Gβγs and the Ras binding domain of p110γ are both important regulators of PI(3)Kγ signalling in neutrophils

Through their ability to regulate production of the key lipid messenger PtdIns(3,4,5)P-3, the class I phosphatidylinositol-3-OH kinases (PI(3)Ks) support many critical cell responses(1,2). They, in turn, can be regulated by cell-surface receptors through signals acting on either their adaptor subunits (for example, through phosphotyrosine or G beta gamma s) or their catalytic subunits (for example, through GTP-Ras). The relative significance of these controlling inputs is undefined in vivo. Here, we have studied the roles of G beta gamma s, the adaptor p101, Ras and the Ras binding domain (RBD) in the control of the class I PI(3)K, PI(3)K gamma, in mouse neutrophils. Loss of p101 leads to major reductions in the accumulation of PtdIns(3,4,5)P-3, activation of protein kinase B (PKB) and in migration towards G-protein activating ligands in vitro, and to an aseptically inflamed peritoneum in vivo. Loss of sensitivity of PI(3)K gamma to Ras unexpectedly caused similar reductions, but additionally caused a substantial loss in production of reactive oxygen species (ROS). We conclude that G beta gamma s, p101 and the Ras-RBD interaction all have important roles in the regulation of PI(3)K gamma in vivo and that they can simultaneously, but differentially, control distinct PI(3)K gamma effectors.