Crystal structures of the kainate receptor GluR5 ligand binding core dimer with novel GluR5-selective antagonists.
Glutamate receptor (GluR) ion channels mediate fast synaptic transmission in the mammalian CNS. Numerous crystallographic studies, the majority on the GluR2-subtype AMPA receptor, have revealed the structural basis for binding of subtype-specific agonists. In contrast, because there are far fewer antagonist-bound structures, the mechanisms for antagonist binding are much less well understood, particularly for kainate receptors that exist as multiple subtypes with a distinct biology encoded by the GluR5-7, KA1, and KA2 genes. We describe here high-resolution crystal structures for the GluR5 ligand-binding core complex with UBP302 and UBP310, novel GluR5-selective antagonists. The crystal structures reveal the structural basis for the high selectivity for GluR5 observed in radiolabel displacement assays for the isolated ligand binding cores of the GluR2, GluR5, and GluR6 subunits and during inhibition of glutamate-activated currents in studies on full-length ion channels. The antagonists bind via a novel mechanism and do not form direct contacts with the E723 side chain as occurs in all previously solved AMPA and kainate receptor agonist and antagonist complexes. This results from a hyperextension of the ligand binding core compared with previously solved structures. As a result, in dimer assemblies, there is a 22 A extension of the ion channel linkers in the transition from antagonist- to glutamate-bound forms. This large conformational change is substantially different from that described for AMPA receptors, was not possible to predict from previous work, and suggests that glutamate receptors are capable of much larger movements than previously thought.
Porter Neuroscience Research Center, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, USA. mayerm@mail.nih.gov
Mark L
ML
Mayer
Alokesh
A
Ghosal
Nigel P
NP
Dolman
David E
DE
Jane
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D018691:Excitatory Amino Acid Antagonists / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D011487:Protein Conformation / Q000187:drug effects; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000737:chemistry; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors / Q000737:chemistry*; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry; D013941:Thymine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D014982:Xenopus laevis; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000097806:GluK2 Kainate Receptor
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000409:Alanine; D018691:Excitatory Amino Acid Antagonists; D018698:Glutamic Acid; D011810:Quinoxalines; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D011993:Recombinant Fusion Proteins; D013941:Thymine; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D000097806:GluK2 Kainate Receptor; C509618:1-(2-amino-2-carboxyethyl)-3-(2-carboxybenzyl)pyrimidine-2,4-dione; C509619:UBP 310; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; C056723:FG 9041; C104722:glutamate receptor ionotropic, AMPA 2