title: Synthesis of GABAA receptor agonists and evaluation of their alpha-subunit selectivity and orientation in the GABA binding site.
abstract: 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.
authors.affiliation: Department of Medicinal Chemistry, Johannes Gutenberg-UniVersity, Mainz, Germany.
authors.forename: Michaela
authors.initials: M
authors.lastname: Jansen
authors.forename: Holger
authors.initials: H
authors.lastname: Rabe
authors.forename: Axelle
authors.initials: A
authors.lastname: Strehle
authors.forename: Sandra
authors.initials: S
authors.lastname: Dieler
authors.forename: Fabian
authors.initials: F
authors.lastname: Debus
authors.forename: Gerd
authors.initials: G
authors.lastname: Dannhardt
authors.forename: Myles H
authors.initials: MH
authors.lastname: Akabas
authors.forename: Hartmut
authors.initials: H
authors.lastname: Lüddens
mesh_terms: 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*
chemical_list: 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