Enteropathogenic Escherichia coli (EPEC) Tir receptor molecule does not undergo full modification when introduced into host cells by EPEC-independent mechanisms
Enteropathogenic Escherichia coli (EPEC) Tir receptor molecule does not undergo full modification when introduced into host cells by EPEC-independent mechanisms
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DOI：
10.1128/iai.69.3.1444-1453.2001
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发表时间：
2001-03-01
影响因子：
3.1
通讯作者：
Warawa, J
中科院分区：
文献类型：
--
作者：
Kenny, B;Warawa, J
肠致病性大肠杆菌（EPEC），像许多其他革兰氏阴性病原体，编码一种III型分泌装置，专门用于释放毒力相关蛋白。一种这样的蛋白质，Tir，被转移到宿主细胞中，在那里它通过添加磷酸基团而被修饰，导致许多具有不同分子量的物质。一个磷酸化事件，酪氨酸残基474的Tir，不有助于分子量的变化，但其肌动蛋白成核功能是必不可少的。非磷酸酪氨酸相关修饰的作用尚不清楚。在本文中，我们证明，使用三种不同的方法，Tir不编码足够的信息，以促进其完整的修改时，引入到宿主细胞中的EPEC独立的机制。每个系统都揭示了Tir是宿主激酶的底物，其作用导致其部分修饰为与EPEC感染的宿主细胞中明显的形式相似的形式。进一步的Tir修饰不能通过用EPEC感染细胞来诱导，这表明Tir必须与其他EPEC因子共表达以使其在宿主细胞内完全修饰。一种方法使用耶尔森氏菌属（Yersinia spp.）将Tir递送到宿主细胞中，并且该系统揭示了Tir分泌和易位可以在不存在Tir伴侣分子CesT（以前称为OrfU）的情况下发生。CesT被认为是一个效率因子，这是不需要的，不像在EPEC中，为Tir的稳定性，这表明它可能起作用，引导Tir的易位装置或保持它在一个分泌能力的形式。
Enteropathogenic Escherichia coli (EPEC), like many other gram-negative pathogens, encodes a type III secretion apparatus dedicated to the release of virulence-associated proteins. One such protein, Tir, is translocated into host cells, where it is modified by the addition of phosphate groups, resulting in a number of species with distinct molecular mass. One phosphorylation event, on tyrosine residue 474 of Tir, does not contribute to shifts in molecular mass but is essential for its actin-nucleating function. The role of the nonphosphotyrosine related modifications is unknown. In this paper, we demonstrate, using three different approaches, that Tir does not encode sufficient information to facilitate its complete modification when introduced into host cells in EPEC-independent mechanisms. Each system revealed that Tir is a substrate for a host kinase whose action results in its partial modification to a form similar to one evident in EPEC-infected host cells. Further Tir modification could not be induced by infecting cells with EPEC, suggesting that Tir must be coexpressed with other EPEC factors to enable its full modification within host cells. One approach used Yersinia spp. to deliver Tir into host cells, and this system revealed that Tir secretion and translocation can occur in the absence of the Tir chaperone molecule, CesT (formerly known as OrfU). CesT was found to be an efficiency factor which was not required, unlike in EPEC, for Tir stability, indicating that it may function to guide Tir to the translocation apparatus or maintain it in a secretion-competent form.