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

描述(申请人提供)：细菌感染现在是，也将继续是一个主要的健康威胁，特别是随着多重耐药病原体的发展。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传感器中找到一个共同的特征，可以为新的抗生素抗击细菌感染产生有效的靶点。在我们对苜蓿中华根瘤菌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，它似乎调节着双组分调控系统的膜传感器的活性，从而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球调节因子。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感受器如EXOS和FixL相互作用，调节宿主细胞入侵所需基因的表达。这一假设是在我们之前的工作和我们实验室的以下新发现的基础上提出的。首先，Exor是一种周质蛋白。其次，Exor调控着700多个基因的表达。第三，Exor基因的表达受氨的调节，Exor蛋白似乎有一个翻译后修饰的位点。第四，遗传学证据表明Exor直接作用于EXOS/Chv1信号转导通路的上游。 为了检验这一假设，我们计划专注于实现两个具体目标。首先，通过(A)确定需要Exor功能的结瘤阶段；(B)确定Exor的细胞位置及其糖胺聚糖修饰；以及(C)确定Exor蛋白-蛋白质相互作用区域，来表征Exor的信号转导机制。第二种是通过(A)鉴定Exor和EXOS之间的分子相互作用；(B)确定Exor和EXOS中对其信号功能重要的区域；以及(C)确定Exor的整体调控功能来表征Exor-EXOS的相互作用。这项工作将首次深入了解周质蛋白的分子信号机制，并为广泛分析该蛋白的全球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标。

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.