title: Two adjacent phenylalanines in the NMDA receptor GluN2A subunit M3 domain interactively regulate alcohol sensitivity and ion channel gating.
abstract: The N-methyl-d-aspartate (NMDA) receptor is a key target of ethanol action in the central nervous system. Alcohol inhibition of NMDA receptor function involves small clusters of residues in the third and fourth membrane-associated (M) domains. Previous results from this laboratory have shown that two adjacent positions in the M3 domain, F636 and F637, can powerfully regulate alcohol sensitivity and ion channel gating. In this study, we report that these positions interact with one another in the regulation of both NMDA receptor gating and alcohol action. Using dual mutant cycle analysis, we detected interactions among various substitution mutants at these positions with respect to regulation of glutamate EC50, steady-state to peak current ratios (Iss:Ip), mean open time, and ethanol IC50. This interaction apparently involves a balancing of forces on the M3 helix, such that the disruption of function due to a substitution at one position can be reversed by a similar substitution at the other position. For example, tryptophan substitution at F636 or F637 increased or decreased channel mean open time, respectively, but tryptophan substitution at both positions did not alter open time. Interestingly, the effects of a number of mutations on receptor kinetics and ethanol sensitivity appeared to depend upon subtle structural differences, such as those between the isomeric amino acids leucine and isoleucine, as they could not be explained on the basis of sidechain molecular volume or hydrophilicity.
authors.affiliation: Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China. Electronic address: hongren169@163.com.
authors.forename: Hong
authors.initials: H
authors.lastname: Ren
authors.affiliation: Laboratory of Membrane Excitability and Disease Mount Sinai School of Medicine, 1425 Madison Avenue, ICAHN 9-26, 28, New York, NY 10029, United States. Electronic address: yulin.zhao@yahoo.com.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States. Electronic address: maw246@pitt.edu.
authors.forename: Man
authors.initials: M
authors.lastname: Wu
authors.affiliation: Department of Psychiatry, Louisiana State University Health Sciences Center, Shreveport, LA, United States. Electronic address: DDwyer@lsuhsc.edu.
authors.forename: Donard S
authors.initials: DS
authors.lastname: Dwyer
authors.affiliation: Department of Biomedical Sciences, Marquette University, Milwaukee, WI 53201-1881, United States. Electronic address: robert.peoples@marquette.edu.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Peoples
mesh_terms: D000431:Ethanol / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D009154:Mutation; D010649:Phenylalanine / Q000737:chemistry*; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D014364:Tryptophan / Q000235:genetics
chemical_list: D000431:Ethanol; D018698:Glutamic Acid; D010649:Phenylalanine; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D014364:Tryptophan
keywords: Ethanol; Glutamate; Ion channel