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.
Biophys J
2009 Jan 01;962:499-509. doi: 10.1016/j.bpj.2008.09.037.
Show Gene links
Show Anatomy links
Distinct structural changes in the GABAA receptor elicited by pentobarbital and GABA.
Muroi Y
,
Theusch CM
,
Czajkowski C
,
Jackson MB
.
???displayArticle.abstract???
The barbiturate pentobarbital binds to gamma-aminobutyric acid type A (GABA(A)) receptors, and this interaction plays an important role in the anesthetic action of this drug. Depending on its concentration, pentobarbital can potentiate (approximately 10-100 microM), activate (approximately 100-800 microM), or block (approximately 1-10 mM) the channel, but the mechanisms underlying these three distinct actions are poorly understood. To investigate the drug-induced structural rearrangements in the GABA(A) receptor, we labeled cysteine mutant receptors expressed in Xenopus oocytes with the sulfhydryl-reactive, environmentally sensitive fluorescent probe tetramethylrhodamine-6-maleimide (TMRM). We then used combined voltage clamp and fluorometry to monitor pentobarbital-induced channel activity and local protein movements simultaneously in real time. High concentrations of pentobarbital induced a decrease in TMRM fluorescence (F(TMRM)) of labels tethered to two residues in the extracellular domain (alpha(1)L127C and beta(2)L125C) that have been shown previously to produce an increase in F(TMRM) in response to GABA. Label at beta(2)K274C in the extracellular end of the M2 transmembrane helix reported a small but significant F(TMRM) increase during application of low modulating pentobarbital concentrations, and it showed a much greater F(TMRM) increase at higher concentrations. In contrast, GABA decreased F(TMRM) at this site. These results indicate that GABA and pentobarbital induce different structural rearrangements in the receptor, and thus activate the receptor by different mechanisms. Labels at alpha(1)L127C and beta(2)K274C change their fluorescence by substantial amounts during channel blockade by pentobarbital. In contrast, picrotoxin blockade produces no change in F(TMRM) at these sites, and the pattern of F(TMRM) signals elicited by the antagonist SR95531 differs from that produced by other antagonists. Thus, with either channel block by antagonists or activation by agonists, the structural changes in the GABA(A) receptor protein differ during transitions that are functionally equivalent.
Akabas,
GABAA receptor structure-function studies: a reexamination in light of new acetylcholine receptor structures.
2004, Pubmed
Akabas,
GABAA receptor structure-function studies: a reexamination in light of new acetylcholine receptor structures.
2004,
Pubmed
Akaike,
gamma-Aminobutyric-acid- and pentobarbitone-gated chloride currents in internally perfused frog sensory neurones.
1985,
Pubmed
Akaike,
Augmentation of GABA-induced current in frog sensory neurons by pentobarbital.
1990,
Pubmed
Akaike,
Kinetic properties of the pentobarbitone-gated chloride current in frog sensory neurones.
1987,
Pubmed
Akaike,
Bicuculline and picrotoxin block gamma-aminobutyric acid-gated Cl- conductance by different mechanisms.
1985,
Pubmed
Akk,
Activation and block of recombinant GABA(A) receptors by pentobarbitone: a single-channel study.
2000,
Pubmed
Amin,
A single hydrophobic residue confers barbiturate sensitivity to gamma-aminobutyric acid type C receptor.
1999,
Pubmed
Amin,
GABAA receptor needs two homologous domains of the beta-subunit for activation by GABA but not by pentobarbital.
1993,
Pubmed
,
Xenbase
Barnard,
International Union of Pharmacology. XV. Subtypes of gamma-aminobutyric acidA receptors: classification on the basis of subunit structure and receptor function.
1998,
Pubmed
Belelli,
A single amino acid confers barbiturate sensitivity upon the GABA rho 1 receptor.
1999,
Pubmed
,
Xenbase
Boileau,
Molecular dissection of benzodiazepine binding and allosteric coupling using chimeric gamma-aminobutyric acidA receptor subunits.
1998,
Pubmed
,
Xenbase
Brejc,
Crystal structure of an ACh-binding protein reveals the ligand-binding domain of nicotinic receptors.
2001,
Pubmed
Buhr,
Two novel residues in M2 of the gamma-aminobutyric acid type A receptor affecting gating by GABA and picrotoxin affinity.
2001,
Pubmed
,
Xenbase
Campo-Soria,
Mechanism of action of benzodiazepines on GABAA receptors.
2006,
Pubmed
,
Xenbase
Cestari,
The agonistic action of pentobarbital on GABAA beta-subunit homomeric receptors.
1996,
Pubmed
,
Xenbase
Chakrapani,
Gating dynamics of the acetylcholine receptor extracellular domain.
2004,
Pubmed
Chang,
Site-specific fluorescence reveals distinct structural changes with GABA receptor activation and antagonism.
2002,
Pubmed
,
Xenbase
Dahan,
A fluorophore attached to nicotinic acetylcholine receptor beta M2 detects productive binding of agonist to the alpha delta site.
2004,
Pubmed
,
Xenbase
Davies,
Modulation by general anaesthetics of rat GABAA receptors comprised of alpha 1 beta 3 and beta 3 subunits expressed in human embryonic kidney 293 cells.
1997,
Pubmed
Dibas,
Identification of a novel residue within the second transmembrane domain that confers use-facilitated block by picrotoxin in glycine alpha 1 receptors.
2002,
Pubmed
Downing,
Benzodiazepine modulation of partial agonist efficacy and spontaneously active GABA(A) receptors supports an allosteric model of modulation.
2005,
Pubmed
Dunn,
Molecular neurobiology of the GABAA receptor.
1994,
Pubmed
Evans,
Potentiation of the effects of GABA by pentobarbitone.
1979,
Pubmed
Hales,
An asymmetric contribution to gamma-aminobutyric type A receptor function of a conserved lysine within TM2-3 of alpha1, beta2, and gamma2 subunits.
2006,
Pubmed
Holden,
Different residues in the GABA(A) receptor alpha 1T60-alpha 1K70 region mediate GABA and SR-95531 actions.
2002,
Pubmed
,
Xenbase
Hosie,
Endogenous neurosteroids regulate GABAA receptors through two discrete transmembrane sites.
2006,
Pubmed
Jackson,
Single channel currents activated by gamma-aminobutyric acid, muscimol, and (-)-pentobarbital in cultured mouse spinal neurons.
1982,
Pubmed
Karlin,
Toward a structural basis for the function of nicotinic acetylcholine receptors and their cousins.
1995,
Pubmed
Kash,
Coupling of agonist binding to channel gating in the GABA(A) receptor.
2003,
Pubmed
Kloda,
Agonist-, antagonist-, and benzodiazepine-induced structural changes in the alpha1 Met113-Leu132 region of the GABAA receptor.
2007,
Pubmed
,
Xenbase
Krishek,
A functional comparison of the antagonists bicuculline and picrotoxin at recombinant GABAA receptors.
1996,
Pubmed
,
Xenbase
Mercado,
Charged residues in the alpha1 and beta2 pre-M1 regions involved in GABAA receptor activation.
2006,
Pubmed
,
Xenbase
Mercado,
Gamma-aminobutyric acid (GABA) and pentobarbital induce different conformational rearrangements in the GABA A receptor alpha1 and beta2 pre-M1 regions.
2008,
Pubmed
,
Xenbase
Miyazawa,
Structure and gating mechanism of the acetylcholine receptor pore.
2003,
Pubmed
Mortensen,
Extrasynaptic alphabeta subunit GABAA receptors on rat hippocampal pyramidal neurons.
2006,
Pubmed
Muroi,
Local and global ligand-induced changes in the structure of the GABA(A) receptor.
2006,
Pubmed
,
Xenbase
Newell,
The GABAA receptor alpha 1 subunit Pro174-Asp191 segment is involved in GABA binding and channel gating.
2003,
Pubmed
,
Xenbase
Newell,
Mutation of glutamate 155 of the GABAA receptor beta2 subunit produces a spontaneously open channel: a trigger for channel activation.
2004,
Pubmed
,
Xenbase
Newland,
On the mechanism of action of picrotoxin on GABA receptor channels in dissociated sympathetic neurones of the rat.
1992,
Pubmed
Pistis,
The interaction of general anaesthetics with recombinant GABAA and glycine receptors expressed in Xenopus laevis oocytes: a comparative study.
1997,
Pubmed
,
Xenbase
Pless,
Conformational variability of the glycine receptor M2 domain in response to activation by different agonists.
2007,
Pubmed
,
Xenbase
Purohit,
A stepwise mechanism for acetylcholine receptor channel gating.
2007,
Pubmed
Rho,
Direct activation of GABAA receptors by barbiturates in cultured rat hippocampal neurons.
1996,
Pubmed
Robertson,
Potassium currents expressed from Drosophila and mouse eag cDNAs in Xenopus oocytes.
1996,
Pubmed
,
Xenbase
Rosen,
Channel opening by anesthetics and GABA induces similar changes in the GABAA receptor M2 segment.
2007,
Pubmed
Rüsch,
Classic benzodiazepines modulate the open-close equilibrium in alpha1beta2gamma2L gamma-aminobutyric acid type A receptors.
2005,
Pubmed
,
Xenbase
Sedelnikova,
Stoichiometry of a pore mutation that abolishes picrotoxin-mediated antagonism of the GABAA receptor.
2006,
Pubmed
,
Xenbase
Serafini,
Structural domains of the human GABAA receptor 3 subunit involved in the actions of pentobarbital.
2000,
Pubmed
Sieghart,
Structure, pharmacology, and function of GABAA receptor subtypes.
2006,
Pubmed
Siegwart,
Mutational analysis of molecular requirements for the actions of general anaesthetics at the gamma-aminobutyric acidA receptor subtype, alpha1beta2gamma2.
2003,
Pubmed
Siegwart,
Molecular determinants for the action of general anesthetics at recombinant alpha(2)beta(3)gamma(2)gamma-aminobutyric acid(A) receptors.
2002,
Pubmed
Sigel,
Role of the conserved lysine residue in the middle of the predicted extracellular loop between M2 and M3 in the GABA(A) receptor.
1999,
Pubmed
,
Xenbase
Smart,
Studies on the mechanism of action of picrotoxinin and other convulsants at the crustacean muscle GABA receptor.
1986,
Pubmed
Wagner,
Structure and dynamics of the GABA binding pocket: A narrowing cleft that constricts during activation.
2001,
Pubmed
,
Xenbase
Xu,
Interaction of picrotoxin with GABAA receptor channel-lining residues probed in cysteine mutants.
1995,
Pubmed
,
Xenbase
Zhang,
A unique amino acid of the Drosophila GABA receptor with influence on drug sensitivity by two mechanisms.
1994,
Pubmed
