Du Juan, Reeves Analise Z, Klein Jessica A, Twedt Donna J, Knodler Leigh A, Lesser Cammie F
Department of Medicine, Division of Infectious Diseases, Massachusetts General Hospital, Cambridge, MA 02139; Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115;
Paul G. Allen School for Global Animal Health, College of Veterinary Medicine, Washington State University, Pullman, WA 99164.
Proc Natl Acad Sci U S A. 2016 Apr 26;113(17):4794-9. doi: 10.1073/pnas.1520699113. Epub 2016 Apr 12.
Upon entry into host cells, intracellular bacterial pathogens establish a variety of replicative niches. Although some remodel phagosomes, others rapidly escape into the cytosol of infected cells. Little is currently known regarding how professional intracytoplasmic pathogens, including Shigella, mediate phagosomal escape. Shigella, like many other Gram-negative bacterial pathogens, uses a type III secretion system to deliver multiple proteins, referred to as effectors, into host cells. Here, using an innovative reductionist-based approach, we demonstrate that the introduction of a functional Shigella type III secretion system, but none of its effectors, into a laboratory strain of Escherichia coli is sufficient to promote the efficient vacuole lysis and escape of the modified bacteria into the cytosol of epithelial cells. This establishes for the first time, to our knowledge, a direct physiologic role for the Shigella type III secretion apparatus (T3SA) in mediating phagosomal escape. Furthermore, although protein components of the T3SA share a moderate degree of structural and functional conservation across bacterial species, we show that vacuole lysis is not a common feature of T3SA, as an effectorless strain of Yersinia remains confined to phagosomes. Additionally, by exploiting the functional interchangeability of the translocator components of the T3SA of Shigella, Salmonella, and Chromobacterium, we demonstrate that a single protein component of the T3SA translocon-Shigella IpaC, Salmonella SipC, or Chromobacterium CipC-determines the fate of intracellular pathogens within both epithelial cells and macrophages. Thus, these findings have identified a likely paradigm by which the replicative niche of many intracellular bacterial pathogens is established.
进入宿主细胞后，细胞内细菌病原体建立了多种复制龛。尽管有些病原体重塑吞噬体，但其他病原体则迅速逃逸到受感染细胞的细胞质中。目前对于包括志贺氏菌在内的专业胞质内病原体如何介导吞噬体逃逸知之甚少。与许多其他革兰氏阴性细菌病原体一样，志贺氏菌利用III型分泌系统将多种蛋白质（称为效应蛋白）递送到宿主细胞中。在这里，我们使用一种基于创新还原论的方法证明，将功能性志贺氏菌III型分泌系统（但不包括其效应蛋白）引入大肠杆菌实验室菌株中，足以促进修饰后的细菌有效裂解液泡并逃逸到上皮细胞的细胞质中。据我们所知，这首次确立了志贺氏菌III型分泌装置（T3SA）在介导吞噬体逃逸中的直接生理作用。此外，尽管T3SA的蛋白质成分在不同细菌物种之间具有中等程度的结构和功能保守性，但我们表明液泡裂解不是T3SA的共同特征，因为无效应蛋白的耶尔森氏菌菌株仍局限于吞噬体中。此外，通过利用志贺氏菌、沙门氏菌和嗜色杆菌T3SA转运体成分的功能互换性，我们证明T3SA转运体的单个蛋白质成分——志贺氏菌IpaC、沙门氏菌SipC或嗜色杆菌CipC——决定了上皮细胞和巨噬细胞内细胞内病原体的命运。因此，这些发现确定了一种可能的模式，许多细胞内细菌病原体通过这种模式建立其复制龛。
