Potentiation of Glycine Receptors by Ethanol

Summary

Principal Investigator: LUIS GERARDO AGUAYO
Abstract: Activation of glycine receptors (GlyRs) in brain stem, spinal cord and brain provides a main inhibitory control for neuronal excitability. Modification of these receptors by toxins and drugs such as ethanol leads to a wide range of effects varying from sedation and muscle relaxation to convulsions, respiratory arrest and death. However, the mechanism by which ethanol affects these receptors is largely unknown. Recent studies have indicated that GlyR function is modified by changes in GTP-binding protein activity. Specifically, using a series of GlyR mutants, the presence of basic amino acid motifs that are responsible for G beta gamma binding and receptor modulation were discovered. More importantly, preliminary results show that basic amino acids in the main intracellular loop of the GlyR determine the sensitivity of the receptor to clinically relevant concentrations of ethanol (10-100 mM). These amino acids also regulate the interaction of the GlyR with G beta gamma. In agreement with these findings, it was found that GlyR sensitivity to ethanol was significantly modified by changing the stoichiometry of the heterotrimeric complex. Therefore, it was hypothesized that important determinants for ethanol sensitivity are within the intracellular loop and that the sensitivity of GlyR to ethanol depends on the state of G protein activation. Remarkably, it was shown that these sites did not participate in the modulation of GlyRs by propofol, isoflurane and long chain alcohols indicating a novel and selective new site for ethanol. Additionally, mutations in these sites did not affect the physiological properties of the GlyR indicating that the ethanol resistant phenotype was not related to changes on channel gating. Therefore, the primary objective of this study is to characterize the intracellular sites responsible for G protein activation and GlyR sensitivity to ethanol by using receptor mutagenesis, kinetic analysis of GTP binding to G proteins, heterologous expression of G protein subunits, patch-clamp and Western blot techniques. In addition, key experiments will be performed using WT and mutant GlyRs expressed in a neuronal background (i.e. DRG neurons). The information obtained from this study will help to understand the mechanism by which ethanol affects glycine receptors, which are important in functions such as convulsions, sensory integration, muscle tone and respiration. Therefore, these results may contribute to the development of new treatments for alcoholism. PUBLIC HEALTH RELEVANCE Excessive consumption of ethanol is a main health-related problem in the US and world wide. However, the main determinants for the changes in the brain functions produced by ethanol are still largely unknown. Therefore, it is important to identify the mechanism and sites of ethanol action in order to understand how ethanol affects the central nervous system and to propose useful therapies to alleviate neurological health problems associated with its excessive consumption.
Funding Period: ----------------2004 - ---------------2011-
more information: NIH RePORT

Top Publications

  1. ncbi Molecular determinants for G protein betagamma modulation of ionotropic glycine receptors
    Gonzalo E Yevenes
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Biol Chem 281:39300-7. 2006
  2. ncbi Regulation of glycinergic and GABAergic synaptogenesis by brain-derived neurotrophic factor in developing spinal neurons
    M A Carrasco
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, P O Box 160 C, Concepcion, Chile
    Neuroscience 145:484-94. 2007
  3. pmc A selective G betagamma-linked intracellular mechanism for modulation of a ligand-gated ion channel by ethanol
    Gonzalo E Yevenes
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, P O Box 160 C, Concepcion, Chile
    Proc Natl Acad Sci U S A 105:20523-8. 2008
  4. pmc Inhibition of the ethanol-induced potentiation of α1 glycine receptor by a small peptide that interferes with Gβγ binding
    Loreto San Martin
    Department of Physiology, Faculty of Biological Sciences, University of Concepcion, 403901 Concepcion, Chile
    J Biol Chem 287:40713-21. 2012
  5. pmc Blockade of ethanol-induced potentiation of glycine receptors by a peptide that interferes with Gbetagamma binding
    Leonardo Guzman
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Pharmacol Exp Ther 331:933-9. 2009
  6. pmc Molecular requirements for ethanol differential allosteric modulation of glycine receptors based on selective Gbetagamma modulation
    Gonzalo E Yevenes
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Biol Chem 285:30203-13. 2010
  7. pmc A Single phenylalanine residue in the main intracellular loop of α1 γ-aminobutyric acid type A and glycine receptors influences their sensitivity to propofol
    Gustavo Moraga-Cid
    Department of Physiology, University of Concepcion, Concepcion, Chile
    Anesthesiology 115:464-73. 2011
  8. pmc Activated G protein α s subunits increase the ethanol sensitivity of human glycine receptors
    Gonzalo E Yevenes
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Pharmacol Exp Ther 339:386-93. 2011
  9. pmc The basic property of Lys385 is important for potentiation of the human α1 glycine receptor by ethanol
    Patricio A Castro
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Pharmacol Exp Ther 340:339-49. 2012

Detail Information

Publications9

  1. ncbi Molecular determinants for G protein betagamma modulation of ionotropic glycine receptors
    Gonzalo E Yevenes
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Biol Chem 281:39300-7. 2006
    ..Our results demonstrate for the first time the sites for G protein betagamma subunit modulation on GlyRs and provide a new framework regarding the ligand-gated ion channel superfamily regulation by intracellular signaling...
  2. ncbi Regulation of glycinergic and GABAergic synaptogenesis by brain-derived neurotrophic factor in developing spinal neurons
    M A Carrasco
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, P O Box 160 C, Concepcion, Chile
    Neuroscience 145:484-94. 2007
    ....
  3. pmc A selective G betagamma-linked intracellular mechanism for modulation of a ligand-gated ion channel by ethanol
    Gonzalo E Yevenes
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, P O Box 160 C, Concepcion, Chile
    Proc Natl Acad Sci U S A 105:20523-8. 2008
    ..Moreover, these data provide an opportunity to develop new genetically modified animal models and novel drugs to treat alcohol-related medical concerns...
  4. pmc Inhibition of the ethanol-induced potentiation of α1 glycine receptor by a small peptide that interferes with Gβγ binding
    Loreto San Martin
    Department of Physiology, Faculty of Biological Sciences, University of Concepcion, 403901 Concepcion, Chile
    J Biol Chem 287:40713-21. 2012
    ..Gβγ interaction with GlyR is an important determinant in ethanol potentiation of this channel...
  5. pmc Blockade of ethanol-induced potentiation of glycine receptors by a peptide that interferes with Gbetagamma binding
    Leonardo Guzman
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Pharmacol Exp Ther 331:933-9. 2009
    ....
  6. pmc Molecular requirements for ethanol differential allosteric modulation of glycine receptors based on selective Gbetagamma modulation
    Gonzalo E Yevenes
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Biol Chem 285:30203-13. 2010
    ....
  7. pmc A Single phenylalanine residue in the main intracellular loop of α1 γ-aminobutyric acid type A and glycine receptors influences their sensitivity to propofol
    Gustavo Moraga-Cid
    Department of Physiology, University of Concepcion, Concepcion, Chile
    Anesthesiology 115:464-73. 2011
    ..Therefore, the influence of the large intracellular loop in propofol sensitivity of both receptors was explored...
  8. pmc Activated G protein α s subunits increase the ethanol sensitivity of human glycine receptors
    Gonzalo E Yevenes
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Pharmacol Exp Ther 339:386-93. 2011
    ..Thus, these data indicate that the activated form of Gα(s) is able to positively influence the effect of ethanol on a type of inhibitory receptor important for motor control, pain, and respiration...
  9. pmc The basic property of Lys385 is important for potentiation of the human α1 glycine receptor by ethanol
    Patricio A Castro
    Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
    J Pharmacol Exp Ther 340:339-49. 2012
    ....