Probing GABAA receptors with inhibitory neurosteroids.
Neuropharmacology
; 136(Pt A): 23-36, 2018 07 01.
Article
in En
| MEDLINE
| ID: mdl-29447845
γ-aminobutyric acid type A receptors (GABAARs) are important components of the central nervous system and they are functionally tasked with controlling neuronal excitability. These receptors are subject to post-translational modification and also to modulation by endogenous regulators, such as the neurosteroids. These modulators can either potentiate or inhibit GABAAR function. Whilst the former class of neurosteroids are considered to bind to and act from the transmembrane domain of the receptor, the domains that are important for the inhibitory neurosteroids remain less clear. In this study, we systematically compare a panel of recombinant synaptic-type and extrasynaptic-type GABAARs expressed in heterologous cell systems for their sensitivity to inhibition by the classic inhibitory neurosteroid, pregnenolone sulphate. Generally, peak GABA current responses were inhibited less compared to steady-state currents, implicating the desensitised state in inhibition. Moreover, pregnenolone sulphate inhibition increased with GABA concentration, but showed minimal voltage dependence. There was no strong dependence of inhibition on receptor subunit composition, the exception being the ρ1 receptor, which is markedly less sensitive. By using competition experiments with pregnenolone sulphate and the GABA channel blocker picrotoxinin, discrete binding sites are proposed. Furthermore, by assessing inhibition using site-directed mutagenesis and receptor chimeras comprising α, ß or γ subunits with ρ1 subunits, the receptor transmembrane domains are strongly implicated in mediating inhibition and most likely the binding location for pregnenolone sulphate in GABAARs. This article is part of the "Special Issue Dedicated to Norman G. Bowery".
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Receptors, GABA-A
/
Neurotransmitter Agents
Limits:
Animals
/
Humans
Language:
En
Journal:
Neuropharmacology
Year:
2018
Document type:
Article
Affiliation country:
United kingdom
Country of publication:
United kingdom