Procedures for analyzing the tyrosine phosphorylation of synaptic glycoproteins

Abstract Synaptic membranes and postsynaptic densities (PSDs) express tyrosine kinase activity and phosphorylate a number of endogenous proteins on tyrosine residues. Isolation of concanavalin A-binding glycoproteins and immunoblotting with anti-phosphotyrosine antibodies identified the postsynaptic density-associated glycoprotein PSD-GP180 as the only glycoprotein that is phosphorylated on tyrosine residues in PSDs. Changes in the tyrosine kinase activity of synaptic membranes and PSDs have suggested that tyrosine phosphorylation may be involved in the formation or maturation of new synaptic contacts in the developing brain. The present paper describes procedures for the analysis of tyrosine kinase activity and the phosphorylation of glycoproteins in postsynaptic densities prepared from rat forebrain.