Resolution, absolute stereochemistry, and enantiopharmacology of the GluR1-4 and GluR5 antagonist 2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid.
The phosphono amino acid, (RS)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl+ ++]propio nic acid (ATPO), is a structural hybrid between the NMDA antagonist (RS)-2-amino-7-phosphonoheptanoic acid (AP7) and the AMPA and GluR5 agonist, (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA). ATPO has been resolved into (S)-ATPO and (R)-ATPO using chiral HPLC, and the absolute stereochemistry of the two enantiomers was established by an X-ray crystallographic analysis of (R)-ATPO. (S)-ATPO and (R)-ATPO were characterized pharmacologically using rat brain membrane binding and electrophysiologically using the cortical wedge preparation as well as homo- or heteromeric GluR1-4, GluR5-6, and KA2 receptors expressed in Xenopus oocytes. (R)-ATPO was essentially inactive as an agonist or antagonist in all test systems. (S)-ATPO was an inhibitor of the binding of [(3)H]AMPA (IC(50) = 16 +/- 1 microM) and of [(3)H]-6-cyano-7-nitroquinoxaline-2,3-dione ([(3)H]CNQX) (IC(50) = 1.8 +/- 0.2 microM), but was inactive in the [(3)H]kainic acid and the [(3)H]-(RS)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid ([(3)H]CPP) binding assays. (S)-ATPO did not show detectable agonist effects at any of the receptors under study, but antagonized AMPA-induced depolarization in the cortical wedge preparation (IC(50) = 15 +/- 1 microM). (S)-ATPO also blocked kainic acid agonist effects at GluR1 (K(i) = 2.0 microM), GluR1+2 (K(i) = 3.6 microM), GluR3 (K(i) = 3.6 microM), GluR4 (K(i) = 6.7 microM), and GluR5 (K(i) = 23 microM), but was inactive at GluR6 and GluR6+KA2. Thus, although ATPO is a structural analog of AP7 neither (S)-ATPO nor (R)-ATPO are recognized by NMDA receptor sites.
Møller
E H
EH
PharmaBiotec Neuroscience Research Centre, Department of Medicinal Chemistry, The Royal Danish School of Pharmacy, Copenhagen. Denmark.
Egebjerg
J
J
Brehm
L
L
Stensbøl
T B
TB
Johansen
T N
TN
Madsen
U
U
Krogsgaard-Larsen
P
P
D000818:Animals; D018360:Crystallography, X-Ray; D018691:Excitatory Amino Acid Antagonists / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D007555:Isoxazoles / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D015394:Molecular Structure; D063065:Organophosphonates / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D017470:Receptors, Glutamate / Q000145:classification / Q000187:drug effects* / Q000378:metabolism; D013237:Stereoisomerism
C111046:2-amino-3-(5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl)propionic acid; D018691:Excitatory Amino Acid Antagonists; D007555:Isoxazoles; D063065:Organophosphonates; D017470:Receptors, Glutamate