OmpR and SsrB Regulation of Salmonella Virulence

描述(由申请人提供)： 项目摘要沙门氏菌感染是世界范围内的一个主要健康问题。沙门氏菌通过表达位于致病岛上的基因来致病。沙门氏菌致病性岛-1(SPI-1)上的基因使沙门氏菌能够附着和入侵上皮细胞，而SPI-2基因是全身感染所必需的。专门的分泌系统称为III型分泌系统，编码在每个致病岛上，为沙门氏菌提供了将效应分子分泌到宿主体内的手段，从而改变宿主功能并促进发病。本提案的重点是控制SPI-2基因的表达。它是沙门氏菌最关键的毒力决定因素之一，但其转录调控的复杂分子生物学，特别是体内基因表达途径的识别，仍然缺乏明确的认识。我们的研究集中在从分子的角度定义这些途径。SPI-2基因的表达由一个双组分调控系统SsrAB控制，SsrAB的表达又受额外的调控网络控制，包括EnvZ-OmpR双组分系统、转录激活因子SlyA和全局抑制因子H-NS。SPI-2的复杂调控需要多种环境信号的整合，以确保这些重要的毒力基因在巨噬细胞吞噬体内的适当时间表达。在这项提案中，将确定在各种环境条件下对ssrA/SSRB表达的关键顺式和反式调控元件。我们假设OmpR位于这个调控体系的顶端，激活ssrA/B双组分调控系统的转录。SSRB刺激感染期间分泌的III型分泌器和效应器编码基因的表达。SSRB在巨噬细胞感染过程中被无应激修饰，这种半胱氨酸修饰对SPI-2基因表达的影响将在小鼠巨噬细胞、巨噬细胞样细胞系和感染沙门氏菌野生型和SSRB突变株的小鼠组织中进行检测。作为我们研究的结果，我们将对沙门氏菌感染引起的分子事件以及这些修饰如何改变宿主中的基因表达有一个更好的了解。 公共卫生相关性： 对退伍军人健康的影响退伍军人患有急性和慢性细菌感染。我们的研究是机械论的，其影响不仅限于沙门氏菌，还延伸到其他病原体。已证明，在霍乱弧菌、志贺氏菌、耶尔森氏菌和其他传染性物种中，ompR是毒力所必需的。此外，耐药沙门氏菌感染是包括退伍军人医院在内的所有医院的一个问题，沙门氏菌引起的败血症是免疫功能低下的艾滋病毒阳性患者的一个问题，在退伍军人中发生的比例很高。沙门氏菌相关性急性胃肠炎是旅行者、部署的军事人员和人口密度高的封闭社区(如军事基地、医院或疗养院)发病的一个重要原因。全世界每年的伤寒病例数量超过3300万例，这仍然是以前接种疫苗的旅行者和军事人员的潜在关切。

DESCRIPTION (provided by applicant): PROJECT SUMMARY Salmonella infections are a major health problem worldwide. Salmonella causes disease by expressing genes that are located on pathogenicity islands. Genes that reside on Salmonella Pathogenicity Island-1 (SPI-1) enable Salmonella to adhere to and invade epithelial cells, whereas SPI-2 genes are required for systemic infection. Specialized secretory systems termed type III secretion systems are encoded on each pathogenicity island that provide Salmonella with the means to secrete effector molecules into the host that alter host functions and promote pathogenesis. The present proposal focuses on the control of SPI-2 gene expression. It is one of the most critical virulence determinants of Salmonella, yet the complex molecular biology of its transcriptional regulation, in particular the identification of the pathways for gene expression in vivo, remains poorly defined. Our research is focused on defining these pathways in molecular terms. SPI-2 gene expression is controlled by a two-component regulatory system SsrAB, whose expression is in turn controlled by additional regulatory networks, including the EnvZ-OmpR two-component system, the transcriptional activator SlyA and the global repressor H-NS. The complex regulation of SPI-2 requires integration of multiple environmental signals to ensure that these important virulence genes are expressed at the appropriate time within the macrophage phagosome. In this proposal, critical cis and trans regulatory elements for ssrA/ssrB expression under a variety of environmental conditions will be identified. We hypothesize that OmpR lies at the top of this regulatory hierarchy, activating transcription of the ssrA/B two-component regulatory system. SsrB stimulates expression of the genes encoding the type III secretory apparatus and effectors that are secreted during infection. SsrB is modified by NO stress during macrophage infection, the consequences of this cysteine-modification to expression of SPI-2 genes will be examined in both mouse macrophages, a macrophage-like cell line and mouse tissues upon infection with Salmonella wild type and ssrB mutant strains. As a result of our studies, we will have an enhanced understanding of the molecular events that occur as a result of Salmonella infection and how these modifications alter gene expression in the host. PUBLIC HEALTH RELEVANCE: Impact on Veteran's Health Veterans suffer from both acute and chronic bacterial infections. Our studies are mechanistic and have implications beyond Salmonella, extending to other pathogens. OmpR has been shown to be required for virulence in Vibrio cholerae, Shigella, Yersinia and other infectious species. Furthermore, drug-resistant Salmonella infections are a problem in all hospitals, including VA hospitals and septicemia due to Salmonella is a problem in immune-compromised HIV positive patients, a high incidence which occurs in veterans. Salmonella-associated acute gastroenteritis is a significant cause of morbidity among travelers, deployed military personnel and high population density closed communities (e.g. military bases, hospitals or nursing homes). The number of typhoid fever cases exceeds 33 million per year worldwide and remains a potential concern among previously vaccinated travelers and military personnel.