Ubiquitin-Dependent Sorting in Endosomes and the TGN

描述（由申请人提供）： 我们已经发现了2种泛素分选受体（Ub-分选受体），其分选泛素化膜蛋白（Ub-货物）以在溶酶体中降解。一种是GGA外壳蛋白，其似乎在TGN处结合Ubcargo并将其掺入靶向递送至内体的囊泡中。另一个是Vps 27和Hse 1（在动物细胞中也称为Mrs和STAM 1/2）之间的复合物，它识别内体上的Ub货物并促进其进入多泡内体（MVB）的腔囊泡。该提案旨在了解这些受体如何与其他推定的Ub分选受体相关，以及它们如何协调可能改变货物泛素化状态的Ub连接酶和Ub肽酶的活性。我们将研究控制这种机器活动的分子机制，在很大程度上通过分析这种机器和其他蛋白质之间的各种相互作用的功能。Vps 27-Hse 1复合物与Ub连接酶和肽酶、网格蛋白、Coatamer和其他蛋白质以及ESCRT-1复合物结合，ESCRT-1复合物也结合Ub并参与MVB生物发生。我们将确定这些相互作用的功能作用是什么，以及Vps 27-Hse 1的Ub分选功能如何与其他推定的Ub分选复合物如ESCRT-I协调。我们还将确定哪些其他蛋白质与Gga蛋白一起作用，通过测试各种候选蛋白质的潜力并进行遗传筛选以识别在该途径中运作的基因，来影响TGN的Ub依赖性分选。

DESCRIPTION (provided by applicant): We have discovered 2 ubiquitin sorting receptors (Ub-sorting receptors) that sort ubiquitinated membrane proteins (Ub-cargo) for degradation in the lysosome. One is the GGA coat protein, which appears to bind Ubcargo at the TGN and incorporate it into vesicles targeted for delivery to the endosome. The other is a complex between Vps27 and Hse1 (aka Mrs and STAM1/2 in animal cells), which recognizes Ub-cargo at the endosome and promotes its entry into luminal vesicles of multivesicular endosomes (MVB). This proposal aims to understand how these receptors work in relation to other putative Ub-sorting receptors and how they coordinate the activity of Ub ligases and Ub-peptidases that may alter the ubiquitination status of cargo. We will examine the molecular mechanisms that control the activity of this machinery, in large part by analyzing the function of various interactions between this machinery and other proteins. The Vps27-Hse1 complex associates with Ub ligases and peptidases, clathrin, Coatamer and other proteins, as well as the ESCRT-I complex that also binds Ub and participates in MVB biogenesis. We will determine what the functional roles of these interactions are and how the Vps27-Hse1 Ub-sorting function of Vps27- Hse1 is coordinated with other putative Ub-sorting complexes is such as ESCRT-I. We will also determine what other proteins work with Gga proteins to effect Ub-dependent sorting at the TGN by testing the potential of a variety of candidate proteins and conducting genetic screens to identify genes that operate in this pathway.