title: Insulin increases membrane and cytosolic protein kinase C activity in BC3H-1 myocytes.
abstract: Insulin treatment stimulated the activity of the Ca2+- and phospholipid-dependent protein kinase (protein kinase C) in both cytosolic and membrane fractions of BC3H-1 myocytes. Within 60 s of insulin treatment, membrane protein kinase C activity increased 2-fold, diminished toward control levels transiently, and then increased 2-fold again after 15 min. Cytosolic protein kinase C activity increased more gradually and steadily up to 80% over a 20-min period. Increases in protein kinase C activity were dose-dependent and were not simply a result of translocation of cytosolic enzyme (although this may have occurred), as total activity was also increased. The increase in protein kinase C activity was not inhibited by cycloheximide (which also increased protein kinase C activity and 2-deoxyglucose transport) and was still evident following anion exchange chromatography. The insulin effect was decidedly different from those of 12-O-tetradecanoylphorbol-13-acetate and phenylephrine using histone III-S as substrate. Phenylephrine decreased cytosolic protein kinase C activity while increasing membrane activity; 12-O-tetradecanoylphorbol-13-acetate only decreased cytosolic protein kinase C activity. The early insulin-induced increases in membrane protein kinase C activity may be related to increased diacylglycerol generation from de novo phosphatidic acid synthesis, as there were rapid increases in [3H]glycerol incorporation into diacylglycerol, and transient increases in phospholipid hydrolysis, as there were transient rapid increases in [3H]diacylglycerol in cells prelabeled with [3H]arachidonate. Later, sustained increases in membrane and cytosolic protein kinase C activity may reflect the continuous activation of de novo phospholipid synthesis, as there were associated increases in [3H]glycerol incorporation into diacylglycerol at later, as well as very early time points.
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D009132:Muscles / Q000201:enzymology; D010656:Phenylephrine / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D007328:Insulin; D010656:Phenylephrine; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate