Mechanisms of SFG Rickettsia-Host Interactions

项目总结/摘要 在美国，一种新出现的、但特征不明显的蜱传疾病是由斑疹热引起的。 组（SFG）立克次体。这些专性细胞内细菌病原体引起轻度至危及生命的血管 人类疾病，并有一套有限的诊断和治疗措施。为促进普遍 疾病时，SFG立克次体物种已经进化出动态策略来侵入宿主细胞，逃逸到胞质溶胶中， 并在细胞间传播我们假设SFG立克次体通过传递 分泌的细菌蛋白质的武库（即，效应子），其重编程宿主细胞过程。可惜 这些分泌的效应物的身份和宿主靶点在很大程度上仍然未知。此外，直接分析 分泌系统和假定的效应器的功能受到阻碍， 在实验室里对这些病原体进行基因操作。为了克服这一障碍，我们最近进行了调整， 遗传学和质粒为基础的互补模式SFG成员立克次体parkeri，允许 SFG立克次体致病机制的功能遗传学研究。使用这些工具，我们发现， 分泌的效应因子Sca 4通过操纵宿主细胞-细胞粘附促进细胞-细胞扩散的晚期阶段。 此外，功能未知的分泌效应子（RARP-1）和 立克次体4型异常分泌系统（VirB 6 e）损害了R. parkeri感染。这 一项提案将利用这些关键进展来研究分泌系统和分泌的效应物如何促进 R. Parkeri感染性生命周期在这里，我们联合收割机结合我们的功能遗传策略， 在宿主细胞生物学的专业知识，与现代生物化学技术，揭示关键，机械的见解， SFG立克次体发病机制。在目标1中，我们将研究T4 SS组分的功能和分泌组 VirB6e。在目标2中，我们将确定分泌的效应子RARP-1如何促进R。parkeri感染。在目标3中， 我们将阐明Sca 4在R. parkeri细胞对细胞 传播.总的来说，拟议的研究将大大提高我们对 立克次体生物学和立克次体-宿主相互作用，并揭示预防或治疗蜱传的治疗靶点 疾病

PROJECT SUMMARY/ABSTRACT A subset of emerging, but poorly characterized tickborne diseases in the U.S. are caused by Spotted Fever Group (SFG) Rickettsia. These obligate intracellular bacterial pathogens cause mild-to-life-threatening vascular diseases in humans and have a limited set of diagnostics and therapeutic interventions. To promote widespread disease, SFG Rickettsia species have evolved dynamic strategies to invade host cells, escape into the cytosol, and spread from cell to cell. We hypothesize that SFG Rickettsia coordinate their complex life cycle by delivering an arsenal of secreted bacterial proteins (i.e., effectors) that reprogram host cell processes. Unfortunately, the identity and host targets of these secreted effectors have remained largely unknown. Furthermore, direct analysis of the secretion systems and putative effectors have been hampered due to challenges in growing and genetically manipulating these pathogens in the lab. To overcome this barrier, we recently adapted forward genetics and plasmid-based complementation to the model SFG member Rickettsia parkeri, allowing for powerful functional-genetic studies of SFG Rickettsia pathogenesis. Using these tools, we discovered that the secreted effector Sca4 promotes a late stage of cell-to-cell spread by manipulating host cell-cell adhesion. Additionally, transposon mutagenesis of a secreted effector of unknown function (RARP-1) and a component of the anomalous Rickettsia Type 4 secretion system (VirB6e) impairs distinct stages of R. parkeri infection. This proposal will leverage these key advances to examine how a secretion system and secreted effectors promote different steps of the R. parkeri infectious life cycle. Here, we combine our functional-genetic strategies and expertise in host cell biology, with modern biochemical techniques to reveal critical, mechanistic insights into SFG Rickettsia pathogenesis. In Aim 1, we will examine the function and secretome of the T4SS component VirB6e. In Aim 2, we will determine how the secreted effector RARP-1 promotes R. parkeri infection. In Aim 3, we will elucidate how Sca4 specifically targets host cell-cell adhesion complexes during R. parkeri cell-to-cell spread. Collectively, the proposed research will dramatically improve our fundamental understanding of Rickettsia biology and Rickettsia-host interactions and reveal therapeutic targets to prevent or treat tickborne diseases.