Molecular Determinants of Chlamydia Extrusion from Host Cells

描述（由申请人提供）：所有细胞内病原体必须离开其宿主细胞才能传播和传播到新宿主，然而这一中心主题很少受到关注。控制细胞内细菌衣原体离开宿主细胞的分子机制也知之甚少，这表明我们对微生物发病机制中这一基本问题的理解存在更大的差距。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。一种途径，挤压，由于其独创性和对传播和免疫逃避的独特影响，特别具有创新性。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。我们的直接目标是阐明衣原体挤压的分子机制，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期间参与的宿主细胞途径的数据，这些途径是细胞挤出所必需的。我们提出衣原体通过液泡膜表面的宿主-衣原体蛋白相互作用特异性靶向这些途径。这项工作的结果将深刻地增强我们对微生物退出的理解-这是该领域一个长期未解决的问题。挤出是宿主-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上对这一过程的认识取得了重大进展，应该直接转化为使用类似退出策略的其他病原体系统，如疟疾寄生虫。衣原体挤压的三个关键主题将通过以下具体目标来解决：(i)确定肌动蛋白向包涵膜募集的分子机制；（ii）明确负责挤压收缩步骤的宿主细胞动力学信号网络；（iii）确定挤压在衣原体细胞间传播和体内发病机制中的功能作用。挤压是微生物发病的新范式。这种新的退出机制可能在病原体的传播、传播和免疫逃避中起着关键作用。我们希望这些研究能够明确衣原体的基本宿主因子，并阐明挤压在体内所起的作用。这项研究将对我们对尚未开发的微生物学领域的理解产生重大影响。最后，随着这项工作揭示了新的分子靶点，我们也将为新的治疗平台——利用微生物退出作为控制传染病的手段——提供工具和基础。

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. PUBLIC HEALTH RELEVANCE: The relevance is to gain a molecular understanding of chlamydial infections, specifically in regards to how these bacteria spread from cell-to-cell. This is a novel research question that will positively impact our knowledge of other important infectious diseases, such as malaria. An appreciation of how Chlamydiae promote their exit from host cells will enable a new spectrum of antimicrobial therapeutics that target the spread of infectious agents.