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The removal of insulin receptors from the cell surface by receptor mediated endocytosis is an important mechanism for insulin resistance in many type 2 diabetics. This type of desensitization can be reversed by
A. the synthesis of a regulatory protein that binds to the insulin receptor
B. the intrinsic GTPase activity of the insulin receptor
C. a serine/threonine specific protein phosphatase that removes phosphate groups from the receptor
D.none of the others. Only de novo synthesis of new insulin receptors can work
E. the phosphorylation of the receptor by protein kinase A
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c,,,,,,,,,,,,
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C...
Phosphorylation of receptor leads to desensitization and endocytosis. Dephosphorylation by phosphatase will prevent receptor endocytosis and reverse this process!
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Desensitization, which is defined as a waning of response in the face of constant stimulation, and is typically seen on sustained activation of GPCRs( G-protein coupled receptors. It may be either homologous (desensitization to the same stimulus) or heterologous (cross-desensitization to a different stimulus). Such desensitization often reflects partial or complete uncoupling of the receptors from their effector proteins, which may occur within seconds-minutes of agonist occupancy (rapid homologous receptor desensitization). Following this, receptors are sequestered from the plasma membrane and are internalized, within minutes to hours, to be either re-cycled to the cell surface or proteolytically degraded in lysosomes. The uncoupling of cell-surface GPCRs from their effector molecules, and removal of GPCRs from the cell surface will promote desensitization, desensitization can be reversed by re-cycling of receptors back to the cell-surface . The receptor may be recycled to the surface by vesicles that bud from the endosome and then target the plasma membrane. After these recycling vesicles fuse with the plasma membrane, the receptor is returned to the cell surface for further binding and activity.
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Insulin recepotor is not GPCR, right? And your explaination dosen't point to answer B as the correct answer? Please help..
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