Differential effects of 4'-chlorodiazepam on expressed human GABAA receptors.
The interactions of the atypical benzodiazepine 4'-chlorodiazepam (Ro 5-4864) with functionally expressed human GABAA receptor cDNAs were determined. Cotransfection of human alpha 2, beta 1, and gamma 2 subunits was capable of reconstituting a 4'-chlorodiazepam recognition site as revealed by a dose-dependent potentiation of t-[35S]butylbicyclophosphorothionate ([35S]-TBPS) binding to the GABA-activated chloride channel. This site is found on GABAA receptor complexes containing sites for GABA agonist-like benzodiazepines and neuroactive steroids. The importance of the alpha subunit was further demonstrated as substitution of either alpha 1 or alpha 3 for the alpha 2 subunit did not reconstitute a 4'-chlorodiazepam recognition site that was capable of modulating [35S]TBPS binding under the same experimental conditions. The 4'-chlorodiazepam modulatory site was shown to be distinct from the benzodiazepine site, but the phenylquinolines PK 8165 and PK 9084 produced effects similar to 4'-chlorodiazepam, consistent with the previous analysis of the 4'-chlorodiazepam site in brain homogenates. Further analysis of the subunit requirements revealed that coexpression of alpha 2 and beta 1 alone reconstituted a 4'-chlorodiazepam recognition site. It is interesting, however, that the 4'-chlorodiazepam site was found to inhibit [35S]TBPS binding to the GABA-activated chloride channel. Thus, the 4'-chlorodiazepam site may be reconstituted with only the alpha and beta polypeptides.
Lan
N C
NC
CoCensys, Inc., University of California-Irvine, College of Medicine 92717.
Chen
J S
JS
Johnson
D
D
Gee
K W
KW
D001570:Benzodiazepinones / Q000494:pharmacology*; D001643:Bridged Bicyclo Compounds / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002460:Cell Line; D002998:Clonazepam / Q000494:pharmacology; D005442:Flumazenil / Q000494:pharmacology; D006801:Humans; D011804:Quinolines / Q000494:pharmacology; D018079:Receptors, GABA / Q000145:classification / Q000187:drug effects*; D014162:Transfection
D001570:Benzodiazepinones; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D011804:Quinolines; D018079:Receptors, GABA; C028513:4'-chlorodiazepam; D005442:Flumazenil; D002998:Clonazepam; C037476:tert-butylbicyclophosphorothionate; C030079:PK 9084; C030078:pipequaline