IDENTIFICATION OF TYROSINE-620 AS THE MAJOR PHOSPHORYLATION SITE OF MYELIN-ASSOCIATED GLYCOPROTEIN AND ITS IMPLICATION IN INTERACTING WITH SIGNALING MOLECULES

Myelin-associated glycoprotein (MAG) is a myelin-specific cell adhesio n molecule of the immunoglobulin supergene family and is tyrosine-phos phorylated in the developing brain. To define the role of MAG in signa l transduction, the tyrosine phosphorylation sites were analyzed. The major tyrosine phosphorylation residue was identified as Tyr-620, whic h was found to interact specifically with the SH2 domains of phospholi pase C (PLC gamma). This domain may represent a novel protein binding motif that can be regulated by tyrosine phosphorylation. MAG also spec ifically bound the Fyn tyrosine kinase, suggesting that MAG serves as a docking protein that allows the interaction between different signal ing molecules.