ABSTRACT
Both Fas and PMA can activate phospholipase D via activation of protein kinase Cbeta in A20 cells. Phospholipase D activity was increased 4 fold in the presence of Fas and 2.5 fold in the presence of PMA. The possible involvement of tyrosine phosphorylation in Fas-induced activation of phospholipase D was investigated. In five minute after Fas cross-linking, there was a prominent increase in tyrosine phosphorylated proteins, and it was completely inhibited by D609, a specific inhibitor of phosphatidylcholine-specific phospholipase C (PC-PLC). A tyrosine kinase inhibitor, genistein, can partially inhibit Fas-induced phospholipase D activation. There were no effects of genistein on Fas-induced activation of PC-PLC and protein kinase C. These results strongly indicate that tyrosine phosphorylation may in part account for the increase in phospholipase D activity by Fas cross-linking and D609 can block not only PC-PLC activity but also tyrosine phosphorylation involved in Fas-induced phospholipase D activation.
Subject(s)
Mice , Animals , Antibodies, Monoclonal/immunology , fas Receptor/immunology , Bridged-Ring Compounds/pharmacology , Cell Line , Cross-Linking Reagents , Dose-Response Relationship, Immunologic , Enzyme Activation , Genistein/pharmacology , Hydrolysis , Lymphoma/pathology , Type C Phospholipases/antagonists & inhibitors , Phospholipase D/metabolism , Phosphorylation , Phosphorylcholine/metabolism , Solubility , Thiones/pharmacology , Tumor Cells, Cultured , Tyrosine/metabolism , Water/chemistryABSTRACT
Both Fas and PMA can activate phospholipase D via activation of protein kinase Cbeta in A20 cells. Phospholipase D activity was increased 4 fold in the presence of Fas and 2.5 fold in the presence of PMA. The possible involvement of tyrosine phosphorylation in Fas-induced activation of phospholipase D was investigated. In five minute after Fas cross-linking, there was a prominent increase in tyrosine phosphorylated proteins, and it was completely inhibited by D609, a specific inhibitor of phosphatidylcholine-specific phospholipase C (PC-PLC). A tyrosine kinase inhibitor, genistein, can partially inhibit Fas-induced phospholipase D activation. There were no effects of genistein on Fas-induced activation of PC-PLC and protein kinase C. These results strongly indicate that tyrosine phosphorylation may in part account for the increase in phospholipase D activity by Fas cross-linking and D609 can block not only PC-PLC activity but also tyrosine phosphorylation involved in Fas-induced phospholipase D activation.
Subject(s)
Mice , Animals , Antibodies, Monoclonal/immunology , fas Receptor/immunology , Bridged-Ring Compounds/pharmacology , Cell Line , Cross-Linking Reagents , Dose-Response Relationship, Immunologic , Enzyme Activation , Genistein/pharmacology , Hydrolysis , Lymphoma/pathology , Type C Phospholipases/antagonists & inhibitors , Phospholipase D/metabolism , Phosphorylation , Phosphorylcholine/metabolism , Solubility , Thiones/pharmacology , Tumor Cells, Cultured , Tyrosine/metabolism , Water/chemistryABSTRACT
Our previous studies have shown that subthreshold concentrations of two platelet agonists exert synergistic effects on platelet aggregation. Here we studied the mechanism of synergistic interaction of 5-hydroxytryptamine (5-HT) and epinephrine mediated platelet aggregation. We show that 5-HT had no or little effect on aggregation but it did potentiate the aggregation response of epinephrine. The synergistic interaction of 5-HT (1-5 microM) and epinephrine (0.5-2 microM) was inhibited by alpha2-adrenoceptor blocker (yohimbine; IC50= 0.4 microM), calcium channel blockers (verapamil and diltiazem with IC50 of 10 and 48 mM, respectively), PLC inhibitor (U73122; IC50=6 microM) and nitric oxide (NO) donor, SNAP (IC50=1.6 microM)). The data suggest that synergistic effects of platelet agonists are receptor-mediated and occur through multiple signalling pathways including the activation PLC/Ca2+ signalling cascades.
Subject(s)
Humans , Blotting, Western , Calcium Channel Blockers/pharmacology , Calcium Signaling , Drug Synergism , Enzyme Activation , Enzyme Inhibitors/pharmacology , Epinephrine/pharmacology , GTP-Binding Protein alpha Subunits, Gi-Go/metabolism , GTP-Binding Proteins/metabolism , Type C Phospholipases/metabolism , Type C Phospholipases/antagonists & inhibitors , Platelet Aggregation/physiology , Platelet Aggregation/drug effects , Serotonin/pharmacology , Signal TransductionABSTRACT
Várias propriedades biológicas têm sido atribuídas ao hidróxido de cálcio, tais como: açäo antiinflamatória, açäo antimicrobiana, solvente de matéria orgânica, inibiçäo da reabsorçäo e induçäo de reparo mineralizado. Neste trabalho, estas propriedades säo discutidas baseado em achados científicos