title: Modulation of Ca2+-activated, phospholipid-dependent protein kinase in platelets treated with a tumor-promoting phorbol ester.
abstract: Incubation of human platelets with 12-0-tetradecanoylphorbol-13-acetate (TPA) caused a rapid decrease in soluble Ca2+, phospholipid-dependent protein kinase activity (protein kinase C) and an increase in protein kinase C associated with the particulate fraction. TPA also induced an increased activity of a Ca2+, phospholipid-independent protein kinase activity in both the soluble and the particulate fractions of platelets. This latter kinase eluted from DEAE cellulose columns at a higher salt concentration than protein kinase C, and was shown by Sephadex G-100 chromatography to have a MW of approx. 50,000 compared with an MW of 80,000 for protein kinase C. The data suggest that TPA treatment of platelets causes irreversible activation of protein kinase C by proteolysis of the enzyme to a form active in the absence of Ca2+ and phospholipid.
mesh_terms: D001792:Blood Platelets / Q000201:enzymology*; D002118:Calcium / Q000502:physiology; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D010704:Phorbols / Q000494:pharmacology*; D010743:Phospholipids / Q000502:physiology; D011493:Protein Kinase C; D011494:Protein Kinases / Q000097:blood*; D012995:Solubility; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D010704:Phorbols; D010743:Phospholipids; D011494:Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium