title: Phosphatidylinositol turnover in platelet activation; calcium mobilization and protein phosphorylation.
abstract: Ca2+-activated, phospholipid-dependent protein kinase (C-kinase) in platelets is normally activated by diacylglycerol, which is derived from phosphatidylinositol through its receptor-linked breakdown. Under appropriate conditions this enzyme can also be activated by synthetic diacylglycerol which is directly added to intact platelets. C-Kinase thus activated preferentially phosphorylates an endogenous platelet protein having a molecular weight of approximately 40,000. This protein phosphorylation is merely a prerequisite but not a sufficient requirement for the release of serotonin. Evidence is presented suggesting that Ca2+ mobilization and C-kinase activation are synergistically involved in the physiological response of platelets to extracellular messengers, such as thrombin, collagen and platelet-activating factor.
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D003094:Collagen / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D010716:Phosphatidylinositols / Q000097:blood*; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects; D011493:Protein Kinase C; D011494:Protein Kinases / Q000097:blood; D013917:Thrombin / Q000494:pharmacology
chemical_list: D001798:Blood Proteins; D004075:Diglycerides; D010716:Phosphatidylinositols; D003094:Collagen; D011494:Protein Kinases; D011493:Protein Kinase C; D013917:Thrombin; D002118:Calcium