Type III effector regulation of host GTPase signaling

描述（由申请人提供）：革兰氏阴性细菌病原体的III型分泌系统是病原体与其宿主之间最直接的界面之一。这些“针状”分子机器将细菌效应蛋白直接注入宿主细胞，目的是破坏先天免疫反应，促进细菌复制、传播和疾病进展。效应蛋白是独特的毒力因子，因为它们经常捕获或模仿宿主信号转导分子的特性。其中一个目标是进化上保守的ras - GTPases超家族。目前的研究重点是最近发现的细菌III型效应家族。相关的III型效应物SifA、IpgB和Map分别是沙门氏菌、志贺氏菌和肠出血性大肠杆菌发病所必需的，它们具有激活rho家族GTPase信号级联的共同能力。本文所述的研究试图通过检查1)Rho gtpase的酶激活，2)gtpase在分子水平上的III型效应物识别，以及3)效应蛋白在宿主细胞内定位的作用来阐明这一大型细菌毒力因子家族的宿主信号机制。通过揭示III型效应家族成员的机制细节，这些研究将为几种感染因子的致病机制及其人类宿主的生物学提供新的见解。公共卫生相关性：人类rho家族gtpase是细菌毒素和效应蛋白的主要靶点。病原体劫持这一关键信号通路，促进细菌复制、传播和疾病进展。本研究旨在研究细菌III型效应蛋白大家族劫持人类Rho gtpase的能力。对这些细菌效应物和人类gtpase之间的酶和生化界面的深入了解将导致对许多致病机制的更完整的认识，并可能揭示人类宿主细胞信号转导的新方面。

DESCRIPTION (provided by applicant): The type III secretion system of Gram-negative bacterial pathogens creates one of the most direct interfaces between pathogens and their hosts. These 'needle-like' molecular machines inject bacterial effector proteins directly into host cells for the purpose of destroying an innate immune response and facilitating bacterial replication, dissemination, and disease progression. Effector proteins are unique virulence factors in that they often capture or mimic the properties of host signal transduction molecules. One such target is the evolutionarily conserved Ras-superfamily of GTPases. The present study focuses on a recently identified bacterial type III effector family. The related type III effectors SifA, IpgB, and Map are required for Salmonella, Shigella, and enterohaemorrhagic E. coli pathogenesis, respectively, through their common ability to activate Rho-family GTPase signaling cascades. The studies described here seek to elucidate the host signaling mechanisms of this large bacterial virulence factor family by examining 1) the enzymatic activation of Rho GTPases, 2) type III effector recognition of GTPases at the molecular level, and 3) the effects of effector protein localization within the host cell. By revealing mechanistic details of type III effector family members, these studies will provide new insights into the pathogenic mechanisms o several infectious agents and into the biology of their human host. PUBLIC HEALTH RELEVANCE: Human Rho-family GTPases are major targets of bacterial toxins and effector proteins. Pathogens hijack this critical signaling pathway to facilitate bacterial replication, dissemination, and disease progression. This proposal examines the ability of a large family of bacterial type III effector proteins to hijack human Rho GTPases. A deeper understanding of the enzymatic and biochemical interface between these bacterial effectors and human GTPases will lead to a more complete knowledge of numerous pathogenic mechanisms and may reveal new aspects of signal transduction in the human host cell.