REGULATION OF VISUAL SIGNAL TRANSDUCTION BY PHOSDUCIN

描述（改编自申请人摘要）：有证据表明，磷酸化蛋白，光导素，是许多G蛋白系统的调节剂，包括脊椎动物光感受器中的视觉信号转导。本研究的长期目标是了解光素调节光感受器和其他细胞中G蛋白的确切机制。光导素作用于G蛋白的β / γ复合物，抑制其在G蛋白α亚基和效应蛋白激活中的功能。当光导素被磷酸化时，它不会影响这些功能。这种提出的光导素作用机制被称为G β / γ封存模型。本提案的具体目的是通过以下方式来验证该模型：(1)测试G β / γ隔离模型对完整杆电生理反应的预测，以确定光导素对体外观察到的G β / γ的影响是否在体内也起作用；(2)从结构上确定光导素是如何被磷酸化失活的；(3)表征决定光导素磷酸化状态的细胞因子。实现这些目标所采用的方法是多学科的。它们包括测量光导素结构磷酸化依赖性变化的生化技术，关键光导素残基的定点诱变，高和低光导素活性条件下的协同电生理研究以及多巴胺对光导素活性影响的生化测量。G蛋白通路成分的缺陷导致视网膜病变和其他非视网膜疾病。因此，了解G蛋白信号是如何工作的，以确定这些疾病的原因并开发治疗方法是必要的。这些研究通过阐明光导素在G蛋白通路调控中的作用，有助于理解G蛋白的功能。

DESCRIPTION (Adapted from applicant's abstract): Evidence suggests that the phospho-protein, phosducin, is a regulator of many G protein systems, including visual signal transduction in vertebrate photoreceptors. The long-term objective of this research is to understand the precise mechanism of phosducin regulation of G proteins in photoreceptors and other cells. Phosducin acts on the beta/gamma complex of G proteins to inhibit its function in the activation of G protein alpha subunits and effector proteins. When phosducin is phosphorylated, it does not affect these functions. This proposed mechanism of phosducin action has been termed the G beta/gamma sequestration model. The specific aims of this proposal are designed to test this model by: (1) testing the predictions of the G beta/gamma sequestration model on the electrophysiological responses of intact rods to determine if the effects of phosducin on G beta/gamma observed in vitro are also functional in vivo; (2) determining structurally how phosducin is inactivated by phosphorylation and (3) characterizing the cellular factors that determine the phosphorylation state of phosducin. The methods to be employed to achieve these aims are multi-disciplinary. They include biochemical techniques for measuring phosphorylation-dependent changes in phosducin structure, site-directed mutagenesis of key phosducin residues, collaborative electrophysiological studies under conditions of high and low phosducin activity and biochemical measurements of the effect of dopamine on phosducin activity. Defects in G protein pathway components cause retinopathies and other non-retinal diseases. Therefore, it is imperative to understand how G protein signaling works in order to identify the causes of such diseases and develop treatments. These studies contribute to the understanding of G protein function by addressing the role of phosducin in G protein pathway regulation.