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Deletion of the N‐Terminal Domain Alters the Ethanol Inhibition of N ‐Methyl‐ d ‐Aspartate Receptors in a Subunit‐Dependent Manner
Author(s) -
Smothers Corigan T.,
Jin Chun,
Woodward John J.
Publication year - 2013
Publication title -
alcoholism: clinical and experimental research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.267
H-Index - 153
eISSN - 1530-0277
pISSN - 0145-6008
DOI - 10.1111/acer.12168
Subject(s) - ifenprodil , nmda receptor , receptor , protein subunit , chemistry , glutamate receptor , biochemistry , pharmacology , biology , gene
Background Ethanol ( E t OH ) inhibition of N ‐methyl‐ d ‐aspartate ( NMDA ) receptors is poorly understood due in part to the organizational complexity of the receptor that provides ample locations for sites of action. Among these, the N‐terminal domain ( NTD ) of NMDA receptor subunits contains binding sites for a variety of modulatory agents including zinc, protons, and GluN2B selective antagonists such as ifenprodil or Ro‐25‐6981. E t OH inhibition of neuronal NMDA receptors expressed in some brain areas has been reported to be occluded by the presence of ifenprodil or similar compounds suggesting that the NTD may be important in regulating the E t OH sensitivity of NMDA receptors. Methods Wild‐type GluN1 and GluN2 subunits and those in which the coding sequence for the NTD was deleted were expressed in HEK 293 cells. Whole‐cell voltage‐clamp recording was used to assess E t OH inhibition of wild‐type and mutant receptors lacking the NTD . Results As compared to wild‐type GluN1/GluN2A receptors, E t OH inhibition was slightly greater in cells expressing GluN2A subunits lacking the NTD . In contrast, GluN2B N‐terminal deletion mutants showed normal E t OH inhibition while those lacking the NTD in both GluN1 and GluN2B subunits had decreased E t OH inhibition as compared to wild‐type receptors. NTD lacking GluN2B receptors were insensitive to ifenprodil but retained normal sensitivity to E t OH . Conclusions These findings indicate that the NTD modestly influences the E t OH sensitivity of NMDA receptors in a subunit‐dependent manner. They also show that ifenprodil's actions on GluN2B‐containing receptors can be dissociated from those of E t OH . These results suggest that while the NTD is not a primary site of action for E t OH on NMDA receptors, it likely affects sensitivity via actions on intrinsic channel properties.