PI3Kgamma differentially regulates FcepsilonRI-mediated degranulation and migration of mast cells by and toward antigen

Abstract

Phosphatidylinositol 3-kinase (PI3K) has been recognized as an important downstream effector of high-affinity receptor for IgE (FcepsilonRI) signaling in mast cells, but little is known about the isoform specificity of PI3Ks on the FcepsilonRI-mediated migration toward the antigen (Ag). In the present study, we explored the role of PI3Kgamma on mast cell migration. The treatment of bone marrow-derived mast cells (BMMCs) with a PI3Kgamma inhibitor, AS605240, significantly repressed FcepsilonRI-induced degranulation and migration. The culture supernatants of wild-type mast cells stimulated with IgE and Ag attracted FcepsilonRIbeta(-/-) mast cells which did not express FcepsilonRI on their cell surface, indicating that the migration appears to be dependent on an autocrine/paracrine secretion of soluble factors from the mast cells. Adenosine, which is produced by mast cells, showed a strong activity to attract mast cells. Pertussis toxin (PTX) significantly inhibited the migration toward both the supernatant and adenosine. The supernatant from mast cells pretreated with wortmannin (Wort) and stimulated with IgE and Ag still exhibited the activity as chemoattractant, while the BMMCs pretreated with Wort did not migrate toward the supernatant. Although PTX significantly reduced the activation of AKT/PKB and migration, PTX had no effects on degranulation. These results suggest that PI3Kgamma activation through PTX-sensitive G-protein-coupled receptor as a secondary response of FcepsilonRI cross-linking regulates FcepsilonRI-mediated mast cell migration toward the Ag, while simultaneously activated PI3Kgamma through a PTX-insensitive pathway might have an effect on degranulation.