Identification of rat EMAP, a delta-glutamate receptor binding protein

While most subtypes of glutamate receptors have been studied extensively, less is known about the delta-glutamate receptors, delta1 and delta2. Although neither forms functional channels when expressed in heterologous cells, genetic analyses have demonstrated the physiological significance of delta2. We used the cytosolic C-terminus of the delta2 glutamate receptor subunit in a yeast two-hybrid screen of a rat brain cDNA library to identify delta-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 delta-glutamate receptor subunits within a 50-amino-acid segment of the delta C-terminus. It is widely expressed in both brain and peripheral tissues, including high expression in brainstem and enrichment in the postsynaptic density.