Given info: p15 is an integral membrane protein,the complete amino acid sequence

Question

Given info: p15 is an integral membrane protein,the complete amino acid sequence of p15 contains 7 putative transmembrane domains,agonist-stimulation of p15 receptor-expressing cell lines results in decreases in forskolin-induced increases in cAMP accumulation and is dependent on a heterotrimeric G protein.

Which of the following actions which occur in response to binding of an agonist to a GPCR like 15, can be mediated by beta-arrestin:

You may choose more than one answer.

Explain both why you made your choices and why you did not select the others.

a) direct inhibition of GTPase activation

b) internalization of the GPCR via clathrin-coated pits

c) activation of protein kinases via scaffold function of beta-arrestins

d) phosphorylation of GPCR

Explanation / Answer

G protein coupled reaction (GPCR) coupling with G protein can be inhibited by arrestin with the help of clathrin adaptor AP2. This protein is helps in clathrin mediated endocytosis of molecules in which clathrin adaptor AP2 internalize the receptor GPCR via coated pit and transport it to endosome.

Phosphorylation at the C terminus end of the GPCR promotes the binding of arrestin molecules. which help to endocytosis of molecules which interact with other trans membrane molecules. also the multiple scaffold function of arresting which helps in activation of endocytosis which is clathrine mediated and promotes in degredation of Phosphorylated GPCR molecules.

However inhibition of GTPase activity do not have any role in trans membrane regulation. Because endocytosis do not required energy in the form of GTP hence GTPase activity is not important in endocytosis.

hence internalization of the GPCR via clathrin- coated pits

activation of protein kinase function via scaffold function of beta arrestins

phosphorylation of GPCR are key steps in endocytosis of GPCR

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