Small GTPase signalling networks utilised by Salmonella Thyphimurium virulence factors

致病菌经常通过靶向肌动蛋白细胞骨架转换来操纵真核宿主细胞。这是通过操纵或模仿控制肌动蛋白动力学的调节因子来实现的，例如小GTPases的Rho家族成员。rho - gtpase充当分子开关，在循环时打开和关闭整个信号通路，就像驱动肌动蛋白重塑一样。沙门氏菌已经进化出多种策略来影响这些信号，例如通过其细菌gef模拟SopE/E2或间接通过磷脂修饰酶（如SopB）。沙门氏菌还含有另外两种假定的细菌gef， SifA和SifB，它们属于一个新的、不断增长的群体，称为wxxxe家族。有趣的是，细菌毒力因子也出现与宿主细胞信号转接器结合，强调这些因子不是简单地引发全局信号通路，而是组装更大的复合物，将信号引导到特定的目的地。这是本提案的目的，揭示沙门氏菌的毒力因子如何影响小GTPase激活完成特异性参与信号复合物。为了实现这一点，我们已经开始使用酵母双杂交筛选来识别相互作用物。利用最先进的生物化学、细胞生物学和成像技术，验证和测试潜在候选药物对毒力因子引发的信号传导的影响。最后，这些复合物的晶体结构将揭示这些复杂的宿主-病原体相互作用的分子细节。

Pathogenic bacteria frequently manipulate eukaryotic host cells by targeting actin cytoskeletal turnover. This is achieved e.g. by manipulating or mimicking the regulators controlling actin dynamics such as members of the Rho family of small GTPases. Rho-GTPases serve as molecular switches that – while cycling - turn entire signalling pathways, on and off, like those driving actin remodelling. Salmonella has evolved multiple strategies to affect these signals e.g. through its bacterial GEF-mimicks SopE/E2 or indirectly by phospholipid-modifying enzymes such as SopB. Salmonella harbours two more putative bacterial GEFs, SifA and SifB, which belong to a novel and growing group termed WxxxE-family. Interestingly, bacterial virulence factors have also emerged to bind to host cell signalling adaptors, underscoring that these factors do not simply elicit global signal pathways, but assemble larger complexes guiding the signal to a specific destination. It is the aim of this proposal to uncover how virulence factors of Salmonella that effect small GTPase activation accomplish specificity by engaging in signalling complexes. To achieve this, we have begun to identify interactors using yeast two hybrid screening. Potential candidates are validated and tested for their influence on virulence factor-elicited signalling using state of the art biochemistry, cell biology and imaging. Finally, crystal structures of these complexes will disclose the molecular details of these intricate host-pathogen interactions.