Rab-3 and unc-18 interactions in alcohol sensitivity are distinct from synaptic transmission.
The molecular mechanisms underlying sensitivity to alcohol are incompletely understood. Recent research has highlighted the involvement of two presynaptic proteins, Munc18 and Rab3. We have previously characterised biochemically a number of specific Munc18 point mutations including an E466K mutation that augments a direct Rab3 interaction. Here the phenotypes of this and other Munc18 mutations were assessed in alcohol sensitivity and exocytosis using Caenorhabditis elegans. We found that expressing the orthologous E466K mutation (unc-18 E465K) enhanced alcohol sensitivity. This enhancement in sensitivity was surprisingly independent of rab-3. In contrast unc-18 R39C, which decreases syntaxin binding, enhanced sensitivity to alcohol in a manner requiring rab-3. Finally, overexpression of R39C could suppress partially the reduction in neurotransmitter release in rab-3 mutant worms, whereas wild-type or E465K mutants showed no rescue. These data indicate that the epistatic interactions between unc-18 and rab-3 in modulating sensitivity to alcohol are distinct from interactions affecting neurotransmitter release.
Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom.
James R
JR
Johnson
Sudhanva
S
Kashyap
Kim
K
Rankin
Jeff W
JW
Barclay
D000818:Animals; D017173:Caenorhabditis elegans / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology*; D010750:Phosphoproteins / Q000235:genetics; D017354:Point Mutation / Q000235:genetics; D009435:Synaptic Transmission / Q000187:drug effects / Q000235:genetics; D033921:Vesicular Transport Proteins / Q000235:genetics
D029742:Caenorhabditis elegans Proteins; D010750:Phosphoproteins; C082636:Unc-18 protein, C elegans; D033921:Vesicular Transport Proteins; D000431:Ethanol