Regulation of Cell Polarity and Exocytosis

描述(申请人提供)：这项建议的目标是了解真核细胞将新的膜生长和分泌定位于细胞表面特定位置的机制，以及这如何与细胞周期中细胞极性的变化相协调。在这项提案中，我们将研究LGL/Sro7和Rho/Cdc42蛋白家族在这一过程中的具体作用。LGL/Sro7蛋白家族首先在果蝇中被鉴定为肿瘤抑制因子，在所有真核细胞中都被发现，并可能在调节极性和胞吐作用方面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鉴定了这个家族的同源物，在这些细胞中，他们被发现与一组特定的SNARE蛋白有物理联系。我们将验证这一假设，即LGL家族成员在极化胞吐中具有保守的结构和功能，并可能作为Rab GTP酶的效应者，在极化生长过程中介导圈套依赖的囊泡融合。我们实验室进行的遗传分析已经确定了Rho/CDc42 GTP酶在胞吐作用中的直接作用。特别是，我们发现了两个Rho GTP酶，Rho3和CDC42，它们的功能是通过直接激活称为胞外的多亚单位复合体来参与胞吐作用的空间调节。在这项提案中，我们将采取综合的方法来确定Sro7、Rho3和Cdc42在极化胞吐调节中的分子机制。最终了解这些过程的分子细节可能有助于开发新的方法和新的疗法来抗击癌症或II型糖尿病以及其他疾病，在这些疾病中，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.