A periplasmic global regulator, ExoR, for Bacterial invasion of host cells

描述（由申请人提供）：细菌感染是并将继续是一个主要的健康威胁，特别是随着多种耐药病原体的发展。细菌感染的成功取决于细菌感知宿主细胞存在的能力，并在适当的时间产生毒力因子。在各种各样的细菌传感传感器中找到一个共同的特征，可以为对抗细菌感染的新抗生素提供有效的靶点。在我们的研究中，我们发现了一种细菌周围质蛋白ExoR，它似乎可以调节双组分调节系统的膜传感器的活性，而双组分调节系统调节细菌毒力因子的产生。我们目前的假设是ExoR是一个控制细菌宿主细胞入侵的全局调节剂。ExoR通过改变ExoR基因的结构构象或表达水平来响应上游或外部信号。ExoR蛋白的活性形式与其他膜传感器（如ExoS和FixL）相互作用，调节宿主细胞侵袭所需基因的表达。这一假设是基于我们之前的工作和我们实验室的以下新发现而提出的。首先，ExoR是一种质周蛋白。其次，ExoR调控了700多个基因的表达。第三，exoR基因的表达受氨的调控，exoR蛋白似乎有翻译后修饰的位点。第四，遗传学证据表明ExoR直接作用于ExoS/Chvl信号转导通路的上游。

DESCRIPTION (provided by applicant): Bacterial infection is and will continue to be a major health threat, especially with the development of multiple drug resistant pathogens. The success of bacterial infection depends on the ability of bacteria to sense the presence of host cells and produce virulence factors at the right time. Finding a common feature among the diverse array of bacterial sensing sensors can yield effective targets for new antibiotics to fight bacterial infection. In our study of signal transduction required for the invasion of host root hair cells by Sinorhizobium meliloti, we found a bacterial periplasmic protein, ExoR, that appears to regulate the activities of membrane sensors of two-component regulatory systems, which regulate the production of bacterial virulence factors. Our current hypothesis is that ExoR is a global regulator controlling bacterial host cell invasion. ExoR responds to upstream or external signals through the changing of structural conformation or levels of exoR gene expression. The active form of ExoR protein interacts with other membrane sensors such as ExoS and FixL in regulating the expression of genes required for host cell invasion. This hypothesis is developed based on our previous work and the following new findings made in our lab. First, ExoR is a periplasmic protein. Second, ExoR regulates the expression of more than 700 genes. Third, the expression of the exoR gene is regulated by ammonia and the ExoR protein appears to have a site for post-translational modification. Fourth, genetic evidences suggest that ExoR functions directly upstream of the ExoS/Chvl signal transduction pathway. To test the hypothesis, we plan to focus on accomplishing two specific aims. The first is to characterize the signaling mechanism of ExoR by (a) identifying the nodulation stage that requires the function of ExoR; (b) determining the cellular location of ExoR and its glycosaminoglycan modification; and (c) identifying ExoR protein-protein interaction domains. The second is to characterize ExoR-ExoS interactions by (a) characterizing molecular interaction between ExoR and ExoS; (b) identifying regions of ExoR and ExoS that are important for their signaling functions; and (c) determining the global regulatory function of ExoR. This work will provide the first insight for the molecular signaling mechanism of a periplasmic protein and provide a solid base for broad analysis of the global regulatory function of the protein, which will lead to the identification of targets for new classes of antibiotics.