COOPERATION OF PHOSPHATIDYLINOSITOL TRANSFER PROTEIN WITH PHOSPHOINOSITIDE 3-KINASE-GAMMA IN THE FORMYLMETHIONYL-LEUCYLPHENYLALANINE-DEPENDENT PRODUCTION OF PHOSPHATIDYLINOSITOL 3,4,5-TRISPHOSPHATE IN HUMAN NEUTROPHILS

Phosphoinositide 3-kinase (PI3K) and its product phosphatidylinositol 3,4,5-trisphosphate (PIP3) play an essential role in the regulation of neutrophil functions by the chemoattractant formylmethionyl-leucylphe nylalanine (FMLP). Here we show that permeabilization of human neutrop hils leads to loss of cytosolic components, including P13K gamma, and causes the loss of FMLP-dependent production of PIP3. FMLP-sensitive s ynthesis of PIP3 could be restored by reconstitution of permeabilized neutrophils with recombinant PI3K gamma, Admixture of recombinant phos phatidylinositol transfer protein (PITP) to the reconstitution cocktai l produced a further increase of PIP3 synthesis, whereas pertussis tox in suppressed the FMLP-dependent production of PIP3. We conclude that FMLP-sensitive PIP3 formation in human neutrophils involves the FMLP r eceptor, heterotrimeric G-proteins of the G(i) type, PI3K gamma and PI TP.