Intracellular IL-17 signaling during Coxiella burnetii infection

项目摘要/摘要 伯氏柯克斯体是Q热的专性胞内细菌，是Q热的病原体。在自然感染期间 柯克斯体以肺泡巨噬细胞为靶标，在肺泡巨噬细胞中，该细菌促进形成类吞噬溶酶体。 液泡称为含有柯克斯氏菌的液泡(CCV)。成功的宿主细胞感染需要IVB型 分泌系统(T4BSS)，它将细菌效应蛋白穿过CCV膜转移到 宿主细胞质，在那里它们操纵各种细胞过程。我们最近证明了柯克斯体 T4BSS下调IL-17靶基因的表达以及IL-17刺激的趋化因子的分泌。 此外，柯克斯体T4BSS对IL-17介导的巨噬细胞杀伤具有保护作用。IL-17是一种专业- 在针对肺部病原体的先天免疫反应中起关键作用的炎性细胞因子。vt.在.的基础上 与IL-17结合，巨噬细胞表面IL-17受体通过激活几条细胞内信号通路 E3-泛素连接酶ACT1。非磷酸化ACT1泛素化TRAF6，触发转录激活 在IL-17靶基因中，当磷酸化的ACT1招募TRAF2/5时，与IL-17靶基因的3‘mRNA结合 并稳定用于翻译的信使核糖核酸。拟议的实验将检验我们的假设，即柯克斯体！T4BSS 效应蛋白下调细胞内IL-17信号通路(S)以逃避宿主天然免疫 响应和促进细菌致病。目标1将确定柯克斯体是否针对ACT1-TRAF6 下调IL-17靶基因转录的途径。目标2将测试柯克斯体是否破坏了mRNA的稳定 通过ACT1-TRAF2/5表达IL-17靶基因。这些研究的完成将不仅揭示特定的宿主 用来对抗伯氏梭菌的先天免疫反应，也是病原体逃脱的一种新策略 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.