Molecular Determinants of Chlamydia Extrusion from Host Cells

描述(申请人提供)：所有细胞内病原体必须离开它们的宿主细胞才能传播和传播给新的宿主，然而这一中心主题几乎没有受到关注。控制细胞内细菌衣原体从宿主细胞中退出的分子机制也鲜为人知，这表明我们在微生物发病机制中对这一基本问题的理解存在较大差距。使用一种新的基于成像的体外模型，我们已经确定了衣原体在细胞内发育周期结束时退出细胞的两条途径。其中一种途径，即挤出，由于其独创性和对传播和免疫逃避的独特影响而特别创新。我们的长期目标是了解细胞内病原体退出宿主细胞的潜在分子基础和总体策略。我们的近期目标是阐明衣原体挤出的分子机制，并首次确定其在体内发病机制中的作用。在这里，我们提供了衣原体在感染过程中参与的宿主细胞通路的数据，这些通路是从细胞中排出所需的。我们认为衣原体通过宿主-衣原体蛋白在液泡膜表面的局部相互作用来特异性地靶向这些途径。这项工作的结果将深刻地加强我们对微生物出口的理解--这是该领域一个长期未解决的问题。排泄是宿主-病原体相互作用的一个新主题，因此，我们在机制水平和受感染宿主中对这一过程的了解取得的重大进展，应该直接转化到其他使用类似退出策略的病原体系统，如疟疾寄生虫。衣原体挤出的三个关键主题将通过以下具体目标来解决：(I)确定肌动蛋白募集到包涵膜的分子机制；(Ii)确定负责挤出收缩步骤的宿主细胞动力学信号网络；以及(Iii)确定挤出在衣原体细胞间传播和体内致病中的功能作用。挤出物是微生物发病机制研究的新范式。这种新的退出机制可能在病原体的传播、传播和免疫逃避中发挥关键作用。我们期望这些研究能够明确衣原体的主要宿主因素，并阐明排泄在体内所起的作用。这项研究将对我们理解一个尚未开发的微生物学领域产生重大影响。最后，随着这项工作揭示出新的分子靶点，我们还将产生一个新的治疗平台的工具和基础-利用微生物出口作为控制传染病的手段。

DESCRIPTION (provided by applicant): All intracellular pathogens must exit their host cells in order to disseminate and transmit to new hosts, yet this central theme has received little attention. The molecular mechanisms that control the exit of the intracellular bacterium Chlamydia from host cells are also poorly understood, and exemplify the greater gap in our understanding of this fundamental question in microbial pathogenesis. Using a novel imaging-based in vitro model, we have identified the two pathways by which Chlamydia exit cells at the end of their intracellular developmental cycle. One pathway, extrusion, is particularly innovative because of its originality and unique impact on dissemination and immune evasion. Our long-range goal is to understand the underlying molecular basis of and overall strategies used by intracellular pathogens to exit host cells. Our immediate objectives are to elucidate the molecular mechanisms of chlamydial extrusion and, for the first time, determine its role in pathogenesis in vivo. Here, we present data for the host cellular pathways engaged by Chlamydia during infection and that are required for extrusion from cells. We propose that Chlamydia specifically target these pathways via localized host-Chlamydia protein interactions on the vacuole membrane surface. The results of this work will profoundly enhance our understanding of microbial exit - a long unaddressed question in the field. Extrusion represents a new theme in host-pathogen interactions, and thus significant advances in our knowledge of this process at the mechanistic level and in the infected host should directly translate to other pathogen systems in which similar exit strategies are used, such as malarial parasites. Three key themes in chlamydial extrusion will be addressed by the following Specific Aims: (i) Identify the molecular mechanism for actin recruitment to the inclusion membrane; (ii) Define the host cytokinetic signaling networks responsible for the contraction step of extrusion; and (iii) Determine the functional role of extrusion in Chlamydia cell-to-cell spread and in vivo pathogenesis. Extrusion is a new paradigm in microbial pathogenesis. This novel exit mechanism likely plays a critical role in pathogen dissemination, transmission and immune evasion. We expect these studies to define the essential host factors involved for Chlamydia, and to illuminate the role extrusion plays in vivo. This research will have a significant impact on our understanding of an untapped area of microbiology. Finally, as new molecular targets are revealed by this work, we will also generate the tools and basis for a new therapeutic platform - leveraging microbial exit as a means of controlling infectious diseases.