TY - JOUR

T1 - Tetrazolyl isoxazole amino acids as ionotropic glutamate receptor antagonists: synthesis, modelling and molecular pharmacology

AU - Frølund, Bente

AU - Greenwood, Jeremy R

AU - Holm, Mai Marie

AU - Egebjerg, Jan

AU - Madsen, Ulf

AU - Nielsen, Birgitte

AU - Bräuner-Osborne, Hans

AU - Stensbøl, Tine B

AU - Krogsgaard-Larsen, Povl

PY - 2005/9/15

Y1 - 2005/9/15

N2 - Two 3-(5-tetrazolylmethoxy) analogues, 1a and 1b, of (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA), a selective AMPA receptor agonist, and (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA), a GluR5-preferring agonist, were synthesized. Compounds 1a and 1b were pharmacologically characterized in receptor binding assays, and electrophysiologically on homomeric AMPA receptors (GluR1-4), homomeric (GluR5 and GluR6) and heteromeric (GluR6/KA2) kainic acid receptors, using two-electrode voltage-clamped Xenopus laevis oocytes expressing these receptors. Both analogues proved to be antagonists at all AMPA receptor subtypes, showing potencies (Kb=38-161 microM) similar to that of the AMPA receptor antagonist (RS)-2-amino-3-[3-(carboxymethoxy)-5-methyl-4-isoxazolyl]propionic acid (AMOA) (Kb=43-76 microM). Furthermore, the AMOA analogue, 1a, blocked two kainic acid receptor subtypes (GluR5 and GluR6/KA2), showing sevenfold preference for GluR6/KA2 (Kb=19 microM). Unlike the iGluR antagonist (S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid [(S)-ATPO], the corresponding tetrazolyl analogue, 1b, lacks kainic acid receptor effects. On the basis of docking to a crystal structure of the isolated extracellular ligand-binding core of the AMPA receptor subunit GluR2 and a homology model of the kainic acid receptor subunit GluR5, we were able to rationalize the observed structure-activity relationships.

AB - Two 3-(5-tetrazolylmethoxy) analogues, 1a and 1b, of (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA), a selective AMPA receptor agonist, and (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA), a GluR5-preferring agonist, were synthesized. Compounds 1a and 1b were pharmacologically characterized in receptor binding assays, and electrophysiologically on homomeric AMPA receptors (GluR1-4), homomeric (GluR5 and GluR6) and heteromeric (GluR6/KA2) kainic acid receptors, using two-electrode voltage-clamped Xenopus laevis oocytes expressing these receptors. Both analogues proved to be antagonists at all AMPA receptor subtypes, showing potencies (Kb=38-161 microM) similar to that of the AMPA receptor antagonist (RS)-2-amino-3-[3-(carboxymethoxy)-5-methyl-4-isoxazolyl]propionic acid (AMOA) (Kb=43-76 microM). Furthermore, the AMOA analogue, 1a, blocked two kainic acid receptor subtypes (GluR5 and GluR6/KA2), showing sevenfold preference for GluR6/KA2 (Kb=19 microM). Unlike the iGluR antagonist (S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid [(S)-ATPO], the corresponding tetrazolyl analogue, 1b, lacks kainic acid receptor effects. On the basis of docking to a crystal structure of the isolated extracellular ligand-binding core of the AMPA receptor subunit GluR2 and a homology model of the kainic acid receptor subunit GluR5, we were able to rationalize the observed structure-activity relationships.

KW - Animals

KW - Cell Line

KW - Computer Simulation

KW - Electrophysiology

KW - Excitatory Amino Acid Agonists

KW - Excitatory Amino Acid Antagonists

KW - Isoxazoles

KW - Models, Molecular

KW - Oocytes

KW - Patch-Clamp Techniques

KW - Propionates

KW - Rats

KW - Receptors, Glutamate

KW - Xenopus laevis

KW - alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid

U2 - 10.1016/j.bmc.2005.06.024

DO - 10.1016/j.bmc.2005.06.024

M3 - Journal article

C2 - 16043357

VL - 13

SP - 5391

EP - 5398

JO - Bioorganic & Medicinal Chemistry

JF - Bioorganic & Medicinal Chemistry

SN - 0968-0896

IS - 18

ER -