Modulation of recombinant alpha 6 beta 2 gamma 2 GABAA receptors by neuroactive steroids.
The sensitivity of the recombinant alpha 6 beta 2 gamma 2 GABAA receptor expressed in HEK 293 cells to neuroactive steroids was studied. The steroids 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha-OH-DHP), pregnenolone sulfate and 3 alpha-OH-DHP sulfate have different modulatory effects on [3H]muscimol or [3H]Ro15-4513 binding to the alpha 6 beta 2 gamma 2 than to the alpha 1 beta 2 gamma 2 receptor. Binding of both radioactive ligands to the alpha 6 beta 2 gamma 2 receptor was maximally potentiated with each steroid used (10 nM) and decreased with further increases in steroid concentration. Using whole-cell recording, the GABA response of clusters of transfected HEK 293 cells was strongly potentiated by 3 or 10 nM 3 alpha-OH-DHP. In contrast, this response was reduced by 100 nM 3 alpha-OH-DHP. This latter effect appears to be related to the acceleration of the GABA response desensitization, observed in isolated cells. 3 alpha-OH-DHP (10 or 100 nM) was able to activate a response in the absence of GABA. It is proposed that the interaction of neuroactive steroids with the alpha 6 beta 2 gamma 2 receptor involves at least two distinct binding sites. One of them might be located close to the GABA binding site.
Hauser
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CA
Institut National de la Santé et de la Recherche Médicale, Lab. Hormones, Le Kremlin Bicêtre, France.
Chesnoy-Marchais
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D
Robel
P
P
Baulieu
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EE
D001386:Azides / Q000494:pharmacology; D001569:Benzodiazepines / Q000494:pharmacology; D001667:Binding, Competitive; D002460:Cell Line; D002478:Cells, Cultured; D004594:Electrophysiology; D009118:Muscimol / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011963:Receptors, GABA-A / Q000187:drug effects*; D011994:Recombinant Proteins / Q000494:pharmacology*; D013256:Steroids / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D001386:Azides; D011963:Receptors, GABA-A; D011994:Recombinant Proteins; D013256:Steroids; D001569:Benzodiazepines; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; C042957:Ro 15-4513