铜绿假单胞菌QscR受体通过下调3-oxo-C12-HSL抑制毒力的作用机制及抗感染应用研究

铜绿假单胞菌毒力因子是导致肺组织损伤的重要因素。群体感应系统QscR受体通过下调3-oxo-C12-HSL抑制毒力因子的表达，但其作用机制不清。申请人前期研究显示QscR受体通过激活PA1891-1894和PA1895-1897操纵子下调3-oxo-C12-HSL。同源分析提示此两操纵子编码蛋白分别具有酰胺酶和氧化还原酶作用，并且预实验显示其代谢产物抑制毒力因子表达。由此提出假设，此两操纵子编码蛋白可能通过酶学作用改变3-oxo-C12-HSL结构，其代谢产物可能通过抑制LasI/LasR功能下调3-oxo-C12-HSL。为此本项目拟纯化此两操纵子编码蛋白，检测其对3-oxo-C12-HSL酶学活性，并分离此两操纵子产生的代谢产物，检测其对LasI/LasR功能影响。本项目拟在细胞和动物感染模型中检测此两操纵子编码蛋白及代谢产物对宿主的保护作用。该成果将为开发新型抗感染药物提供理论依据。

The virulence factors of Pseudomonas aeruginosa are main causes of lung injuries. Quorum sensing receptor QscR can inhibit the expression of virulence factors by suppressing the level of 3-oxo-C12-HSL. However, its mechanism is still unclear. Our previous work shows that QscR suppresses the level of 3-oxo-C12-HSL by activating the operons of PA1891-1894 and PA1895-1897. Homology to known proteins suggests that the encoded proteins of the two operons possibly have enzymatic function of amidase and oxidoreductase, and our preliminary experiments indicate their metabolites could inhibit the expression of virulence factors. We hypothesize that the encoded proteins of the two operons could change the structure of 3-oxo-C12-HSL through enzymatic effects, and their metabolites could suppress the level of 3-oxo-C12-HSL through inhibiting the function of LasI/LasR. To test this hypothesis, we plan to purify the encoded proteins of the two operons and investigate their enzymatic effects on 3-oxo-C12-HSL. We also plan to separate the metabolites produced by the two operons and investigate their effects on LasI/LasR function. Meanwhile, we are going to test if the encoded proteins and metabolites of the two operons could protect host from injuries caused by Pseudomonas aeruginosa infection in the models of cells and animals. The results of this project will provide theoretical basis for the development of new-type anti-infection medicine.