Stimulus-Coupled Activation of Phospholipase D

Activation of phospholipase D in rabbit neutrophils by fMet‐Leu‐Phe is mediated by a pertussis toxin‐sensitive GTP‐binding protein that may be distinct from a phospholipase C‐regulating protein

“…As already reported in human n©utropifils [2] When neutroDhils were treated with lAP for 3 h, [3H]PA formation stimulated by 10 "v M fMLP was inhibited by lAP in a concentration-dependent f.ashion, reaching complete inhibition at I0-I00 ng IAP/ml (Fig. 2).…”

“…Taking advantage of the latter reaction, activation of PLD in neutrophils has been well examined. A ehemotactic peptide N-formyl-Met-LeuPhe (fMLP) and a complement CSa stimulate the PLD activity in human neutrophils [2,3]. The PLD activation by fMLP in human neutrophils seems to be mediated by a pertussis toxin (IAP)-sensitive GTP-binding protein (G-protein) [4].…”

Oscillating intracellular Ca2+ signals evoked by activation of receptors linked to inositol lipid hydrolysis: Mechanism of generation

“…Diacylglycerol (DAG) is, of course, generated together with Ins (1,4,5) P3, and it cannot be excluded that different proportions of the two messengers are produced by different agonists due to differences in the relative rates of breakdown of phosphatidylinositolphosphate and phosphatidylinositol bisphosphate (Berridge, 1987). It is also now known that many stimuli can activate a phospholipase D causing hydrolysis of phosphatidylcholine which would generate DAG (Billah et al, 1989). Varying the balance between phospholipase C and D stimulation would therefore produce different Ins (1,4,5) PJDAG ratios.…”

ARF1‐regulated phospholipase D in human neutrophils is enhanced by PMA and MgATP

“…In intact cells, this enzyme activity is stimulated by a number of cell-surface receptors including G-protein-coupled receptors as well as receptors that use tyrosine kinase as their signaling mechanism [1,2]. In addition to receptor-directed agonists, both PMA, a protein kinase C (PKC) activator, and Ca" ionophores activate PLD activity in many cell types [l] including neutrophils [2][3][4]. Further evidence in support of PKC comes from studies where down regulation of PKC abolished agonist-stimulated PLD activity [5] whilst overexpression of PKC a or /I1 isoforms upregulates both PMA-activated as well as receptor-activated PLD activity [68].…”