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.
Tryptophan scanning mutagenesis in TM2 of the GABA(A) receptor alpha subunit: effects on channel gating and regulation by ethanol.
Ueno S
,
Lin A
,
Nikolaeva N
,
Trudell JR
,
Mihic SJ
,
Harris RA
,
Harrison NL
.
???displayArticle.abstract???
1. Each residue in the second transmembrane segment (TM2) of the human GABA(A) receptor alpha(2) subunit was individually mutated to tryptophan. The wild-type or mutant alpha(2) subunits were expressed with the wild-type human GABA(A) receptor beta(2) subunit in Xenopus oocytes, and the effects of these mutations were investigated using two-electrode voltage-clamp recording. 2. Four mutations (V257W, T262W, T265W and S270W) produced receptors which were active in the absence of agonist, and this spontaneous open channel activity was blocked by both picrotoxin and bicuculline, except in the alpha(2)(V257W)beta(2) mutant receptor, which was not sensitive to picrotoxin. 3. Six mutations (V257W, V260W, T262W, T267W, S270W and A273W) enhanced the agonist sensitivity of the receptor, by 10 - 100 times compared with the wild-type alpha(2)beta(2) receptor. Other mutations (T261W, V263W, L269W, I271W and S272W) had little or no effect on the apparent affinity of the receptor to GABA. Eight of the tryptophan mutations (R255, T256, F258, G259, L264, T265, M266 or T268) resulted in undetectable GABA-induced currents. 4. The S270W mutation eliminated potentiation of GABA by ethanol, whereas T261W markedly increased the action of ethanol. The T262W mutation produced direct activation (10% of maximal GABA response) by ethanol in the absence of GABA, while other mutations did not alter the action of ethanol significantly. 5. These results are consistent with a unique role for S270 in the action of ethanol within the TM2 region, and with models of GABA(A) receptor channel function, in which specific residues within TM2 are critical for the regulation of channel gating (S270, L264), while other residues (L269, I271 and S272) have little effect on these functions and may be non-critical structural residues.
Akabas,
Identification of acetylcholine receptor channel-lining residues in the M1 segment of the alpha-subunit.
1995, Pubmed,
Xenbase
Akabas,
Identification of acetylcholine receptor channel-lining residues in the M1 segment of the alpha-subunit.
1995,
Pubmed
,
Xenbase
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
Blanton,
Identifying the lipid-protein interface of the Torpedo nicotinic acetylcholine receptor: secondary structure implications.
1994,
Pubmed
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
Crews,
Effects of ethanol on ion channels.
1996,
Pubmed
Cutting,
Cloning of the gamma-aminobutyric acid (GABA) rho 1 cDNA: a GABA receptor subunit highly expressed in the retina.
1991,
Pubmed
,
Xenbase
Diamond,
Cellular and molecular neuroscience of alcoholism.
1997,
Pubmed
Farrar,
Stoichiometry of a ligand-gated ion channel determined by fluorescence energy transfer.
1999,
Pubmed
Franks,
Molecular and cellular mechanisms of general anaesthesia.
1994,
Pubmed
Harris,
Ethanol, flunitrazepam, and pentobarbital modulation of GABAA receptors expressed in mammalian cells and Xenopus oocytes.
1997,
Pubmed
,
Xenbase
Harris,
Ethanol actions on multiple ion channels: which are important?
1999,
Pubmed
Harrison,
Positive modulation of human gamma-aminobutyric acid type A and glycine receptors by the inhalation anesthetic isoflurane.
1993,
Pubmed
Koltchine,
Agonist gating and isoflurane potentiation in the human gamma-aminobutyric acid type A receptor determined by the volume of a second transmembrane domain residue.
1999,
Pubmed
Krasowski,
Propofol and other intravenous anesthetics have sites of action on the gamma-aminobutyric acid type A receptor distinct from that for isoflurane.
1998,
Pubmed
Lasalde,
Tryptophan substitutions at the lipid-exposed transmembrane segment M4 of Torpedo californica acetylcholine receptor govern channel gating.
1996,
Pubmed
,
Xenbase
Levitan,
Biophysical and pharmacological properties of cloned GABAA receptor subunits expressed in Xenopus oocytes.
1988,
Pubmed
,
Xenbase
Mihic,
Sites of alcohol and volatile anaesthetic action on GABA(A) and glycine receptors.
1997,
Pubmed
,
Xenbase
Mihic,
Anaesthetic concentrations of alcohols potentiate GABAA receptor-mediated currents: lack of subunit specificity.
1994,
Pubmed
,
Xenbase
Mihic,
Potentiation of gamma-aminobutyric acid type A receptor-mediated chloride currents by novel halogenated compounds correlates with their abilities to induce general anesthesia.
1994,
Pubmed
,
Xenbase
Ortells,
Evolutionary history of the ligand-gated ion-channel superfamily of receptors.
1995,
Pubmed
Peoples,
Lipid vs protein theories of alcohol action in the nervous system.
1996,
Pubmed
Pritchett,
Importance of a novel GABAA receptor subunit for benzodiazepine pharmacology.
1989,
Pubmed
Samson,
Neurobiology of alcohol abuse.
1992,
Pubmed
Thompson,
Mutation at the putative GABA(A) ion-channel gate reveals changes in allosteric modulation.
1999,
Pubmed
,
Xenbase
Tretter,
Stoichiometry and assembly of a recombinant GABAA receptor subtype.
1997,
Pubmed
Ueno,
Subunit mutations affect ethanol actions on GABA(A) receptors expressed in Xenopus oocytes.
1999,
Pubmed
,
Xenbase
Whiting,
Molecular and functional diversity of the expanding GABA-A receptor gene family.
1999,
Pubmed
Wick,
Mutations of gamma-aminobutyric acid and glycine receptors change alcohol cutoff: evidence for an alcohol receptor?
1998,
Pubmed
,
Xenbase
Williams,
Gamma-aminobutyric acid increases the water accessibility of M3 membrane-spanning segment residues in gamma-aminobutyric acid type A receptors.
1999,
Pubmed
Xu,
Interaction of picrotoxin with GABAA receptor channel-lining residues probed in cysteine mutants.
1995,
Pubmed
,
Xenbase
Xu,
Identification of channel-lining residues in the M2 membrane-spanning segment of the GABA(A) receptor alpha1 subunit.
1996,
Pubmed
,
Xenbase
Ye,
Enhancement of glycine receptor function by ethanol is inversely correlated with molecular volume at position alpha267.
1998,
Pubmed
,
Xenbase
