泛素连接酶TRIM27在结核分枝杆菌感染过程中的作用机制研究

TRIM27 is a potential restriction factor for pathogenic bacteria and usually acts as a ubiquitin ligase or a transcription factor to stimulate immune-regulatory signaling pathway such as JNK/p38 MAPK pathway as well as cell apoptosis. But the role of TRIM27 during Mycobacterium.tuberculosis (Mtb) infetion remains unknown. Mtb often secretes a variety of effector proteins into host cells during the infection process. These proteins interfere with normal host immune response to promote the intracellular survival of mycobacteria. Our findings revealed that Mtb effector factor PtpA inhibits innate immunity by coopting host ubiquitin. Yeast Two-hybrid System and Co-immunoprecipitation data further showed that PtpA interacts with host protein TRIM27. Survival of mycobacteria in macrophages is inhibited by TRIM27, while the interaction of PtpA and TRIM27 significantly inhibits the activation of JNK/p38 pathway. Based on the existing experimental results, we will investigate the regulatory functions of TRIM27 on inflammatory signaling pathways, gene transcription and apoptosis during M. tuberculosis infection. Results from this study would provide knowledge and novel targets for the development and optimization of more effective anti-TB drugs.

已有研究表明，TRIM27常作为泛素连接酶或转录因子激活JNK/p38等免疫信号通路及细胞凋亡过程，因而可能是病原体感染潜在的宿主限制因子，但TRIM27在结核分枝杆菌感染过程中调控作用及分子机制尚不清楚。结核分枝杆菌感染宿主过程中会分泌各种效应蛋白干扰宿主正常的免疫反应促进分枝杆菌胞内存活。我们最新研究发现，结核分枝杆菌效应蛋白PtpA可利用泛素干扰宿主的固有免疫，进一步通过酵母双杂交和免疫共沉淀实验发现结核分枝杆菌效应蛋白PtpA与TRIM27蛋白相互作用。同时发现TRIM27蛋白可抑制分枝杆菌的胞内存活，而PtpA干扰TRIM27对JNK/p38信号通路的激活作用。本项目拟深入研究TRIM27蛋白在结核感染过程中对宿主炎症信号通路、基因转录及细胞凋亡的调控作用及分子机制。相关研究结果将为抗结核新药研发提供新的思路和靶标。

巨噬细胞介导的天然免疫反应在宿主抗病原菌感染过程中发挥重要作用。已有研究揭示某些宿主蛋白在抗病毒感染过程中发挥宿主限制因子作用，可以有效抑制病毒在宿主细胞内复制。然而，病原细菌感染宿主过程中发挥重要抗菌作用的潜在宿主限制因子蛋白尚不清楚。本项目中我们鉴定到一个重要的具有抗分枝杆菌感染作用的潜在宿主限制因子TRIM27。以往研究报道TRIM27蛋白包含一个保守的RING结构域，可以发挥泛素连接酶的功能。我们研究发现TRIM27在分枝杆菌感染宿主过程中参与调控宿主天然免疫信号通路、细胞凋亡等多种细胞进程。TRIM27可以促进JNK/p38 MAPK信号通路的活化从而促进细胞因子的转录，进而抑制病原菌的胞内存活。同时TRIM27抑制NF-κB信号通路活化促进细胞凋亡，进而促进病原菌的清除。进一步我们建立了小鼠感染分枝杆菌的动物模型，其结果与细胞感染实验结果一致，即TRIM27抑制分枝杆菌在小鼠体内的存活。有意思的是， Mtb PtpA通过与TRIM27的RING结构域互作拮抗TRIM27的抗菌功能。以上研究结果提示，TRIM27是宿主抗分枝杆菌感染的潜在的重要宿主限制因子，同时提供了一种基于PtpA-TRIM27互作界面的抗结核新靶点和新策略。