title: Enterotoxigenic Escherichia coli vesicles target toxin delivery into mammalian cells.
abstract: Enterotoxigenic Escherichia coli (ETEC) is a prevalent cause of traveler's diarrhea and infant mortality in third-world countries. Heat-labile enterotoxin (LT) is secreted from ETEC via vesicles composed of outer membrane and periplasm. We investigated the role of ETEC vesicles in pathogenesis by analyzing vesicle association and entry into eukaryotic cells. Fluorescently labeled vesicles from LT-producing and LT-nonproducing strains were compared in their ability to bind adrenal and intestinal epithelial cells. ETEC-derived vesicles, but not control nonpathogen-derived vesicles, associated with cells in a time-, temperature-, and receptor-dependent manner. Vesicles were visualized on the cell surface at 4 degrees C and detected intracellularly at 37 degrees C. ETEC vesicle endocytosis depended on cholesterol-rich lipid rafts. Entering vesicles partially colocalized with caveolin, and the internalized vesicles accumulated in a nonacidified compartment. We conclude that ETEC vesicles serve as specifically targeted transport vehicles that mediate entry of active enterotoxin and other bacterial envelope components into host cells. These data demonstrate a role in virulence for ETEC vesicles.
authors.affiliation: Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Nicole C
authors.initials: NC
authors.lastname: Kesty
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Mason
authors.forename: Mary
authors.initials: M
authors.lastname: Reedy
authors.forename: Sara E
authors.initials: SE
authors.lastname: Miller
authors.forename: Meta J
authors.initials: MJ
authors.lastname: Kuehn
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004705:Endocytosis; D004768:Enterotoxins / Q000378:metabolism*; D004926:Escherichia coli / Q000472:pathogenicity / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D019073:HT29 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D021962:Membrane Microdomains / Q000378:metabolism; D051379:Mice; D046529:Microscopy, Electron, Transmission; D019897:Periplasm / Q000378:metabolism; D022161:Transport Vesicles / Q000502:physiology* / Q000648:ultrastructure; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; C495540:CAV1 protein, human; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D037521:Virulence Factors; C027538:heat-labile enterotoxin, E coli