Biochemical Basis for Alcohol Toxicity in the Brain

Chronic exposure to alcohol induces many changes in the brains of vertebrates. These include enhances the activity of an inhibitory neurotransmitter known as GABA and inhibition of the excitatory neurotransmitter N-methyl D-aspartate (NMDA). In what appears to be an adaptive process, long term exposure to ethanol results in increased levels of the NMDA receptors and changes in the expression levels of alcohol sensitive subunits of the GABAA receptor. As a result chronic exposure to ethanol followed by withdrawal can induce seizures and neuronal cell death that are associated with the increased levels of receptor activity once ethanol is removed. There is increasing evidence that the effects of alcohol are exerted partly through a direct interaction with the neurotransmitter receptors. Mutations in alcohol sensitive receptors such as the can significantly modify or even abolish their sensitivity to alcohol. The identification and characterization of alcohol binding sites in CNS receptors would provide targets for the development of pharmacological agents to control both alcohol toxicity and also alcohol dependency. Research in my laboratory is currently aimed at using NMR spectroscopy to determine the structure of the protein LUSH. This protein has a unique alcohol binding function in fruit flies. We are using this protein as a model to define the molecular nature of alcohol binding sites in proteins in order to try and understand the molecular basis of alcohol's action in the brains of mammals.

Development of New NMR Methods

NMR Spectroscopy is an inherently insensitive technique for studying biological macromolecules. It requires a lot of material in relatively high concentrations which is not always available. Part of my research involves developing more sensitive NMR experiments for the study of proteins, carbohydrates and nucleic acids. An example from a recent paper is shown below. (Click the small figures to see larger versions) This experiment was designed for oligosaccharides that have been labeled with C-13 acetyl groups. The experiment is very sensitive and also has the advantage that the complete stereochemistry of the sugar rings can be defined from this single experiment.

The HCmeCOH-HEHAHA experiment used to look at connections between acetyl groups and protons on the rings of sugars. The resulting spectrum is shown below. Taken from Jones & Bendiak, J. Biomol. NMR, 1999 ( in press)

 

 

The 2D Spectrum of an acetylated oligosaccharide using the sequence above. The spectrum shows correlations from the acetyl ring CO group to all protons in the sugar ring.

 

 

 

 

 

 

 

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