ACTIVATION OF MULTIPLE PROTEIN-KINASES INCLUDING A MAP KINASE UPON FC-EPSILON-RI CROSS-LINKING

Previous studies have shown that protein-serine/threonine kinases and protein-tyrosine kinase(s) are activated by cross-linking of the high- affinity receptor for IgE, FcepsilonRI, on mast cells and basophils. I n vitro kinase assays (ISDR kinase assays) on cellular proteins immobi lized on polyvinylidene difluoride membrane after denaturation and ren aturation were employed to estimate the complexity of protein kinases expressed in mouse mast cells. The results demonstrated that a large n umber (more than 60) of both serine/threonine- and tyrosine-specific k inases are present in a mouse mast cell line, PT-18. Cross-linking of FcepsilonRI-induced activation of a subset of both serine/threonine ki nases and tyrosine kinases in PT-18 as well as bone marrow-derived mou se mast cells, as revealed by the ISDR kinase assay. Among them, MAP k inase (or ERK2) was shown to be tyrosine -phosphorylated and activated transiently upon FcepsilonRI cross-linking, suggesting its potential role in mast cell signal transduction.