Differential Effects of 4'-Chlorodiazepam on Expressed Human GABAA Receptors |
| |
Authors: | Nancy C Lan Jie-Sheng Chen Deborah Johnson † Kelvin W Gee |
| |
Institution: | CoCensys, Inc., and; Department of Pharmacology, University of California-Irvine, College of Medicine, Irvine;and; Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles, California, U.S.A. |
| |
Abstract: | Abstract: The interactions of the atypical benzodiazepine 4'-chlorodiazepam (Ro 5-4864) with functionally expressed human GABAA receptor cDNAs were determined. Cotransfection of human α2, β1, and γ2 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 α subunit was further demonstrated as substitution of either α1 or α3 for the α2 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 α2 and β1 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 α and β polypeptides. |
| |
Keywords: | GABA GABAA receptor Benzodiazepines 4'-Chlorodiazepam Benzodiazepine receptor Ligand-gated ion channel |
|
|