Regarding light sensing in the retina; what is predicted to happen if light acti

Question

Regarding light sensing in the retina; what is predicted to happen if light activation of a GPCR occurs in the presence of an arrestin inhibitor?

Wrong Answer:

Rhodopsin will perpetually induce activation of cGMP gated cation channels

Answers:

Rhodopsin will not be phosphorylated by rhodopsin kinase

Rhodopsin will perpetually induce activation of cGMP gated cation channels

Rhodopsin will perpetually induce cGMP breakdown

Regarding light sensing in the retina; what is predicted to happen if light activation of a GPCR occurs in the presence of an arrestin inhibitor?

Wrong Answer:

Rhodopsin will perpetually induce activation of cGMP gated cation channels

Answers:

Rhodopsin will not be phosphorylated by rhodopsin kinase

Rhodopsin will perpetually induce activation of cGMP gated cation channels

Rhodopsin will perpetually induce cGMP breakdown

Explanation / Answer

Arrestin usually desensitizes the GPCR receptor for further signaling and internalizes the receptor. Here, you have inhibitor for arrestin that makes hyperpolarization of GPCR and breakdown of cGMP by phosphodiesterase, therefore, there is no further activation of cation gated channels.

Metarhodopsin II usually activates the G protein transducin for visual phototransduction and is deactivated rapidly by rhodopsin kinase and arrestin. In order, here, arrestin will be unavailable due to inhibitor and I think, Rhodopsin will not be phosphorylated by rhodopsin kinase in the hyperpolarization of GPCR.

Rhodopsin will not be phosphorylated by rhodopsin kinase, Rhodopsin will perpetually induce cGMP breakdown these two events might occur in above conditions

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