Mechanisms of intracellular pathogen dissemination

单核细胞增多性李斯特菌和福氏志贺氏菌是人类肠道病原体，它们在 感染细胞，并直接从主要感染细胞传播到邻近细胞。传播过程是一个 致病的基本方面是传播缺陷的细菌突变体本质上是无毒的。这个 单核细胞增多性李斯特菌和福氏志贺氏菌在细胞间传播的能力与它们展示肌动蛋白的能力有关。 基于感染细胞胞浆中的运动性。这些细菌产生毒力因子，导致 在它们的表面募集到一个重要的宿主细胞肌动蛋白核因子，Arp2/3复合体。这就产生了肌动蛋白 在细菌的一端聚合，从而推动杆状物穿过细胞质。种子电子 显微镜研究表明，当细菌到达细胞皮质时，它们形成质膜延伸。 投射到相邻细胞的胞浆中。这些突起在相邻的细胞中被分解成两个 细胞膜空泡，病原体通过产生破坏完整性的毒力因子而逃脱。 真核细胞膜。与我们对支持的分子机制的高级理解相反 基于胞浆肌动蛋白的运动，支持病原体通过膜传播的机制 突出层未解决。为了解决这一知识差距，我们开发了创新的 细胞内病原体传播和识别细胞和细菌因素的成像程序 支持细菌病原体在细胞间传播。在之前的工作中，我们定义了细胞机械和 单核细胞增多性李斯特菌所特需的细菌因子在细胞间传播。最近，我们发现了 尽管在胞浆中利用了类似的基于肌动蛋白的运动机制，但单核细胞增多性乳杆菌 和福氏志贺氏菌进化出不同的细胞间传播策略。与单核细胞增多性乳杆菌不同，福氏志贺氏菌 劫持突起中的磷脂酰肌醇(PI(3)P)信号，以促进其分解成空泡。 在这里，我们建议首次从机制上深入了解支持S。 Flexneri PI(3)依赖P的传播(Aim1和Aim2)；以及PI(3)依赖P的传播在 发病机制(Aim3)。

Listeria monocytogenes and Shigella flexneri are human intestinal pathogens that replicate in the cytosol of infected cells and spread directly from primary infected cells to adjacent cells. The dissemination process is a fundamental aspect of pathogenesis as spreading-defective bacterial mutants are essentially avirulent. The ability of L. monocytogenes and S. flexneri to spread from cell to cell is related to their ability to display actin- based motility in the cytosol of infected cells. These bacteria produce virulence factors that lead to the recruitment at their surface of an essential host cell actin nucleator, the ARP2/3 complex. This results in actin polymerization at one pole of the bacteria, which propels the rods throughout the cytosol. Seminal electron microscopy studies revealed that, when bacteria reach the cell cortex, they form plasma membrane extensions that project into the cytosol of adjacent cells. These protrusions are resolved in adjacent cells into double membrane vacuoles, from which the pathogens escape by producing virulence factors that disrupt the integrity of eukaryotic membranes. In contrast to our advanced understanding of the molecular mechanisms supporting cytosolic actin-based motility, the mechanisms supporting pathogen dissemination through membrane protrusion formation are unresolved. To address this gap in knowledge, we have developed innovative procedures for imaging intracellular pathogen dissemination and identified cellular and bacterial factors supporting bacterial pathogen spread from cell to cell. In previous work, we defined the cellular machinery and the bacterial factors specifically required for L. monocytogenes spread from cell to cell. Recently, we uncovered the notion that, although utilizing similar mechanisms of actin-based motility in the cytosol, L. monocytogenes and S. flexneri have evolved different strategies of cell-to-cell spread. Unlike L. monocytogenes, S. flexneri hijacks phosphoinositide (PI(3)P) signaling in protrusions in order to facilitate their resolution into vacuoles. Here, we propose to gain the first mechanistic insight into the bacterial and cellular mechanisms supporting S. flexneri PI(3)P-dependent dissemination (Aim1 and Aim2); and the role of PI(3)P-dependent dissemination in pathogenesis (Aim3).