A novel allosteric modulatory site on the GABAA receptor β subunit

Wafford, Keith A.; Bain, C J; Quirk, Kathleen; McKernan, R.M.; Wingrove, Peter B.; Whiting, Paul J.; Kemp, John A.

doi:10.1016/0896-6273(94)90330-1

Cited by 166 publications

(103 citation statements)

References 29 publications

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“…We show that this component disappears in ␣4␤3␦ receptors that contain a mutation in the ␤3 subunit (␤3N265M). This mutation has been previously shown to essentially abolish (in ␤3N265M knockin mice) the in vivo anesthetic actions of etomidate and propofol (35), consistent with the identification of this residue in determining the ␤ subunit selectivity for enhancement of recombinant GABA A Rs by loreclezole and etomidate (36,37). Homologous residues in GABA A R subunits have been identified as important for high-dose alcohol and volatile anesthetic actions on recombinant GABA A Rs (38).…”

mentioning

confidence: 68%

Low-dose alcohol actions on α4β3δ GABA _A receptors are reversed by the behavioral alcohol antagonist Ro15-4513

Wallner

Hanchar

Olsen

2006

Proc. Natl. Acad. Sci. U.S.A.

109

114

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Although it is now more than two decades since it was first reported that the imidazobenzodiazepine Ro15-4513 reverses behavioral alcohol effects, the molecular target(s) of Ro15-4513 and the mechanism of alcohol antagonism remain elusive. Here, we show that Ro15-4513 blocks the alcohol enhancement on recombinant ''extrasynaptic'' ␣4͞6␤3␦ GABAA receptors at doses that do not reduce the GABA-induced Cl ؊ current. At low ethanol concentrations (<30 mM), the Ro15-4513 antagonism is complete. However, at higher ethanol concentrations (>100 mM), there is a Ro15-4513-insensitive ethanol enhancement that is abolished in receptors containing a point mutation in the second transmembrane region of the ␤3 subunit (␤3N265M). Therefore, ␣4͞6␤3␦ GABA receptors have two distinct alcohol modulation sites: (i) a low-dose ethanol site present in ␣4͞6␤3␦ receptors that is antagonized by the behavioral alcohol antagonist Ro15-4513 and (ii) a site activated at high (anesthetic) alcohol doses, defined by mutations in membrane-spanning regions. Receptors composed of ␣4␤3N265M␦ subunits that lack the high-dose alcohol site show a saturable ethanol dose-response curve with a half-maximal enhancement at 16 mM, close to the legal blood alcohol driving limit in most U.S. states (17.4 mM). Like in behavioral experiments, the alcohol antagonist effect of Ro15-4513 on recombinant ␣4␤3␦ receptors is blocked by flumazenil and ␤-carboline-ethyl ester (␤-CCE). Our findings suggest that ethanol͞Ro15-4513-sensitive GABA A receptors are important mediators of behavioral alcohol effects.alcohol intoxication ͉ alcohol receptor ͉ anesthetics A lthough alcohol is one of the most widely used and abused drugs, the molecular targets that mediate alcohol effects at concentrations relevant for mild social intoxication are only beginning to be revealed. Neurotransmitter receptors for GABA, NMDA and glycine, and G protein-gated K ϩ channels have been identified as potential alcohol targets that are sensitive to intoxicating alcohol concentrations (1-4). GABA A receptors (GABA A Rs) have long been suspected to be important mediators of alcohol effects (5, 6) because benzodiazepines (BZs) and barbiturates, classic GABA A R agonists, share common pharmacological properties with ethanol, such as sedativehypnotic, anti-anxiety, and motor in-coordinating and anticonvulsant effects and have additive, possibly even synergistic effects, when taken together with ethanol (7). In addition, BZs, barbiturates, and ethanol produce tolerance and cross-tolerance to each other (8), consistent with GABA A Rs as targets of action.We have recently identified subtypes of GABA A Rs, those containing the ␦ and the ␤3 subunit, that are uniquely sensitive to low alcohol concentrations (9). Consistent with the view that ␦ subunit-containing receptors are important mediators of alcohol actions is the finding that GABA A R ␦-subunit knockout mice show multiple defects in behavioral responses to ethanol (10). Receptors containing the ␦ subunit have an exclusively nonsynaptic distribution, ...

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mentioning

confidence: 68%

Low-dose alcohol actions on α4β3δ GABA _A receptors are reversed by the behavioral alcohol antagonist Ro15-4513

Wallner

Hanchar

Olsen

2006

Proc. Natl. Acad. Sci. U.S.A.

109

114

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“…Whereas, in receptors containing β 1 , potentiation was abolished, it was reduced to approximately one third in receptors containing β 3 . To test whether 2-AG shares the binding site with loreclezole (24), another allosteric activator of GABA A receptors, we evaluated the point mutation β 2 N265S in α 1 β 2 γ 2 receptors that abolishes the potentiation by loreclezole. As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

The major central endocannabinoid directly acts at GABA _A receptors

Sigel

Baur

Rácz

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

155

129

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GABA A receptors are the major ionotropic inhibitory neurotransmitter receptors. The endocannabinoid system is a lipid signaling network that modulates different brain functions. Here we show a direct molecular interaction between the two systems. The endocannabinoid 2-arachidonoyl glycerol (2-AG) potentiates GABA A receptors at low concentrations of GABA. Two residues of the receptor located in the transmembrane segment M4 of β 2 confer 2-AG binding. 2-AG acts in a superadditive fashion with the neurosteroid 3α, 21-dihydroxy-5α-pregnan-20-one (THDOC) and modulates δ-subunit-containing receptors, known to be located extrasynaptically and to respond to neurosteroids. 2-AG inhibits motility in CB 1 /CB 2 cannabinoid receptor double-KO, whereas β 2 -KO mice show hypermotility. The identification of a functional binding site for 2-AG in the GABA A receptor may have far-reaching consequences for the study of locomotion and sedation.retrograde signaling | electrophysiology | allosteric modulation

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“…Similarly, the ␤2/␤3 selective agent loreclezole has sedative properties. 197,198 Substantial effort has been devoted to obtaining GABA A receptor positive allosteric modulators that have reduced activity on GABA receptors containing ␣1 subunits, to avoid the sedation that is believed to be mediated by these receptors. The compounds developed so far are generally nonbenzodiazepines that bind to the benzodiazepine site on all benzodiazepine-sensitive isoforms, but at certain isoforms are partial agonists with reduced efficacy.…”

Section: Cys-loop Ligand-gated Channelsmentioning

confidence: 99%

Molecular Targets for Antiepileptic Drug Development

2007

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Summary:This review considers how recent advances in the physiology of ion channels and other potential molecular targets, in conjunction with new information on the genetics of idiopathic epilepsies, can be applied to the search for improved antiepileptic drugs (AEDs). Marketed AEDs predominantly target voltage-gated cation channels (the ␣ subunits of voltagegated Na ϩ channels and also T-type voltage-gated Ca 2ϩ channels) or influence GABA-mediated inhibition. Recently, ␣2-␦ voltage-gated Ca 2ϩ channel subunits and the SV2A synaptic vesicle protein have been recognized as likely targets. Genetic studies of familial idiopathic epilepsies have identified numerous genes associated with diverse epilepsy syndromes, including genes encoding Na ϩ channels and GABA A receptors, which are known AED targets. A strategy based on genes associated with epilepsy in animal models and humans suggests other potential AED targets, including various voltage-gated Ca 2ϩ channel subunits and auxiliary proteins, A-or M-type voltage-gated K ϩ channels, and ionotropic glutamate receptors. Recent progress in ion channel research brought about by molecular cloning of the channel subunit proteins and studies in epilepsy models suggest additional targets, including G-protein-coupled receptors, such as GABA B and metabotropic glutamate receptors; hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel subunits, responsible for hyperpolarization-activated current I h ; connexins, which make up gap junctions; and neurotransmitter transporters, particularly plasma membrane and vesicular transporters for GABA and glutamate. New information from the structural characterization of ion channels, along with better understanding of ion channel function, may allow for more selective targeting. For example, Na ϩ channels underlying persistent Na ϩ currents or GABA A receptor isoforms responsible for tonic (extrasynaptic) currents represent attractive targets. The growing understanding of the pathophysiology of epilepsy and the structural and functional characterization of the molecular targets provide many opportunities to create improved epilepsy therapies.

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A novel allosteric modulatory site on the GABAA receptor β subunit

Cited by 166 publications

References 29 publications

Low-dose alcohol actions on α4β3δ GABA _A receptors are reversed by the behavioral alcohol antagonist Ro15-4513

Low-dose alcohol actions on α4β3δ GABA _A receptors are reversed by the behavioral alcohol antagonist Ro15-4513

The major central endocannabinoid directly acts at GABA _A receptors

Molecular Targets for Antiepileptic Drug Development

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A novel allosteric modulatory site on the GABAA receptor β subunit

Cited by 166 publications

References 29 publications

Low-dose alcohol actions on α4β3δ GABA A receptors are reversed by the behavioral alcohol antagonist Ro15-4513

Low-dose alcohol actions on α4β3δ GABA A receptors are reversed by the behavioral alcohol antagonist Ro15-4513

The major central endocannabinoid directly acts at GABA A receptors

Molecular Targets for Antiepileptic Drug Development

Contact Info

Product

Resources

About

Low-dose alcohol actions on α4β3δ GABA _A receptors are reversed by the behavioral alcohol antagonist Ro15-4513

Low-dose alcohol actions on α4β3δ GABA _A receptors are reversed by the behavioral alcohol antagonist Ro15-4513

The major central endocannabinoid directly acts at GABA _A receptors