THY-1 GLYCOPROTEIN AND SRC-LIKE PROTEIN-TYROSINE KINASE P53/P56(LYN) ARE ASSOCIATED IN LARGE DETERGENT-RESISTANT COMPLEXES IN RAT BASOPHILIC LEUKEMIA-CELLS

Thy-1 is a surface glycoprotein that is attached to the plasma membrane by a glycosyl-phosphatidylinositol anchor. Crosslinking of Thy-1 in rat mast cells and basophilic leukemia cells (RBL-2H3) induces cell activation including histamine release and tyrosine phosphorylation of several proteins. Here we show that glycosyl-phosphatidylinositol-linked Thy-1 forms noncovalent complexes with src-related protein-tyrosine kinase p53/p56lyn and other protein-tyrosine kinases and/or their substrates. These complexes are resistant to solubilization by a nonionic detergent, sedimentable at 200,000 x g, and very large (>10 MDa) as determined by gel chromatography. Activation of RBL-2H3 cells by crosslinking of the high-affinity IgE receptors resulted in decreased recovery of the complexes. The combined data indicate the existence of large detergent-resistant domains in the surface membrane of mast cells that may play an important role in their activation.