Recovery of Phototransduction

描述(申请人提供)：我们的长期目标是应用光转导知识来理解异源三聚体G蛋白的一般信号机制。在之前的资助期间，我们成功地将转导蛋白失活确定为视杆细胞恢复的正常限速步骤。我们将在另外两个视网膜G-Protein介导的途径中测试这一发现的普遍性，即视锥细胞光转导和ON型双极细胞的mGluR6途径。了解视觉信号在这三种细胞中是如何处理的意义在于，它们在许多遗传性视网膜疾病中受到不利影响。我们将使用小鼠功能获得和功能丧失遗传操作，然后进行生化、组织学和电生理特性测试，以验证下列假设：1)视紫红质失活是视杆细胞恢复过程中第二慢的步骤；2)视锥转导蛋白失活，而不是视锥色素，限制了正常视锥细胞的恢复；3)Gbeta5/RGS7和Gbeta5/RGS11蛋白质复合体在上型双极细胞树突的末端在功能上是多余的，因为Gbeta5/RGS7和Gbeta5/RGS11是mGluR6通路中Galpao的缺口。这三个目标与NEI视网膜疾病小组提出的计划目标之一一致，有可能阐明视杆/视锥的差异以及R7RGS蛋白和异源三聚体G蛋白在视网膜中的作用。这项建议研究了转基因小鼠视网膜中视觉信号转导的分子和细胞机制。被研究的三种细胞类型：视杆细胞、视锥细胞和双极细胞，在各种遗传性视网膜疾病中经常受到影响。

DESCRIPTION (provided by applicant): Our long-term objective is to apply the knowledge of phototransduction to understand general signaling mechanisms of heterotrimeric G-proteins. During the previous funding period we successfully identified transducin deactivation as the normal rate-limiting step of rod's recovery. We will test the generality of this finding in two other retinal G-proptein mediated pathways, namely, cone phototransduction and the mGluR6 pathway of the ON-type bipolar cells. The significance of understanding how visual signal is processed in these three cell types lies in the fact that they are adversely affected in many inherited retinal diseases. We will use gain-of-function and loss-of-function genetic manipulations in mice followed by biochemical, histological, and electrophysiological characterizations to test the following hypotheses: 1) rhodopsin deactivation is the second slowest step in rods' recovery; 2) the deactivation of cone transducin, rather than cone pigments, rate-limits normal cone recovery and 3) Gbeta5/RGS7 and Gbeta5/RGS11 protein complex are functionally redundant at the tips of the ON-type bipolar cell dendrites as the GAP for Galphao in the mGluR6 pathway. The three aims are in accordance with one of the program objectives set forth by NEI Retina Diseases Panel and have the potential to shed light into rod/cone differences and the roles of R7 RGS proteins and heterotrimeric G-proteins in the retina. This proposal examines the molecular and cellular mechanisms of visual signal transduction in retinas of genetically modified mice. The three cell types to be studied: rods, cones, and bipolar cells, are frequently affected in a variety of inherited retinal diseases.