Src family tyrosine kinase p53/56 super(lyn), a serine kinase and Fc epsilon RI associate with alpha -galactosyl derivatives of ganglioside GD sub(1b) in rat basophilic leukemia RBL-2H3 cells

The monoclonal antibody (mAb) AA4 recognizes two alpha -galactosyl derivatives of the GD sub(1b) ganglioside on rat mast cells and on the rat basophilic leukemia RBL-2H3 cultured cell line. Here we demonstrate that mAb AA4 coprecipitated both protein tyrosine and serine kinases. In contrast, a monoclonal antibody to the GD sub(3) ganglioside did not coprecipitate any kinase activity. In kinase assays of mAb AA4 immunoprecipitates there were phosphorylated proteins of 71-80, 53/56, and 41/42 kDa. All proteins were phosphorylated on tyrosine, whereas the 71-80- and 41/42-kDa proteins were also phosphorylated on serine residues. The precipitation of these proteins by mAb AA4 correlated with the presence of the alpha -galactosyl derivatives of GD sub(1b). The 53/56-kDa proteins were identified as the Src-related tyrosine kinase p53/56 super(lyn). The presence of p53/56 super(lyn) in the mAb AA4 immunoprecipitates was specific and was observed when several different detergents were used. The same 71-80-kDa tyrosine-phosphorylated proteins were immunoprecipitated by mAb AA4 and anti-Lyn antibodies and may play a role in the interaction of p53/56 super(lyn) with the gangliosides. Although there is a weak association of the high affinity IgE receptor with these gangliosides, the coprecipitation of p53/56 super(lyn) with mAb AA4 was not secondary to the association of this kinase with receptor. These complexes of gangliosides and several proteins that include p53/56 super(lyn), a serine kinase, and the high affinity IgE receptor could play an important role in receptor-mediated signal transduction.