Stimulation of human neutrophils by chemotactic factors is associated with the activation of phosphatidylinositol 3-kinase γ

The activation of human polymorphonuclear neutrophil leukocytes (neutrophils) is associated with an increased synthesis of the highly phosphorylated phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P-3). The aims of the present investigation were to determine whether the newly described, G protein-dependent phosphatidylinositol 3-kinase (PI3K), p110 gamma, was involved in the responses to chemotactic factors interacting with G protein-coupled receptors. The presence of p110 gamma in neutrophils was first established both at the protein and the mRNA level. Stimulation of the cells with fMet-Leu-Phe or interleukin-8 increased the PI3K activity in p110 gamma, but not p85, immunoprecipitates. The time course of this effect (threshold within less than 5 s, maximal activation at 10-15 s) was consistent with that of the generation of PtdIns(3,4,5)P-3. Wortmannin, a PI3K inhibitor, abrogated the effects of Met-Leu-Phe, which were also significantly inhibited by pertussis toxin. Finally, fMet-Leu-Phe also induced a significant translocation of p110 gamma to a particulate fraction derived from these cells. These data indicate that p110 gamma represent the major PI3K activated by fMet-Leu-Phe and interleukin-8 at very early time points following the stimulation of human neutrophils.