Synthesis of GABAA receptor agonists and evaluation of their alpha-subunit selectivity and orientation in the GABA binding site.
Drugs used to treat various disorders target GABA A receptors. To develop alpha subunit selective compounds, we synthesized 5-(4-piperidyl)-3-isoxazolol (4-PIOL) derivatives. The 3-isoxazolol moiety was substituted by 1,3,5-oxadiazol-2-one, 1,3,5-oxadiazol-2-thione, and substituted 1,2,4-triazol-3-ol heterocycles with modifications to the basic piperidine substituent as well as substituents without basic nitrogen. Compounds were screened by [(3)H]muscimol binding and in patch-clamp experiments with heterologously expressed GABA A alpha ibeta 3gamma 2 receptors (i = 1-6). The effects of 5-aminomethyl-3 H-[1,3,4]oxadiazol-2-one 5d were comparable to GABA for all alpha subunit isoforms. 5-piperidin-4-yl-3 H-[1,3,4]oxadiazol-2-one 5a and 5-piperidin-4-yl-3 H-[1,3,4]oxadiazol-2-thione 6a were weak agonists at alpha 2-, alpha 3-, and alpha 5-containing receptors. When coapplied with GABA, they were antagonistic in alpha 2-, alpha 4-, and alpha 6-containing receptors and potentiated alpha 3-containing receptors. 6a protected GABA binding site cysteine-substitution mutants alpha 1F64C and alpha 1S68C from reacting with methanethiosulfonate-ethylsulfonate. 6a specifically covalently modified the alpha 1R66C thiol, in the GABA binding site, through its oxadiazolethione sulfur. These results demonstrate the feasibility of synthesizing alpha subtype selective GABA mimetic drugs.
Jansen
Michaela
M
Department of Medicinal Chemistry, Johannes Gutenberg-UniVersity, Mainz, Germany.
Rabe
Holger
H
Strehle
Axelle
A
Dieler
Sandra
S
Debus
Fabian
F
Dannhardt
Gerd
G
Akabas
Myles H
MH
Lüddens
Hartmut
H
D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line; D004594:Electrophysiology; D005260:Female; D058785:GABA-A Receptor Agonists; D006801:Humans; D007555:Isoxazoles / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D008958:Models, Molecular; D015394:Molecular Structure; D009118:Muscimol / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D009865:Oocytes; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D021122:Protein Subunits / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011963:Receptors, GABA-A / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014982:Xenopus laevis; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D058785:GABA-A Receptor Agonists; D007555:Isoxazoles; D010880:Piperidines; D021122:Protein Subunits; D011963:Receptors, GABA-A; C073009:5-(4-piperidyl)isoxazol-3-ol; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; C015542:gaboxadol