Stimulation of human neutrophils by chemotactic factors is associated withthe activation of phosphatidylinositol 3-kinase gamma

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