Regulation of cytolysin production in Enterococcus feacalis

描述（由申请人提供）：粪肠球菌是人类肠道菌群的常见居民，也是人类感染的常见原因。由于肠球菌能够在住院患者中引起致命感染，并且能够轻易地将毒力决定因素（如抗生素耐药性）转移给其他微生物，因此在过去几十年里，肠球菌变得越来越突出。这种生物在环境中持续存在的能力，定殖于各种宿主，并将毒力能力传递给其他病原体，使得阐明这种细菌的毒力机制势在必行。其中一个被认为对粪肠杆菌的毒力有贡献的因素是毒素，细胞溶素。细胞溶素是一种新型毒素，能够裂解多种细胞类型和生物体-细菌和真核生物。胞溶素毒素由两个亚基CylLL和CylLs组成，这两个亚基都经过广泛的修饰以产生活性形式。两个独特的调节蛋白CylR1和CylR2是控制毒素表达所必需的。这个系统的不同寻常之处在于，CylR1和CylR2与其他细菌系统中已知的调节成分没有明显的同源性，并且通过一种未知的机制来禁用细胞溶解素操纵子的转录。此外，一种毒素亚单位，细胞，已被证明可以诱导细胞溶解素的产生。由于细胞溶素毒素是粪肠杆菌的重要毒力因子，并且受到独特的调节机制的影响，了解这种毒素是如何被调节的，以期改善治疗措施，以破坏这种生物体的感染，这是很有意义的。因此，本申请旨在确定CylR1和CylR2调控胞溶素表达的机制，并确定cyl在这一调控过程中的作用。为了实现这些目标，我们将研究CylR1和CylR2的细胞定位，评估它们彼此和cyl2相互作用的能力，并研究这些相互作用对溶细胞素操纵子调控的影响。

DESCRIPTION (provided by applicant): Enterococcus faecalis is a common resident of human intestinal flora and a frequent cause of infection in humans. Enterococci have grown in prominence over the past few decades due to their ability to cause fatal infections in hospitalized persons and their capacity to readily transfer virulence determinants, such as antibiotic resistances, to other microbes. The ability of this organism to persist in the environment, colonize a variety of hosts, and pass virulence capabilities to other pathogens makes elucidation of virulence mechanisms in this bacterium imperative. One such factor that has been recognized for its contribution to the virulence of E. faecalis is the toxin, cytolysin. Cytolysin is a novel toxin, capable of lysing a wide variety of cell types and organisms - both bacterial and eukaryotic. The cytolysin toxin consists of two subunits, CylLL and CylLs, both of which are extensively modified to generate their active forms. Two unique regulatory proteins, CylR1 and CylR2, are essential for controlling toxin expression. What makes this system unusual is that CylR1 and CylR2 bear no significant homology to known regulatory components in other bacterial systems, and function by an unknown mechanism to disable transcription of the cytolysin operon. Furthermore, one of the toxin subunits, CylLs, has been shown to induce cytolysin production. As cytolysin toxin is both a significant virulence factor of E. faecalis, and is subject to unique regulatory mechanisms, it is of interest to understand how this toxin is regulated in hopes of improving therapeutic measures to subvert infections by this organism. Therefore, this application aims to identify the mechanisms by which CylR1 and CylR2 regulate expression of cytolysin and to determine the role of CylLs in this regulatory process. To achieve these aims, we will examine the cellular localization of both CylR1 and CylR2, assess their ability to interact with each other and CylLs, and study the effects of these interactions on the regulation of the cytolysin operon.