Structural Dynamics in Rhodopsin Activation and Attenuation

项目摘要 我们研究的一个长期目标是了解G蛋白偶联的分子机制 受体（GPCR）被激活和减弱。GPCR是人类基因组中最大的家族， 大多数药物的目标。一个例外是视紫红质-尽管第一个GPCR 发现，它迄今为止一直难以直接药物治疗。 在这里，Kliger和Farrens实验室联合起来定义了 人类视紫红质和视锥光蛋白的光活化，确定视紫红质如何与其配体相互作用， 视网膜，确定其功能如何随着视网膜疾病的突变而变化，并确定如何 这些相互作用使得能够与其附属蛋白抑制蛋白相互作用，并且通过与其附属蛋白抑制蛋白相互作用来调节。虽然 视网膜，视紫红质和抑制蛋白的结构现在是已知的，动态过程使它们能够 相互之间没有互动。因此，我们在这里提出的研究类型是必要的。 具体目标1将确定人红色和绿色锥状色素的光活化动力学，确定 人类视紫红质的激活是如何通过与ADRP相关的突变短路的，并测试如何 这些动力学受用于处理和稳定错误折叠视蛋白的小分子伴侣的影响。具体 目的2将确定新的受体构象在视网膜摄取和释放过程中起什么作用， 测试先前未鉴定的受体构象是否能够结合11-顺式视黄醛（11 CR）， 我们发现视蛋白在释放全反式视黄醇（ATR）后可以暂时停留在活性样状态。 最后，特异性目标3将确定抑制蛋白结合是否使ATR能够结合光漂白的视紫红质。 平衡，并定义抑制蛋白结合视紫红质二聚体对这种现象的影响。 了解什么调节视紫红质光活化过程，视网膜吸收和释放， 从健康的角度来看，arrestin如何调节这些行为至关重要。视网膜必须 适应这些事件中的巨大变化，因为它适应了广泛不同的光线条件， 随着时间的推移，这一过程被认为会导致氧化视网膜加合物的形成， 比如萎缩性年龄相关性黄斑变性（AMD）。因此，似乎arrestin必须走一条细线， 一方面控制在变化的光照条件下释放的游离视网膜的量，另一方面 在适当的时间从受体释放视网膜及其本身，以避免形成稳定的视紫红质抑制蛋白 复合物，可以有助于细胞凋亡和某些形式的视网膜色素变性。 这里的工作补充了我们最近的发现，ATR可以交换平衡与一些视紫红质 光产物，以及其他人最近发现的结合和稳定错误折叠的视蛋白的非视网膜配体。 这些发现极大地增加了药物开发的可能性， 增强视网膜结合，从而打开了用药理学试剂治疗这一关键感光体的大门。

Project Summary A long-term goal of our research is to understand the molecular mechanisms through which G-protein coupled receptors (GPCRs) are activated and attenuated. GPCRs are the largest family in the human genome, and the target of most pharmaceutical drugs. One exception has been rhodopsin – although the first GPCR discovered, it has so far been refractory to direct pharmacological treatments. Here the Kliger and Farrens lab join forces to define the dynamic events and mechanisms involved in the photo-activation of human rhodopsin and cone photopsins, determine how rhodopsin interacts with its ligand, retinal, determine how its function changes with mutations responsible for retinal diseases and determine how these interactions enable, and are modulated by, interactions with its affiliate protein arrestin. Although the structures of retinal, rhodopsin, and arrestin are now known, the dynamic processes that enable them to interact with each other are not. Thus, the types of studies we propose here are required. Specific Aim 1 will determine the photoactivation kinetics of human red and green cone pigments, determine how the activation of human rhodopsin is short-circuited by mutations associated with ADRP, and test how these kinetics are effected by small molecule chaperones used to treat and stabilize misfolded opsins. Specific Aim 2 will determine what role novel receptor conformations play in the process of retinal uptake and release, test if a previously unidentified receptor conformation enables binding of 11-cis retinal (11CR), and expand on our discovery that opsin can transiently linger in an active-like state after releasing all-trans retinal (ATR). Finally, Specific Aim 3 will determine if arrestin binding enables ATR to bind photobleached rhodopsin in equilibrium, and define what effect arrestin binding to rhodopsin dimers has on this phenomenon. Understanding what regulates the process of rhodopsin photoactivation, and retinal uptake and release, and how arrestin regulates these actions is critically important from a health perspective. The retina must accommodate huge variations in these events as it adapts to widely different light conditions, yet aberrations in this process over time are thought to result in the formation of oxidative retinal adducts that promote diseases like atrophic age-related macular degeneration (AMD). Thus, it appears that arrestin must walk a fine line – on the one hand controlling the amount of free retinal released under varying light conditions, and on the other releasing retinal and itself from the receptor at the appropriate time to avoid forming stable rhodopsin-arrestin complexes that can contribute to apoptosis and some forms of retinitis pigmentosa. The work here complements our recent discovery that ATR can exchange in equilibrium with some rhodopsin photoproducts, and recent discoveries by others of non-retinal ligands that bind and stabilize misfolded opsins. These findings dramatically increase the possibility that drugs can be developed to either compete with or enhance retinal binding, thus opening the door for treating this key photoreceptor with pharmacological agents.