title: Ionophore A23187 stimulates phosphorylation of the 40,000 dalton protein in human platelets without phospholipase C activation.
abstract: The Ca2+ ionophore A23187 (0.2-5 microM) stimulates the phosphorylation of the substrates of protein kinase C (40,000 dalton protein) and myosin light chain kinase (20,000 dalton protein) in the presence or absence of cyclooxygenase inhibitors. In the presence of cyclooxygenase inhibitors or millimolar Ca2+ there is no stimulation of phospholipase C by A23187. Fingerprints of the 32P-labeled 40,000 dalton protein isolated from platelets that have been stimulated with A23187, thrombin, phorbol 12,13-dibutyrate and 1,2-didecanoylglycerol were identical. Higher concentrations of A23187 (1-5 microM) induced the loss of polyphosphoinositides through phosphomonoesterase activity.
mesh_terms: D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000097:blood; D008970:Molecular Weight; D010712:Phosphatidic Acids / Q000097:blood; D010716:Phosphatidylinositols / Q000097:blood; D010750:Phosphoproteins / Q000097:blood*; D010766:Phosphorylation; D010738:Type C Phospholipases / Q000097:blood*
chemical_list: D001798:Blood Proteins; D007295:Inositol Phosphates; D010712:Phosphatidic Acids; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D000001:Calcimycin; D010738:Type C Phospholipases; D002118:Calcium