Cloning and expression of the ε4 subunit of the NMDA receptor channel

The primary structure of a novel subunit of the mouse NMDA (N-methyl-d-aspartate) receptor channel, designated ε4, has been revealed by cloning and sequencing the cDNA. The ε4 subunit shares high amino acid sequence identity with the ε1, ε2 and ε3 subunits of the mouse NMDA. receptor channel, thus constituting the ε subfamily of the glutamate receptor channel. Expression from cloned cDNAs of the ε4 subunit together with the ζ1 subunit in Xenopus oocytes yields Functional NMDA receptor channels. The ε4/ζ1 heteromeric channel exhibits high apparent affinities for agonists and low sensitivities to competitive antagonists. The ε4 subunit is thus distinct in Functional properties from the ε1, ε2 and ε3 subunits, and contributes further diversity of the NMDA receptor channel.