Regulation of Signaling in the Retina by RGS Proteins

描述(由申请人提供)：视网膜中的G蛋白信号通路在视觉刺激的接收和转导中起着至关重要的作用。人体的生理操作 这些途径依赖于G蛋白信号转导蛋白(RGS)蛋白的严密调控。我们的长期目标是阐明RGS蛋白在形成视网膜信号中的分子和细胞机制，作为了解视觉功能障碍及其治疗方法的必要前提。在第一个视觉突触，由mGluR6受体驱动的G蛋白级联，介导双极细胞对光诱导的神经递质谷氨酸释放的变化的反应。双极通路上信号传递的失调导致先天性静止性夜盲，这是一种以视力模糊为特征的视觉疾病。RGS蛋白R7亚家族的成员RGS7和RGS11特异性地集中在双极细胞突触上，在那里它们与辅助亚基G5、R7BP和R9AP以及主要受体mGluR6形成物理复合体。R7RGS蛋白或mGluR6的破坏会导致突触缺陷，并取消双极细胞对光的反应。这些观察结果导致了中心假说，即R7RGS复合体的组成部分在调节mGluR6途径和介导突触动态平衡方面发挥着重要作用。这一假说将通过追求三个互补的特定目标来检验：(1)建立RGS复合体在第一视觉突触功能稳态中的作用，(2)确定RGS复合体选择性递送到on-BC树突的机制，以及(3)了解mGluR6级联中G蛋白失活的动力学要求。为解决这些目标而提出的战略将需要生物化学、分子生物学、电生理和生理学方法的协同组合，每一种方法都利用了一系列强大的试剂和动物模型的存在。更好地了解RGS蛋白的功能和mGluR6通路的调控将对G蛋白参与突触传递事件的一般原理产生重要的见解，并可能为设计用于治疗遗传性夜盲的治疗策略提供新的干预节点。 与公共健康相关：正常视力取决于视网膜神经元细胞内G蛋白信号通路的功能。这些通路的失调影响了细胞生存、光接收和突触传递等基本过程，是导致视觉障碍和失明的主要原因。本文提出的工作将使人们更清楚地了解参与调节视网膜G蛋白通路的分子，从而有助于合理设计有效的治疗干预措施。

DESCRIPTION (provided by applicant): G protein signaling pathways in the retina are critically involved in reception and transduction of visual stimuli. The physiological operation of these pathways depends on the tight control provided by the Regulators of G protein signaling (RGS) proteins. Our long term goal is to elucidate molecular and cellular mechanisms of RGS protein function in shaping retina signaling as a necessary prerequisite to understanding visual dysfunctions and therapeutic means of their treatment. At the first visual synapse, G protein cascade driven by mGluR6 receptor, mediates the responses of ON-bipolar cells to light induced changes in neurotransmitter glutamate release from the photoreceptors. The dysregulation of signal transmission in ON-bipolar pathway causes congenital stationary night blindness, a visual disease characterized by the loss of dim vision. The members of the R7 subfamily of RGS protein, RGS7 and RGS11, are specifically concentrated at the ON-bipolar cell synapses where they form physical complexes with their auxiliary subunits G 5, R7BP, and R9AP as well as with the principal receptor, mGluR6. Disruption of R7 RGS proteins or mGluR6 leads to synaptic deficits and abolishes the responses of ON-bipolar cells to light. These observations lead to the central hypothesis of the proposal that components of R7 RGS complexes play essential role in regulating mGluR6 pathway and mediating synapse homeostasis. This hypothesis will be tested by pursuing three complementary Specific Aims: (1) To establish a role of the RGS complexes in functional homeostasis of the first visual synapse, (2) To determine mechanisms underlying selective delivery of the RGS complexes to the ON-BC dendrites, and (3) To understand kinetic requirements of G protein inactivation in the mGluR6 cascade. The strategy proposed to address these aims will entail a synergistic combination of biochemical, molecular biological, electrophysiological, and physiological approaches, each exploiting the existence of a powerful array of reagents and animal models. Better understanding of the RGS protein function and mGluR6 pathway regulation will yield important insights into the general principles of G protein involvement in synaptic transmission events and may suggest novel nodes of intervention for therapeutic strategies designed to treat inherited types of night blindness. PUBLIC HEALTH RELEVANCE: Normal vision is hinged on the function of the intracellular G protein signaling pathways in retina neurons. Dysregulation of these pathways affects fundamental processes including cellular survival, light reception, and synaptic transmission, and is a leading cause of visual disorders and blindness. The work proposed herein will yield a clearer understanding of the molecules involved in the regulation of G protein pathways in the retina and thus will aid in the rational design of effective therapeutic interventions.