Antagonist Properties of a Phosphono Isoxazole Amino Acid at Glutamate R1–4 (R,S)-2-Amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic Acid Receptor Subtypes

  1. Philip Wahl1,
  2. Charlotte Anker1,
  3. Stephen F. Traynelis2,
  4. Jan Egebjerg3,
  5. Jesper S. Rasmussen3,
  6. Povl Krogsgaard-Larsen4 and
  7. Ulf Madsen4
  1. 1Department of Molecular Pharmacology, Novo Nordisk A/S, Novo Nordisk Park, DK-2760 Maaloev, Denmark (P.W., C.A.), 2Department of Pharmacology, Emory University, Atlanta, GA 30322-3090, USA (S.F.T.),3Department of Molecular Genetics, Novo Nordisk A/S, DK-2880 Bagsværd, Denmark (J.E., J.S.R.) and 4Department of Medicinal Chemistry, The Royal Danish School of Pharmacy, DK-2100 Copenhagen, Denmark (P.K.-L., U.M.)

    Abstract

    The activity of the (R,S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptor antagonist, (R,S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid (ATPO), at recombinant ionotropic glutamate receptors (GluRs) was evaluated using electrophysiological techniques. Responses at homo- or heterooligomeric AMPA-preferring GluRs expressed in human embryonic kidney (HEK) 293 cells (GluR1-flip) or Xenopus laevisoocytes (GluR1–4-flop or GluR1-flop + GluR2) were potently inhibited by ATPO with apparent dissociation constants (Kb values) ranging from 3.9 to 26 μm. A Schild analysis for kainate (KA)-activated GluR1 receptors showed ATPO to have aKB of 8.2 μmand a slope of unity, indicating competitive inhibition. The antagonism by ATPO at GluR1 was of similar magnitude at holding potentials between −100 mV and +20 mV. In contrast, ATPO (<300 μm), does not inhibit responses to kainate at homomeric GluR6 or heterooligomeric GluR6/KA2 expressed in HEK 293 cells but activated GluR5 and GluR5/KA2 expressed in X. laevis oocytes. ATPO produced <15% inhibition at the maximal concentration (300 μm) of current responses through NR1A + NR2B receptors expressed in X.laevis oocytes. Thus, ATPO shows a unique pharmacological profile, being an antagonist at GluR1–4 and a weak partial agonist at GluR5 and GluR5/KA2.

    Footnotes

    • Send reprint requests to: Philip Wahl, Ph.D., Department of Molecular Pharmacology, Novo Nordisk A/S, Novo Nordisk Park, DK 2760 Maaloev, Denmark. E-mail: pwa{at}novo.dk

    • This work was supported by grants from the European Economic Community (BIO2-CT93-0243) and the John Merck Fund.

    • Abbreviations:
      AMOA
      (R,S)-2-amino-3-[3-(carboxymethoxy)-5-methyl-4-isoxazolyl]propionic acid
      AMPA
      (R,S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid
      ATPO
      (R,S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid
      GluR
      glutamate receptor
      HEK
      human embryonic kidney
      KA
      kainate
      NBQX
      2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(f)quinoxaline
      NMDA
      N-methyl-d-aspartate
      NR1
      N-methyl-d-aspartate receptor subunits 1
      NR2
      N-methyl-d-aspartate receptor subunits 2
      BAPTA
      1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid
      HEPES
      4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
      • Received July 18, 1997.
      • Accepted November 5, 1997.
    « Previous | Next Article »Table of Contents

    This Article

    1. Molecular Pharmacology March 1, 1998 vol. 53 no. 3 590-596
    1. » Abstract
    2. Full Text
    3. Full Text (PDF)

    Classifications

    Responses

    1. Submit a response
    2. No responses published

    Current Issue

    1. November 2009, 76 (5)
    1. Current Issue
    1. Alert me to new issues of Molecular Pharmacology