Ubiquitin-dependent sorting in endosomes and the TGN

描述(由申请人提供)：将膜蛋白分选到腔内小泡中，形成于晚期内小体中是调节许多生物途径的基本过程，这些途径依赖于维持一组给定的细胞表面膜蛋白的适当水平。这是引导溶酶体内蛋白质传递和降解的途径。这一途径是由泛素驱动的，泛素在连接到膜蛋白货物上时起到分类信号的作用。这一过程控制着几乎所有细胞表面膜蛋白的降解，了解这一降解过程意义重大，因为它影响到广泛的正常和致病过程，这些过程依赖于特定膜蛋白的适当活性，如细胞表面的转运体和信号受体。竞争性更新提案的长期目标是了解这种依赖泛素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，癌症等疾病状态可能会如何实现。为了实现这一目标，我们设计的目标是：1)发现Nedd4相关泛素连接酶的主要家族是如何针对不同的细胞表面膜蛋白进行编程的；2)发现泛素化的膜蛋白是如何被内体分拣机器识别的，以及该货物如何在组织分拣装置本身中发挥积极作用；以及3)使用一系列基因筛查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.