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Anesthesiology
2012 Jun 01;1166:1235-44. doi: 10.1097/ALN.0b013e3182567df3.
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Two etomidate sites in α1β2γ2 γ-aminobutyric acid type A receptors contribute equally and noncooperatively to modulation of channel gating.
Guitchounts G
,
Stewart DS
,
Forman SA
.
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Etomidate is a potent hypnotic agent that acts via γ-aminobutyric acid receptor type A (GABA(A)) receptors. Evidence supports the presence of two etomidate sites per GABA(A) receptor, and current models assume that each site contributes equally and noncooperatively to drug effects. These assumptions remain untested. We used concatenated dimer (β2-α1) and trimer (γ2-β2-α1) GABA(A) subunit assemblies that form functional α1β2γ2 channels, and inserted α1M236W etomidate site mutations into both dimers (β2-α1M236W) and trimers (γ2-β2-α1M236W). Wild-type or mutant dimers (D(wt) or D(αM236W)) and trimers (T(wt) or T(αM236W)) were coexpressed in Xenopus oocytes to produce four types of channels: D(wt)T(wt), D(αM236W)T(wt), D(wt)T(αM236W), and D(αM236W)T(αM236W). For each channel type, two-electrode voltage clamp was performed to quantitatively assess GABA EC(50), etomidate modulation (left shift), etomidate direct activation, and other functional parameters affected by αM236W mutations. Concatenated wild-type D(wt)T(wt) channels displayed etomidate modulation and direct activation similar to α1β2γ2 receptors formed with free subunits. D(αM236W)T(αM236W) receptors also displayed altered GABA sensitivity and etomidate modulation similar to mutated channels formed with free subunits. Both single-site mutant receptors (D(αM236W)T(wt) and D(wt)T(αM236W)) displayed indistinguishable functional properties and equal gating energy changes for GABA activation (-4.9 ± 0.48 vs. -4.7 ± 0.48 kJ/mol, respectively) and etomidate modulation (-3.4 ± 0.49 vs. -3.7 ± 0.38 kJ/mol, respectively), which together accounted for the differences between D(wt)T(wt) and D(αM236W)T(αM236W) channels. These results support the hypothesis that the two etomidate sites on α1β2γ2 GABA(A) receptors contribute equally and noncooperatively to drug interactions and gating effects.
Bali,
GABA-induced intersubunit conformational movement in the GABAA receptor alpha 1M1-beta 2M3 transmembrane subunit interface: experimental basis for homology modeling of an intravenous anesthetic binding site.
2009, Pubmed,
Xenbase
Bali,
GABA-induced intersubunit conformational movement in the GABAA receptor alpha 1M1-beta 2M3 transmembrane subunit interface: experimental basis for homology modeling of an intravenous anesthetic binding site.
2009,
Pubmed
,
Xenbase
Baumann,
Forced subunit assembly in alpha1beta2gamma2 GABAA receptors. Insight into the absolute arrangement.
2002,
Pubmed
,
Xenbase
Baumann,
Individual properties of the two functional agonist sites in GABA(A) receptors.
2003,
Pubmed
,
Xenbase
Baumann,
Subunit arrangement of gamma-aminobutyric acid type A receptors.
2001,
Pubmed
,
Xenbase
Belelli,
The interaction of the general anesthetic etomidate with the gamma-aminobutyric acid type A receptor is influenced by a single amino acid.
1997,
Pubmed
,
Xenbase
Belelli,
The in vitro and in vivo enantioselectivity of etomidate implicates the GABAA receptor in general anaesthesia.
2003,
Pubmed
,
Xenbase
Boileau,
Effects of gamma2S subunit incorporation on GABAA receptor macroscopic kinetics.
2003,
Pubmed
,
Xenbase
Boileau,
The relative amount of cRNA coding for gamma2 subunits affects stimulation by benzodiazepines in GABA(A) receptors expressed in Xenopus oocytes.
2002,
Pubmed
,
Xenbase
Boulineau,
Consequence of the presence of two different beta subunit isoforms in a GABA(A) receptor.
2005,
Pubmed
,
Xenbase
Bracamontes,
Steroid interaction with a single potentiating site is sufficient to modulate GABA-A receptor function.
2009,
Pubmed
,
Xenbase
Chang,
Stoichiometry of a recombinant GABAA receptor.
1996,
Pubmed
,
Xenbase
Chang,
Allosteric activation mechanism of the alpha 1 beta 2 gamma 2 gamma-aminobutyric acid type A receptor revealed by mutation of the conserved M2 leucine.
1999,
Pubmed
,
Xenbase
Desai,
Gamma-amino butyric acid type A receptor mutations at beta2N265 alter etomidate efficacy while preserving basal and agonist-dependent activity.
2009,
Pubmed
,
Xenbase
Forman,
Clinical and molecular pharmacology of etomidate.
2011,
Pubmed
Forman,
Molecular approaches to improving general anesthetics.
2010,
Pubmed
Hosie,
Endogenous neurosteroids regulate GABAA receptors through two discrete transmembrane sites.
2006,
Pubmed
Jurd,
General anesthetic actions in vivo strongly attenuated by a point mutation in the GABA(A) receptor beta3 subunit.
2003,
Pubmed
Li,
Identification of a GABAA receptor anesthetic binding site at subunit interfaces by photolabeling with an etomidate analog.
2006,
Pubmed
Olsen,
GABA A receptors: subtypes provide diversity of function and pharmacology.
2009,
Pubmed
Olsen,
GABA(A) receptors as molecular targets of general anesthetics: identification of binding sites provides clues to allosteric modulation.
2011,
Pubmed
Rüsch,
Gating allosterism at a single class of etomidate sites on alpha1beta2gamma2L GABA A receptors accounts for both direct activation and agonist modulation.
2004,
Pubmed
,
Xenbase
Sieghart,
Structure, pharmacology, and function of GABAA receptor subtypes.
2006,
Pubmed
Steinbach,
Use of concatemers of ligand-gated ion channel subunits to study mechanisms of steroid potentiation.
2011,
Pubmed
Stewart,
Tryptophan mutations at azi-etomidate photo-incorporation sites on alpha1 or beta2 subunits enhance GABAA receptor gating and reduce etomidate modulation.
2008,
Pubmed
,
Xenbase
Yang,
Mechanisms of etomidate potentiation of GABAA receptor-gated currents in cultured postnatal hippocampal neurons.
1996,
Pubmed
