Bacterial surface association of heat-labile enterotoxin through lipopolysaccharide after secretion via the general secretory pathway.

Published

Journal Article

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 G(M1) ganglioside binding site and that LT binds lipopolysaccharide and G(M1) 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.

Full Text

Duke Authors

Cited Authors

  • Horstman, AL; Kuehn, MJ

Published Date

  • September 6, 2002

Published In

Volume / Issue

  • 277 / 36

Start / End Page

  • 32538 - 32545

PubMed ID

  • 12087095

Pubmed Central ID

  • 12087095

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.M203740200

Language

  • eng

Conference Location

  • United States