Down-modulation of epidermal growth factor receptor affinity in fibroblasts treated with interleukin 1 or tumor necrosis factor is associated with phosphorylation at a site other than threonine 654.
Interleukin 1 or tumor necrosis factor alpha can cause a transient down-modulation of epidermal growth factor (EGF) binding to quiescent fibroblast monolayers; the effect results from a reduction in EGF receptor (EGF-R) affinity and appears to be mediated by a protein kinase C (PKC)-independent mechanism. Here we show transient increases in EGF-R serine/threonine phosphorylation which are temporally coordinated with the effects on EGF binding; we also demonstrate that the cytokine-mediated phosphorylations, unlike those caused by PKC activators, have little discernible effect upon intrinsic EGF-R-associated tyrosine kinase activity. Cytokine-mediated EGF-R phosphorylation is resistant to staurosporine, an extremely potent inhibitor of PKC. Analysis of tryptic 32P-phosphopeptides reveals that Thr654, the unique site of PKC-mediated phosphorylation, is not phosphorylated in cytokine-treated cells, but a different, relatively acidic, peptide containing phosphoserine can be detected instead.
Cytokine Biochemistry Group, Strangeways Research Laboratory, Wort's Causeway, Cambridge, United Kingdom.
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Saklatvala
D002460:Cell Line; D015536:Down-Regulation; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D005881:Gingiva; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D007700:Kinetics; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism*; D019000:Phosphotyrosine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013912:Threonine / Q000031:analogs & derivatives*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D010769:Phosphothreonine; D010768:Phosphoserine; D019000:Phosphotyrosine; D013912:Threonine; D014443:Tyrosine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D013755:Tetradecanoylphorbol Acetate