Sites in the fourth membrane-associated domain regulate alcohol sensitivity of the NMDA receptor.
N-methyl-D-aspartate (NMDA) receptors are important target sites of alcohol action in the central nervous system. Alcohol inhibits NMDA receptor current by an action on ion channel gating, apparently through a direct action on a region of the NMDA receptor accessible from the extracellular environment. Our previous studies have revealed an important role for a methionine residue (Met823) in membrane-associated domain 4 (M4) of the NR2A subunit in channel gating as well as alcohol sensitivity of the NMDA receptor. The role of sites in M4 of the NMDA receptor NR2A subunit adjacent to Met823 was investigated using tryptophan-scanning mutagenesis and electrophysiological recording. Receptors containing NR1 and NR2A(V820W) or NR2A(M817W) mutant subunits expressed in HEK 293 cells were not functional. The mutation Ala826Trp modified apparent desensitization, and the mutations Ala825Trp and Ala826Trp changed the mean open time of the channel as determined by fluctuation analysis. In addition, the mutations Tyr822Trp and Ala825Trp significantly altered the concentration-response curves for ethanol inhibition. The changes in mean open time did not appear to be able to account for the observed differences in ethanol sensitivity. These results indicate that this region in M4 of the NR2A subunit may be involved in the action of alcohol.
Unit on Cellular Neuropharmacology, Laboratory of Molecular and Cellular Neurobiology and Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-8115, USA. yhonse@mail.nih.gov
Yumiko
Y
Honse
Hong
H
Ren
Robert H
RH
Lipsky
Robert W
RW
Peoples
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*
D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D000431:Ethanol