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的存在并在正确的时间产生毒力因子的能力。在各种各样的细菌传感器中找到一个共同的特征，可以为新的抗生素提供有效的靶标来对抗细菌感染。在我们对苜蓿中华根瘤菌（Sinorhizobium meliloti）入侵宿主根毛细胞所需的信号转导的研究中，我们发现了一种细菌周质蛋白ExoR，它似乎调节双组分调节系统的膜传感器的活性，该系统调节细菌毒力因子的产生。我们目前的假设是ExoR是控制细菌宿主细胞侵袭的全局调节剂。exoR通过改变结构构象或exoR基因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以前的工作和我们实验室的以下新发现而提出的。首先，ExoR是周质蛋白。其次，ExoR调节700多个基因的表达。第三，exoR基因的表达受氨调节，并且ExoR蛋白似乎具有翻译后修饰的位点。第四，遗传学证据表明ExoR直接在ExoS/Chvl信号转导途径的上游起作用。 为了验证这个假设，我们计划集中精力实现两个具体目标。第一个是通过以下方式表征ExoR的信号传导机制：（a）鉴定需要ExoR功能的促凝阶段;（B）确定ExoR及其糖胺聚糖修饰的细胞位置;以及（c）鉴定ExoR蛋白-蛋白相互作用结构域。第二个是通过（a）表征ExoR和ExoS之间的分子相互作用;（B）鉴定ExoR和ExoS的对其信号传导功能重要的区域;和（c）确定ExoR的全局调节功能来表征ExoR-ExoS相互作用。这项工作将为周质蛋白的分子信号传导机制提供第一个见解，并为广泛分析蛋白质的全局调节功能提供坚实的基础，这将导致识别新类别抗生素的靶点。

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.