Nature2014-06-18 5:56 PM

能啃小肠细胞的阿米巴虫 Trogocytosis by Entamoeba histolytica contributes to cell killing and tissue invasion


Entamoeba histolytica是发展中国家儿童致命腹泻病的致病病原体,之所以这样来命名是因为它能够破坏宿主组织,尽管该效应的机制并不清楚。Katherine Ralston等人在这篇论文中介绍了这些阿米巴虫是怎样通过咬下一块细胞并将其消化来杀死小肠上皮细胞的,这样一个过程让人想起免疫细胞之间的“胞啃”现象。将咬下的碎块消化是杀死细胞所必需的,这个机制在组织培养中和在小肠外植体的入侵过程中都发挥作用。作者提出,通过“胞啃”所发生的细胞间交换在演化上可能要比以前所假设的更古老、更普遍。这项研究还显示,阿米巴“胞啃”是用来治疗阿米巴病(一种被忽视的重要疾病)的新药的一个潜在目标。


Entamoeba histolytica is the causative agent of amoebiasis, a potentially fatal diarrhoeal disease in the developing world. The parasite was named “histolytica” for its ability to destroy host tissues, which is probably driven by direct killing of human cells. The mechanism of human cell killing has been unclear, although the accepted model was that the parasites use secreted toxic effectors to kill cells before ingestion. Here we report the discovery that amoebae kill by ingesting distinct pieces of living human cells, resulting in intracellular calcium elevation and eventual cell death. After cell killing, amoebae detach and cease ingestion. Ingestion of human cell fragments is required for cell killing, and also contributes to invasion of intestinal tissue. The internalization of fragments of living human cells is reminiscent of trogocytosis (from Greek trogo, nibble) observed between immune cells, but amoebic trogocytosis differs because it results in death. The ingestion of live cell material and the rejection of corpses illuminate a stark contrast to the established model of dead cell clearance in multicellular organisms. These findings change the model for tissue destruction in amoebiasis and suggest an ancient origin of trogocytosis as a form of intercellular exchange.






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