Heparin-binding epidermal growth factor cleavage mediates zinc-induced epidermal growth factor receptor phosphorylation.
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.
Wu
Weidong
W
Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. Weidong_Wu@med.unc.edu
Samet
James M
JM
Silbajoris
Robert
R
Dailey
Lisa A
LA
Sheppard
Dean
D
Bromberg
Philip A
PA
Graves
Lee M
LM
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
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