Deactivation mechanisms of rod phototransduction

描述（由申请人提供）：视网膜视杆细胞和视锥细胞对光子的吸收激活了一系列生化反应（光转导级联），产生对光的电反应。级联的激活和失活最终限制了转导信号的幅度和动力学，从而限制了视觉的灵敏度和时间分辨率。本研究的总体目标是了解关闭完整小鼠光感受器光反应的机制。基因靶向技术将被用来操纵一个子集的蛋白质，已建议发挥关键作用，在级联的失活的功能，并在单杆细胞的光响应所产生的变化将被确定的电记录。使用这种方法，我们将解决3个重要问题：（1）视紫红质磷酸化的速度有多快，是什么决定了这个时间过程？(2)arrestin易位对光反应的功能影响是什么？(3)RGS 9复合物的光受体特异性剪接变体是否唯一适合于失活转导素/PDE，以及如何失活？4）光适应过程中加速transducin/PDE失活的机制是什么？本研究解决了视网膜疾病小组（http：//www.nei.nih.gov/strategicplanning/np_retinal.asp#obj）推荐的目标之一，即“分析光转导后光适应和恢复的潜在机制，并了解光/暗适应中神经编码的变化。“这项研究将有助于澄清正常视觉过程的初始步骤，以及失活失败引起的疾病的发病机制，例如某些形式的视网膜色素变性和夜盲症。在更广泛的背景下，这些实验将提供深入了解G蛋白级联的失活机制，所有真核细胞都使用G蛋白级联将细胞外信号转化为细胞内反应。

DESCRIPTION (provided by applicant): The absorption of photons in rods and cones of the retina activates a cascade of biochemical reactions (phototransduction cascade) that generates the electrical response to light. The activation and deactivation of the cascade ultimately limits the amplitude and kinetics of the transduced signal, and thus the sensitivity and temporal resolution of vision. The overall goal of this study is to understand the mechanisms that turn off the light response in intact mouse photoreceptors. Gene targeting techniques will be used to manipulate the function of a subset of proteins that have been suggested to play key roles in deactivation of the cascade, and the resulting changes in the photoresponses of single rod cells will be determined by electrical recording. Using this approach, we will address 3 important questions: (1) How rapidly does rhodopsin become phosphorylated, and what determines this time course? (2) What are the functional consequences of arrestin translocation on the photoresponse? (3) Are the photoreceptor-specific splice variants of the RGS9 complex uniquely suited for deactivating transducin/PDE, and how? and 4) What are the mechanisms that speed transducin/PDE deactivation during light adaptation? This research addresses 1 of the objectives recommended by the Retinal Diseases Panel (http://www.nei.nih.gov/strategicplanning/np_retinal.asp#obj), which is to "Analyze the mechanisms underlying light adaptation and recovery following phototransduction and understand the changes in neural coding in light/dark adaptation." This research will help clarify the initial steps in the normal visual process, as well as the pathogenesis of diseases that arise from failures of deactivation, such as in some forms of retinitis pigmentosa and nightblindness. In a broader context, these experiments will provide insights into the mechanisms of deactivation of G protein cascades, which all eucaryotic cells use to transduce extracellular signals into intracellular responses.