title: Platelet-derived growth factor mimics phorbol diester action on epidermal growth factor receptor phosphorylation at threonine-654.
abstract: Addition of platelet-derived growth factor (PDGF) to quiescent WI-38 human fetal lung fibroblasts mimics the effect of tumor-promoting phorbol diesters to inhibit the high-affinity binding of 125I-labeled epidermal growth factor (125I-EGF). PDGF, like phorbol diesters, was found to increase the phosphorylation state of EGF receptors immunoprecipitated from intact fibroblasts that were labeled to equilibrium with [32P]phosphate. Phosphoamino acid analysis of the EGF receptors indicated that both PDGF and phorbol diesters increased the level of [32P]phosphoserine and [32P]phosphothreonine. Phosphopeptide mapping of the EGF receptor demonstrated that PDGF increased the phosphorylation of several sites and induced the phosphorylation of a site that was not observed to be phosphorylated on EGF receptors isolated from control cells. This latter phosphorylation site on the EGF receptor was identified as threonine-654, previously shown to be phosphorylated in response to phorbol diesters in intact cells or by purified protein kinase C in vitro. Further, it was observed that PDGF mimicked the action of phorbol diesters to inhibit the EGF-dependent tyrosine phosphorylation of the EGF receptor in [32P]phosphate-labeled fibroblasts. These results are consistent with the hypothesis that increases in diacylglycerol and Ca2+ levels caused by addition of PDGF to fibroblasts activate protein kinase C and that this kinase, at least in part, mediates the effect of PDGF on the phosphorylation of the EGF receptor. The data further suggest that protein kinase C may play an important role in the regulation of cellular metabolism and proliferation by PDGF.
authors.forename: R J
authors.initials: RJ
authors.lastname: Davis
authors.forename: M P
authors.initials: MP
authors.lastname: Czech
mesh_terms: D002460:Cell Line; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors; D006801:Humans; D009857:Oncogenes; D010446:Peptide Fragments / Q000032:analysis; D010704:Phorbols / Q000494:pharmacology*; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013912:Threonine / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D010704:Phorbols; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D013912:Threonine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D013755:Tetradecanoylphorbol Acetate