Modulation of Host Cell Responses by Francisella tularensis

项目摘要 土拉热弗朗西丝菌是人畜共患病土拉菌病的病原体。F.土拉热是一种剧毒的 当气溶胶化时容易传播给人类并因此具有使用潜力的细胞内病原体 生物恐怖分子阐明了F.土拉热病不是很好 明白F.土拉热必须逃避细胞先天免疫检测;然而， 对F.缺乏土拉热菌在感染期间破坏宿主反应的能力。我们 已确定TolC对F.土拉热。TolC是外膜通道蛋白 参与多药外排和I型多药耐药菌分泌多种细菌效应蛋白 蛋白质分泌途径我们有证据表明，通过TolC分泌的因子可以抑制先天免疫 宿主的反应，包括程序性细胞死亡途径，为细菌提供了延长的时间， 在受保护的细胞内生态位内复制，并延长在宿主组织内的存活，从而使 宿主-病原体平衡有利于病原体。这些与TolC功能相关的宿主抑制活性是 可能是F.土拉热菌的极端毒性至关重要。这项建议 将研究TolC在弗朗西斯菌发病机制中的作用机制，总体目标是揭示分子水平， 细胞内病原体与宿主细胞相互作用、逃避宿主防御和操纵宿主细胞的细节。 应答该提案的第一个目的将定义TolC在调节宿主反应中的作用， 体内感染以及这些活动与F.土拉菌毒力建议的第二个目的 将鉴定宿主细胞感染期间通过TolC和其他途径分泌的弗朗西斯菌效应子， 确定宿主细胞死亡途径的TolC依赖性颠覆所需的基因。第三个目标 建议将确定F.土拉菌抑制巨噬细胞先天性免疫 在感染期间以TolC依赖性方式产生应答。该提案产生的数据将导致详细的， 对F.土拉热。通过对细菌分泌的效应物或毒素的鉴定， F.土拉热将是该领域的一个重大进展。这一建议不仅会使 F的知识。土拉菌毒力机制，但也将提供新的见解所使用的战略， 细胞内病原体在宿主体内存活并引起疾病。

PROJECT SUMMARY Francisella tularensis is the causative agent of the zoonotic disease tularemia. F. tularensis is a highly virulent intracellular pathogen that is easily transmitted to humans when aerosolized and thus has the potential for use as a bioterrorism agent. The molecular basis for the high infectivity and virulence of F. tularensis is not well understood. As an intracellular pathogen, F. tularensis must evade cellular innate immune detection; however, a mechanistic understanding for how F. tularensis subverts the host response during infection is lacking. We have identified TolC as critical for the virulence of F. tularensis. TolC is an outer membrane channel protein involved in both multidrug efflux and the secretion of a wide range of bacterial effector proteins by the type I protein secretion pathway. We have evidence that factors secreted via TolC function to dampen innate immune responses of the host, including programmed cell death pathways, providing the bacteria extended time to replicate within the protected intracellular niche and prolonging survival within host tissues, thereby tipping the host-pathogen balance in favor of the pathogen. These host suppressive activities related to TolC function are likely key to the successful intracellular lifestyle of F. tularensis and critical to its extreme virulence. This proposal will investigate the mechanism of TolC in Francisella pathogenesis, with the overall goal of revealing molecular details by which intracellular pathogens interact with host cells, evade host defenses, and manipulate host responses. The first aim of the proposal will define the role of TolC in modulation of host responses during in vivo infection and the connection of these activities to F. tularensis virulence. The second aim of the proposal will identify Francisella effectors secreted via TolC, and by other routes, during host cell infection and will determine genes required for TolC-dependent subversion of host cell death pathways. The third aim of the proposal will determine the mechanism by which F. tularensis suppresses macrophage innate immune responses during infection in a TolC-dependent manner. Data generated by this proposal will lead to a detailed, mechanistic understanding of TolC function in F. tularensis. The identification of effectors or toxins secreted by F. tularensis would represent a significant advance for the field. This proposal will not only lead to better knowledge of F. tularensis virulence mechanisms, but will also provide new insights into strategies used by intracellular pathogens to survive within the host and cause disease.