Induction of cytosolic phospholipase A sub(2) activity by phosphatidic acid and diglycerides in permeabilized human neutrophils: Interrelationship between phospholipases D and A sub(2)

• Published in: Biochemical journal Vol. 322; no. 2; pp. 353 - 363
• Main Authors: Bauldry, SA, Wooten, R E
• Format: Journal Article
• Language: English
• Published: 01.03.1997
• ISSN: 0264-6021

Relationships between phospholipases are poorly understood, but phosphatidic acid (PA) and diglycerides (DGs), produced by phospholipase D (PLD) and phosphatidate phosphohydrolase actions, might function as second messengers coupling cell stimulation to cellular responses. This study investigates the role of PLD-mediated PA and DG formation in inducing phospholipase A sub(2) (PLA sub(2)) activity in intact human neutrophils (PMNs) and in PMNs permeabilized with Staphylococcus aureus alpha -toxin. PMNs were labelled with [ super(3)H]arachidonic acid (AA) to assess AA release and metabolism and diacylglycerol formation, or with [ super(3)H]1-O-hexadecyl-2-lyso-glycerophosphatidylcholine for the determination of platelet-activating factor (PAF), PA and alkylacylglycerol production. In intact PMNs primed with tumour necrosis factor alpha before stimulation with N-formyl-Met-Leu-Phe, AA release and metabolism and PAF formation increased in parallel with enhanced PA and DG formation, and inhibition of PA and DG production led to a decrease in both AA release and PAF accumulation. In alpha -toxin-permeabilized PMNs, AA release and PAF production result from the specific activation of cytosolic PLA sub(2) (cPLA sub(2)). In this system, PA and DG formation were always present when cPLA sub(2) activation occurred; blocking PA and DG production inhibited AA release and PAF accumulation. Adding either PA or DG back to permeabilized cells (with endogenous PA and DG formation blocked) led to a partial restoration of AA release and PAF formation; a combination of PA and DGs reconstituted full cPLA sub(2) activity. These results strongly suggest that products of PLD participate in activating cPLA sub(2) in PMNs.