UNC-18 modulates ethanol sensitivity in Caenorhabditis elegans.

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Acute ethanol exposure impacts the nervous system, acting as a stimulant at low doses and a depressant at higher doses, ultimately causing motor dysfunction.
• A genetic study linked ethanol preference in mice to a polymorphism (D216N) in the synaptic protein Munc18-1.
• Munc18-1 is crucial for exocytosis, interacting with the SNARE protein syntaxin-1.

Purpose of the Study:

• To investigate the functional consequences of the Munc18-1 D216N mutation on syntaxin-1 binding and exocytosis.
• To determine if this mutation confers resistance to the acute effects of ethanol.
• To explore the role of Munc18-1 in ethanol's mechanism of action.

Main Methods:

• Investigated the binding interaction of the Munc18-1 D216N mutant with syntaxin-1 and the SNARE complex.
• Assessed the impact of the mutation on the duration of single exocytotic events.
• Generated transgenic Caenorhabditis elegans expressing the orthologous D214N mutation in the UNC-18 null background.
• Tested the ethanol response (stimulatory and sedative effects) in transgenic worms.

Main Results:

• The D216N mutation specifically impairs Munc18-1 binding to the assembled SNARE complex, not through closed conformation or N-terminus binding.
• The mutation broadens the duration of individual exocytotic events.
• Transgenic C. elegans expressing the D214N mutation exhibited normal locomotion and significant resistance to both stimulatory and sedative effects of acute ethanol.
• An independent mutation (I133V) in Munc18-1 also linked reduced SNARE complex binding to ethanol resistance.

Conclusions:

• Ethanol's acute effects are mediated, at least in part, by vesicle fusion processes.
• Specific point mutations in Munc18-1 can ameliorate the acute behavioral effects of ethanol.
• Munc18-1's interaction with the SNARE complex is a potential target for modulating ethanol's neurological impact.