Drunken lipid membranes, not drunken SNARE proteins, promote fusion in a model of neurotransmitter release.
Robert E Coffman, Katelyn N Kraichely, Alex J B Kreutzberger, Volker Kiessling, Lukas K Tamm, Dixon J Woodbury
Author Information
Robert E Coffman: Neuroscience Center, Brigham Young University, Provo, UT, United States.
Katelyn N Kraichely: Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA, United States.
Alex J B Kreutzberger: Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA, United States.
Volker Kiessling: Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA, United States.
Lukas K Tamm: Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA, United States.
Dixon J Woodbury: Neuroscience Center, Brigham Young University, Provo, UT, United States.
Alcohol affects many neuronal proteins that are upstream or down-stream of synaptic vesicle fusion and neurotransmitter release. Less well studied is alcohol's effect on the fusion machinery including SNARE proteins and lipid membranes. Using a SNARE-driven fusion assay we show that fusion probability is significantly increased at 0.4% v/v (68 mM) ethanol; but not with methanol up to 10%. Ethanol appears to act directly on membrane lipids since experiments focused on protein properties [circular dichroism spectrometry, site-directed fluorescence interference contrast (sdFLIC) microscopy, and vesicle docking results] showed no significant changes up to 5% ethanol, but a protein-free fusion assay also showed increased lipid membrane fusion rates with 0.4% ethanol. These data show that the effects of high physiological doses of ethanol on SNARE-driven fusion are mediated through ethanol's interaction with the lipid bilayer of membranes and not SNARE proteins, and that methanol affects lipid membranes and SNARE proteins only at high doses.
