ROLE OF PHOSPHATIDYLINOSITOL 3-KINASE IN DEGRANULATION INDUCED BY IGE-DEPENDENT AND IGE-INDEPENDENT MECHANISMS IN RAT BASOPHILIC RBL-2H3(ML)-CELLS

We have examined the role of phosphatidylinositol 3-kinase (PI3-kinase ) in the degranulation induced by the antigen, an IgE-dependent stimul ant, and by carbachol and thapsigargin, IgE-independent stimulants, in the muscarine ml receptor-transfected mast cell line RBL-2H3 (ml) cel ls. These stimulants commonly increased PI3-kinase activity in the ant i-phosphotyrosine immunoprecipitate. The PI3-kinase inhibitors wortman nin and LY294002 inhibited the degranulation induced by these stimulan ts. The membrane ruffling induced by the antigen or carbachol was also inhibited by wortmannin. In contrast, thapsigargin induced by membran e ruffling but induced microspikes, which was not affected by wortmann in. In the permeabilized RBL-2H3 (mi) cells, wortmannin inhibited the GTP gamma S-induced membrane ruffling without inhibiting the GTP gamma S-induced degranulation. These findings suggest that PI3-kinase is in volved not only in IgE-dependent degranulation but also in IgE-indepen dent degranulation, and that the GTP gamma S-sensitive protein at the downstream of PI3-kinase is responsible for the degranulation but not for the membrane ruffling. (C) 1997 Elsevier Science Inc.