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.
Mutation at the putative GABA(A) ion-channel gate reveals changes in allosteric modulation.
Thompson SA
,
Smith MZ
,
Wingrove PB
,
Whiting PJ
,
Wafford KA
.
???displayArticle.abstract???
We have mutated a conserved leucine in the putative membrane-spanning domain to serine in human GABA(A) beta2 and investigated the actions of a number of GABA(A) agonists, antagonists and modulators on human alpha1beta2deltaL259Sgamma2s compared to wild type alpha1beta2gamma2s GABA(A) receptors, expressed in Xenopus oocytes. The mutation resulted in smaller maximum currents to gamma-aminobutyric acid (GABA) compared to alpha1beta2gamma2s receptors, and large leak currents resulting from spontaneous channel opening. As reported, this mutation significantly decreased the GABA EC50 (110 fold), and reduced desensitization. Muscimol and the partial agonists 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) and piperidine-4-sulphonic acid (P4S) also displayed a decrease in EC50. In addition to competitively shifting GABA concentration response curves, the antagonists bicuculline and SR95531 both inhibited the spontaneous channel activity on alpha1beta2deltaL259Sgamma2s receptors, with different degrees of maximum inhibition. The effects of a range of allosteric modulators, including benzodiazepines and anaesthetics were examined on a submaximal GABA concentration (EC20). Compared to wild type, none of these modulators potentiated the EC20 response of alpha1beta2deltaL259Sgamma2s receptors, however they all directly activated the receptor in the absence of GABA. To conclude, the above mutation resulted in receptors which exhibit a degree of spontaneous activity, and are more sensitive to agonists. Benzodiazepines and other agents modulate constitutive activity, but positive modulation of GABA is lost. The competitive antagonists bicuculline and SR95531 can also act as allosteric channel modulators through the same GABA binding site.
Akabas,
Identification of acetylcholine receptor channel-lining residues in the entire M2 segment of the alpha subunit.
1994, Pubmed,
Xenbase
Akabas,
Identification of acetylcholine receptor channel-lining residues in the entire M2 segment of the alpha subunit.
1994,
Pubmed
,
Xenbase
Amin,
GABAA receptor needs two homologous domains of the beta-subunit for activation by GABA but not by pentobarbital.
1993,
Pubmed
,
Xenbase
Bertrand,
Unconventional pharmacology of a neuronal nicotinic receptor mutated in the channel domain.
1992,
Pubmed
,
Xenbase
Chang,
Stoichiometry of a recombinant GABAA receptor.
1996,
Pubmed
,
Xenbase
Chang,
Substitutions of the highly conserved M2 leucine create spontaneously opening rho1 gamma-aminobutyric acid receptors.
1998,
Pubmed
,
Xenbase
Ebert,
Differences in agonist/antagonist binding affinity and receptor transduction using recombinant human gamma-aminobutyric acid type A receptors.
1997,
Pubmed
,
Xenbase
Filatov,
The role of conserved leucines in the M2 domain of the acetylcholine receptor in channel gating.
1995,
Pubmed
,
Xenbase
Krishek,
Homomeric beta 1 gamma-aminobutyric acid A receptor-ion channels: evaluation of pharmacological and physiological properties.
1996,
Pubmed
,
Xenbase
Labarca,
Channel gating governed symmetrically by conserved leucine residues in the M2 domain of nicotinic receptors.
1995,
Pubmed
,
Xenbase
McKernan,
Which GABAA-receptor subtypes really occur in the brain?
1996,
Pubmed
Pan,
Agonist-induced closure of constitutively open gamma-aminobutyric acid channels with mutated M2 domains.
1997,
Pubmed
,
Xenbase
Pistis,
The interaction of general anaesthetics with recombinant GABAA and glycine receptors expressed in Xenopus laevis oocytes: a comparative study.
1997,
Pubmed
,
Xenbase
Revah,
Mutations in the channel domain alter desensitization of a neuronal nicotinic receptor.
1991,
Pubmed
,
Xenbase
Sieghart,
Structure and pharmacology of gamma-aminobutyric acidA receptor subtypes.
1995,
Pubmed
Sigel,
The benzodiazepine binding site of GABAA receptors.
1997,
Pubmed
Sigel,
The rat beta 1-subunit of the GABAA receptor forms a picrotoxin-sensitive anion channel open in the absence of GABA.
1989,
Pubmed
,
Xenbase
Thompson,
Mutation at the putative GABA(A) ion-channel gate reveals changes in allosteric modulation.
1999,
Pubmed
,
Xenbase
Thompson,
Barbiturate interactions at the human GABAA receptor: dependence on receptor subunit combination.
1996,
Pubmed
,
Xenbase
Tierney,
Effects of mutating leucine to threonine in the M2 segment of alpha1 and beta1 subunits of GABAA alpha1beta1 receptors.
1996,
Pubmed
Ueno,
Bicuculline and gabazine are allosteric inhibitors of channel opening of the GABAA receptor.
1997,
Pubmed
Unwin,
Acetylcholine receptor channel imaged in the open state.
1995,
Pubmed
Wafford,
A novel allosteric modulatory site on the GABAA receptor beta subunit.
1994,
Pubmed
,
Xenbase
Whiting,
Structure and pharmacology of vertebrate GABAA receptor subtypes.
1995,
Pubmed
Whiting,
Neuronally restricted RNA splicing regulates the expression of a novel GABAA receptor subunit conferring atypical functional properties [corrected; erratum to be published].
1997,
Pubmed
,
Xenbase
Wingrove,
Key amino acids in the gamma subunit of the gamma-aminobutyric acidA receptor that determine ligand binding and modulation at the benzodiazepine site.
1997,
Pubmed
,
Xenbase
Xu,
Identification of channel-lining residues in the M2 membrane-spanning segment of the GABA(A) receptor alpha1 subunit.
1996,
Pubmed
,
Xenbase
Yakel,
Single amino acid substitution affects desensitization of the 5-hydroxytryptamine type 3 receptor expressed in Xenopus oocytes.
1993,
Pubmed
,
Xenbase
