Regulation of Rho Family GTPases by G Proteins

描述（由申请人提供）：异三聚体G蛋白将各种信号从七层膜结合受体转导到细胞内效应器。RGS （Regulator of G protein signaling）蛋白家族成员调控G蛋白介导的信号。单体GTPases的Rho家族成员控制肌动蛋白细胞骨架的组织，并参与多种细胞功能。本研究旨在通过异源三聚体G蛋白介导的信号通路，了解Rho家族gtpase的调控机制。在异三聚体G蛋白中，Galpha12和Galpha13参与细胞转化、神经突收缩或胚胎发育等细胞过程。Rho激活参与了这些信号通路。本研究的直接目标是了解Galpha12和Galpha13调控Rho活性的生化机制。Rho家族gtpase受鸟嘌呤核苷酸交换因子（gef）调控。具有氨基末端RGS结构域的rhogef （RGS- rhogef）、p115RhoGEF、LARG和PDZ-RhoGEF被鉴定为Galpha12和Galpha13的效应物。Galpha12/13与这些RhoGEF的RGS结构域相互作用，调控其RhoGEF活性。p115和LARG的RGS结构域是Galpha12和Galpha13特异性的GTPase激活蛋白。本文将分析Galpha12和Galpha13调控RGS-RhoGEFs的机制结构基础。研究了Galpha12或Galpha13及其与LARG的配合物的晶体结构。Galpha12/13或LARG中参与其功能相互作用的区域将被表征。研究LARG或PDZ-RhoGEF调控RhoGEF活性的生化机制。进一步分析神经元细胞中Galpha12/13-LARG/PDZRhoGEF信号通路。在秀丽隐杆线虫中发现了Galpha12-RhoGEF通路，并证实其参与神经元功能和胚胎发育。该途径在秀丽隐杆线虫中的生理意义将通过遗传学和生化方法进行研究。

DESCRIPTION (provided by applicant): Heterotrimeric G proteins transduce a variety of signals from heptahetical membrane-bound receptors to intracellular effectors. Members of RGS (Regulator of G protein signaling) protein family regulate G protein mediated signals. Members of the Rho family of monomeric GTPases control the organization of the actin cytoskeleton and are involved in a variety of cellular functions. The objective of this proposal is to understand the mechanism of regulation of Rho family GTPases through heterotrimeric G protein-mediated signaling pathways. Among heterotrimeric G proteins, Galpha12 and Galpha13 participate in cellular processes such as cell transformation, neurite retraction, or embryonic development. Rho activation is involved in these signaling pathways. The immediate goal of this proposal is to understand biochemical mechanisms of regulation of the activity of Rho by Galpha12 and Galpha13. Rho family GTPases are regulated by guanine nucleotide exchange factors (GEFs). RhoGEFs with amino terminal RGS domain (RGS-RhoGEFs), p115RhoGEF, LARG, and PDZ-RhoGEF, were identified to function as effectors for Galpha12 and Galpha13. Galpha12/13 interacts with RGS domain of these RhoGEFs and regulates their RhoGEF activity. RGS domains of p115 and LARG act as GTPase activating proteins specific for Galpha12 and Galpha13. The structure basis of the mechanism of regulation of RGS-RhoGEFs by Galpha12 and Galpha13 will be analyzed. The crystal structures of Galpha12 or Galpha13 and its complex with LARG will be solved. The regions of Galpha12/13 or LARG that are involved in their functional interaction will be characterized. The biochemical mechanisms of regulation of RhoGEF activity of LARG or PDZ-RhoGEF will be investigated. Furthermore, Galpha12/13-LARG/PDZRhoGEF signaling pathway in neuronal cells will be analyzed. Galpha12-RhoGEF pathway was identified in C. elegans and its involvement in neuronal function and embryonic development was demonstrated. The physiological significance of this pathway in C. elegans will be investigated using genetical and biochemical methods.