Serratia grimesii are facultative pathogenic bacteria that can penetrate a wide range of host cells and cause infection, especially in immunocompromised patients. Previously, we have found that bacterial metalloprotease grimelysin is a potential virulence determinant of S. grimesii invasion (E. S. Bozhokina et al., (2011). Cell Biology International, 35(2), 111–118). Protease is characterized as an actin‐hydrolyzing enzyme with a narrow specificity toward other cell proteins. It is not known, however, whether grimelysin is transported into eukaryotic cells. Here, we show, for the first time, that S. grimesii can generate outer membrane vesicles (OMVs) displayed specific proteolytic activity against actin, characteristic of grimelysin. The presence of grimelysin was also confirmed by the Western blot analysis of S. grimesii OMVs lysate. Furthermore, confocal microscopy analysis revealed that the S. grimesii grimelysin‐containing OMVs attached to the host cell membrane. Finally, pretreatment of HeLa cells with S. grimesii OMVs before the cells were infected with bacteria increased the bacterial penetration several times. These data strongly suggest that protease grimelysin promotes S. grimesii internalization by modifying bacterial and/or host molecule(s) when it is delivered as a component of OMVs.

中文翻译：

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Serratia grimesii 外膜囊泡相关的grimelysin 触发真核细胞的细菌入侵。

Serratia grimesii是兼性病原菌，可以穿透广泛的宿主细胞并引起感染，尤其是在免疫功能低下的患者中。此前，我们已经发现细菌金属蛋白酶 grimelysin 是S. grimesii入侵的潜在毒力决定因素（ES Bozhokina 等，（2011）。 国际细胞生物学，35（2），111-118）。蛋白酶的特征是一种肌动蛋白水解酶，对其他细胞蛋白具有狭窄的特异性。然而，不知道grimelysin 是否被转运到真核细胞中。在这里，我们第一次展示了S. grimesii可以产生外膜囊泡 (OMV)，显示出针对肌动蛋白的特异性蛋白水解活性，这是 Grimelysin 的特征。Grimelysin 的存在也通过S.grimesii OMV 裂解物的蛋白质印迹分析得到证实。此外，共聚焦显微镜分析显示，含有S. grimesii grimelysin 的 OMV 附着在宿主细胞膜上。最后，在细胞被细菌感染之前，用S.grimesii OMV对 HeLa 细胞进行预处理可使细菌渗透增加数倍。这些数据强烈表明蛋白酶 grimelysin在作为 OMV 的组分递送时通过修饰细菌和/或宿主分子来促进S.grimesii内化。