ALCOHOL ACTIONS--MOLECULAR TARGETS ON BRAIN PROTEINS

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Our hypotheses are that ethanol alters the function of ion channels by binding within protein cavities and that some structural features of these cavities will be similar for related and unrelated ion channels. In addition, we propose that some behavioral actions of ethanol require enhancement of glycine or GABAA receptor function. Our overall goals are (l) to determine the specific protein regions of several brain receptors/channels that are responsible for ethanol action, and (2) to test the importance of two of these receptors in vivo. The first goal will be accomplished by in vitro testing of chimeric and mutated receptors/channels, and the second will use transgenic mice to express mutated receptors that are insensitive to ethanol in vitro. First, we will define the role of specific amino acids in the TM2-3 region of GABAA and glycine receptors in ethanol modulation of receptor function. These studies will be carried out in Xenopus oocytes. To determine if results from GABAA and glycine receptors generalize to another, related, ligand-gated ion channel, we will characterize the response of recombinant neuronal nicotinic acetylcholine receptors to ethanol. Next, we will extend our recent studies showing ethanol activation of G-protein activated inwardly rectifying potassium (GIRK) channels by elucidating the molecular basis of ethanol action on this channel. This will be done by construction of chimeric receptors between GIRK2 and IRK1 channels, followed by mutation of single amino acids. Structural determinants (i.e., amino acid properties and locations) of ethanol sensitivity will be compared for glycine, GABAA, and GIRK channels. Lastly, we will determine the in vivo significance of the glycine and GABA receptors for specific behavioral actions of ethanol by constructing transgenic mice with mutant receptors that are ethanol-resistant. The long-term, health-related, goal of this research is to identify molecular sites of alcohol action that would be useful targets for pharmacotherapies that would reduce alcohol actions such as reinforcement, craving, and dependence.