鼠疫耶尔森氏菌效应分子YopT通过RIG-I阻断先天免疫应答信号通路参与其致病的分子机制研究

Bubonic plague is one of acute onset, rapid spread, high mortality and infectious natural focal diseases. Previous studies have shown that type III secretion system effector protein YopT represents a crucial virulence factor of Yersinia pestis. However the host targets and pathogenic mechanisms of YopT remain unclear. Here we show that RIG-I was a novel target of the YopT protein. Remarkably, YopT interacted with RIG-I and decreased polyubiquitylation of RIG-I. We proposed that the deubiquitylation of RIG-I during Yersinia pestis infection presents a new bacterial strategy to modulate host antibacterial responses. Therefore, we would like to delineate the molecular mechanism of YopT on RIG-I-mediated IFN-β/NF-κB activation and uncover the role of YopT on the virulence of Yersinia pestis. Nonetheless, our work suggests that the interaction of the YopT protein and RIG-I is a critical determinant of pestis replication and may be used as a potential target for anti-bacterialtherapy.

鼠疫是一种发病急、传播快、病死率高、传染性强的自然疫源性烈性传染病。研究表明三型分泌系统效应分子YopT是鼠疫耶尔森氏菌非常重要的毒力因子，但是其宿主的靶点以及致病的分子机制尚不十分清楚。我们前期研究发现鼠疫菌不同的效应蛋白中，只有YopT可以抑制RIG-I介导的IRF3和IFN-β的转录激活。它能与先天性免疫应答的重要分子RIG-I发生相互作用，减少RIG-I的泛素化修饰。因此，YopT很有可能通过阻断RIG-I介导的IFN-β/NF-κB信号通路激活参与鼠疫菌的致病。本项目拟用免疫共沉淀、RNA干扰、泛素化实验、细菌易感性实验等手段，进一步研究YopT通过RIG-I参与阻断宿主先天性免疫应答通路的分子机制，揭示YopT作为鼠疫菌重要致病因子参与致病的可能机制，为新型抗细菌治疗药物的开发打下基础。

革兰氏阴性细菌病原体耶尔森氏菌将六种效应蛋白送入宿主细胞，以阻断宿主先天免疫反应。效应子之一的YopT是一种有效的半胱氨酸蛋白酶，可引起肌动蛋白细胞骨架的破坏，从而抑制病原体的吞噬作用。然而，其分子机制及其发病机制的关系尚需进一步研究。在本研究中，我们发现RIG-I是YopT蛋白新的靶点，值得注意的是，YopT与RIG-I相互作用并抑制RLH介导的NF-κB和IRF3的激活。进一步研究发现，YopT能够增加RIG-I的K48的泛素化。这些结果说明，YopT通过靶向RIG-I负调节其介导的细胞抗菌反应。