Pharmacological and structural characterization of conformationally restricted (S)-glutamate analogues at ionotropic glutamate receptors.
Conformationally restricted glutamate analogues have been pharmacologically characterized at AMPA and kainate receptors and the crystal structures have been solved of the ligand (2S,1'R,2'S)-2-(2'-carboxycyclobutyl)glycine (CBG-IV) in complex with the ligand binding domains of the AMPA receptor GluA2 and the kainate receptor GluK3. These structures show that CBG-IV interacts with the binding pocket in the same way as (S)-glutamate. The binding affinities reveal that CBG-IV has high affinity at the AMPA and kainate receptor subtypes. Appreciable binding affinity of CBG-IV was not observed at NMDA receptors, where the introduction of the carbocyclic ring is expected to lead to a steric clash with binding site residues. CBG-IV was demonstrated to be an agonist at both GluA2 and the kainate receptor GluK1. CBG-IV showed high affinity binding to GluK1 compared to GluA2, GluK2 and GluK3, which exhibited lower affinity for CBG-IV. The structure of GluA2 LBD and GluK3 LBD in complex with CBG-IV revealed similar binding site interactions to those of (S)-glutamate. No major conformational rearrangements compared to the (S)-glutamate bound conformation were found in GluK3 in order to accommodate CBG-IV, in contrast with GluA2 where a shift in lobe D2 binding site residues occurs, leading to an increased binding cavity volume compared to the (S)-glutamate bound structure.
Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
Lina
L
Juknaitė
Raminta
R
Venskutonytė
Zeinab
Z
Assaf
Sophie
S
Faure
Thierry
T
Gefflaut
David J
DJ
Aitken
Birgitte
B
Nielsen
Michael
M
Gajhede
Jette S
JS
Kastrup
Lennart
L
Bunch
Karla
K
Frydenvang
Darryl S
DS
Pickering
D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003503:Cyclobutanes / Q000737:chemistry*; D005971:Glutamates / Q000737:chemistry*; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011485:Protein Binding; D051381:Rats; D018091:Receptors, AMPA / Q000819:agonists / Q000737:chemistry*; D018092:Kainic Acid Receptors / Q000819:agonists / Q000737:chemistry*; D013237:Stereoisomerism; D000097808:GluK3 Kainate Receptor
D003503:Cyclobutanes; D005971:Glutamates; D005998:Glycine; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D000097808:GluK3 Kainate Receptor; C515234:2-(2-carboxycyclobutyl)glycine; C104722:glutamate receptor ionotropic, AMPA 2