title: Cloning of cDNAs encoding the human gamma-aminobutyric acid type A receptor alpha 6 subunit and characterization of the pharmacology of alpha 6-containing receptors.
abstract: A cDNA encoding the human gamma-aminobutyric acidA (GABAA) receptor alpha 6 subunit has been cloned and sequenced. The deduced amino acid sequence of this cDNA shows 91.4% identity with the published rat alpha 6 subunit. In situ hybridization histochemistry reveals the alpha 6 mRNA to be located within the granule cell layer of the human cerebellar cortex. Recombinant human alpha 6 beta gamma 2S GABAA receptors have been expressed in both stably transfected cells and Xenopus oocytes, and the pharmacology of the benzodiazepine binding site has been determined. The recombinant receptor has a diazepam-insensitive pharmacology, with negligible affinity for a number of classic benzodiazepines. A number of compounds that bind to the benzodiazepine site potentiated the GABA response of alpha 6 beta 2 gamma 2 receptors. Most importantly, the classic benzodiazepine antagonist ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a] [1,4]benzodiazepine-3-carboxylate (Ro 15-1788) and the partial inverse agonist ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a] [1,4]benzodiazepine-3-carboxylate (Ro 15-4513) both acted as agonists at the alpha 6 containing receptor. This observation demonstrates definitively that efficacy of benzodiazepine compounds cannot be generalized across receptor subtypes and may also help explain some of the behavioral effects that have been reported for these compounds.
authors.affiliation: Merck Sharp & Dohme Research Laboratories, Harlow, Essex, UK.
authors.forename: K L
authors.initials: KL
authors.lastname: Hadingham
authors.forename: E M
authors.initials: EM
authors.lastname: Garrett
authors.forename: K A
authors.initials: KA
authors.lastname: Wafford
authors.forename: C
authors.initials: C
authors.lastname: Bain
authors.forename: R P
authors.initials: RP
authors.lastname: Heavens
authors.forename: D J
authors.initials: DJ
authors.lastname: Sirinathsinghji
authors.forename: P J
authors.initials: PJ
authors.lastname: Whiting
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016375:Antisense Elements (Genetics); D001345:Autoradiography; D001483:Base Sequence; D002525:Cerebellar Cortex / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D005260:Female; D005445:Flunitrazepam / Q000494:pharmacology; D006801:Humans; D017403:In Situ Hybridization; D007700:Kinetics; D007739:L Cells; D008024:Ligands; D046911:Macromolecular Substances; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D010424:Pentobarbital / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011280:Pregnanolone / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D011963:Receptors, GABA-A / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014982:Xenopus laevis; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D016375:Antisense Elements (Genetics); D017931:DNA Primers; D018076:DNA, Complementary; D008024:Ligands; D046911:Macromolecular Substances; D012333:RNA, Messenger; D011963:Receptors, GABA-A; D011994:Recombinant Proteins; D005680:gamma-Aminobutyric Acid; D005445:Flunitrazepam; D011280:Pregnanolone; D010424:Pentobarbital