Mass spectrometry uncovers intermediates and off-pathway complexes for SNARE complex assembly

Area of Science:

• Molecular Biology
• Neuroscience
• Biochemistry

Background:

• The SNARE complex, comprising Synaptobrevin-2, Syntaxin-1, and SNAP25, drives synaptic vesicle fusion and neurotransmitter exocytosis.
• While SNARE complex assembly is generally understood, the precise nature of intermediates and off-pathway complexes remains unclear.

Purpose of the Study:

• To elucidate the stepwise assembly pathway of the SNARE complex.
• To characterize intermediates, sub-complexes, and interactions with Complexin-1.
• To investigate the regulatory role of Complexin-1 in SNARE complex formation.

Main Methods:

• Native mass spectrometry was employed to determine the stoichiometry of SNARE sub-complexes and monitor oligomerization.
• Chemical cross-linking was used to gain detailed insights into protein interactions within the SNARE complex.
• The study focused on individual SNARE proteins, binary and ternary sub-complexes, and their interactions with Complexin-1.

Main Results:

• Native mass spectrometry identified the stoichiometry of various SNARE complex intermediates and off-pathway assemblies.
• Complexin-1 was found to significantly reduce the multimerization of the ternary SNARE complex.
• Chemical cross-linking data suggested a role for these interactions in membrane fusion processes.

Conclusions:

• This research provides a comprehensive roadmap of SNARE complex assembly, detailing the stoichiometry of key intermediates.
• Complexin-1 acts as a regulator, modulating SNARE complex formation and potentially influencing membrane fusion.
• The findings advance our understanding of the molecular mechanisms underlying synaptic exocytosis.