Competitive antagonism of AMPA receptors by ligands of different classes: crystal structure of ATPO bound to the GluR2 ligand-binding core, in comparison with DNQX.
Ionotropic glutamate receptors (iGluRs) constitute a family of ligand-gated ion channels that are essential for mediating fast synaptic transmission in the central nervous system. This study presents a high-resolution X-ray structure of the competitive antagonist (S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid (ATPO) in complex with the ligand-binding core of the receptor. Comparison with the only previous structure of the ligand-binding core in complex with an antagonist, 6,7-dinitro-2,3-quinoxalinedione (DNQX) (Armstrong, N.; Gouaux, E. Neuron 2000, 28, 165-181), reveals that ATPO and DNQX stabilize an open form of the ligand-binding core by different sets of interactions. Computational techniques are used to quantify the differences between these two ligands and to map the binding site. The isoxazole moiety of ATPO acts primarily as a spacer, and other scaffolds could potentially be used. Whereas agonists induce substantial domain closures compared to the apo structure, ATPO only induces minor conformational changes. These results are consistent with the hypothesis that domain closure is related to receptor activation. To facilitate the design of novel AMPA receptor antagonists, we present a modified model of the binding site that includes key residues involved in ligand recognition.
Hogner
Anders
A
Department of Medicinal Chemistry, Royal Danish School of Pharmacy, Universitetsparken 2, DK 2100 Copenhagen, Denmark.
Greenwood
Jeremy R
JR
Liljefors
Tommy
T
Lunn
Marie-Louise
ML
Egebjerg
Jan
J
Larsen
Ingrid K
IK
Gouaux
Eric
E
Kastrup
Jette S
JS
D001665:Binding Sites; D018360:Crystallography, X-Ray; D018691:Excitatory Amino Acid Antagonists / Q000737:chemistry*; D007555:Isoxazoles / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D063065:Organophosphonates / Q000737:chemistry*; D011810:Quinoxalines / Q000737:chemistry*; D018091:Receptors, AMPA / Q000737:chemistry*
C111046:2-amino-3-(5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl)propionic acid; D018691:Excitatory Amino Acid Antagonists; D007555:Isoxazoles; D008024:Ligands; D063065:Organophosphonates; D011810:Quinoxalines; D018091:Receptors, AMPA; C056723:FG 9041; C104722:glutamate receptor ionotropic, AMPA 2