Chemoattractant receptor-induced hydrolysis of phosphatidylinositol 4,5-bisphosphate in human polymorphonuclear leukocyte membranes. Requirement for a guanine nucleotide regulatory protein

Incubation of plasma membranes from human polymorphonuclear leukocytes (PMNs) with [γ-³²P]ATP in the presence of MgCl₂ resulted in the formation of ³²P-labeled phosphatidic acid (PA), phosphatidylinositol 4-phosphate (PIP), and phosphatidylinositol 4,5-bisphosphate (PIP₂). Membranes from PMN specific and azurophil granules synthesized only PIP, suggesting that PIP₂ metabolism is confined to the plasma membrane in PMNs. Further incubations of the labeled plasma membranes for 60 s in the presence of 1 mM CaCl₂ resulted in the hyrolysis of approximately 40 and 50% of the labeled PIP and PIP₂, respectively. In the presence of 2 μM added CaCl₂, PIP and PIP₂ levels were unchanged by incubation with either the chemoattractant N-formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) at 0.1 μM or by 10 μM GTP; however, addition of fMet-Leu-Phe plus GTP together resulted in a 11 and 28% decrease in PIP and PIP₂, respectively. These treatments had no effect on PA levels. No additional radiolabeled organic-soluble products were detected after treatment with fMet-Leu-Phe plus GTP. Incubation of intact PMNs, with the Bordetella pertussis toxin (islet-activating protein) eliminated the ability of fMet-Leu-Phe plus GTP to promote PIP₂ breakdown in the isolated plasma membranes, but did not inhibit PIP₂ degradation in the presence of 1 mM CaCl₂. These results provide the first direct evidence that the fMet-Leu-Phe receptor in PMN membranes is coupled to polyphosphoinositide hydrolysis through an islet-activating protein-sensitive guanine nucleotide regulatory protein.