Deactivation mechanisms of rod phototransduction

描述(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(光转导反应)，从而产生对光的电反应。级联的激活和去激活最终限制了被转换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。这项研究的总体目标是了解关闭完整小鼠光感受器的光反应的机制。基因打靶技术将被用来操纵一组蛋白质的功能，这些蛋白质被认为在级联失活中发挥关键作用，由此导致的单杆细胞光反应的变化将通过电记录来确定。使用这种方法，我们将解决三个重要的问题：(1)视紫红质被磷酸化的速度有多快，是什么决定了这一时间过程？(2)arrestin易位对光反应的功能影响是什么？(3)RGS9复合体的光感受器特异性剪接变体是否唯一适合于去激活转导蛋白/PDE，以及如何？以及4)在光适应过程中，是什么机制加速了转导蛋白/PDE的失活？这项研究涉及视网膜疾病专家小组(http://www.nei.nih.gov/strategicplanning/np_retinal.asp#obj)，建议的目标之一，即“分析光适应和光转导后恢复的潜在机制，并了解神经编码在明/暗适应中的变化。”这项研究将有助于阐明正常视觉过程的最初步骤，以及由于失活失败而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。在更广泛的背景下，这些实验将提供对G蛋白级联失活机制的见解，所有真核细胞都利用G蛋白级联将细胞外信号转换为细胞内反应。

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.