In vivo regulation of protein kinase C by trans-phosphorylation followed by autophosphorylation

Erica M. Dutil, Lisa M. Keranen, Anna A. DePaoli-Roach, Alexandra C. Newton

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Dephosphorylation by the catalytic subunits of protein phosphatases 1 (CS1) and 2A (CS2) reveals that mature protein kinase C is phosphorylated at two distinct sites. Treatment of protein kinase C βII with CS1 causes a significant increase in the protein's electrophoretic mobility (approximately 4 kDa) and a coincident loss in catalytic activity. The CS1-dephosphorylated enzyme cannot autophosphorylate or be phosphorylated by mature protein kinase C, indicating that a different kinase catalyzes the phosphorylation at this site. The loss of activity is consistent with dephosphorylation on protein kinase C's activation loop (Orr, J. W., and Newton, A. C., (1994) J. Biol. Chem. 269, 27715-27718). Treatment with CS2 results in a smaller shift in electrophoretic mobility (approximately 2 kDa) and no loss in catalytic activity. Furthermore, the CS2-dephosphorylated form can autophosphorylate and thus regain the electrophoretic mobility of mature enzyme, consistent with dephosphorylation at protein kinase C's carboxyl-terminal autophosphorylation site, which is modified in vivo (Flint, A. J., Paladini, R. D., and Koshland, D. E., Jr. (1990) Science 249, 408-411). In summary, two phosphorylations process protein kinase C to generate the mature form: a transphosphorylation that renders the kinase catalytically competent and an autophosphorylation that may be important for the subcellular localization of the enzyme.

Original languageEnglish (US)
Pages (from-to)29359-29362
Number of pages4
JournalJournal of Biological Chemistry
Issue number47
StatePublished - Nov 25 1994

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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