Abstract
Wild-type α1β2γ2 γ-aminobutyric acid (GABA)Areceptors and receptors containing a point-mutated subunit γ2F77Y were expressed by transient transfection in human embryonic kidney 293 cells. Mutant receptors bound the benzodiazepine binding site ligand [3H]flumazenil with similar, subnanomolar affinity as wild-type receptor. Displacement studies with diazepam showed that the affinity for this compound was reduced 250-fold on mutation, indicating that the tyrosine hydroxyl group interferes with diazepam binding. This differential behavior then was used to find the chemical entity presumably interacting with the phenyalanine residue in position 77 of the γ2 subunit of wild-type receptors. Thirty-four substances were analyzed in this respect. Our results suggest that the phenyl substituent of diazepam is located close to γF77. Similarly, we investigated the possible location of α1T206 and γ2M130. Electrophysiological data obtained with the wild-type receptor furthermore suggest a simple overlap between positive allosteric modulators acting at the benzodiazepine binding site with its antagonists.
Footnotes
- Received May 4, 1998.
- Accepted September 3, 1998.
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Send reprint requests to: Dr. Erwin Sigel, Department of Pharmacology, University of Bern, Friedbühlstr. 49, CH-3010 Bern, Switzerland. E-mail: sigel{at}pki.unibe.ch
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This study was supported by grants 31–37192.93 from the Swiss National Science Foundation and EU Grant BIO4-CT96–0585 (BBW 96.0010).
- The American Society for Pharmacology and Experimental Therapeutics
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