title: Elastase in intestinal mucus enhances the cytotoxicity of Shiga toxin type 2d.
abstract: Shiga toxin variant type 2d (Stx2d) produced by some strains of Shiga toxin-producing Escherichia coli is composed of an enzymatically active A subunit and a B (binding) pentamer. The cytotoxicity of Stx2d is increased (activated) 10-1000-fold for Vero cells when the toxin is incubated with mucus obtained from the small intestine of mice. In this study we isolated an Stx2d activator and identified it as a mouse elastase with strong homology to human elastase IIIB. Moreover, commercially available porcine pancreatic elastase preparations also activated Stx2d cytotoxicity although with a lower specific activity than isolated mouse elastase. Elastase directly nicked the Stx2d A subunit to A(1) and A(2), an event that did not correlate with activation. However, elastase also reduced the size and changed the isoelectric point of the A(2) peptide, as determined by SDS-polyacrylamide gel electrophoresis and two-dimensional electrophoresis followed by Western immunoblot analysis. This elastase-mediated size and charge shift in the A(2) peptide of Stx2d occurred concurrently with activation of the toxin. Both the reduction in size of the Stx2d A(2) peptide by incubation with elastase as well as the associated activation of Stx2d cytotoxicity were fully inhibited by elastatinal, an elastase-specific inhibitor.
authors.affiliation: Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Kokai-Kun
authors.forename: A R
authors.initials: AR
authors.lastname: Melton-Celsa
authors.forename: A D
authors.initials: AD
authors.lastname: O'Brien
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism* / Q000633:toxicity; D004768:Enterotoxins / Q000378:metabolism / Q000633:toxicity; D004926:Escherichia coli; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology; D051379:Mice; D008969:Molecular Sequence Data; D009093:Mucus / Q000201:enzymology; D010196:Pancreatic Elastase / Q000378:metabolism* / Q000633:toxicity; D022603:Shiga Toxins; D012760:Shigella
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D022603:Shiga Toxins; D010196:Pancreatic Elastase