Protein G q modulates termination of phototransduction and prevents retinal degeneration

Abstract

Appropriate termination of the phototransduction cascade is critical for photoreceptors to achieve high temporal resolution and to prevent excessive Ca 2+-induced cell toxicity. Using a genetic screen to identify defective photoresponse mutants in Drosophila, we isolated and identified a novel Gα q mutant allele, which has defects in both activation and deactivation. We revealed that G q modulates the termination of the light response and that metarhodopsin/G q interaction affects subsequent arrestin-rhodopsin (Arr2-Rh1) binding, which mediates the deactivation of metarhodopsin.Wefurther showed that the Gα q mutant undergoes light-dependent retinal degeneration, which is due to the slow accumulation of stable Arr2-Rh1 complexes. Our study revealed the roles of G q in mediating photoresponse termination and in preventing retinal degeneration. This pathway may represent a general rapid feedback regulation of G protein- coupled receptor signaling. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.