Reversal of Ethanol-induced Intoxication by a Novel Modulator of Gßγ Protein Potentiation of the Glycine Receptor.

The acute intoxicating effects of ethanol in the central nervous system result from the modulation of several molecular targets. It is widely accepted that ethanol enhances the activity of the glycine receptor (GlyR), thus enhancing inhibitory neurotransmission, leading to motor effects, sedation, and respiratory depression. We previously reported that small peptides interfered with the binding of Gßγ to the GlyR and consequently inhibited the ethanol-induced potentiation of the receptor. Now, using virtual screening, we identified a subset of small molecules capable of interacting with the binding site of Gßγ. One of these compounds, M554, inhibited the ethanol potentiation of the GlyR in both evoked currents and synaptic transmission in vitro When this compound was tested in vivo in mice treated with ethanol (1-3.5 g/kg), it was found to induce a faster recovery of motor incoordination in rotarod experiments and a shorter sedative effect in loss of righting reflex assays. This study describes a novel molecule that might be relevant for the design of useful therapeutic compounds in the treatment of acute alcohol intoxication.

Inhibition of the ethanol-induced potentiation of α1 glycine receptor by a small peptide that interferes with Gßγ binding.

BACKGROUND: Gßγ interaction with GlyR is an important determinant in ethanol potentiation of this channel. RESULTS: A small peptide, RQH(C7), can inhibit ethanol potentiation of GlyR currents. CONCLUSION: Results with RQH(C7) indicate that ethanol mediated potentiation of GlyR is in part by Gßγ activation. SIGNIFICANCE: Molecular interaction between Gßγ and GlyR could be used as a target for pharmacological modification of ethanol effects. Previous studies indicate that ethanol can modulate glycine receptors (GlyR), in part, through Gßγ interaction with basic residues in the intracellular loop. In this study, we show that a seven-amino acid peptide (RQH(C7)), which has the primary structure of a motif in the large intracellular loop of GlyR (GlyR-IL), was able to inhibit the ethanol-elicited potentiation of this channel from 47 ± 2 to 16 ± 4%, without interfering with the effect of Gßγ on GIRK (G protein activated inwardly rectifying potassium channel) activation. RQH(C7) displayed a concentration-dependent effect on ethanol action in evoked and synaptic currents. A fragment of GlyR-IL without the basic amino acids did not interact with Gßγ or inhibit ethanol potentiation of GlyR. In silico analysis using docking and molecular dynamics allowed to identify a region of ~350Å(2) involving aspartic acids 186, 228, and 246 in Gßγ where we propose that RQH(C7) binds and exerts its blocking action on the effect of ethanol in GlyR.