Role of cyclo(Phe-Pro) in Vibrio cholerae virulence factor production

描述(申请人提供)：霍乱弧菌是一种兼性人类病原体，可引起严重的腹泻疾病霍乱。霍乱弧菌致病的能力依赖于毒力因子的调节表达。例如，编码产生霍乱毒素和毒素协同调节菌毛的毒力基因似乎在感染早期被诱导，在感染后期被抑制，然后离开人类胃肠道。在感染后期诱导的其他基因被认为对建立人类毛发弧菌表现出的高度感染表型和在水生生态系统中的生存至关重要。在体内控制基因表达的机制在很大程度上是未知的。群体感应被认为是控制体内晚期基因表达的一种潜在机制。然而，观察到许多流行的霍乱弧菌对群体敏感不敏感，这表明肯定存在其他调控机制。我们的实验室已经证明，二酮基哌嗪类药物能抑制霍乱弧菌毒力因子的产生。在这项授权中，我们将检验这一假设，即环状(Phe-Pro)，一种由霍乱弧菌产生的天然二酮基哌嗪，作为信号来调节毒力基因的表达，而不依赖于已知的群体感应系统。提出了两个具体目标。在特定的目标1中，我们将对环状蛋白(Phe-Pro)进行表征，并定义参与其合成的基因。在具体目标2中，我们将定义环状病毒(Phe-Pro)调节毒力因子产生的机制。这些研究将揭示一种控制毒力因子产生的新的调控系统，并可能促进未来治疗霍乱的新治疗方法的发展。

DESCRIPTION (provided by applicant): Vibrio cholerae is a facultative human pathogen that causes the severe diarrheal disease cholera. The ability of V. cholerae to cause disease is dependent upon the regulated expression of virulence factors. For example, the virulence genes encoding for production of cholera toxin and the toxin coregulated pilus appear to be induced early in infection and repressed late in infection before exiting the human gastrointestinal tract. Other genes that are induced late during infection are believed to be important for the establishment of the hyperinfective phenotype exhibited by human shed vibrios, and for survival in the aquatic ecosystem. The mechanisms that control gene expression in vivo are largely unknown. Quorum sensing has been proposed as one potential mechanism to govern late gene expression in vivo. However, the observation that many epidemic V. cholerae strains are quorum sensing insensitive suggests that other regulatory mechanisms must exist. Our laboratory has shown that diketopiperazines inhibit virulence factor production in V. cholerae. In this grant we will test the hypothesis that cyclo(Phe-Pro), a natural diketopiperazine produced by V. cholerae, functions as a signal to modulate virulence gene expression independent of the known quorum sensing systems. Two specific aims are proposed. In specific aim 1 we will characterize cyclo(Phe-Pro) and define genes that are involved in its synthesis . In specific aim 2 we will define the mechanism by which cyclo(Phe-Pro) regulates virulence factor production. These studies will shed light on a novel regulatory system that controls virulence factor production and may facilitate the future development of novel therapeutic approaches for treatment of cholera.