title: Escherichia coli Shiga toxins induce apoptosis in epithelial cells that is regulated by the Bcl-2 family.
abstract: Human intestinal cells lack globotriaosylceramide (Gb(3)), the receptor for Shiga toxin-1 (Stx1) and Shiga toxin-2 (Stx2). Therefore, the role of these toxins in mediating intestinal disease during infection with Shiga toxin-producing Escherichia coli is unclear. The aims of this study were to determine whether Stx1 and Stx2 induce apoptosis in epithelial cells expressing (HEp-2, Caco-2) or lacking (T84) Gb(3) and to characterize the role of the Bcl-2 family. Stx1 (12.5 ng/ml) induced apoptosis in both HEp-2 (21.9 +/- 7.9% vs. 0.8 +/- 0.3%, P = 0.01) and Caco-2 (10.1 +/- 1.2% vs. 3.1 +/- 0.4%, P = 0.006) cells but not in Gb(3)-deficient T84 cells. Toxin-mediated apoptosis of HEp-2 cells was associated with enhanced expression of the proapoptotic protein Bax. Inhibition of caspase activation prevented toxin-stimulated apoptosis. In addition, overexpression of Bcl-2 by transient transfection blocked Stx1-stimulated cell death. These findings indicate that Shiga toxins produced by E. coli signal Gb(3)-expressing epithelial cells to undergo apoptosis in association with enhanced Bax expression, thereby resulting in activation of the caspase cascade.
authors.affiliation: Research Institute, Hospital for Sick Children, University of Toronto, Toronto M5G 1X8, Canada L8N 3Z5.
authors.forename: N L
authors.initials: NL
authors.lastname: Jones
authors.forename: A
authors.initials: A
authors.lastname: Islur
authors.forename: R
authors.initials: R
authors.lastname: Haq
authors.forename: M
authors.initials: M
authors.lastname: Mascarenhas
authors.forename: M A
authors.initials: MA
authors.lastname: Karmali
authors.forename: M H
authors.initials: MH
authors.lastname: Perdue
authors.forename: B W
authors.initials: BW
authors.lastname: Zanke
authors.forename: P M
authors.initials: PM
authors.lastname: Sherman
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001427:Bacterial Toxins / Q000633:toxicity*; D016923:Cell Death / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004768:Enterotoxins / Q000633:toxicity*; D004926:Escherichia coli; D049452:Green Fluorescent Proteins; D006801:Humans; D007413:Intestinal Mucosa; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D008954:Models, Biological; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000502:physiology; D011994:Recombinant Proteins / Q000096:biosynthesis; D022603:Shiga Toxins; D014162:Transfection; D014281:Trihexosylceramides / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; D001427:Bacterial Toxins; D015853:Cysteine Proteinase Inhibitors; D004768:Enterotoxins; D008164:Luminescent Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D022603:Shiga Toxins; D014281:Trihexosylceramides; D051028:bcl-2-Associated X Protein; D049452:Green Fluorescent Proteins; C018549:globotriaosylceramide