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Abstract：
To establish an infection, Salmonella has to interact with eukaryotic cells. Invasion of non-phagocytic cells (i.e., epithelial, fibroblast and endothelial cells) involves either a trigger or a zipper mechanism mediated by the T3SS-1 or the invasin Rck, respectively. Another outer membrane protein, PagN, was also implicated in the invasion. However, other unknown invasion factors have been previously suggested. Our goal was to evaluate the invasion capability of a Salmonella Typhimurium strain invalidated for the three known invasion factors. Non-phagocytic cell lines of several animal origins were tested in a gentamicin protection assay. In most cells, we observed a drastic decrease in the invasion rate between the wild-type and the triple mutant. However, in five cell lines, the triple mutant invaded cells at a similarly high level to the wild-type, suggesting the existence of unidentified invasion factors. For the wild-type and the triple mutant, scanning-electron microscopy, confocal imaging and use of biochemical inhibitors confirmed their cellular uptake and showed a zipper-like mechanism of internalization involving both clathrin- and non-clathrin-dependent pathways. Despite a functional T3SS-1, the wild-type bacteria seemed to use the same entry route as the mutant in our cell model. All together, these results demonstrate the existence of unknown Salmonella invasion factors, which require further characterization.
摘要：
为了建立感染，沙门氏菌必须与真核细胞相互作用。非吞噬细胞的侵袭(即，上皮，成纤维细胞和内皮细胞）涉及由T3SS-1或侵袭素Rck介导的触发或拉链机制，分别。另一种外膜蛋白，PagN,也与入侵有关。然而,以前曾提出过其他未知的入侵因素。我们的目标是评估鼠伤寒沙门氏菌菌株在三种已知入侵因素下无效的入侵能力。在庆大霉素保护测定中测试了几种动物来源的非吞噬细胞系。在大多数细胞中，我们观察到野生型和三重突变体之间的侵袭率急剧下降。然而,在五种细胞系中，三重突变体以与野生型相似的高水平侵入细胞，提示存在身份不明的入侵因素。对于野生型和三重突变体，扫描电子显微镜，共聚焦成像和生化抑制剂的使用证实了它们的细胞摄取,并显示了拉链样的内化机制,涉及网格蛋白依赖性和非网格蛋白依赖性途径.尽管具有功能性T3SS-1，但野生型细菌似乎与我们的细胞模型中的突变体使用相同的进入途径。一起,这些结果表明存在未知的沙门氏菌入侵因素，这需要进一步表征。
