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The mechanism of SR95531 inhibition at GABA receptors examined in human alphabeta and alphabetagamma receptors.

Lindquist, Catarina LU ; Laver, Derek R and Birnir, Bryndis LU (2005) In Journal of Neurochemistry 94(2). p.491-501
Abstract
We examined the interaction of GABA and the competitive inhibitor SR95531 at human α1β1γ2S and α1β1 GABAA receptors expressed in Sf9 cells. The efficacy and potency of inhibition depended on the relative timing of the GABA and SR95531 applications. In saturating (10 mm) GABA, the half-inhibitory concentrations of SR95531 (IC50) when coapplied with GABA to α1β1γ2S or α1β1 receptors were 49 and 210 µm for the peak and 18 and 130 µm for the plateau current, respectively. Our data are explained by an inhibition mechanism in which SR95531 and GABA bind to two sites on the receptor where the binding of GABA allows channel opening but SR95531 does not. The SR95531 affinity for both receptor types was ~200 nm and the binding rate was found to be... (More)
We examined the interaction of GABA and the competitive inhibitor SR95531 at human α1β1γ2S and α1β1 GABAA receptors expressed in Sf9 cells. The efficacy and potency of inhibition depended on the relative timing of the GABA and SR95531 applications. In saturating (10 mm) GABA, the half-inhibitory concentrations of SR95531 (IC50) when coapplied with GABA to α1β1γ2S or α1β1 receptors were 49 and 210 µm for the peak and 18 and 130 µm for the plateau current, respectively. Our data are explained by an inhibition mechanism in which SR95531 and GABA bind to two sites on the receptor where the binding of GABA allows channel opening but SR95531 does not. The SR95531 affinity for both receptor types was ~200 nm and the binding rate was found to be 10-fold faster than that for GABA. The dual binding-site model gives insights into the differential effects of GABA and SR95531 on the peak and plateau currents. The model predicts the effect of SR95531 on GABA currents in the synapse (GABA concentration ~ mm) and at extrasynaptic (GABA concentration ≤ µm) sites. The IC50 (50–100 nm) for the synaptic response to SR95531 was insensitive to the GABA affinity of the receptors whereas the IC50 (50–800 nm) for extrasynaptic inhibition correlated with the GABA affinity. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
patch-clamp, GABA(A) receptors, gabazine, Sf9 cells, SR95531, gating models
in
Journal of Neurochemistry
volume
94
issue
2
pages
491 - 501
publisher
Wiley-Blackwell
external identifiers
  • wos:000230289200020
  • pmid:15998299
  • scopus:22244471649
ISSN
1471-4159
DOI
10.1111/j.1471-4159.2005.03240.x
language
English
LU publication?
yes
id
337847dd-b0c4-497b-bf96-1e99f30deed2 (old id 153632)
alternative location
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15998299&dopt=Abstract
date added to LUP
2007-07-16 16:29:53
date last changed
2017-01-01 07:11:00
@article{337847dd-b0c4-497b-bf96-1e99f30deed2,
  abstract     = {We examined the interaction of GABA and the competitive inhibitor SR95531 at human α1β1γ2S and α1β1 GABAA receptors expressed in Sf9 cells. The efficacy and potency of inhibition depended on the relative timing of the GABA and SR95531 applications. In saturating (10 mm) GABA, the half-inhibitory concentrations of SR95531 (IC50) when coapplied with GABA to α1β1γ2S or α1β1 receptors were 49 and 210 µm for the peak and 18 and 130 µm for the plateau current, respectively. Our data are explained by an inhibition mechanism in which SR95531 and GABA bind to two sites on the receptor where the binding of GABA allows channel opening but SR95531 does not. The SR95531 affinity for both receptor types was ~200 nm and the binding rate was found to be 10-fold faster than that for GABA. The dual binding-site model gives insights into the differential effects of GABA and SR95531 on the peak and plateau currents. The model predicts the effect of SR95531 on GABA currents in the synapse (GABA concentration ~ mm) and at extrasynaptic (GABA concentration ≤ µm) sites. The IC50 (50–100 nm) for the synaptic response to SR95531 was insensitive to the GABA affinity of the receptors whereas the IC50 (50–800 nm) for extrasynaptic inhibition correlated with the GABA affinity.},
  author       = {Lindquist, Catarina and Laver, Derek R and Birnir, Bryndis},
  issn         = {1471-4159},
  keyword      = {patch-clamp,GABA(A) receptors,gabazine,Sf9 cells,SR95531,gating models},
  language     = {eng},
  number       = {2},
  pages        = {491--501},
  publisher    = {Wiley-Blackwell},
  series       = {Journal of Neurochemistry},
  title        = {The mechanism of SR95531 inhibition at GABA receptors examined in human alphabeta and alphabetagamma receptors.},
  url          = {http://dx.doi.org/10.1111/j.1471-4159.2005.03240.x},
  volume       = {94},
  year         = {2005},
}