title: Regulation of erythrocyte Ca2+ pump activity by protein kinase C.
abstract: Using either inside-out vesicles (IOV) prepared from human erythrocytes or purified Ca2+-ATPase from the same source, the effects of protein kinase C (Ca2+/phospholipid-dependent enzyme) on Ca2+ transport and Ca2+-ATPase activity were measured. Incubation of IOV with protein kinase C in the presence, but not absence, of either 12-O-tetradecanoylphorbol-13-acetate or diolein led to a Ca2+-dependent stimulation of ATP-dependent calcium uptake. The effect was a 5-7-fold increase of Vmax without a significant change in the apparent Km for Ca2+. By comparison, the effect of calmodulin was a 14-fold stimulation of Vmax and a 4-fold reduction in apparent Km. The effect of protein kinase C and calmodulin on Ca2+ uptake were nearly additive. Stimulation of IOV Ca2+ transport by protein kinase C was entirely reversible by treatment of activated IOV with alkaline phosphatase. Incubation of purified Ca2+-ATPase with protein kinase C in the presence of 12-O-tetradecanoylphorbol-13-acetate or diolein led to a stimulation of Ca2+-dependent ATPase activity. These results indicate that protein kinase C stimulates the activity of the plasma membrane Ca2+ pump by a direct effect on the pump protein.
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000097:blood*; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D011493:Protein Kinase C / Q000097:blood*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D004075:Diglycerides; D011493:Protein Kinase C; D000469:Alkaline Phosphatase; D000252:Calcium-Transporting ATPases; D013755:Tetradecanoylphorbol Acetate; C013965:diolein