title: Shiga toxin (Stx)1B and Stx2B induce von Willebrand factor secretion from human umbilical vein endothelial cells through different signaling pathways.
abstract: Diarrhea-associated hemolytic uremic syndrome (D(+)HUS) is caused by the ingestion of Escherichia coli that produce Shiga toxin (Stx), which is composed of a cytotoxic A subunit and pentameric B subunits that bind globotriaosylceramide on susceptible cells. Stx occurs in 2 types, Stx1 and Stx2. B subunits of either type stimulate von Willebrand factor (VWF) secretion from human umbilical vein endothelial cells (HUVECs), and Stx2B can cause thrombotic microangiopathy in Adamts13(-/-) mice. We have now determined that Stx1B and Stx2B activate different signaling pathways in HUVECs. VWF secretion induced by Stx1B is associated with a transient rise in intracellular Ca(2+) level that is blocked by chelation with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, removal of extracellular Ca(2+), the phospholipase C inhibitor U73122, the protein kinase inhibitor staurosporine, or small interfering RNA knockdown of protein kinase Cα. In contrast, Stx2B-induced VWF secretion is associated with activation of protein kinase A (PKA) and is blocked by the PKA inhibitor H89 or small interfering RNA knockdown of PKA. Stx2B does not increase cAMP levels and may activate PKA by a cAMP-independent mechanism. The activation of distinct signaling pathways may be relevant to understanding why E coli that express Stx2 are more likely to cause D(+)HUS than are E coli expressing only Stx1.
authors.affiliation: Department of Medicine, Washington University School of Medicine, St Louis, MO, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Jing
authors.initials: J
authors.lastname: Huang
authors.forename: J Evan
authors.initials: JE
authors.lastname: Sadler
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D003967:Diarrhea / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism; D004927:Escherichia coli Infections / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D020868:Gene Silencing / Q000187:drug effects; D006463:Hemolytic-Uremic Syndrome / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D006801:Humans; D051379:Mice; D011485:Protein Binding; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D022622:Shiga Toxin 1 / Q000009:adverse effects / Q000494:pharmacology; D022641:Shiga Toxin 2 / Q000009:adverse effects / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014281:Trihexosylceramides / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; D014281:Trihexosylceramides; D014841:von Willebrand Factor; D004533:Egtazic Acid; C018549:globotriaosylceramide; D017868:Cyclic AMP-Dependent Protein Kinases; D051571:Protein Kinase C-alpha; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium