Regulation of Cell Polarity and Exocytosis

描述（由申请人提供）：本提案的目的是了解真核细胞将新膜生长和分泌靶向细胞表面特定位点的机制，以及这如何与细胞周期期间细胞极性的变化相协调。在这个提议中，我们将研究Lgl/Sro 7和Rho/Cdc 42蛋白家族在这个过程中的具体作用。首先在果蝇中鉴定为肿瘤抑制因子的Lgl/Sro 7蛋白质家族在所有真核细胞中发现，并且可能在极性和胞吐调节中具有高度保守的功能。我们已经在酵母和哺乳动物上皮细胞中发现了这个家族的同源物，它们与一组特定的SNARE蛋白存在物理联系。我们将测试Lgl家族成员在极化胞吐中具有保守的结构和功能，并且可能在极化生长期间作为Rab GTP酶的效应物介导SNARE依赖性囊泡融合的假设。在我们实验室进行的遗传分析导致了Rho/Cdc 42 GTP酶在胞吐中的直接作用的鉴定。特别是，我们已经发现了两种Rho GTP酶，Rho 3和Cdc 42，它们在一种途径中起作用，该途径涉及通过直接激活称为外囊的多亚基复合物来空间调节胞吐作用。在这个建议中，我们将采取一个全面的方法来确定Sro 7，Rho 3和Cdc 42在调节极化胞吐作用的分子机制。最终了解这些过程的分子细节可能会允许开发新的方法和新的治疗方法来对抗癌症或II型糖尿病，以及其他疾病，其中细胞表面运输的调节是疾病病因的核心。

DESCRIPTION (provided by applicant): The goal of this proposal is to understand the mechanism by which eukaryotic cells target new membrane growth and secretion to specific sites on the cell surface and how this is coordinated with changes in cell polarity during the cell cycle. In this proposal we will examine the specific role of Lgl/Sro7 and Rho/Cdc42 protein families in this process. The Lgl/Sro7 family of proteins, first.identified as a tumor suppressor in Drosophila, is found in all eukaryotic cells and is likely to have a highly conserved function in regulation of polarity and exocytosis. We have characterized homologs of this family in both yeast and mammalian epithelial cells where they are found in physical association with a specific set of SNARE proteins. We will test the hypothesis that Lgl family members have a conserved structure and function in polarized exocytosis and may act as effectors of Rab GTPases in mediating SNARE-dependent vesicle fusion during polarized growth. Genetic analyses performed in our lab have led to the identification of a direct role for Rho/Cdc42 GTPases in exocytosis. In particular we have found two Rho GTPases, Rho3 and Cdc42, that function in a pathway which involves spatial regulation of exocytosis through direct activation of a multisubunit complex known as the Exocyst. In this proposal we will take a comprehensive approach to identify the molecular mechanism by which Sro7, Rho3, and Cdc42 function in the regulation of polarized exocytosis. Ultimately understanding the molecular details of these processes may allow the development of new approaches and novel therapeutics to combating cancer, or type II diabetes, as well as other diseases in which regulation of cell surface trafficking is central to the etiology of the disease.