Small GTPase signalling networks utilised by Salmonella Thyphimurium virulence factors

病原菌经常通过靶向肌动蛋白细胞骨架的周转来操纵真核宿主细胞。例如，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Rho小GTP酶家族的成员。Rho-GTP酶充当分子开关，在骑行时开启和关闭整个信号通路，就像那些驱动肌动蛋白重塑的通路一样。沙门氏菌已经进化出多种策略来影响这些信号，例如通过其细菌环境基金模拟物Sope/E2或间接通过磷脂修饰酶如SopB。沙门氏菌还含有另外两个假定的细菌GEF，SifA和SifB，它们属于一个新的且不断增长的组，称为WxxxE-家族。有趣的是，细菌毒力因子也出现了与宿主细胞信号适配器结合的情况，这突显出这些因子不仅仅是引发全球信号通路，还会组装更大的复合体，将信号引导到特定的目的地。这项建议的目的是揭示影响小GTP酶激活的沙门氏菌毒力因子是如何通过参与信号复合体来实现特异性的。为了实现这一点，我们已经开始使用酵母双杂交筛选来鉴定交互作用子。使用最先进的生物化学、细胞生物学和成像技术来验证和测试潜在的候选基因对毒力因子引发的信号的影响。最后，这些复合体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.