TLR-4 mediated group IVA phospholipase A(2) activation is phosphatidic acid phosphohydrolase 1 and protein kinase C dependent.
Group IVA phospholipase A(2) (GIVA PLA(2)) catalyzes the release of arachidonic acid (AA) from the sn-2 position of glycerophospholipids. AA is then further metabolized into terminal signaling molecules including numerous prostaglandins. We have now demonstrated the involvement of phosphatidic acid phosphohydrolase 1 (PAP-1) and protein kinase C (PKC) in the Toll-like receptor-4 (TLR-4) activation of GIVA PLA(2). We also studied the effect of PAP-1 and PKC on Ca+2 induced and synergy enhanced GIVA PLA(2) activation. We observed that the AA release induced by exposure of RAW 264.7 macrophages to the TLR-4 specific agonist Kdo(2)-Lipid A is blocked by the PAP-1 inhibitors bromoenol lactone (BEL) and propranolol as well as the PKC inhibitor Ro 31-8220; however these inhibitors did not reduce AA release stimulated by Ca+2 influx induced by the P2X7 purinergic receptor agonist ATP. Additionally, stimulation of cells with diacylglycerol (DAG), the product of PAP-1 mediated hydrolysis, initiated AA release from unstimulated cells as well as restored normal AA release from cells treated with PAP-1 inhibitors. Finally, neither PAP-1 nor PKC inhibition reduced GIVA PLA(2) synergistic activation by stimulation with Kdo(2)-Lipid A and ATP.
Grkovich
Andrej
A
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0601, USA.
Armando
Aaron
A
Quehenberger
Oswald
O
Dennis
Edward A
EA
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D004357:Drug Synergism; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D054513:Group IV Phospholipases A2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D009281:Naphthalenes / Q000494:pharmacology; D000073718:Pancreatitis-Associated Proteins; D010711:Phosphatidate Phosphatase / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011753:Pyrones / Q000494:pharmacology; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
D004075:Diglycerides; C506188:Kdo2-lipid A; D008070:Lipopolysaccharides; D009281:Naphthalenes; D000073718:Pancreatitis-Associated Proteins; C516390:Pla2g4a protein, mouse; D011753:Pyrones; C000612141:REG3A protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D016718:Arachidonic Acid; D004533:Egtazic Acid; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D000255:Adenosine Triphosphate; D004492:Edetic Acid; D011433:Propranolol; D011493:Protein Kinase C; D054513:Group IV Phospholipases A2; D010711:Phosphatidate Phosphatase