Complexin maintains vesicles in the primed state in C. elegans.

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Complexin is a synaptic protein that interacts with the SNARE complex.
• Its role in regulating neurotransmitter release has shown contradictory findings across different species.
• Previous studies in flies suggest inhibition, while mouse studies indicate promotion of evoked responses.

Purpose of the Study:

• To investigate the function of complexin in the nematode Caenorhabditis elegans.
• To elucidate the specific roles of complexin in synaptic vesicle fusion and neurotransmission.

Main Methods:

• Characterization of a complexin mutant in C. elegans.
• Analysis of spontaneous and evoked synaptic vesicle fusion.
• Measurement of synaptic current amplitudes.
• Quantification of docked synaptic vesicles.

Main Results:

• Complexin mutants showed a twofold increase in spontaneous vesicle fusion without extracellular calcium.
• Evoked responses were severely impaired, with a 94% reduction in current amplitudes.
• A significant 70% decrease in the number of docked synaptic vesicles was observed in complexin-1 mutants.

Conclusions:

• Complexin exhibits bipolar functions in neurotransmission, inhibiting spontaneous fusion and promoting evoked release.
• The protein is essential for stabilizing docked vesicles at the synaptic plasma membrane.
• Complexin's primary role is maintaining the docked state through fusion inhibition and priming promotion.