Bacterial surface association of heat-labile enterotoxin through lipopolysaccharide after secretion via the general secretory pathway
Bacterial surface association of heat-labile enterotoxin through lipopolysaccharide after secretion via the general secretory pathway
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DOI：
10.1074/jbc.m203740200
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发表时间：
2002-09-06
影响因子：
4.8
通讯作者：
Kuehn, MJ
中科院分区：
文献类型：
--
作者：
Horstman, AL;Kuehn, MJ
不耐热肠毒素（LT）是产肠毒素大肠杆菌表达的重要毒力因子。通过外膜的LT分泌的途径和分泌的LT的细胞和细胞外定位进行了检查。使用荧光标记的受体，LT被发现特异性分泌到野生型肠毒素大肠杆菌的表面上。在K-12菌株中，一般分泌途径（GSP）的主要终末分支是将LT定位于细菌表面所必需和充分的。LT是一种异聚体毒素，我们确定其细胞表面定位是由其B亚基介导的，独立于完整的Gm，神经节苷脂结合位点，LT结合脂多糖和Gm，同时。在大肠杆菌中，大部分LT通过GSP分泌到培养上清中。与囊泡相关的大肠杆菌。只有一个突变的hns，而不是过度表达的GSP或LT，引起囊泡产量的增加，支持特定的囊泡形成机制调节的核相关蛋白HNS。我们提出了一个模型，其中LT是分泌的GSP跨外膜，分泌的LT结合脂多糖通过G（M1）的非依赖性的结合区域上的B亚基，和LT释放的外膜囊泡表面与宿主细胞受体相互作用，导致中毒。这些数据解释了囊泡介导的受体依赖性递送细菌毒素进入宿主细胞的新机制。
Heat-labile enterotoxin (LT) is an important virulence factor expressed by enterotoxigenic Escherichia coli. The route of LT secretion through the outer membrane and the cellular and extracellular localization of secreted LT were examined. Using a fluorescently labeled receptor, LT was found to be specifically secreted onto the surface of wild type enterotoxigenic Escherichia coli. The main terminal branch of the general secretory pathway (GSP) was necessary and sufficient to localize LT to the bacterial surface in a K-12 strain. LT is a heteromeric toxin, and we determined that its cell surface localization was mediated by the its B subunit independent of an intact Gm, ganglioside binding site and that LT binds lipopolysaccharide and Gm, concurrently. The majority of LT secreted into the culture supernatant by the GSP in E. coli associated with vesicles. Only a mutation in hns, not overexpression of the GSP or LT, caused an increase in vesicle yield, supporting a specific vesicle formation machinery regulated by the nucleoid-associated protein HNS. We propose a model in which LT is secreted by the GSP across the outer membrane, secreted LT binds lipopolysaccharide via a G(M1)-independent binding region on its B subunit, and LT on the surface of released outer membrane vesicles interacts with host cell receptors, leading to intoxication. These data explain a novel mechanism of vesicle-mediated receptor-dependent delivery of a bacterial toxin into a host cell.