Ubiquitin-Dependent Sorting in Endosomes and the TGN

描述(由申请人提供)： 我们已经发现了两种泛素分类受体(Ub分类受体)，它们对溶酶体内降解的泛素化膜蛋白(Ub-Cargo)进行分类。一种是GGA外壳蛋白，它似乎与TGN处的UbCargo结合，并将其合并到目标为输送到内体的囊泡中。另一种是Vps27和Hse1之间的复合体(在动物细胞中也称为MRS和STAM1/2)，它识别内吞体内的Ub-Cargo，并促进其进入多囊泡内小体(MVB)的腔小泡。这项建议旨在了解这些受体如何与其他假定的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。我们将在很大程度上通过分析这一机械与其他蛋白质之间各种相互作用的功能来研究控制这一机械活动的分子机制。Vps27-Hse1复合体与Ub连接酶和多肽酶、笼蛋白、Coatamer等蛋白质以及ESCRT-I复合体结合，ESCRT-I复合体也与Ub结合并参与MVB的生物发生。我们将确定这些相互作用的功能作用是什么，以及Vps27-Hse1的Ub分选功能如何与其他假定的Ub分选复合体协调，如ESCRT-I。我们还将通过测试各种候选蛋白质的潜力并进行遗传筛选来确定在这一途径中操作的基因，从而确定哪些其他蛋白质与GGA蛋白质一起作用于TGN上的Ub依赖分选。

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.