The roles of Gbeta5 and R7 RGS protein in vision

描述（由申请人提供）：异源三聚体g蛋白在人类生物学中的作用最好的代表是视紫红质/转导素信号在杆状光导中的作用。具有讽刺意味的是，在光感受器之外，其他g蛋白是如何为哺乳动物的视觉服务的，我们知之甚少。本应用程序将通过阐明第五个Gb亚基（Gb5）及其指定伙伴R7 RGS蛋白（RGS6, RGS7, RGS9, RGS11）在小鼠视网膜中的作用来填补这一知识空白。我们在Gb5-/-小鼠中发现了多种视觉缺陷，包括：1)光导恢复延迟；2)出生后发育过程中视网膜波异常，视网膜原状突起未完全细化；3)缺乏ERG b波；4)星爆无突细胞（SAC）树突状区减少；5)视网膜外网状层三联带突触断裂。我们推测Gb5在体内通过稳定R7 RGS蛋白而只与R7 RGS蛋白起作用，而在缺乏Gb5的情况下，Gao的信号状态异常延长，从而导致这些视觉缺陷。一个具有四个独立目标的多学科方法将严格检查上述Gb5-/-小鼠视觉缺陷的病理机制。Aim-1将通过检测四种R7 RGS基因排列和全部缺失的突变小鼠各组织中Gb5的水平，来检验Gb5和R7 RGS蛋白之间相互作用的排他性。Aim- 2将测试RGS7和RGS11的表达是否需要以细胞自主的方式来维持去极化双极细胞（DBC）的正常发育和功能。Aim-3将检测正常的SAC结构和功能在视网膜发育过程中是否需要RGS6和RGS7。Aim-4将测试长时间的高信号传导是否会延缓各种视网膜细胞（包括DBCs、SACs和某些视网膜神经节细胞（RGCs））的树突发育，以及它是否在缺乏Gb5的情况下在这些视网膜神经元中观察到树突缺陷。通过完成这些目标，我们期望通过明确Gb5、R7、RGS和Gao在视觉系统中的作用，显著推进异源三聚体g蛋白和视野的研究。

DESCRIPTION (provided by applicant): The role of heterotrimeric G-proteins in human biology is best represented by rhodopsin/transducin signaling in rod phototransduction. Ironically, how other G-proteins subserve mammalian vision outside photoreceptors is poorly understood. This application will start to fill this knowledge gap by elucidating the roles of the fifth Gb subunit (Gb5) and its obligate partners R7 RGS proteins (RGS6, RGS7, RGS9, RGS11) in mouse retina. We have found a multitude of visual defects in Gb5-/- mice which include: 1) delayed phototransduction recovery; 2) abnormal retinal waves and incomplete refinement of retinogeniculate projections during postnatal development; 3) lack of ERG b-wave; 4) reduced starburst amacrine cell (SAC) dendritic field; and 5) disrupted triadic ribbon synapses in retinal outer plexiform layer. We hypothesize that Gb5 works exclusively with R7 RGS proteins in vivo by stabilizing them and that in its absence the signaling state of Gao is abnormally prolonged to cause these visual defects. A multidisciplinary approach with four independent aims will critically examine the pathologic mechanisms of aforementioned Gb5-/- mouse visual defects. Aim-1 will test the exclusivity of the interaction between Gb5 and R7 RGS proteins by examining the level of Gb5 in various tissues of mutant mice with permutated and total loss of the four R7 RGS genes. Aim- 2 will test whether RGS7 and RGS11 expression is required in a cell autonomous manner for normal development and function of depolarizing bipolar cell (DBC). Aim-3 will examine whether normal SAC structure and function requires RGS6 and RGS7 during retinal development. Aim-4 will test whether prolonged Gao signaling retards dendritic development in various retinal cells including DBCs, SACs, and certain retinal ganglion cells (RGCs) and whether it underlies the dendritic defects observed in these retinal neurons in the absence of Gb5. By completing these aims we expect to significantly advance the heterotrimeric G-protein and the vision fields by firmly establishing the roles of Gb5, R7 RGS, and Gao in the visual system.