Regulation of Rho Family GTPases by G Proteins

描述(申请人提供)：异三聚体G蛋白将各种信号从七面体膜结合受体转导到细胞内效应器。G蛋白信号转导调节蛋白(RGS)家族成员调节G蛋白介导的信号转导。Rho家族的单体GTP酶控制着肌动蛋白细胞骨架的组织，并参与多种细胞功能。这项建议的目的是了解Rho家族GTP酶通过异源三聚体G蛋白介导的信号通路调节的机制。在异源三聚体G蛋白中，Galpha12和Galpha13参与细胞转化、轴突回缩或胚胎发育等细胞过程。Rho激活参与了这些信号通路。这项建议的直接目标是了解Galpha12和Galpha13调节Rho活性的生化机制。Rho家族GTP酶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，并调节它们的Rhogef活性。P115和LARG的RGS结构域是Galpha12和Galpha13所特有的GTP酶激活蛋白。分析Galpha12和Galpha13对RGS-RhoGEF调控机制的结构基础。Galpha12或Galpha13及其与LARG的络合物的晶体结构将得到解决。将描述参与其功能相互作用的Galpha12/13或LARG区域。LARG或PDZ-Rhogef对Rhogef活性调节的生化机制将被研究。此外，还将分析神经细胞中的Galpha12/13-LARG/PDZRhogef信号通路。Galpha12-Rhogef通路已在线虫中被鉴定，并被证实参与神经功能和胚胎发育。这一途径在线虫中的生理学意义将用遗传学和生物化学方法进行研究。

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.