    Which G protein is primarily involved in the reduction of cAMP levels?

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

    What is the first step in the generation of second messengers from phosphatidylinositol bisphosphate (PIP2)?

    <p>Ligand binding activates G protein</p> Signup and view all the answers

    What is NOT a direct role served by calcium ions released into the cytosol?

    <p>Synthesize cAMP from ATP</p> Signup and view all the answers

    Which PKC isozymes require DAG for activation but do not require Ca2+?

    <p>δ, ε</p> Signup and view all the answers

    What is one of the primary functions of elevated intracellular Ca2+ levels?

    <p>Triggering apoptosis</p> Signup and view all the answers

    Muscarinic receptors categorized as type 1, 3, and 5 are associated with which function?

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

    Which mechanism does NOT contribute to maintaining low cytosolic Ca2+ levels?

    <p>Passive diffusion of Ca2+ into the cytosol</p> Signup and view all the answers

    What is the final product after PIP2 is cleaved by phospholipase C?

    <p>IP3 and DAG</p> Signup and view all the answers

    What type of PKC isoforms are classified as atypical?

    <p>ζ, ι, λ</p> Signup and view all the answers

    In relation to G Protein-Coupled Receptors (GPCRs), what does IP3 primarily facilitate?

    <p>Release of Ca2+ from the endoplasmic reticulum</p> Signup and view all the answers

    Which of the following diseases is NOT linked to abnormal PKC signaling?

    <p>Bacterial infections</p> Signup and view all the answers

    What role does Ca2+ play in T cell activation?

    <p>Facilitates signaling pathways essential for activation</p> Signup and view all the answers

    Which of the following is a characteristic of conventional PKC isozymes?

    <p>Require DAG and Ca2+ for activation</p> Signup and view all the answers

    What cellular function does NOT typically involve Ca2+ signaling?

    <p>Active transport of nutrients</p> Signup and view all the answers

    Which is an effect of increased intracellular Ca2+ concentration?

    <p>Induction of exocytosis</p> Signup and view all the answers

    What effect does light have on cGMP levels in rod cells?

    <p>cGMP levels decrease significantly</p> Signup and view all the answers

    Which process is primarily activated by the cleavage of PIP2?

    <p>Formation of IP3 and DAG</p> Signup and view all the answers

    Which G protein is involved in the signaling pathway that results in a decrease of cAMP levels?

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

    What is the primary role of RGS9 in the context of light signaling in vision?

    <p>To inactivate transducin during light termination</p> Signup and view all the answers

    What happens to Na+ and Ca2+ channels in rod cells when cGMP levels decrease due to light exposure?

    <p>They close, preventing ion influx</p> Signup and view all the answers

    Which of the following is a consequence of decreased cGMP levels in rod cells?

    <p>Increased membrane hyperpolarization</p> Signup and view all the answers

    How does phospholipase C contribute to intracellular signaling?

    <p>By producing second messengers IP3 and DAG</p> Signup and view all the answers

    What role does diacylglycerol (DAG) play in cell signaling?

    <p>It functions as a second messenger alongside IP3</p> Signup and view all the answers

    Which factor primarily contributes to bradyopsia in patients with mutations in the RGS9 gene?

    <p>Unregulated cGMP activity and slower membrane depolarization</p> Signup and view all the answers

    What is the immediate effect of activating Gq-coupled receptors?

    <p>Activation of phospholipase C</p> Signup and view all the answers

    Study Notes

    HSS2305: Molecular Mechanisms of Disease

    • Lecture 16 covered Signal Transduction, specifically IP3, DAG, and PKC.
    • Today's outline included announcements and sections on Signal Transduction.

    Cell Signaling Overview

    • Cell signaling involves three key steps:
      • Reception: Signaling molecule binds to receptor on plasma membrane
      • Transduction: Relay molecules within signaling pathway
      • Response: Activation of cellular response (e.g., gene expression, metabolic changes)

    Signal Transduction

    • Two primary routes:
      • Generation of intracellular second messengers via effector enzymes: Second messengers activate/inactivate target proteins
      • Recruit signaling proteins to their intracellular domains to initiate a protein-activated cascade: Proteins initiate further cascade of protein activation.

    G Protein-Coupled Receptors

    • Receptors in cell membrane bind signaling molecules.
    • The activated receptor triggers a response by altering an enzyme.
    • G protein system converts extracellular signal to intracellular signaling.

    G Protein-Coupled Receptors (Effectors)

    • G proteins are involved in signaling pathways that influence many cellular processes.
    • Different G proteins lead to diverse second messengers.
    • Two main categories of second messengers are cAMP and IP3/DAG.

    G Protein-Coupled Receptors (2nd messengers - cAMP)

    • cAMP triggers a biochemical cascade in a cell.
    • The pathway affects many aspects of cell function.
    • CREB: cAMP response element-binding protein acts as a transcription factor.
    • Increased cAMP transcription of genes influences many processes like gluconeogenesis.

    G Protein-Coupled Receptors (2nd messengers - IP3 & DAG)

    • DAG activates another enzyme, protein kinase C (PKC).
    • PKC regulates cellular processes like growth, differentiation, metabolism, and death.
    • IP3 activates calcium channels, leading to calcium influx into the cytosol.

    G Protein-Coupled Receptors (Ca2+ Signaling)

    • Cystolic Ca2+ concentration is kept low through active transport and sequestration.
    • Increases in cytosolic Ca2+ trigger various intracellular responses.
    • Ca2+ signaling is involved in muscle contraction, neurotransmitter release, and other cellular processes.

    G Protein-Coupled Receptors (Calcium Signaling and Fertilization)

    • Sperm binding triggers a calcium influx.
    • This induces a cortical reaction in the egg, preventing polyspermy (multiple fertilization).

    Next Lecture

    • The next lecture will focus on RTKs and MAPK signaling pathways.

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    HSS2305A - 2024 - Lecture 16 PDF

    Description

    This quiz focuses on Lecture 16 of the HSS2305 course, covering Signal Transduction mechanisms, including IP3, DAG, and PKC. Explore the fundamental steps of cell signaling, the role of second messengers, and the function of G Protein-Coupled Receptors in cellular responses. Test your understanding of these critical molecular mechanisms of disease.

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