Recovery of Phototransduction

描述（由申请人提供）：由异源三聚体G蛋白介导的信号转导在整个自然界中发生，最好的代表是视网膜杆中的光转导。然而，三聚体G蛋白如何在光感受器之外辅助脊椎动物视觉仍然知之甚少。同样，光转导的基本信息，如敏感性和视杆细胞和视锥细胞之间的动力学差异的机制，是失踪。视觉G蛋白通路的突变会导致衰弱性疾病，如先天性静止性夜盲症、视物迟缓和感光细胞变性。该应用建立在三个新的初步发现上：1）视紫红质激酶可能作为GT3加速蛋白（GAP），以确保在弱光条件下光转导的及时恢复。2)视锥细胞光转导恢复受到视锥细胞转导蛋白关闭的速率限制。3)不止一种G？亚基介导去极化双极细胞光反应。 我们在这里建议使用一个综合的方法，结合小鼠遗传学，生物化学，基因组学，细胞生物学，成像，视网膜电图，和单细胞电生理学研究上述发现的机制和生理相关性。目的1探讨视紫红质激酶介导的光传导恢复加速的机制和功能，以确定视锥细胞中更高水平的视紫红质激酶是否有助于改善人类视缓患者的症状。目的-2将寻求定量验证锥光转导恢复的速率限制步骤，并探索视杆光转导恢复的第二慢步骤的身份。将开发有用的小鼠品系和程序，以比较来自同一动物的视杆细胞和视锥细胞。Aim-3将审查G 3和G？13在视网膜中的表达水平及其与G？亚基赋予不同类型的去极化双极细胞不同的光响应特性。通过完成这些目标，我们希望了解三聚体G蛋白如何用于光转导以外的视觉，以及视杆细胞和视锥细胞对光的敏感性和响应速度如何不同。许多有用的小鼠品系将在这里制作、鉴定、保存和分发，以方便将来的发现。最后，了解正常的视觉机制是必不可少的有效预防，保护和恢复视力的患者患有各种衰弱性致盲疾病。

DESCRIPTION (provided by applicant): Signal transduction mediated by heterotrimeric G-proteins occurs throughout nature and is best represented by phototransduction in retinal rods. However, how trimeric G-proteins subserve vertebrate vision outside photoreceptors is still poorly understood. Likewise, basic information in phototransduction, such as the mechanisms underlying sensitivity and kinetic differences between rods and cones, is missing. Mutations in visual G-protein pathways cause debilitating diseases such as congenital stationary night blindness, bradyopsia, and photoreceptor degeneration. This application is built on three novel preliminary findings: 1) rhodopsin kinase may act as a GTPase accelerating protein (GAP) to ensure timely recovery of phototransduction under dim light condition. 2) cone phototransduction recovery is rate-limited by cone transducin turn-off. 3) more than one type of G¿? subunits mediate depolarizing bipolar cell light responses. We propose here to use an integrated approach combining mouse genetics, biochemistry, genomics, cell biology, imaging, ERG, and single cell electrophysiology to study the mechanisms and physiological relevance of the aforementioned findings. Aim-1 will investigate mechanism and function of rhodopsin kinase mediated acceleration of phototransduction recovery to determine whether a higher level of rhodopsin kinase in cone help to ameliorate symptoms of human bradyopsia patients. Aim-2 will seek quantitative validation of the rate- limiting step of cone phototransduction recovery and explore the identity of the second slowest step of rod phototransduction recovery. Useful mouse strains and procedures will be developed to allow comparisons between rods and cones derived from the same animal. Aim-3 will examine the role of G¿3 and G?13 in retina to see whether their expression levels and interactions with G? subunit confer different light response properties to different types of depolarizing bipolar cells. By completing these aims we expect to know how trimeric G-proteins are used in vision beyond phototransduction and how rod and cone may differ in their sensitivity and speed of their responses to light. Many useful mouse lines will be made, characterized, preserved, and distributed here to facilitate future discovery. Finally, knowing the normal visual mechanism is indispensable for efficient prevention, preservation, and restoration of vision in patients suffering from various debilitating blinding diseases.