title: Thrombin-induced effects are selectively inhibited following treatment of intact human platelets with okadaic acid.
abstract: The involvement of protein phosphatases in regulating platelet activation was studied. The major portion of the phosphorylase phosphatase activity found in platelet lysates appears to be of the type 1 variety. The identification of this enzyme was based on the finding that greater than 80% of protein phosphatase activity was inhibited by the heat-stable inhibitor protein inhibitor 2 and, while only 20% of the phosphorylase phosphatase activity in platelet extracts was inhibited by 2 nM okadaic acid, greater than 95% of the activity was inhibited in the presence of 1 microM okadaic acid. Increases in protein phosphorylations occurred and thrombin-induced release of serotonin was prevented as a result of artificially inhibiting the enzyme with okadaic acid in intact platelets. This implies either that the regulation of okadaic acid sensitive protein phosphatases is necessary for some agonist-induced effects or that okadaic acid sensitive phosphatases are required for maintaining platelets in a responsive state.
authors.affiliation: Department of Cell Biology and Anatomy, New York Medical College, Valhalla 10595.
authors.forename: K M
authors.initials: KM
authors.lastname: Lerea
mesh_terms: D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002352:Carrier Proteins; D004722:Endoribonucleases; D004988:Ethers, Cyclic / Q000494:pharmacology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D015539:Platelet Activation / Q000187:drug effects; D011506:Proteins / Q000494:pharmacology*; D016601:RNA-Binding Proteins; D012694:Serine / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D013912:Threonine / Q000378:metabolism; D013917:Thrombin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000097847:Protein Phosphatase Inhibitory Proteins
chemical_list: D002352:Carrier Proteins; D004722:Endoribonucleases; D004988:Ethers, Cyclic; D047908:Intracellular Signaling Peptides and Proteins; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases; D011506:Proteins; D016601:RNA-Binding Proteins; D012694:Serine; D012701:Serotonin; D013912:Threonine; D013917:Thrombin; C021042:protein phosphatase inhibitor-1; C024833:protein phosphatase inhibitor-2; D000097847:Protein Phosphatase Inhibitory Proteins; C097081:PPP1R8 protein, human