Host factors in Shigella flexneri infection

项目总结。宿主相互作用在细菌病原体感染过程中起着至关重要的作用。对许多人来说 细菌病原体，3型分泌系统(T3SS)介导了许多与宿主的相互作用。寄主 相互作用反过来调节T3SS的激活。一旦激活，T3SS效应器就会被传递到 宿主细胞通过哺乳动物质膜上的小孔(转运子)，它由两个T3SS转位酶组成。 T3SS效应器以促进感染的方式调节宿主细胞。我们发现宿主因素的参与度 导致激活效应器分泌所需的转运子的特定构象变化。 我们发现细菌转位酶在宿主胞液区域的残基至少是暂时存在的。 在孔道内。我们发现志贺氏菌OSPB操纵哺乳动物的中枢调节因子mTORC1 在志贺氏菌感染过程中，OSPB改变了细胞的增殖能力。 我们建议研究细胞与天然释放的血浆相互作用的机制。 福氏志贺菌转运子有助于在细胞入侵之前激活转运子， 为了揭示质膜嵌合转运蛋白在入侵前的作用机制， 包括开孔、激活效应器分泌、效应器移位和 膜褶皱。此外，我们建议计划利用我们最近的发现来确定 OSPB操纵mTORC1的机制，特异性识别哺乳动物底物(S)，表征 哺乳动物底物裂解的机制，以及OSPB的作用机制 哺乳动物底物(S)改变mTORC 1活性。 我们的总体目标是确定哺乳动物细胞蛋白质和相互作用如何调节细菌感染 和发病机制，特别是T3SS的激活以及T3SS效应器如何与T3SS相互作用和改变 哺乳动物细胞。鉴于T3SS和OSPB在医学上重要的细菌病原体中的保守性， 我们的见解很可能会对更广泛的宿主-病原体相互作用产生广泛的影响， 因此，对发病机制社区有相当大的兴趣。

Project summary. Host interactions play critical roles during infection with bacterial pathogens. For many bacterial pathogens, type 3 secretion systems (T3SSs) mediate numerous interactions with the host. Host interactions, in turn, regulate the activation of the T3SSs. Once activated, T3SS effectors are delivered into host cells via pores in mammalian plasma membranes (translocons) that consist of two T3SS translocases. T3SS effectors modulate host cells in ways that promote infection. We found that engagement of host factors leads to specific conformational changes in the translocon that are required for activation of effector secretion. We found that residues in the host cytosolic domains of the bacterial translocases reside at least transiently within the pore channel. We found that Shigella OspB manipulates mTORC1, the mammalian central regulator of cell growth and proliferation, leading to OspB alteration of cell proliferation during Shigella infection. We propose to investigate the mechanisms by which cellular interactions with natively delivered plasma membrane-embedded Shigella flexneri translocons contribute to translocon activation prior to cell invasion, with the goal of uncovering mechanisms of pre-invasion roles of plasma-membrane embedded translocons, including the mechanisms of pore opening, activation of effector secretion, effector translocation, and membrane ruffling. Additionally, we propose to plan to leverage our recent findings to determine the mechanisms of OspB manipulation of mTORC1, specifically identifying mammalian substrate(s), characterizing the mechanism of mammalian substrate cleavage, and interrogating the mechanism by which OspB mammalian substrate(s) alter mTORC1 activity. Our overall goal is to determine how mammalian cell proteins and interactions modulate bacterial infection and pathogenesis, specifically the activation of the T3SS, and how T3SS effectors interact with and alter mammalian cells. Given the conservation of T3SSs and OspB among medically important bacterial pathogens, it is highly likely that our insights will have broad implications for host-pathogen interactions more generally, therefore be of considerable interest to the pathogenesis community.