Retention of specific protein kinase C isozymes following chronic phorbol ester treatment in BC3H-1 myocytes

Biochem Biophys Res Commun. 1989 May 30;161(1):327-34. doi: 10.1016/0006-291x(89)91600-8.


Since insulin effects on glucose transport persist in phorbol ester "desensitized" or "down-regulated" BC3H-1 myocytes, we reexamined the evidence for protein kinase C (PKC) depletion. After 24 hrs of 5 microM 12-0-tetradecanoyl phorbol-13-acetate (TPA) treatment, PKC-directed histone phosphorylation and acute TPA effects on glucose transport were lost, but PKC-dependent vinculin phosphorylation was still evident. Hydroxylapatite (HAP) chromatography revealed loss of a type III, but not a type II, PKC-dependent vinculin phosphorylation. Immunoblots of cytosolic preparations of PKC-"depleted" myocytes confirmed the retention of PKC. Our findings indicate that TPA "down-regulated" BC3H-1 myocytes contain immunoreactive and functionally active PKC. The latter may explain the continued effectiveness of both insulin and diacylglycerol (DiC8) for stimulating glucose transport in "down-regulated" cells.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • Cells, Cultured
  • Diglycerides / metabolism
  • Histones / metabolism
  • Isoenzymes / metabolism*
  • Mice
  • Muscles / enzymology
  • Phosphorylation
  • Protein Kinase C / metabolism*
  • Rats
  • Tetradecanoylphorbol Acetate / pharmacology*
  • Time Factors


  • Diglycerides
  • Histones
  • Isoenzymes
  • 1,2-dioctanoylglycerol
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate