PT - JOURNAL ARTICLE AU - Hong Ren AU - Yulin Zhao AU - Man Wu AU - Robert W. Peoples TI - A Novel Alcohol-Sensitive Position in the NMDA Receptor GluN2A Subunit M3 Domain Regulates Agonist Affinity and Ion Channel Gating AID - 10.1124/mol.113.085993 DP - 2013 Jul 11 TA - Molecular Pharmacology PG - mol.113.085993 4099 - http://molpharm.aspetjournals.org/content/early/2013/07/11/mol.113.085993.short 4100 - http://molpharm.aspetjournals.org/content/early/2013/07/11/mol.113.085993.full AB - Abundant evidence supports a role for NMDA receptor inhibition in the behavioral actions of ethanol, but the underlying molecular mechanisms have not been fully elucidated. We recently found that clusters of five positions in the third and fourth membrane-associated domains (M3 and M4) at the intersubunit interfaces form putative sites of alcohol action. In the present study, we found that one of these positions, GluN2A(F636), can strongly regulate ethanol sensitivity, glutamate potency, and apparent desensitization: ethanol IC50 values, peak (Ip) and steady-state (Iss) glutamate EC50 values, and steady-state to peak current ratio (Iss:Ip) values differed significantly among the mutants tested. Changes in glutamate affinity among the various mutants were not attributable to agonist trapping due to desensitization, as glutamate peak EC50 values were correlated with values of both steady-state EC50 and Iss:Ip. Mean open times determined in selected mutants could be altered up to four-fold, but did not account for changes in ethanol sensitivity. Ethanol sensitivity was significantly correlated with glutamate EC50 and Iss:Ip values, but the changes in ethanol IC50 among mutants at this position do not appear to be secondary to changes in ion channel kinetics. Substitution of the isomeric amino acids leucine and isoleucine had markedly different effects on ethanol sensitivity, agonist potency, and desensitization, which is consistent with a stringent structural requirement for ion channel modulation by the side chain at this position. Our results indicate that GluN2A(F636) plays an important role in both channel function and ethanol inhibition in NMDA receptors.