Effects of Zn2+ ions on protein phosphorylation in epithelial cell membranes.
The regulation of protein phosphorylation by Zn2+ ions and by other divalent cations was studied in membrane vesicles from a normal mouse epithelial cell line, MMC-E (Mus musculus castaneous). Four major phosphoacceptor polypeptides were found in these membranes. Micromolar concentrations of Zn2+ ions inhibited the phosphorylation of the epidermal growth factor (EGF) receptor and of threonine residues in a 47,000-dalton polypeptide. In contrast, two polypeptides with molecular weights of 54,000 and 57,000 showed increased phosphorylation, mainly of serine residues, in the p.esence of Zn2+ ions. These results were not obtained using similar concentrations of other divalent cations and were apparently not due to an effect of Zn2+ ions on phosphoprotein phosphatases. Thus, the effects of Zn2+ ions on protein phosphorylation in membrane vesicles are complex and are not restricted to an inhibition of a single protein phosphatase or kinase.
D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004848:Epithelium; D066246:ErbB Receptors; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*
D002413:Cations, Divalent; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D010769:Phosphothreonine; D010768:Phosphoserine; D004815:Epidermal Growth Factor; D011494:Protein Kinases; D066246:ErbB Receptors; D010749:Phosphoprotein Phosphatases; D015032:Zinc