ADP-RIBOSYLATION-FACTOR-REGULATED PHOSPHOLIPASE-D ACTIVITY LOCALIZES TO SECRETORY VESICLES AND MOBILIZES TO THE PLASMA-MEMBRANE FOLLOWING N-FORMYLMETHIONYL-LEUCYL-PHENYLALANINE STIMULATION OF HUMAN NEUTROPHILS

Phospholipase D (PLD) is responsible for the hydrolysis of phosphatidy lcholine to produce phosphatidic acid and choline. Human neutrophils c ontain PLD activity which is regulated by the small GTPases, ADP-ribos ylation factor (ARF) and Rho proteins. In this study we have examined the subcellular localization of the ARF-regulated PLD activity in non- activated neutrophils and cells 'primed' with N-formylmethionyl-leucyl -phenylalanine (fMetLeuPhe). We report that PLD activity is localized at the secretory vesicles in control cells and is mobilized to the pla sma membrane upon stimulation with fMetLeuPhe. We conclude that the AR F-regulated PLD activity is translocated to the plasma membrane by sec retory vesicles upon stimulation of neutrophils with fMetLeuPhe in inf lammatory/priming doses. We propose that this relocalization of PLD is important for the subsequent events occurring during neutrophil activ ation.