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C-kinase phosphorylates the epidermal growth factor receptor and reduces its epidermal growth factor-stimulated tyrosine protein kinase activity.

Abstract
The Ca2+- and phospholipid-dependent protein kinase (C-kinase) binds tightly in the presence of Ca2+ to purified membranes of A431 human epidermoid carcinoma cells. The major membrane substrate for C-kinase is the epidermal growth factor (EGF) receptor. Phosphorylation of the EGF receptor is Ca2+-dependent and occurs at threonine and serine residues. After tryptic digestion of the receptor, three major phosphothreonine-containing peptides were identified. These are identical with three new phosphopeptides present in the EGF receptor isolated from A431 cells treated with either of the tumor promoters 12-O-tetradecanoylphorbol 13-acetate or teleocidin. C-kinase catalyzes phosphorylation at these same sites in purified EGF receptor protein. These results indicate that, in A431 cells exposed to tumor promoters, C-kinase catalyzes phosphorylation of a significant population of EGF receptor molecules. This phosphorylation of EGF receptors results in decreased self-phosphorylation of the EGF receptor at tyrosine residues both in vivo and in vitro and in decreased EGF-stimulated tyrosine kinase activity in vivo.
AuthorsC Cochet, G N Gill, J Meisenhelder, J A Cooper, T Hunter
JournalThe Journal of biological chemistry (J Biol Chem) Vol. 259 Issue 4 Pg. 2553-8 (Feb 25 1984) ISSN: 0021-9258 [Print] United States
PMID6321473 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References
  • Peptide Fragments
  • Receptors, Cell Surface
  • Epidermal Growth Factor
  • Protein Kinases
  • ErbB Receptors
  • Protein-Tyrosine Kinases
  • Protein Kinase C
  • Calcium
Topics
  • Animals
  • Brain (enzymology)
  • Calcium (pharmacology)
  • Carcinoma, Squamous Cell
  • Cell Line
  • Cell Membrane (metabolism)
  • Epidermal Growth Factor (metabolism)
  • ErbB Receptors
  • Humans
  • Kinetics
  • Molecular Weight
  • Peptide Fragments (analysis)
  • Phosphorylation
  • Protein Kinase C
  • Protein Kinases (isolation & purification, metabolism)
  • Protein-Tyrosine Kinases
  • Rats
  • Receptors, Cell Surface (metabolism)

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