OmpR依赖TCS调控钩端螺旋体主要外膜蛋白抗原表达及LPS合成与变构分子机制研究

感染是病原与宿主相互作用过程。我们发现钩端螺旋体（简称钩体）感染细胞时主要外膜蛋白（OMPs）抗原表达减少且LPS合成增加和脂质A变构毒力增强，其机制不明。近年报道细菌组氨酸激酶EnvZ/PmrB与基因表达调控蛋白OmpR/PmrA组成二元信号系统（TCS）感知环境信号后调控OMPs表达和LPS修饰。本项目拟研究钩体EnvZ/PmrB基因敲除前后感知感染细胞或不同温度、pH、渗透压、ROS、Ca2+感染微环境信号后靶蛋白磷酸化激活以及OmpR/PmrA与不同靶基因启动子区域结合，下调主要OMPs表达或经microRNAs降解其mRNAs，上调LPS限速酶LpxB/LpxC和脂质A修饰酶LpxD2/HtrB表达导致LPS合成增加和脂质A变构，阐明EnvZ/OmpR-TCS和PmrB/PmrA-TCS感知的感染微环境信号及其下调OMPs抗原表达有助于免疫逃逸并促进LPS相关毒力增强作用与机制。

Infection is a process of interaction between pathogens and hosts. We recently found that the expression of major outer membrane proteins (OMPs) of Leptospira interrogans during infection of host cells was significantly decreased, the synthesis of LPS was increased and the structure of lipid A was changed for enhancement of virulence, but their mechanisms remain unknown. Recent reports showed that bacterial histidine kinases, EnvZ/PmrB, and gene expression modulins, OmpR/PmrA, can compose two-component systems (TCS) to regulate the expression of OMPs and modify the structure of LPS after sensing environmental signals. In this project, we will determine that the EnvZ/PmrB gene knockout or wild-type Leptospira sense the infection of host cells or different infectious microenvironmental signals such as temperature, pH, osmotic pressure, ROS and Ca2+ levels to induce the activation of target proteins by phosphorylation and the combination of OmpR/PmrA with different regions in the promoters of target genes, which down-regulate the expression or degrade the mRNAs of major OMPs, up-regulate the expression of LPS rate-limiting enzymes LpxB/LpxC and lipid A modification enzymes LpxD2/HtrB to cause the increase of LPS synthesis and modification of lipid A. The aim of this project is to illuminate the roles and mechanisms of EnvZ/OmpR-TCS and PmrB/PmrA-TCS can sense infectious microenvironmental signals and then down-regulate the expression of OMPs antigens for immune escape and promote the enhancement of LPS-associated virulence.