The roles of Gbeta5 and R7 RGS protein in vision

描述(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地代表了视紫红质/转导蛋白在杆状光转导中的信号。具有讽刺意味的是，其他G蛋白是如何在光感受器之外削弱哺乳动物的视觉的，人们知之甚少。这项应用将通过阐明第五GB亚单位(GB5)及其专有伙伴R7 RGS蛋白(RGS6、RGS7、RGS9、RGS11)在小鼠视网膜中的作用开始填补这一知识空白。我们在GB5-/-小鼠中发现了许多视觉缺陷，包括：1)光转导恢复延迟；2)出生后发育过程中视网膜波异常和视网膜原基投射不完全细化；3)缺乏ERG b波；4)星爆无长突细胞(SAC)树突域减少；5)视网膜外网状层三叉带突触中断。我们假设，在体内，GB5通过稳定R7 RGS蛋白而与R7 RGS蛋白独家发挥作用，并且在没有GB5的情况下，GAO的信号状态被异常延长，从而导致这些视觉缺陷。具有四个独立目标的多学科方法将批判性地检查上述GB5/小鼠视觉缺陷的病理机制。AIM-1将通过检测四个R7 RGS基因突变和完全缺失的突变小鼠不同组织中GB5的水平，来测试GB5和R7 RGS蛋白相互作用的排他性。AIM-2将测试RGS7和RGS11是否在细胞自主方式下表达是正常发育和去极化双极细胞(DBC)所必需的。AIM-3将研究正常的SAC结构和功能在视网膜发育过程中是否需要RGS6和RGS7。AIM-4将测试延长的GAO信号是否阻碍包括DBCS、囊和某些视网膜神经节细胞(RGC)在内的各种视网膜细胞的树突发育，以及它是否是在缺乏GB5的情况下在这些视网膜神经元中观察到的树突缺陷的基础。通过完成这些目标，我们希望通过牢固地确定GB5、R7RGS和GAO在视觉系统中的角色，显著推进异三聚体G蛋白和视野领域的发展。

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.