title: Binding mode of an α-amino acid-linked quinoxaline-2,3-dione analogue at glutamate receptor subtype GluK1.
abstract: Two α-amino acid-functionalized quinoxalines, 1a (CNG-10301) and 1b (CNG-10300), of a quinoxaline moiety coupled to an amino acid moiety were designed, synthesized, and characterized pharmacologically. While 1a displayed low affinity at native AMPA, KA, and NMDA receptors, and at homomeric GluK1,3 receptors, the affinity for GluK2 was in the midmicromolar range (Ki = 136 μM), 1b displayed low to midmicromolar range binding affinity at all the iGluRs (Ki = 9-126 μM). In functional experiments (outside-out patches excised from transfected HEK293T cells), 100 μM 1a partially blocked GluK1 (33% peak response), while GluK2 was unaffected (96% peak response). Furthermore, 1a was shown not to be an agonist at GluK1 and GluK2 at 100 μM. On the other hand, 100 μM 1b fully antagonized GluK1 (8% peak response) but only partially blocked GluK2 (33% peak response). An X-ray structure at 2.3 Å resolution of 1b in the GluK1-LBD (ligand-binding domain) disclosed an unexpected binding mode compared to the predictions made during the design phase; the quinoxaline moiety remains to act as an amino acid bioisostere, but the amino acid moiety is oriented into a new area within the GluK1 receptor. The structure of the GluK1-LBD with 1b showed a large variation in domain openings of the three molecules from 25° to 49°, demonstrating that the GluK1-LBD is capable of undergoing major domain movements.
authors: Charles S
authors: CS
authors: Demmer
authors: Charlotte
authors: C
authors: Møller
authors: Patricia M G E
authors: PM
authors: Brown
authors: Liwei
authors: L
authors: Han
authors: Darryl S
authors: DS
authors: Pickering
authors: Birgitte
authors: B
authors: Nielsen
authors: Derek
authors: D
authors: Bowie
authors: Karla
authors: K
authors: Frydenvang
authors: Jette S
authors: JS
authors: Kastrup
authors: Lennart
authors: L
authors: Bunch
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D018360:Crystallography, X-Ray; D015195:Drug Design; D018691:Excitatory Amino Acid Antagonists / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D015394:Molecular Structure; D018408:Patch-Clamp Techniques; D011810:Quinoxalines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014162:Transfection; D000097806:GluK2 Kainate Receptor
chemical_list: D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D018092:Kainic Acid Receptors; D000097806:GluK2 Kainate Receptor
keywords: Design; X-ray crystallography; domain opening; radioligand binding; synthesis