GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR (GM-CSF) PRIMES HUMAN NEUTROPHILS FOR ENHANCED PHOSPHATIDYLCHOLINE BREAKDOWN BY PHOSPHOLIPASE-D

GM-CSF has previously been shown to increase human neutrophil phospholipase D (PLD) activity in response to fMLP. To further define the mechanism by which GM-CSF up-regulates PLD activity, we investigated the effect of GM-CSF pretreatment of neutrophils on phosphatidylcholine breakdown in response to a receptor-coupled stimulus N-formyl-methionyl-leucyl-phenylalanine (fMLP) and to a receptor-independent stimulus phorbol-myristate-acetate (PMA). Treatment of 1-0-[H-3]alkyl-2-acetylsn-glycero-3-phosphocholine-prelabeled human neutrophils with 200 pM GM-CSF for 1 hour at 37-degrees-C led to a more rapid and increased accumulation (2-3 fold) of [H-3]-alkyl-phosphatidic acid (or [H-3]-alkyl-phosphatidylethanol when cells are stimulated in presence of 0.5% ethanol) in response to both fMLP or PMA. The data indicate GM-CSF up-regulates phosphatidylcholine hydrolysis by a PLD by interfering with the excitation-response coupling sequence at a site distal to the fMLP receptor.