Recovery of Phototransduction

描述（由申请人提供）：我们的长期目标是应用光导的知识来理解异源三聚体g蛋白的一般信号传导机制。在之前的资助期间，我们成功地确定了转导蛋白失活是杆状细胞恢复的正常限速步骤。我们将在另外两种视网膜g蛋白介导的通路，即on型双极细胞的视锥光传导和mGluR6通路中测试这一发现的普遍性。了解视觉信号如何在这三种细胞类型中处理的意义在于，它们在许多遗传性视网膜疾病中受到不利影响。我们将在小鼠中使用功能获得和功能丧失的基因操作，然后进行生化、组织学和电生理表征，以验证以下假设：1)视紫红质失活是视杆细胞恢复的第二慢步骤；2)锥体转导素的失活，而不是锥体色素的失活，限制了锥体正常恢复的速度；3)Gbeta5/RGS7和Gbeta5/RGS11蛋白复合物在on型双极细胞树突尖端作为mGluR6通路中Galphao的GAP功能冗余。这三个目标与NEI视网膜疾病小组制定的项目目标之一一致，并有可能揭示视网膜中视杆/视锥细胞的差异以及R7 RGS蛋白和异源三聚体g蛋白的作用。本研究旨在探讨转基因小鼠视网膜视觉信号转导的分子和细胞机制。要研究的三种细胞类型：杆状细胞、锥状细胞和双极细胞，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.