G?q splice variants mediate phototransduction, rhodopsin synthesis, and retinal integrity in Drosophila
G?q splice variants mediate phototransduction, rhodopsin synthesis, and retinal integrity in Drosophila
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G?q 剪接变异介导果蝇的光转导、视紫红质合成和视网膜完整性
DOI：
10.1074/jbc.ra120.012764
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发表时间：
2020-04-24
影响因子：
4.8
通讯作者：
Han，Junhai
中科院分区：
文献类型：
--
作者：
Gu，Qiuxiang;Wu，Jinglin;Han，Junhai
异源三聚体G蛋白通过将G蛋白偶联受体偶联至细胞内效应分子来介导多种信号传导过程。在果蝇中，G α q基因编码几种Gαq剪接变体，其中Gαq1同种型蛋白在果蝇光转导中起主要作用。然而，Gα q1无效突变果蝇仍然表现出残留的光反应，表明其他Gαq剪接变体或额外的Gq α亚基参与光转导。在这里，我们分离出一种突变果蝇，它没有可检测到的光反应，视紫红质（Rh）水平降低，视网膜迅速变性。通过电生理学和遗传学研究、生化分析、免疫印迹、实时荧光定量PCR和电镜分析，我们发现G α q基因的突变破坏了光反应，并证明Gαq3亚型蛋白负责G α q1无效突变体的残余光反应。此外，我们报告Gαq3介导视紫红质的合成。由于形成稳定的Rh 1-arrestin 2（Arr 2）复合物，所有Gαq剪接变体的耗尽导致快速光依赖性视网膜变性。我们的研究结果阐明了几种不同的Gαq剪接变体在果蝇光转导和视网膜完整性中的重要作用，并揭示了Gαq3在视紫红质合成中的功能。
Heterotrimeric G proteins mediate a variety of signaling processes by coupling G protein–coupled receptors to intracellular effector molecules. InDrosophila,theGαqgene encodes several Gαq splice variants, with the Gαq1 isoform protein playing a major role in fly phototransduction. However,Gαq1null mutant flies still exhibit a residual light response, indicating that other Gαq splice variants or additional Gq α subunits are involved in phototransduction. Here, we isolated a mutant fly with no detectable light responses, decreased rhodopsin (Rh) levels, and rapid retinal degeneration. Using electrophysiological and genetic studies, biochemical assays, immunoblotting, real-time RT-PCR, and EM analysis, we found that mutations in theGαqgene disrupt light responses and demonstrate that the Gαq3 isoform protein is responsible for the residual light response inGαq1null mutants. Moreover, we report that Gαq3 mediates rhodopsin synthesis. Depletion of all Gαq splice variants led to rapid light-dependent retinal degeneration, due to the formation stable Rh1-arrestin 2 (Arr2) complexes. Our findings clarify essential roles of several different Gαq splice variants in phototransduction and retinal integrity inDrosophilaand reveal that Gαq3 functions in rhodopsin synthesis.