title: Pharmacological characterization of glutamatergic agonists and antagonists at recombinant human homomeric and heteromeric kainate receptors in vitro.
abstract: An increasing body of evidence suggests that native kainate receptors form ion channels from homomeric and heteromeric combinations of five receptor subunits: GluR5, GluR6, GluR7, KA1 and KA2. We have examined the activity of agonists and antagonists at recombinant human kainate receptors expressed in HEK293 cells, using both whole-cell electrophysiological recording and 96-well plate fluo-3 based calcium microfluorimetry (FLIPR). Both homomeric (GluR5 and GluR6) and heteromeric (GluR5/6, GluR5/KA2 and GluR6/KA2) receptors were examined. Heteromeric receptor assemblies showed electrophysiological and pharmacological profiles which were distinct from homomeric channels. Several agonists, including AMPA, ATPA and (S)-5-iodowillardiine, and antagonists, including gamma-D-glutamylaminomethylsulphonic acid (GAMS) and the decahydroisoquinoline compounds LY293558, LY377770 and LY382884, were found to act at GluR5-containing channels while having no effect at GluR6 homomers. AMPA, ATPA and (S)-5-iodowillardiine did activate GluR6/KA2 heteromers, but only as partial agonists. Additionally, ATPA was shown to act as an antagonist at homomeric GluR6 receptors at high concentrations (IC50 approximately 2 mM). Kynurenic acid was also found to differentiate between GluR6 and GluR6/KA2 receptors, antagonizing glutamate at GluR6 (IC50 = 0.4 mM), while having no effect at GluR6/KA2 channels. The results of the current study provide a broad pharmacological characterization of both homomeric and heteromeric recombinant human kainate receptors, and identify which compounds are likely to be useful tools for studying these various receptor subtypes.
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Neuroscience Discovery Research, Lilly Corporate Center, Indianapolis, IN 46285, USA. alt_andrew_jason@lilly.com
authors.forename: A
authors.initials: A
authors.lastname: Alt
authors.forename: B
authors.initials: B
authors.lastname: Weiss
authors.forename: A M
authors.initials: AM
authors.lastname: Ogden
authors.forename: J L
authors.initials: JL
authors.lastname: Knauss
authors.forename: J
authors.initials: J
authors.lastname: Oler
authors.forename: K
authors.initials: K
authors.lastname: Ho
authors.forename: T H
authors.initials: TH
authors.lastname: Large
authors.forename: D
authors.initials: D
authors.lastname: Bleakman
mesh_terms: D000818:Animals; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017470:Receptors, Glutamate / Q000502:physiology; D018092:Kainic Acid Receptors / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000502:physiology; D011994:Recombinant Proteins / Q000819:agonists / Q000037:antagonists & inhibitors
chemical_list: D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D018092:Kainic Acid Receptors; D011994:Recombinant Proteins