Involvement of phosphatidate phosphohydrolase in arachidonic acid mobilization in human amnionic WISH cells.
Prostaglandins are known to play a central role in the initiation of labor in humans, and amnionic cells constitute a major source of these compounds. Prostaglandin synthesis and release by amnion cells in response to hormones and ligands takes place after a characteristic 4-5 h lag. However, we report herein that free arachidonic acid (AA), the metabolic precursor of prostaglandins, can be induced at much shorter times (1 h) in human amnionic WISH cells by phorbol 12-myristate 13-acetate (PMA) through activation of protein kinase Calpha (PKCalpha). WISH cells were found to possess both cytosolic group IV phospholipase A2 (cPLA2) and Group VI Ca2+-independent phospholipase A2 (iPLA2). Of these, the cPLA2 was found to be the likely mediator of AA mobilization in PMA-activated WISH cells. PMA also activates phospholipase D (PLD) in these cells and ethanol, a compound that inhibits PLD-mediated phosphatidic acid (PA) formation, blocked AA release. Moreover, prevention of PA dephosphorylation by the PA phosphohydrolase inhibitors propranolol and bromoenol lactone, resulted in inhibition of AA release by PMA-treated WISH cells. Collectively, these data suggest that activation of cPLA2 and attendant AA release by phorbol esters in WISH cells requires prior generation of DAG by phosphatidate phosphohydrolase.
Balboa
M A
MA
Department of Chemistry and Biochemistry, School of Medicine and Revelle College, University of California at San Diego, La Jolla, California 92093-0601, USA.
Balsinde
J
J
Dennis
E A
EA
D000650:Amnion / Q000378:metabolism*; D016718:Arachidonic Acid / Q000378:metabolism*; D001095:Arachidonic Acids / Q000494:pharmacology; D002478:Cells, Cultured; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D063065:Organophosphonates; D010711:Phosphatidate Phosphatase / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010766:Phosphorylation; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001095:Arachidonic Acids; D004791:Enzyme Inhibitors; D007211:Indoles; C095553:LY 311727; D063065:Organophosphonates; C104810:methyl arachidonylfluorophosphonate; D016718:Arachidonic Acid; D010741:Phospholipases A; D054467:Phospholipases A2; D010711:Phosphatidate Phosphatase; D010739:Phospholipase D; D013755:Tetradecanoylphorbol Acetate