Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
J Pharmacol Exp Ther
2012 Feb 01;3402:445-56. doi: 10.1124/jpet.111.188037.
Show Gene links
Show Anatomy links
The TM2 6' position of GABA(A) receptors mediates alcohol inhibition.
Johnson WD, Howard RJ, Trudell JR, Harris RA.
???displayArticle.abstract???
Ionotropic GABA(A) receptors (GABA(A)Rs), which mediate inhibitory neurotransmission in the central nervous system, are implicated in the behavioral effects of alcohol and alcoholism. Site-directed mutagenesis studies support the presence of discrete molecular sites involved in alcohol enhancement and, more recently, inhibition of GABA(A)Rs. We used Xenopus laevis oocytes to investigate the 6' position in the second transmembrane region of GABA(A)Rs as a site influencing alcohol inhibition. We asked whether modification of the 6' position by substitution with larger residues or methanethiol labeling [using methyl methanethiosulfonate (MMTS)] of a substituted cysteine, reduced GABA action and/or blocked further inhibition by alcohols. Labeling of the 6' position in either α2 or β2 subunits reduced responses to GABA. In addition, methanol and ethanol potentiation increased after MMTS labeling or substitution with tryptophan or methionine, consistent with elimination of an inhibitory site for these alcohols. Specific alcohols, but not the anesthetic etomidate, competed with MMTS labeling at the 6' position. We verified a role for the 6' position in previously tested α2β2 as well as more physiologically relevant α2β2γ2s GABA(A)Rs. Finally, we built a novel molecular model based on the invertebrate glutamate-gated chloride channel receptor, a GABA(A)R homolog, revealing that the 6' position residue faces the channel pore, and modification of this residue alters volume and polarity of the pore-facing cavity in this region. These results indicate that the 6' positions in both α2 and β2 GABA(A)R subunits mediate inhibition by short-chain alcohols, which is consistent with the presence of multiple counteracting sites of action for alcohols on ligand-gated ion channels.
Alifimoff,
Anaesthetic potencies of primary alkanols: implications for the molecular dimensions of the anaesthetic site.
1989, Pubmed
Alifimoff,
Anaesthetic potencies of primary alkanols: implications for the molecular dimensions of the anaesthetic site.
1989,
Pubmed Blednov,
Loss of ethanol conditioned taste aversion and motor stimulation in knockin mice with ethanol-insensitive α2-containing GABA(A) receptors.
2011,
Pubmed
,
Xenbase Boehm,
gamma-Aminobutyric acid A receptor subunit mutant mice: new perspectives on alcohol actions.
2004,
Pubmed Borghese,
Sites of excitatory and inhibitory actions of alcohols on neuronal alpha2beta4 nicotinic acetylcholine receptors.
2003,
Pubmed
,
Xenbase Brams,
Crystal structures of a cysteine-modified mutant in loop D of acetylcholine-binding protein.
2011,
Pubmed Chester,
GABA(A) receptor modulation of the rewarding and aversive effects of ethanol.
2002,
Pubmed Crawford,
Evidence that ethanol acts on a target in Loop 2 of the extracellular domain of alpha1 glycine receptors.
2007,
Pubmed
,
Xenbase Cromer,
Anxiety over GABA(A) receptor structure relieved by AChBP.
2002,
Pubmed Enoch,
The role of GABA(A) receptors in the development of alcoholism.
2008,
Pubmed Farrant,
The cellular, molecular and ionic basis of GABA(A) receptor signalling.
2007,
Pubmed Guzman,
Blockade of ethanol-induced potentiation of glycine receptors by a peptide that interferes with Gbetagamma binding.
2009,
Pubmed Harris,
Ethanol's molecular targets.
2008,
Pubmed Hibbs,
Principles of activation and permeation in an anion-selective Cys-loop receptor.
2011,
Pubmed Horenstein,
Protein mobility and GABA-induced conformational changes in GABA(A) receptor pore-lining M2 segment.
2001,
Pubmed
,
Xenbase Hosie,
Zinc-mediated inhibition of GABA(A) receptors: discrete binding sites underlie subtype specificity.
2003,
Pubmed Howard,
Structural basis for alcohol modulation of a pentameric ligand-gated ion channel.
2011,
Pubmed
,
Xenbase Howard,
Alcohol-binding sites in distinct brain proteins: the quest for atomic level resolution.
2011,
Pubmed Karlin,
Substituted-cysteine accessibility method.
1998,
Pubmed Krystal,
Gamma-aminobutyric acid type A receptors and alcoholism: intoxication, dependence, vulnerability, and treatment.
2006,
Pubmed Li,
Neurosteroids allosterically modulate binding of the anesthetic etomidate to gamma-aminobutyric acid type A receptors.
2009,
Pubmed Lobo,
GABA(A) receptors and alcohol.
2008,
Pubmed Mascia,
Specific binding sites for alcohols and anesthetics on ligand-gated ion channels.
2000,
Pubmed
,
Xenbase McCracken,
A transmembrane amino acid in the GABAA receptor β2 subunit critical for the actions of alcohols and anesthetics.
2010,
Pubmed
,
Xenbase Mehta,
Effect of chronic administration of ethanol on GABAA receptor assemblies derived from alpha2-, alpha3-, beta2- and gamma2-subunits in the rat cerebral cortex.
2005,
Pubmed Mihic,
Sites of alcohol and volatile anaesthetic action on GABA(A) and glycine receptors.
1997,
Pubmed
,
Xenbase Miller,
Genetic manipulation of ion channels: a new approach to structure and mechanism.
1989,
Pubmed Möhler,
GABA(A) receptor diversity and pharmacology.
2006,
Pubmed Perkins,
Loop 2 structure in glycine and GABA(A) receptors plays a key role in determining ethanol sensitivity.
2009,
Pubmed
,
Xenbase Quinlan,
Anesthesia sensitivity in mice that lack the beta3 subunit of the gamma-aminobutyric acid type A receptor.
1998,
Pubmed Rosen,
Channel opening by anesthetics and GABA induces similar changes in the GABAA receptor M2 segment.
2007,
Pubmed Shan,
Comparative surface accessibility of a pore-lining threonine residue (T6') in the glycine and GABA(A) receptors.
2002,
Pubmed
,
Xenbase Trudell,
Molecular modeling and mutagenesis reveals a tetradentate binding site for Zn2+ in GABA(A) alphabeta receptors and provides a structural basis for the modulating effect of the gamma subunit.
2008,
Pubmed Trudell,
Unique assignment of inter-subunit association in GABA(A) alpha 1 beta 3 gamma 2 receptors determined by molecular modeling.
2002,
Pubmed Ueno,
Tryptophan scanning mutagenesis in TM2 of the GABA(A) receptor alpha subunit: effects on channel gating and regulation by ethanol.
2000,
Pubmed
,
Xenbase Werner,
Knockin mice with ethanol-insensitive alpha1-containing gamma-aminobutyric acid type A receptors display selective alterations in behavioral responses to ethanol.
2006,
Pubmed Xu,
Identification of channel-lining residues in the M2 membrane-spanning segment of the GABA(A) receptor alpha1 subunit.
1996,
Pubmed
,
Xenbase Yang,
Closed-state cross-linking of adjacent beta1 subunits in alpha1beta1 GABAa receptors via introduced 6' cysteines.
2007,
Pubmed
