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Tyrosine Phosphorylation Is Involved In Receptor Coupling To Phospholipase D But Not Phospholipase C In The Human Neutrophil

I J Uings, N T Thompson, R W Randall, G D Spacey, R W Bonser, A T Hudson, L G Garland

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The tyrosine kinase inhibitors ST271, ST638 and erbstatin inhibited phospholipase D (PLD) activity in human neutrophils stimulated by fMet-Leu-Phe, platelet-activating factor and leukotriene B4. These compounds did not inhibit phorbol ester-stimulated PLD, indicating that they do not inhibit PLD per se, but probably act at a site between the receptor and the phospholipase. In contrast, the protein kinase C inhibitor Ro-31-8220 inhibited phorbol 12,13-dibutyrate- but not fMet-Leu-Phe-stimulated PLD activity, arguing against the involvement of protein kinase C in the receptor-mediated activation of PLD. ST271 did not inhibit Ins(1,4,5)P3 generation, but did inhibit protein tyrosine phosphorylation stimulated by fMet-Leu-Phe. The phosphotyrosine phosphatase inhibitor pervanadate increased tyrosine phosphorylation and stimulated PLD. These results suggest that tyrosine kinase activity is involved in receptor coupling to PLD but not to PtdIns(4,5)P2-specific phospholipase C in the human neutrophil.