转录调控因子OhrR在霍乱弧菌应答厌氧-好氧环境转换中的分子机制

Vibrio cholerae is one of the important pathogens in human history, even in today, an estimated 3-5 million cases and over 100,000 deaths occur each year around the world. Between epidemics, this facultative pathogen resides predominantly in a variety of aqueous environments, and infects human host through contaminated water and aquatic products. Apparently, the status of redox potential between its host gastrointestinal tract and the environmental reservoir is opposite. A fast and sensitive tuning gene expression in response to redox potential switches is definitely one of the important mechanisms why Vibrio cholearae successfully survive and become pandemic in this planet. Through high throughput sequence technology, we have screened the non-redundant transposon mutant library in infant mouse model, and identified ohrR encoding organic hydroperoxide resistance enzyme regulator (OhrR), which coordinates Vibrio cholerae virulence gene expression during colonization in infant mouse. Meanwhile, OhrR directly modulates the transcriptional expression of ohrA encoding organic hydroperoxide resistance enzyme A, which contributes to Vibrio cholerae resistance to oxidative burst stress. We proposed to study the molecular mechanism how OhrR regulates Vibrio cholerae virulence gene expression, especially the cysteine thiol-dependent oxidative modification dynamic of OhrR protein in response to transient changes of redox potential status, including the protein structure conformation transformation, the correlative regulation activity difference, and the consequential physiological function and roles of OhrR post-translational modification on Vibrio cholerae colonization in host gastrointestinal tract and resistance against oxidative burst happened in host environment after pathogen infection. Our proposal will not only help us discover the detailed information how Vibrio cholerae tuning rapid and accurate response to the transient redox switches during endemics, but also shed a light on the potential rational design for Cholera control and prevention .

霍乱弧菌是人类历史上重要的病原菌，每年仍然造成3-5百万病例和超过10万人的死亡。霍乱弧菌一般存活于水环境，通过污染水体或水产品感染宿主。显而易见，水体环境和宿主肠道环境中氧化还原状态迥异，敏感而迅速的应答氧化还原环境的转变是霍乱弧菌长期肆虐的原因之一。通过高通量测序技术，结合非冗余转座子突变文库体内筛选，我们发现有机过氧化物还原酶调控因子OhrR参与霍乱弧菌毒力基因表达的调控。同时，OhrR直接调控有机过氧化物还原酶OhrA的表达，帮助细菌抵御氧胁迫环境。本课题拟研究OhrR调控霍乱弧菌毒力基因表达的机理，尤其是定量研究不同氧化还原条件下，OhrR蛋白半胱氨酸氧化修饰状态的动态变化，包括蛋白质结构变化，及调控功能的差异，最后阐明OhrR蛋白质翻译后修饰在霍乱弧菌宿主肠道定殖和抵御氧迸发的分子机制和生理意义。该课题有助于阐明霍乱弧菌对环境变化快速适应机制，为霍乱的有效防治提供策略。

霍乱弧菌能够敏感外界厌氧-好氧环境变化，快速调整基因表达，实现在宿主肠道环境中的快速定殖和对逆境环境的抵御。本项目发现有机过氧化物还原酶调控因子OhrR参与霍乱弧菌体内定殖毒力基因表达的调控。通过和经典ToxR途径的AphB蛋白协同作用，通过调控tcpP基因的表达，实现在肠道中的快速定殖。同时OhrR/AphB还共同作用于霍乱弧菌抗逆基因ohrA，实现霍乱弧菌对氧胁迫的抵御。同时我们通过生物信息学分析，对霍乱弧菌应答外界环境信号，调整基因表达的网络进行了系统分析，鉴定出NorR/AphB-hmpA途径对霍乱弧菌应对活性氮的机制，CBS以来的硫化氢对ROS的清除机制，以及MarR蛋白家族对霍乱弧菌生物被膜、ROS、毒力表达的分子通路。我们的研究为阐明霍乱弧菌流行和致病分子机理奠定了基础。氧化还原环境转换