Phototransduction in health and disease

描述(申请人提供)：暗视是在视紫红质分子捕获光的光子后启动的，视紫红质存在于视杆感光细胞。光感受器视紫红质的激活启动了一系列称为光转导的生化反应，导致细胞超极化。这项研究计划的长期目标是了解正常和疾病状态下光转导中生化事件的分子机制。起点将是视紫红质的结构-功能研究。这种分子的重要性超出了它在光传导中的中心作用。视紫红质基因是导致遗传性视力障碍的突变的热点，这些突变是常染色体显性遗传性视网膜色素变性疾病的主要原因，常染色体显性视网膜色素变性是一组不同类型的遗传性视网膜退行性疾病。尽管视紫红质有丰富的知识可用，但其准确的作用机制仍不清楚，光感受器突变导致视力障碍的机制也不清楚。我们的直接目标是探索关于该系统的新想法，这些想法在经典教条的基础上进行扩展；即，视紫红质的多个活性状态的概念以及视紫红质组织成二聚体簇的概念。该提案的目的是围绕理解控制人类正常和疾病条件下视紫红质活性的基本分子原理进行主题联系。在第一个目标中，我们将测试在大多数研究中做出的隐含的假设，即人类视紫红质的结构和功能类似于研究得更好的哺乳动物物种(牛和小鼠)用于理解人类疾病病理学的受体。在第二个目标中，我们将测试该受体有多个活跃状态的假设，即这些状态中至少有一个会导致导致先天性静止性夜盲的视紫红质突变体的结构性活动。在第三个目标中，我们将测试一个假定的视紫红质二聚体模型，并确定受体寡聚是否有助于导致常染色体显性遗传性视网膜色素变性的视紫红质突变的表型。需要重大的技术进步来克服在研究膜蛋白以观察自然结构和分子细节方面的固有困难，这些细节对于理解该系统是重要的。我们的方案利用了几种高分辨率的生物物理方法，包括原子力显微镜、单分子力谱和Forster共振能量转移。将这些方法与更传统的生化、生物物理和遗传学方法相结合，将克服传统检测方法的局限性，使我们能够直接测试关于视紫红质结构和功能的新兴范例。这些新概念的成功测试将导致一个更准确的分子框架，以了解该系统在正常条件下的功能以及遗传性人类疾病中的功能障碍。

DESCRIPTION (provided by applicant): Scotopic vision is initiated upon capture of a photon of light by rhodopsin molecules present in rod photoreceptor cells. The activation of the light receptor rhodopsin sets into motion a series of biochemical reactions called phototransduction, which leads to the hyperpolarization of the cell. The long-term goal of this research program is to understand the molecular mechanisms underlying the biochemical events in phototransduction under normal and diseased states. The starting point will be structure-function studies of rhodopsin. The importance of this molecule extends beyond its central role in phototransduction. The rhodopsin gene is a hot spot for mutations causing inherited vision disorders and these mutations are the leading cause of autosomal dominant retinitis pigmentosa, a heterogeneous group of inherited retinal degenerative diseases. Despite the wealth of knowledge available for rhodopsin, an accurate mechanism of its action is still unavailable and the mechanism underlying mutations in the light receptor causing vision disorders is unclear. Our immediate goal is to explore emerging ideas about the system that expand on classical dogma; namely, the notion of multiple active states of rhodopsin and the organization of rhodopsin into clusters of dimers. The aims of the proposal are thematically linked around understanding the fundamental molecular principles governing the activity of rhodopsin in normal and diseased conditions in people. In the first aim, we will test the implicit assumption made in most studies that the structure and function of human rhodopsin is similar to that of the receptor from better-studied mammalian species (bovine and mouse) used to understand human disease pathology. In the second aim, we will test the hypothesis that there are multiple active states of the receptor and that at least one of these states leads to constitutive activity in a rhodopsn mutant causing congenital stationary night blindness. In the third aim, we will test a putative rhodopsin dimer model and determine whether receptor oligomerization contributes to the phenotype of a rhodopsin mutant causing autosomal dominant retinitis pigmentosa. Significant technological advances are required to overcome the intrinsic difficulties in studying membrane proteins to observe native structural and molecular details that are important to understand the system. Our proposal utilizes several high-resolution biophysical methods including atomic force microscopy, single-molecule force spectroscopy and Forster resonance energy transfer. The combination of these methods with more traditional biochemical, biophysical, and genetic approaches will overcome the limitations of traditional assays alone and allow us to directly test emerging paradigms about rhodopsin structure and function. The successful testing of these new concepts will lead to a more accurate molecular framework to understand the function of the system under normal conditions and dysfunctions in inherited human disease.