Delivery of signaling and structural proteins to photoreceptor outer segment

描述（由申请人提供）：本提案的总体目标是将我们对感光细胞外节中发生的信号传导过程的机械理解与负责维持该细胞器蛋白质组成的细胞过程的框架相结合。为此，目标1将继续我们长期以来的研究GT3激活蛋白复合物的转导与细胞和催化方面的功能之间的相互作用的重点。在目标2和3中，将分析视紫红质的类似相互作用，视紫红质在光感受器细胞中具有三种不同的作用：信号传导（光转导级联的激活）、结构（盘膜的构建材料）和靶向（引导运输视紫红质和可能的其他蛋白质（例如，GT3激活复合物）的囊泡流到外节）。我们将首先测试视紫红质在指导外节囊泡运输的作用是否可以从其其他主要功能中分离出来，然后确定视紫红质的结构功能是否可以被其他膜蛋白所取代，以定位于感光盘。最后，目标4将阐明负责外节中其他蛋白质功能的运输途径。我们将专注于感光盘边缘蛋白，peripherin-2/RDS，这是最有可能使用的细胞内靶向机制替代视紫红质已知的候选人。拟议的实验与理解感光细胞生物学中最基本的问题有关，并且是理解与蛋白质信号传导，靶向和贩运缺陷相关的许多类型的感光细胞变性的原因的关键。 公共卫生相关性：本申请中提出的研究解决了负责感光细胞的光敏隔室（外节）功能的分子和细胞机制。由于每日光照的不利影响，外节的构建材料必须大约每十天更换一次，这需要大量高度组织化的蛋白质从细胞内生物合成机器运输到该隔室。这些途径的功能障碍导致一些最严重类型的遗传性视网膜退行性疾病，突出了理解蛋白质信号传导、运输和组装成大型功能复合物的机制的重要性。阐明这些机制对于制定疾病预防和未来治疗干预策略至关重要。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to integrate our mechanistic understanding of the signaling processes that take place in the outer segment of photoreceptor cells with the framework of the cellular processes responsible for maintenance of the protein composition of this organelle. To this end, Aim 1 will continue our longstanding investigation of the GTPase activating protein complex for transducin with an emphasis on the interplay between the cellular and catalytic aspects of its function. In Aims 2 and 3 a similar interplay will be analyzed for rhodopsin, which has three distinct roles in photoreceptor cells: signaling (activation of the phototransduction cascade), structural (building material of the disc membranes) and targeting (directing the flow of vesicles transporting rhodopsin and likely other proteins, e.g. the GTPase activating complex, to the outer segment). We will first test whether the role of rhodopsin in directing outer segment vesicular transport can be dissociated from its other major functions and then determine whether the structural function of rhodopsin can be replaced by other membrane proteins made to localize to the photoreceptor discs. Finally, Aim 4 will elucidate trafficking pathways responsible for the delivery of other proteins functioning in the outer segment. We will focus on a photoreceptor disc rim protein, peripherin-2/RDS, which is the most likely known candidate for using an intracellular targeting mechanism alternative to rhodopsin. The proposed experiments are relevant to understanding the most basic issues in photoreceptor cell biology and are key for understanding the causes of many types of photoreceptor degeneration associated with defects in protein signaling, targeting and trafficking. PUBLIC HEALTH RELEVANCE: The studies proposed in this application address the molecular and cellular mechanisms responsible for the functioning of the light-sensitive compartment of the photoreceptor cells, the outer segment. Because of adverse effects of daily light exposure, the building materials of the outer segment have to be replaced approximately every ten days, which requires an enormous flow of highly organized protein trafficking from the intracellular biosynthetic machinery to this compartment. Dysfunction of these pathways causes some of the most severe types of inherited degenerative diseases of the retina, highlighting the importance of understanding the mechanisms underlying protein signaling, trafficking and assembly into large functional complexes. Elucidating these mechanisms is essential for developing strategies for disease prevention and future therapeutic interventions.