Holmström A, Petterson J, Rosqvist R, Håkansson S, Tafazoli F, Fällman M, Magnusson K E, Wolf-Watz H, Forsberg A
Department of Microbiology, National Defence Research Establishment, Umeå, Sweden.
Mol Microbiol. 1997 Apr;24(1):73-91. doi: 10.1046/j.1365-2958.1997.3211681.x.
Introduction of anti-host factors into eukaryotic cells by extracellular bacteria is a strategy evolved by several Gram-negative pathogens. In these pathogens, the transport of virulence proteins across the bacterial membranes is governed by closely related type III secretion systems. For pathogenic Yersinia, the protein transport across the eukaryotic cell membrane occurs by a polarized mechanism requiring two secreted proteins, YopB and YopD. YopB was recently shown to induce the formation of a pore in the eukaryotic cell membrane, and through this pore, translocation of Yop effectors is believed to occur (Håkansson et al., 1996b). We have previously shown that YopK of Yersinia pseudotuberculosis is required for the development of a systemic infection in mice. Here, we have analysed the role of YopK in the virulence process in more detail. A yopK-mutant strain was found to induce a more rapid YopE-mediated cytotoxic response in HeLa cells as well as in MDCK-1 cells compared to the wild-type strain. We found that this was the result of a cell-contact-dependent increase in translocation of YopE into HeLa cells. In contrast, overexpression of YopK resulted in impaired translocation. In addition, we found that YopK also influenced the YopB-dependent lytic effect on sheep erythrocytes as well as on HeLa cells. A yopK-mutant strain showed a higher lytic activity and the induced pore was larger compared to the corresponding wild-type strain, whereas a strain overexpressing YopK reduced the lytic activity and the apparent pore size was smaller. The secreted YopK protein was found not to be translocated but, similar to YopB, localized to cell-associated bacteria during infection of HeLa cells. Based on these results, we propose a model where YopK controls the translocation of Yop effectors into eukaryotic cells.
细胞外细菌将抗宿主因子导入真核细胞是几种革兰氏阴性病原体进化出的一种策略。在这些病原体中，毒力蛋白跨细菌膜的转运由密切相关的III型分泌系统控制。对于致病性耶尔森菌来说，蛋白质跨真核细胞膜的转运通过一种极化机制发生，该机制需要两种分泌蛋白YopB和YopD。最近发现YopB能诱导真核细胞膜上形成一个孔，据信Yop效应蛋白就是通过这个孔进行转运的（哈坎松等人，1996年b）。我们之前已经表明，假结核耶尔森菌的YopK是小鼠全身感染发展所必需的。在此，我们更详细地分析了YopK在毒力过程中的作用。与野生型菌株相比，发现一个yopK突变株在HeLa细胞以及MDCK - 1细胞中能诱导更快的YopE介导的细胞毒性反应。我们发现这是YopE向HeLa细胞转运的细胞接触依赖性增加的结果。相比之下，YopK的过表达导致转运受损。此外，我们发现YopK还影响YopB对绵羊红细胞以及HeLa细胞的溶细胞作用。与相应的野生型菌株相比，一个yopK突变株表现出更高的溶细胞活性，诱导形成的孔更大，而一个过表达YopK的菌株降低了溶细胞活性，明显的孔径更小。发现分泌的YopK蛋白不会被转运，但与YopB类似，在HeLa细胞感染期间定位于与细胞相关的细菌。基于这些结果，我们提出一个模型，其中YopK控制Yop效应蛋白向真核细胞的转运。
