Ubiquitin-dependent sorting in endosomes and the TGN

描述（由申请人提供）：将膜蛋白分选到晚期内体内形成的腔内囊泡中是调节许多生物学途径的基本过程，这些生物学途径依赖于维持给定一组细胞表面膜蛋白的适当水平。这是引导蛋白质在溶酶体中的递送和降解的途径。该途径由泛素驱动，泛素在连接到膜蛋白货物时作为分选信号起作用。该过程控制几乎所有细胞表面膜蛋白的降解，并且理解该降解过程是重要的，因为它影响依赖于特定膜蛋白（例如细胞表面的转运蛋白和信号受体）的适当活性的广泛的正常和致病过程。竞争性更新提案的长期目标是了解这种泛素依赖的分选途径是如何控制的，并将导致深入了解当这一过程出错时如何实现癌症等疾病状态。为了实现这一点，我们设计了以下目标：1）发现Nedd 4相关的泛素连接酶的主要家族如何被编程以靶向不同的细胞表面膜蛋白; 2）发现泛素化的膜蛋白如何被内体分选机制识别以及货物如何在组织分选机制本身中发挥积极作用;和3）使用一系列遗传筛选发现参与腔内囊泡形成过程的新蛋白质。

DESCRIPTION (provided by applicant): Sorting membrane proteins into intralumenal vesicles that form within late endosomes is a fundamental process that regulates many biological pathways that rely on maintaining appropriate levels of a given set of cell surface membrane proteins. This is the pathway that guides the delivery and degradation of proteins in lysosomes. This pathway is driven by ubiquitin, which works as a sorting signal when attached to membrane protein cargo. This process controls the degradation of almost all cell surface membrane proteins and understanding this degradative process is significant since it impacts a wide array of normal and pathogenic processes that rely on proper activity of particular membrane proteins such as transporters and signaling receptors at the cell surface. The long-term goal of the competitive renewal proposal is to understand how this ubiquitin-dependent sorting pathway is controlled, and will lead to insights into how disease states such as cancer might be achieved when this process goes awry. To accomplish this we have devised aims to 1) discover how the major family of Nedd4- related ubiquitin ligases are programed to target different cell surface membrane proteins; 2) discover how ubiquitinated membrane proteins are recognized by the endosomal sorting machinery and how that cargo plays an active role in organizing the sorting apparatus itself; and 3) discover new proteins that participate in the process of intralumenal vesicle formation using a series of genetic screens.