Module 7.2 - GPCR 2
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Questions and Answers

What is the role of arrestins in GPCR desensitization?

  • Inhibiting GPCR internalization
  • Promoting signaling by activating GPCR
  • Enhancing GPCR sensitivity to ligands
  • Stopping signaling by binding to desensitized GPCR (correct)

    • Which region of arrestins mediates binding to second messenger kinases?

  • Third loop
  • C-terminal
  • N-terminal (correct)
  • SHUTS domain

    • Which proteins are restricted to retinal cones in the visual system?

  • Arrestin-3 and Arrestin-4
  • Arrestin 1 and Arrestin 4 (correct)
  • Beta arrestin-1 and Beta arrestin-2
  • Arrestin and Arrestin-2

    • What is the second function of arrestins?

    <p>Adaptor protein to direct binding partner to the site of forming clathrin-coated pits</p> Signup and view all the answers

    What happens to the fluorescent form of Beta-arrestin-2-GFP when the cell is stimulated?

    <p>Becomes localized to the cell surface</p> Signup and view all the answers

    What is the composition of caveolae?

    <p>Formed by myelin and can take shapes of clathrin-coated pits or bigger clustered shapes</p> Signup and view all the answers

    What happens to the coat of clathrin-coated vesicles once they have been internalized?

    <p>The coat dissolves as the cargo fuses with early endosomes</p> Signup and view all the answers

    What is the pH in endocytic compartments compared to the cytosol?

    <p>Lower (more acidic)</p> Signup and view all the answers

    What is the role of accessory proteins in GPCR internalization?

    <p>Needed for internalization and to regulate once the cargo is in an early endosome</p> Signup and view all the answers

    What is the structural organization of arrestins?

    <p>Linear proteins and adaptor proteins</p> Signup and view all the answers

    Which region of arrestins mediates binding to GPCR, clathrin, and AP2?

    <p>C-terminal domain</p> Signup and view all the answers

    What is the first function of arrestins in GPCR desensitization?

    <p>Stopping signaling by binding to desensitized GPCR</p> Signup and view all the answers

    What is the pH reached in endosomes along the degradation pathway?

    <p>pH 5</p> Signup and view all the answers

    What is the purpose of acidification in endosomes?

    <p>To separate receptors from their ligands and discourage protein-protein interactions without denaturing proteins</p> Signup and view all the answers

    What is the approximate time taken for the eventual return of internalized sst2A receptors to the cell surface?

    <p>60 minutes</p> Signup and view all the answers

    Where do internalized sst2A receptors reside, as indicated in the text?

    <p>In a syntaxin-6positive compartment distinct from the TGN and the recycling endosome</p> Signup and view all the answers

    What happens to Glucose transporter type 4 (GLUT4) in response to insulin?

    <p>Rapid transport and fusion of Glut4 storage vesicles to the plasma membrane</p> Signup and view all the answers

    What is the role of GSV-like carriers (GSVLs) as mentioned in the text?

    <p>Mediate a regulated type of recycling similar to GSVs and internalize SSTR2 receptors</p> Signup and view all the answers

    What does the drug Brefeldin A put into question regarding internalized somatostatin receptors?

    <p>The idea that internalized receptors are stored in the TGN</p> Signup and view all the answers

    Where does Glucose transporter type 4 (GLUT4) mostly reside in basal conditions?

    <p>In storage vesicles inside the cell</p> Signup and view all the answers

    What is the role of GSV-like vesicles (GSVLs) in response to hormonal signaling?

    <p>Mediate a regulated type of recycling similar to GSVs</p> Signup and view all the answers

    What is the function of acidification in endosomes?

    <p>To separate receptors from their ligands and discourage protein-protein interactions without denaturing proteins</p> Signup and view all the answers

    What is the role of GSV-like carriers (GSVLs) in the regulation of SSTR2 receptors?

    <p>Internalize SSTR2 receptors and lead to their return to normal levels after stimulation</p> Signup and view all the answers

    What is the role of acidification in endosomes?

    <p>To separate receptors from their ligands and discourage protein-protein interactions without denaturing proteins</p> Signup and view all the answers

    What is the approximate time taken for the eventual return of internalized sst2A receptors to the cell surface?

    <p>60 minutes</p> Signup and view all the answers

    What is the pH reached in endosomes along the degradation pathway?

    <p>pH 5</p> Signup and view all the answers

    What is the role of GSV-like carriers (GSVLs) in response to hormonal signaling?

    <p>Regulated recycling and internalization of SSTR2 receptors</p> Signup and view all the answers

    Where does Glucose transporter type 4 (GLUT4) mostly reside in basal conditions?

    <p>Inside storage vesicles</p> Signup and view all the answers

    What happens to Glucose transporter type 4 (GLUT4) in response to insulin?

    <p>Rapid transport and fusion of storage vesicles to the plasma membrane</p> Signup and view all the answers

    What does the drug Brefeldin A put into question regarding internalized somatostatin receptors?

    <p>The idea that internalized receptors are stored in the TGN</p> Signup and view all the answers

    What is the function of GSV-like carriers (GSVLs) as mentioned in the text?

    <p>Regulated recycling similar to GSVs and internalization of SSTR2 receptors</p> Signup and view all the answers

    What is the role of internalized sst2A receptors in living cells?

    <p>Rapid internalization and slow recycling</p> Signup and view all the answers

    What is the composition of the compartment where internalized sst2A receptors reside?

    <p>Syntaxin-6positive, distinct from the TGN and the recycling endosome</p> Signup and view all the answers

    What is the role of GSV-like vesicles (GSVLs) in response to hormonal signaling?

    <p>Regulated recycling similar to GSVs in response to hormonal signaling</p> Signup and view all the answers

    Study Notes

    Endosome Acidification and Receptor Internalization

    • Endosomes along the degradation pathway have progressively lower pH, reaching pH 5, to enhance the function of enzymes like lysosomes.
    • Acidification in endosomes occurs to separate receptors from their ligands and discourage protein-protein interactions without denaturing proteins.
    • Ectopically expressed sst2A somatostatin receptors are rapidly internalized in living cells and recycle slowly.
    • Postendocytic trafficking of sst2A involves desensitization, internalization through clathrin-coated vesicles, transport to endosomes, and eventual return to the cell surface in a slow process taking approximately 60 minutes.
    • Internalized sst2A receptors reside in a syntaxin-6positive compartment distinct from the TGN and the recycling endosome.
    • The drug Brefeldin A does not disperse internalized somatostatin receptors, putting into question the idea that internalized receptors are stored in the TGN.
    • Internalized sst2A receptors reside in vesicles containing syntaxin-6 but not TGN38 or PIST, suggesting a new model of sequestration and regulated recycling.
    • Glucose transporter type 4 (GLUT4) in basal conditions has very few on the plasma membrane and mostly sits in storage vesicles inside the cell.
    • Insulin triggers rapid transport and fusion of Glut4 storage vesicles to the plasma membrane to bring glucose rapidly.
    • GSV-like vesicles (GSVLs) mediate a regulated type of recycling similar to GSVs, and they are recycled in response to hormonal signaling.
    • GSV-like carriers (GSVLs) are recycled in response to hormonal signaling and internalize SSTR2 receptors, leading to their return to normal levels after stimulation.
    • GSV-like carriers (GSVLs) mediate a similar system to Glut4 storage vesicles, releasing insulin under stress in adipose tissue, and regulate activity of adrenal gland, stimulating cortisol hormone production.

    Endosome Acidification and Receptor Internalization

    • Endosomes along the degradation pathway have progressively lower pH, reaching pH 5, to enhance the function of enzymes like lysosomes.
    • Acidification in endosomes occurs to separate receptors from their ligands and discourage protein-protein interactions without denaturing proteins.
    • Ectopically expressed sst2A somatostatin receptors are rapidly internalized in living cells and recycle slowly.
    • Postendocytic trafficking of sst2A involves desensitization, internalization through clathrin-coated vesicles, transport to endosomes, and eventual return to the cell surface in a slow process taking approximately 60 minutes.
    • Internalized sst2A receptors reside in a syntaxin-6positive compartment distinct from the TGN and the recycling endosome.
    • The drug Brefeldin A does not disperse internalized somatostatin receptors, putting into question the idea that internalized receptors are stored in the TGN.
    • Internalized sst2A receptors reside in vesicles containing syntaxin-6 but not TGN38 or PIST, suggesting a new model of sequestration and regulated recycling.
    • Glucose transporter type 4 (GLUT4) in basal conditions has very few on the plasma membrane and mostly sits in storage vesicles inside the cell.
    • Insulin triggers rapid transport and fusion of Glut4 storage vesicles to the plasma membrane to bring glucose rapidly.
    • GSV-like vesicles (GSVLs) mediate a regulated type of recycling similar to GSVs, and they are recycled in response to hormonal signaling.
    • GSV-like carriers (GSVLs) are recycled in response to hormonal signaling and internalize SSTR2 receptors, leading to their return to normal levels after stimulation.
    • GSV-like carriers (GSVLs) mediate a similar system to Glut4 storage vesicles, releasing insulin under stress in adipose tissue, and regulate activity of adrenal gland, stimulating cortisol hormone production.

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    Description

    Test your knowledge of endosome acidification and receptor internalization with this quiz. Explore the processes of receptor internalization, postendocytic trafficking, and the roles of different vesicles such as GSV-like carriers and Glut4 storage vesicles. Delve into the mechanisms of regulated recycling and the impact of hormonal signaling on receptor levels.

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