USP22促进NLRP3溶酶体途径降解负向调控NLRP3炎症小体活化的作用及机制研究

炎症小体促进机体抵抗入侵病原体，而过度活化会损伤机体导致疾病。因此，炎症小体的活化和调控是一个有待深入研究的前沿科学问题。我们前期利用去泛素化酶质粒库，筛选到调控NLRP3蛋白稳定性的去泛素化酶USP22，发现其可促进NLRP3降解；小鼠腹腔巨噬细胞敲低USP22，NLRP3蛋白增加，LPS诱导的IL-1β分泌增多；利用USP22体内敲低小鼠构建腹膜炎模型，发现腹腔浸出液中炎性细胞数量、炎症因子分泌等明显升高。机制研究发现USP22通过溶酶体途径促进NLRP3降解，并且USP22-ATG5-NLRP3三者存在相互作用。据此我们提出：USP22调控ATG5介导的溶酶体途径促进NLRP3降解，负向调控NLRP3炎症小体活化。本项目拟利用USP22髓系条敲小鼠，通过体内外实验进一步研究USP22调控NLRP3炎症小体活化的功能和分子机制，为炎症相关疾病如肥胖、败血症等新药开发提供新的思路。

NLRP3 inflammasome is essential for eliciting immune response to pathogens. However, excessive activation contributes to the tissue pathogenesis. Therefore, it must be under tight control. Mechanisms of the NLRP3 inflammasome activation and regulation have been the forefront scientific research realm. In this study, we used a plasmid library to screen the deubiquitinating enzymes which regulated the stability of NLRP3. And we found that ubiquitin specific peptidase 22 (USP22)，a member of ubiquitin specific peptidase family, could significantly promote NLRP3 post-translation degradation. In mouse peritoneal macrophages, knocking-down USP22 increased NLRP3 expression and promoted LPS-induced IL-1β secretion, which showed that USP22 could negatively regulate the activation of NLRP3 inflammasome. We also in vivo knockdown the expression of USP22 in mouse peritonitis model, and found that silencing of USP22, the number of inflammatory cells and the secretion of IL-1β in peritoneal lavage fluid. In mechanism, we found that USP22 promote NLRP3 degradation through lysosomal pathway; In addition, the autophagy related 5 (ATG5) could also interact with USP22-NLRP3 complex. All the results indicated that USP22 negatively regulated inflammasome activation might via ATG5 mediated NLRP3 lysosomal degradation. In the present study, we have constructed the USP22 CKO mice to further go into their functions and mechanisms both in vitro and in vivo. Our investigation will be helpful in developing new therapeutic target to inflammation disease such as obesity and sepsis.