CLONING AND LOCALIZATION OF EXON 5-CONTAINING ISOFORMS OF THE NMDAR1 SUBUNIT IN HUMAN AND RAT BRAINS

Nine isoforms of the rat NMDAR1 receptor subunit have been previously identified, of which several have an alternatively spliced N-terminal insert believed to be important in proton sensitivity of the receptor. The cloning of the human homologues of NMDAR1-36 (hNMDA1-1) and NMDAR 1-4b (hNMDA1-2), both bearing the insert, is reported here. A monoclon al antibody generated against the N-terminal region of these isoforms showed reactivity with at least two distinct human brain proteins of s imilar to-115 kDa. This antibody was further characterized by using a series of truncated fusion proteins and splice variants of NMDAR1 demo nstrating its specific recognition of an epitope within the 21-amino a cid N-terminal insert, encoded by exon 5. Western blot and immunocytoc hemical studies were performed to examine the expression of the exon 5 -containing isoforms of the NMDAR1 subunit in both rat and human brain .