TY - JOUR

T1 - Stereochemistry and molecular pharmacology of (S)-thio-ATPA, a new potent and selective GluR5 agonist

AU - Stensbøl, T B

AU - Jensen, H S

AU - Nielsen, B

AU - Johansen, T N

AU - Egebjerg, J

AU - Frydenvang, Karla Andrea

AU - Krogsgaard-Larsen, P

PY - 2001

Y1 - 2001

N2 - (RS)-2-Amino-3-(5-tert-butyl-3-hydroxy-4-isothiazolyl)propionic acid (thio-ATPA), a 3-isothiazolol analogue of (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA), has previously been shown to be a relatively weak AMPA receptor agonist at native (S)-glutamic acid ((S)-Glu) receptors (EC(50)=14 microM), comparable in potency with ATPA (EC(50)=34 microM). Recent findings, that (S)-ATPA is a potent (EC(50)=0.48 microM) and selective agonist at homomerically expressed ionotropic GluR5, prompted us to resolve thio-ATPA using chiral chromatography and pharmacologically characterize the two enantiomers at native as well as cloned ionotropic glutamate receptors. The enantiomers, (S)- and (R)-thio-ATPA, were obtained in high enantiomeric excess, and their absolute stereochemistry established by an X-ray crystallographic analysis. Electrophysiologically, the two enantiomers were evaluated in the rat cortical wedge preparation, and the S-enantiomer was found to be an AMPA receptor agonist (EC(50)=8.7 microM) twice as potent as the racemate, whereas the R-enantiomer was devoid of activity. In accordance with this, (S)-thio-ATPA proved to be an agonist at homomerically expressed recombinant AMPA receptors (GluR1o, GluR3o, and GluR4o) with EC(50) values of 5, 32 and 20 microM, respectively, producing maximal steady state currents of 78--168% of those maximally evoked by kainic acid, and 120-1600% of those maximally evoked by (S)-ATPA. At homomerically expressed GluR5, (S)-thio-ATPA was found to be a potent agonist (EC(50)=0.10 microM), thus being approximately five times more potent than (S)-ATPA. (R)-Thio-ATPA induced saturating currents with an estimated EC(50) value of 10 microM, most likely due to a contamination with (S)-thio-ATPA. At heteromerically expressed GluR6+KA2 receptors, (S)-thio-ATPA showed relatively weak agonistic properties (EC(50)=4.9 microM). Thus, (S)-thio-ATPA has been shown to be a very potent agonist at GluR5, and may be a valuable tool for the investigation of desensitization properties of AMPA receptors.

AB - (RS)-2-Amino-3-(5-tert-butyl-3-hydroxy-4-isothiazolyl)propionic acid (thio-ATPA), a 3-isothiazolol analogue of (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA), has previously been shown to be a relatively weak AMPA receptor agonist at native (S)-glutamic acid ((S)-Glu) receptors (EC(50)=14 microM), comparable in potency with ATPA (EC(50)=34 microM). Recent findings, that (S)-ATPA is a potent (EC(50)=0.48 microM) and selective agonist at homomerically expressed ionotropic GluR5, prompted us to resolve thio-ATPA using chiral chromatography and pharmacologically characterize the two enantiomers at native as well as cloned ionotropic glutamate receptors. The enantiomers, (S)- and (R)-thio-ATPA, were obtained in high enantiomeric excess, and their absolute stereochemistry established by an X-ray crystallographic analysis. Electrophysiologically, the two enantiomers were evaluated in the rat cortical wedge preparation, and the S-enantiomer was found to be an AMPA receptor agonist (EC(50)=8.7 microM) twice as potent as the racemate, whereas the R-enantiomer was devoid of activity. In accordance with this, (S)-thio-ATPA proved to be an agonist at homomerically expressed recombinant AMPA receptors (GluR1o, GluR3o, and GluR4o) with EC(50) values of 5, 32 and 20 microM, respectively, producing maximal steady state currents of 78--168% of those maximally evoked by kainic acid, and 120-1600% of those maximally evoked by (S)-ATPA. At homomerically expressed GluR5, (S)-thio-ATPA was found to be a potent agonist (EC(50)=0.10 microM), thus being approximately five times more potent than (S)-ATPA. (R)-Thio-ATPA induced saturating currents with an estimated EC(50) value of 10 microM, most likely due to a contamination with (S)-thio-ATPA. At heteromerically expressed GluR6+KA2 receptors, (S)-thio-ATPA showed relatively weak agonistic properties (EC(50)=4.9 microM). Thus, (S)-thio-ATPA has been shown to be a very potent agonist at GluR5, and may be a valuable tool for the investigation of desensitization properties of AMPA receptors.

KW - Alanine

KW - Animals

KW - Chromatography, High Pressure Liquid

KW - Cloning, Molecular

KW - Excitatory Amino Acid Agonists

KW - Kinetics

KW - Membrane Potentials

KW - Molecular Conformation

KW - Oocytes

KW - Patch-Clamp Techniques

KW - Rats

KW - Receptors, AMPA

KW - Stereoisomerism

KW - Thiazoles

KW - Transcription, Genetic

KW - Xenopus laevis

M3 - Journal article

C2 - 11164381

VL - 411

SP - 245

EP - 253

JO - European Journal of Pharmacology

JF - European Journal of Pharmacology

SN - 0014-2999

IS - 3

ER -