Identification of Rat EMAP, a δ-Glutamate Receptor Binding Protein

While most subtypes of glutamate receptors have been studied extensively, less is known about the δ-glutamate receptors, δ1 and δ2. Although neither forms functional channels when expressed in heterologous cells, genetic analyses have demonstrated the physiological significance of δ2. We used the cytosolic C-terminus of the δ2 glutamate receptor subunit in a yeast two-hybrid screen of a rat brain cDNA library to identify δ-glutamate receptor binding proteins. We isolated rat EMAP, the rat homolog of a microtubule-associated protein initially isolated and characterized in echinoderms. Rat EMAP contains 10 WD-repeats, which are domains important for mediating protein–protein interactions in a wide variety of proteins. Rat EMAP binds to δ-glutamate receptor subunits within a 50-amino-acid segment of the δ C-terminus. It is widely expressed in both brain and peripheral tissues, including high expression in brainstem and enrichment in the postsynaptic density.