Alcohol (ethanol) is a major drug of abuse in the U.S. and worldwide, with deaths from alcohol-related cases numbering over a hundred thousand per year. New pharmacotherapies for treating alcohol use disorders are urgently needed. Repeated alcohol consumption alters the neural activity in the brain through ethanol's direct modulation of different types of ion channels. The pharmacological effects of ethanol occur with milliMolar concentrations. In order to understand how ethanol alters brain circuits it is essential to elucidate the molecular and chemical mechanisms underlying ethanol's low affinity modulation of brain proteins. Studies of GIRK channels have provided one of the best examples of modulation by ethanol. GIRK channels are activated directly by ethanol and have been clearly implicated in ethanol-drinking behaviors. Mice lacking GIRK2 subunits self-administer more ethanol than wild-type mice while mice lacking GIRK3 subunits increase binge- drinking of alcohol. These studies suggest that GIRK2 and GIRK3 subunits may differ in their sensitivity to ethanol. GIRK channels possess a pocket for alcohol that has been described at the atomic resolution for GIRK2 channels. However, little is known about the structure of heteromeric GIRK3-containing channels. It is hypothesized that the alcohol pocket in heteromeric GIRK3-containing channels coordinates ethanol better than GIRK2 channels, resulting in a higher sensitivity to alcohol. This grant will determine the chemical and structural differences in alcoho-sensitive properties of GIRK channel subunits using purified homo- and hetero- tetrameric GIRK channels reconstituted into defined lipids with cholesterol, and solving atomic structures of alcohol pockets. The effect of alcohol on microscopic gating properties of purified GIRK channels will also be determined to test the hypothesis that alcohol increases the open channel probability via an increase in the frequency of opening, in contrast to the mechanism of G proteins that stabilize an open state. Lastly, the atomic resolution structure of the GIRK alcohol pocket will be used to identify novel ethanol modulators, using in silico screening. Candidate drugs will be tested using a high-throughput flux assay with purified GIRK channels and then with native GIRK channels expressed in ventral tegmental area dopamine neurons for ex vivo studies. Defining the physical pocket for ethanol is critical for understanding how the low affinit binding of ethanol changes channel activity and affects brain function. Results from this grant could pioneer the development of novel treatments for alcohol abuse and dependence.

Public Health Relevance

Alcohol use disorders are common in the U.S. Alcohol (ethanol) directly modulates ion channels that control the excitability of neurons. The goal of thi grant is to investigate the molecular and structural mechanisms underlying ethanol-dependent activation of potassium channels and develop novel pharmaceutical agents that specifically modulate the effects of ethanol in the brain.

Agency
National Institute of Health (NIH)
Institute
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Type
Research Project (R01)
Project #
5R01AA018734-07
Application #
9260729
Study Section
Neurotoxicology and Alcohol Study Section (NAL)
Program Officer
Liu, Qi-Ying
Project Start
2009-12-01
Project End
2021-03-31
Budget Start
2017-04-01
Budget End
2018-03-31
Support Year
7
Fiscal Year
2017
Total Cost
$368,816
Indirect Cost
$148,642
Name
Icahn School of Medicine at Mount Sinai
Department
Neurosciences
Type
Schools of Medicine
DUNS #
078861598
City
New York
State
NY
Country
United States
Zip Code
10029
Rifkin, Robert A; Huyghe, Deborah; Li, Xiaofan et al. (2018) GIRK currents in VTA dopamine neurons control the sensitivity of mice to cocaine-induced locomotor sensitization. Proc Natl Acad Sci U S A 115:E9479-E9488
Prytkova, Iya; Goate, Alison; Hart, Ronald P et al. (2018) Genetics of Alcohol Use Disorder: A Role for Induced Pluripotent Stem Cells? Alcohol Clin Exp Res 42:1572-1590
Glaaser, Ian W; Slesinger, Paul A (2017) Dual activation of neuronal G protein-gated inwardly rectifying potassium (GIRK) channels by cholesterol and alcohol. Sci Rep 7:4592
Lacin, Emre; Aryal, Prafulla; Glaaser, Ian W et al. (2017) Dynamic role of the tether helix in PIP2-dependent gating of a G protein-gated potassium channel. J Gen Physiol :
Tcw, Julia; Wang, Minghui; Pimenova, Anna A et al. (2017) An Efficient Platform for Astrocyte Differentiation from Human Induced Pluripotent Stem Cells. Stem Cell Reports 9:600-614
Alexander, Stephen Ph; Kelly, Eamonn; Marrion, Neil V et al. (2017) THE CONCISE GUIDE TO PHARMACOLOGY 2017/18: Overview. Br J Pharmacol 174 Suppl 1:S1-S16
Rifkin, Robert A; Moss, Stephen J; Slesinger, Paul A (2017) G Protein-Gated Potassium Channels: A Link to Drug Addiction. Trends Pharmacol Sci 38:378-392
Munoz, Michaelanne B; Padgett, Claire L; Rifkin, Robert et al. (2016) A Role for the GIRK3 Subunit in Methamphetamine-Induced Attenuation of GABAB Receptor-Activated GIRK Currents in VTA Dopamine Neurons. J Neurosci 36:3106-14
Herman, Melissa A; Sidhu, Harpreet; Stouffer, David G et al. (2015) GIRK3 gates activation of the mesolimbic dopaminergic pathway by ethanol. Proc Natl Acad Sci U S A 112:7091-6
Kotecki, Lydia; Hearing, Matthew; McCall, Nora M et al. (2015) GIRK Channels Modulate Opioid-Induced Motor Activity in a Cell Type- and Subunit-Dependent Manner. J Neurosci 35:7131-42

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