title: Structural determinants of agonist efficacy at the glutamate binding site of N-methyl-D-aspartate receptors.
abstract: N-methyl-d-aspartate (NMDA) receptors are ligand-gated ion channels assembled from GluN1 and GluN2 subunits. We used a series of N-hydroxypyrazole-5-glycine (NHP5G) partial agonists at the GluN2 glutamate binding site as tools to study activation of GluN1/GluN2A and GluN1/GluN2D NMDA receptor subtypes. Using two-electrode voltage-clamp electrophysiology, fast-application patch-clamp, and single-channel recordings, we show that propyl- and ethyl-substituted NHP5G agonists have a broad range of agonist efficacies relative to the full agonist glutamate (<1-72%). Crystal structures of the agonist binding domains (ABDs) of GluN2A and GluN2D do not reveal any differences in the overall domain conformation induced by binding of the full agonist glutamate or the partial agonist propyl-NHP5G, which is strikingly different from ABD structures of 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propanoate (AMPA) and kainate receptors bound to full and partial agonists. Subsequent evaluation of relative NHP5G agonist efficacy at GluN2A-GluN2D chimeric subunits implicates the amino-terminal domain (ATD) as a strong determinant of agonist efficacy, suggesting that interdomain interactions between the ABD and the ATD may be a central element in controlling the manner by which agonist binding leads to channel opening. We propose that variation in the overall receptor conformation, which is strongly influenced by the nature of interdomain interactions in resting and active states, mediates differences in agonist efficacy and partial agonism at the GluN2 subunits.
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, 1510 Clifton Road, Rollins Research Center, Atlanta, GA 30322, USA.
authors.forename: Kasper B
authors.initials: KB
authors.lastname: Hansen
authors.forename: Nami
authors.initials: N
authors.lastname: Tajima
authors.forename: Rune
authors.initials: R
authors.lastname: Risgaard
authors.forename: Riley E
authors.initials: RE
authors.lastname: Perszyk
authors.forename: Lars
authors.initials: L
authors.lastname: Jørgensen
authors.forename: Katie M
authors.initials: KM
authors.lastname: Vance
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Ogden
authors.forename: Rasmus P
authors.initials: RP
authors.lastname: Clausen
authors.forename: Hiro
authors.initials: H
authors.lastname: Furukawa
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Traynelis
mesh_terms: D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D005260:Female; D018698:Glutamic Acid / Q000737:chemistry* / Q000378:metabolism*; D005998:Glycine / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D018092:Kainic Acid Receptors / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry* / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D018690:Excitatory Amino Acid Agonists; D018698:Glutamic Acid; D005998:Glycine; D021122:Protein Subunits; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid