Retention of specific protein kinase C isozymes following chronic phorbol ester treatment in BC3H-1 myocytes.
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.
Cooper
D R
DR
James A. Haley Veterans' Administration Hospital, Tampa, FL 33612.
Watson
J E
JE
Acevedo-Duncan
M
M
Pollet
R J
RJ
Standaert
M L
ML
Farese
R V
RV
D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004075:Diglycerides / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism*; D051379:Mice; D009132:Muscles / Q000201:enzymology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013997:Time Factors
D004075:Diglycerides; D006657:Histones; D007527:Isoenzymes; C044295:1,2-dioctanoylglycerol; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate