Mechanisms of signal-dependent photoreceptor protein localization and transport

描述（由申请人提供）：视网膜杆光感受器中参与光信号传导的三种高表达蛋白，转导蛋白，恢复蛋白和阻滞蛋白，根据环境光照条件定位于不同的光感受器区室。这种转运对于调节光感受器的光敏感性是重要的。此外，它在保护杆状光感受器免受我们每天经历的光水平持续刺激造成的损伤以及可能导致许多先天性视网膜退行性疾病的异常光感受器活动方面发挥作用。然而，这些蛋白质定位于光感受器腔室的机制，它们在腔室之间运输的机制以及环境光水平的变化引发这种重新定位的机制尚不清楚。

DESCRIPTION (provided by applicant): Three highly expressed proteins involved in light signaling in retinal rod photoreceptors, transducin, recoverin and arrestin, localize to different photoreceptor compartments depending on the conditions of ambient illumination. This transport is important for adjusting photoreceptor light sensitivity. Moreover, it plays a role in protecting rod photoreceptors from damage caused by continual stimulation from light levels we experience every day, and from aberrant photoreceptor activity that may underlie many congenital retinal degenerative diseases. Yet the mechanisms by which these proteins are localized to photoreceptor compartments, by which they are transported among compartments and by which changes in ambient light levels initiate this re-localization are not known. We have developed new methods using multiphoton microscopy to directly examine local, compartment-specific behavior of the proteins and local changes in signaling molecules within living, functioning photoreceptors. Using these new methods we will examine the: Aim 1: Mechanisms underlying protein localization to rod photoreceptor compartments. Aim 2: Mode of signal-dependant protein transport between rod compartments. Aim 3: Signals that initiate protein transport. Experiments in aims 1 and 2 will quantitatively examine the local and long distance mobilities of the proteins fused with a variant of the green fluorescent protein, photoactivatable GFP, to identify the mechanisms of localization and modes of transport. We will then take what we have learned from these studies and construct a quantitative model to test if the mobility parameters are sufficient to explain the patterns of protein localization and light-driven transport. Experiments in aim 3 are designed to identify the signals that tell the proteins to move using newly developed, expressible signal transduction sensors. Understanding the mechanisms of light-induced protein transport could reveal experimental strategies for testing adaptive or protective roles of transport directly and may lead to strategies for therapeutic intervention to slow or reverse photoreceptor degeneration in congenital disease. The proposed work fits into the National Plan for Eye and Vision Research under the Retinal Disease Program.