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?

Rhodopsin will not be phosphorylated by rhodopsin kinase

Rhodopsin will perpetually induce activation of cGMP gated cation channels

Rhodopsin will perpetually induce cGMP breakdown

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. Thus, the GPCR cannot activate G proteins. They further help in signaling and internalize the receptor. The arrestin acts as inhibitor and causes hyperpolarization of GPCR and breakdown of cGMP by phosphodiesterase. Therefore, there is no further activation of cation gated channels.

The G protein transducin is usually activated by meta-rhodopsin II that results in visual photo-transduction and is deactivated rapidly by rhodopsin kinase and arrestin.

Thus, the correct option among the following is - rhodopsin perpetually induce cGMP breakdown.

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