Intracellular IL-17 signaling during Coxiella burnetii infection

项目总结/摘要 贝氏柯克斯体是一种专性胞内细菌，是Q热的病原体。在自然感染过程中 柯克斯体以肺泡巨噬细胞为目标，在那里细菌促进吞噬溶酶体样蛋白的形成。 空泡称为Coxiella Containing cycloole（CCV）。成功的宿主细胞感染需要IVB型 分泌系统（T4 BSS），其将细菌效应蛋白跨CCV膜易位到CCV中。 宿主细胞质，在那里它们操纵各种细胞过程。我们最近证明了 T4 BSS下调IL-17靶基因的表达以及IL-17刺激的趋化因子分泌。 此外，Coxiella T4 BSS赋予针对IL-17介导的巨噬细胞杀伤的保护。IL-17是一种亲- 在针对肺部病原体的先天免疫应答中具有关键作用的炎性细胞因子。后 IL-17结合，巨噬细胞表面IL-17受体激活几种细胞内信号传导途径， E3-泛素连接酶ACT 1。未磷酸化的ACT 1泛素化TRAF 6，触发转录激活 而磷酸化的ACT 1募集TRAF 2/5，结合IL-17靶基因的3' mRNA 并稳定mRNA进行翻译。拟议的实验将测试我们的假设，Coxiella！T4BSS 效应蛋白下调细胞内IL-17信号传导途径，以逃避宿主先天免疫 反应并促进细菌致病。目的1将确定Coxiella是否靶向ACT 1-TRAF 6 下调IL-17靶基因转录的途径。目的2将测试Coxiella是否使mRNA不稳定 通过ACT 1-TRAF 2/5的IL-17靶基因。这些研究的完成不仅会揭示特定的宿主 先天性免疫反应用于C. burnetii，而且也是病原体逃避的一种新策略 感染初期的免疫反应

PROJECT SUMMARY/ABSTRACT Coxiella burnetii is an obligate intracellular bacterium and the etiological agent of Q fever. During natural infection Coxiella targets alveolar macrophages, where the bacterium promotes formation of a phagolysosome-like vacuole called the Coxiella Containing Vacuole (CCV). Successful host cell infection requires the Type IVB Secretion System (T4BSS), which translocates bacterial effector proteins across the CCV membrane into the host cytoplasm, where they manipulate a variety of cell processes. We recently demonstrated that the Coxiella T4BSS downregulates expression of IL-17 target genes as well as IL-17-stimulated chemokine secretion. Further, the Coxiella T4BSS confers protection against IL-17 mediated killing by the macrophage. IL-17 is a pro- inflammatory cytokine that has a key role in the innate immune response against pulmonary pathogens. Upon IL-17 binding, the macrophage surface IL-17 receptor activates several intracellular signaling pathways through the E3-ubiquitin ligase ACT1. Unphosphorylated ACT1 ubiquitinates TRAF6, triggering transcriptional activation of IL-17 target genes, while phosphorylated ACT1 recruits TRAF2/5, binds to the 3’ mRNA of IL-17 target genes and stabilizes the mRNA for translation. The proposed experiments will test our hypothesis that Coxiella!T4BSS effector proteins downregulate intracellular IL-17 signaling pathway(s) in order to evade the host innate immune response and promote bacterial pathogenesis. Aim 1 will determine whether Coxiella targets the ACT1-TRAF6 pathway to downregulate IL-17 target gene transcription. Aim 2 will test whether Coxiella destabilizes the mRNA of IL-17 target genes through ACT1-TRAF2/5. Completion of these studies will not only reveal a specific host innate immune response used against C. burnetii, but also a novel strategy employed by pathogens to escape the immune response during the initial stages of infection.