沙门氏菌效应蛋白SseJ和PipB2与宿主互作的分子机制

Salmonellae are important Gram-negative bacterial pathogens with a wide range of hosts which can result in several diseases such as such as typhoid fever and enteritis. Within the host cell，the survival and reproduction of Salmonella relies on the special structure called Salmonella-containing vacuoles (SCV). Successful bacterial replication within the SCV is associated with formation of Salmonella-induced filaments (Sif), which bud from the SCV at the later period of maturation. SseJ and PipB2，which are essential effector proteins for the the survival and reproduction of Salmonella in host cell, have shown to modulate maturation of SCV and occurrence of Sifs. SseJ, which hijack the small GTPase RhoA , inhibits the Sif formation with its RhoA-dependent lipase activity .However，PipB2 plays an opposite role in modulating the Sif formation via interacting with kinesin light chain 1 (KLC1). In addition to solving the crytal structures of SseJ and PipB2-KLC1 complex , we will perform point mutation and biochemical assays to unravel how SseJ is activated by RhoA and to clarify the molecular mechanism of the interaction between PipB2 and KLC1. This research project will have fundamental significance for elucidating regulatory mechanism of Sif formation, and will provide the potential targets for drug design.

沙门氏菌是宿主广泛的革兰氏阴性致病菌，可引发伤寒和肠炎等疾病。它能够在宿主细胞内一种称为SCV的膜性结构中生存和增殖，在成熟晚期SCV表面以出芽的方式生成Sif，这决定了沙门氏菌能否在细胞内完成增殖。SseJ和PipB2是沙门氏菌在细胞内生存和增殖的必需效应蛋白，在SCV成熟及Sif形成中发挥重要的调控作用：SseJ特异性劫持宿主小G蛋白RhoA，从而激活它的脂酶活性并抑制Sif的形成；PipB2与驱动蛋白轻链KLC1相互作用，对Sif形成起正调控作用。项目通过解析SseJ、SseJ-RhoA和PipB2-KLC1的晶体结构，利用定点突变和生化分析等手段，揭示RhoA调控SseJ活性的分子机制，阐明PipB2与KLC1相互作用的分子机理。为研究Sif形成的调控机制提供理论基础，同时也为设计新型抗菌药物提供潜在的靶点。

沙门氏菌是宿主广泛的革兰氏阴性致病菌，可引发伤寒和肠炎等疾病。它能够在宿主细胞内一种称为SCV的膜性结构中生存和增殖，在成熟晚期SCV表面以出芽的方式生成管状结构Sif，这决定了沙门氏菌能否在细胞内完成增殖。在宿主细胞内III型系统分泌的效应因子SseJ和PipB2分别劫持小G蛋白RhoA和驱动蛋白轻链KLC1，它们共同促进了SCV成熟及Sif形成，因此SseJ和RhoA是沙门氏菌致病的必需效应因子。本项目解析了SseJ模拟小G蛋白效应蛋白而特异性结合RhoA的分子机制以及RhoA作为辅脂酶解除SseJ自抑制的机理，上述机理表明沙门氏菌可以多层次调控和利用小G蛋白这一重要分子开关。此外我们的研究表明PipB2的C端是其与KLC1相互作用的功能区域。本项目的研究成果为深入研究沙门氏菌感染致病机理以及病原体与宿主协同进化提供了理论依据。