Purified rabbit brain protein kinase C relaxes skinned vascular smooth muscle and phosphorylates myosin light chain.
To clarify the role of protein kinase C in the mechanical response, the effects of exogenous protein kinase C and its cofactors were investigated on skinned smooth muscle preparations of the rabbit mesenteric artery. Addition of protein kinase C with 12-O-tetradecanoylphorbol-13-acetate (TPA) and phosphatidylserine (PS) caused slow inactivation of a maximal Ca2+ contraction of the muscle fiber and correspondingly increased protein kinase C phosphorylation of myosin light chain. Neither protein kinase C nor enzyme cofactors (PS and TPA) produced relaxation of this tissue and all three components caused significant relaxation. Furthermore, when the muscle fiber was activated by Ca2+-insensitive fragment of MLC-kinase, addition of protein kinase C with PS and TPA decreased the tension and increased protein kinase C phosphorylation of myosin light chain. This evidence suggests that protein kinase C phosphorylation of myosin light chain may play an inhibitory role in the contraction of vascular smooth muscle.
D000818:Animals; D001921:Brain / Q000201:enzymology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D010718:Phosphatidylserines / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000494:pharmacology / Q000502:physiology*; D011817:Rabbits; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D010718:Phosphatidylserines; D011493:Protein Kinase C; D009219:Myosin-Light-Chain Kinase; D009218:Myosins; D013755:Tetradecanoylphorbol Acetate