G-PROTEIN-COUPLED RECEPTORS AND FC-GAMMA-RECEPTORS MEDIATE ACTIVATIONOF AKT PROTEIN-KINASE-B IN HUMAN PHAGOCYTES

Activation of the serine/threonine kinase Akt, also called protein kin ase B (PRE), was investigated in human neutrophils. Stimulation of the cells with the chemoattractant fMet-Leu-Phe or the chemokines IL-8 an d GRO alpha leads to the rapid and transient activation of PKB. Maximu m PKB activation correlates with the well documented kinetics of respi ratory burst and exocytosis. Wortmannin, a selective inhibitor of phos phoinositide 3-kinases (PI 3-kinases) in neutrophils; abrogates PKB ac tivation. Similarly homo and heterotypic crosslinking of Fc gamma IIA and Fc gamma IIIB causes a transient activation of PKB that is sensiti ve to wortmannin treatment. Kinase activity measurements in immunoprec ipitates from lysates of the myelocytic GM-1 cells or GM-1/CXCR1 cells , which are transfected with the IL-8 receptor 1, confirmed the transi ent activation of PKB observed in neutrophils. Stimulation of human mo nocytes with the CC chemokine RANTES (regulated on activation normal T cell expressed and secreted) also results in the activation of PKB. P reincubation of monocytes and neutrophils with Bordetella pertussis to xin inhibits fMet-Leu-Phe and RANTES-stimulated PKB activation, demons trating that coupling of the receptors to heterotrimeric Gi-protein is required. The data show, that activation of PKB by G(i)-protein-coupl ed receptors is mediated by PI 3-kinase and suggest that PRE is a cons tituent of neutrophil activating pathways.