title: Heparin-binding epidermal growth factor cleavage mediates zinc-induced epidermal growth factor receptor phosphorylation.
abstract: We have previously shown that exposure to zinc ions can activate epidermal growth factor (EGF) receptor (EGFR) signaling in murine fibroblasts and A431 cells through a mechanism involving Src kinase. While studying the effects of zinc ions in normal human bronchial epithelial cell, we uncovered evidence for an additional mechanism of Zn(2+)-induced EGFR activation. Exposure to Zn(2+) induced phosphorylation of EGFR at tyrosine 1068, a major autophosphorylation site, in a dose- and time-dependent fashion. This effect of Zn(2+) on EGFR was significantly blocked with an antibody against the ligand-binding domain of the receptor. Neutralizing antibodies against EGFR ligands revealed the involvement of heparin-binding EGF (HB-EGF) in Zn(2+)-induced EGFR phosphorylation. This observation was further supported by immunoblots showing elevated levels of HB-EGF released by Zn(2+)-exposed cells. Zymography showed the existence of matrix metalloproteinase-3 in Zn(2+)-challenged cells. Incubation with a specific matrix metalloproteinase-3 inhibitor suppressed Zn(2+)-induced EGFR phosphorylation as well as HB-EGF release. Therefore, these data support an autocrine or paracrine mechanism whereby Zn(2+) induces EGFR phosphorylation through the extracellular release of EGFR ligands, which may be mediated by metalloproteinases.
authors.affiliation: Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. Weidong_Wu@med.unc.edu
authors.forename: Weidong
authors.initials: W
authors.lastname: Wu
authors.forename: James M
authors.initials: JM
authors.lastname: Samet
authors.forename: Robert
authors.initials: R
authors.lastname: Silbajoris
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Dailey
authors.forename: Dean
authors.initials: D
authors.lastname: Sheppard
authors.forename: Philip A
authors.initials: PA
authors.lastname: Bromberg
authors.forename: Lee M
authors.initials: LM
authors.lastname: Graves
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D001980:Bronchi / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D066246:ErbB Receptors / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D061965:Matrix Metalloproteinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011799:Quinazolines / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism; D015032:Zinc / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000906:Antibodies; D004151:Dipeptides; D004791:Enzyme Inhibitors; C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D061965:Matrix Metalloproteinase Inhibitors; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D011799:Quinazolines; D014443:Tyrosine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D015032:Zinc; C088860:4-((3-bromophenyl)amino)-6,7-dimethoxyquinazoline