title: Characterisation of the human NMDA receptor subunit NR3A glycine binding site.
abstract: In this study, we characterise the binding site of the human N-methyl-d-aspartate (NMDA) receptor subunit NR3A. Saturation radioligand binding of the NMDA receptor agonists [(3)H]-glycine and [(3)H]-glutamate showed that only glycine binds to human NR3A (hNR3A) with high affinity (K(d)=535nM (277-793nM)). Eight amino acids, which correspond to amino acids that are critical for ligand binding to other NMDA receptor subunits, situated within the S1S2 predicted ligand binding domain of hNR3A were mutated, which resulted in complete or near complete loss of [(3)H]-glycine binding to hNR3A. The NMDA NR1 glycine site agonist d-serine and partial agonist HA-966 (3-amino-1-hydroxypyrrolid-2-one), similarly to glycine displaced [(3)H]-glycine monophasically, suggesting a single common binding site. However, neither the partial agonist d-cycloserine nor the antagonist 7-chlorokynurenic acid displaced [(3)H]-glycine. Using homology modelling, a model of the NR3A binding pocket was generated which we suggest can be used to identify candidate agonists and antagonists. Our data show that glycine is a ligand, and most probably the endogenous ligand, for native NR3A at a binding site with unique pharmacological characteristics.
authors.affiliation: Division of Neurodegeneration and Neuroinflammation, Department of Neurobiology, Caring Sciences and Society, Karolinska Institutet, Novum, S-141 86 Stockholm, Sweden. anna.nilsson.2@ki.se
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
authors.forename: J
authors.initials: J
authors.lastname: Duan
authors.forename: L-L
authors.initials: LL
authors.lastname: Mo-Boquist
authors.forename: E
authors.initials: E
authors.lastname: Benedikz
authors.forename: E
authors.initials: E
authors.lastname: Sundström
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects*; D001921:Brain / Q000187:drug effects; D002461:Cell Line, Transformed; D003523:Cycloserine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005998:Glycine / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D007736:Kynurenic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008958:Models, Molecular; D009154:Mutation / Q000502:physiology; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D014162:Transfection
chemical_list: D018691:Excitatory Amino Acid Antagonists; C464437:NR3A NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D003523:Cycloserine; D007736:Kynurenic Acid; C057013:7-chlorokynurenic acid; D005998:Glycine