Alcohol (ethanol) consumption alters neural activity in the brain by modulating different types of ion channels. An emerging concept in the field is that some of the physiological effects of ethanol are mediated by direct modulation of ion channels in the brain. One of the targets in the brain for ethanol is the G protein-gated inwardly rectifying potassium (GIRK) channel, which is activated by ethanol. Mice lacking GIRK2 channels exhibit diminished ethanol-induced tolerance to pain and self-administer more ethanol than wild-type mice. Moreover, a quantitative trait loci with a large effect on predisposition to sedative withdrawal, such as from ethanol, was narrowed to a region on chromosome 1 in mice that contains Girk3 gene. GIRK3 knockout mice exhibit less severe sedative-hypnotic withdrawal. Though GIRK2 and GIRK2/3 channels are implicated in ethanol-related behaviors, the molecular mechanism underlying this response is not well understood. Recently, we showed with high-resolution structural studies that alcohols bind directly to hydrophobic pockets of inwardly rectifying potassium channels. Mutations in the alcohol-binding pocket of GIRK2 channels significantly alter ethanol activation. We hypothesize that ethanol binds to hydrophobic pockets in GIRK2/3 channels and facilitate a conformational change that is relayed to the channel's gate and opens the channel. In this research proposal, we plan to use an innovative approach of high-resolution crystallographic studies, structure-based mutagenesis and advanced electrophysiological recordings to investigate this hypothesis. Specifically, we will conduct a structure-function analysis of the ethanol-binding pocket in GIRK2/3 channels (1), solve high-resolution structures of GIRK channels complexed with ethanol to reveal conformational changes in the channel protein that occur with ethanol-dependent gating (2), and elaborate mechanistic models for ethanol-dependent activation of GIRK channels, utilizing single-channel recordings and chemical modification of cysteine-substituted channels (3). Completion of these proposed experiments will reveal the structural basis of ethanol modulation of GIRK channels, which will provide insights into the mechanism of ethanol-modulation of other types of ion channels. Understanding the molecular mechanism underlying ethanol modulation of ion channels could lead to development of novel pharmaceutical agents for treating alcohol-dependence, directly benefiting human health.

Public Health Relevance

Ethanol, a major drug of addiction and abuse in the U.S., directly modulates brain ion channels, which control the excitability of brain neurons. The goal of this grant is to investigate the molecular and structural mechanisms underlying ethanol-dependent activation of neuronal potassium channels. Results from these studies could lead to the development of novel pharmaceutical agents that specifically modulate potassium channels or antagonize actions of ethanol.

Agency
National Institute of Health (NIH)
Institute
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Type
Research Project (R01)
Project #
5R01AA018734-02
Application #
8107852
Study Section
Neurotoxicology and Alcohol Study Section (NAL)
Program Officer
Liu, Qi-Ying
Project Start
2010-07-10
Project End
2012-06-30
Budget Start
2011-07-01
Budget End
2012-06-30
Support Year
2
Fiscal Year
2011
Total Cost
$434,883
Indirect Cost
Name
Salk Institute for Biological Studies
Department
Type
DUNS #
078731668
City
La Jolla
State
CA
Country
United States
Zip Code
92037
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
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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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