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Updated: Jun 26, 2026
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Single-Cell Calcium Imaging for Studying the Activation of Calcium Ion Channels
Published on: December 13, 2024
Direct interaction of SNARE complex binding protein synaphin/complexin with calcium sensor synaptotagmin 1
Hiroshi Tokumaru1, Chigusa Shimizu-Okabe, Teruo Abe
1Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa 769-2193, Japan. tokumaruh@kph.bunri-u.ac.jp
Brain Cell Biology
|January 10, 2009
Summary
Synaphin directly binds to synaptotagmin 1, a calcium sensor, influencing fast neurotransmitter release. This interaction is crucial for synaptic vesicle exocytosis, mediated by synaphin's C-terminal region.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Synaphin (complexin) binding to SNARE complexes is vital for synaptic vesicle exocytosis.
- The precise function of synaphin in this process remains incompletely understood.
Purpose of the Study:
- To elucidate the direct interaction between synaphin and synaptotagmin 1.
- To identify the specific regions and residues involved in synaphin-synaptotagmin 1 binding.
- To understand the role of this interaction in synaptic vesicle exocytosis.
Main Methods:
- Protein binding assays to determine stoichiometry and interaction sites.
- Site-directed mutagenesis of synaphin's C-terminal region.
- Peptide inhibition assays.
- Immunoprecipitation from brain membrane extracts.
Main Results:
- Synaphin binds synaptotagmin 1 in a 1:1 stoichiometry.
- The C-terminal region of synaphin, particularly residues 108-114 (seven glutamic acids), is essential for synaptotagmin 1 binding.
- Mutating these glutamic acid residues significantly reduces binding.
- A C-terminal synaphin peptide inhibits synaptotagmin 1 binding, an effect dependent on the glutamic acid residues.
- Synaphin, synaptotagmin 1, and SNAREs form a complex in brain extracts.
Conclusions:
- Synaphin directly recruits synaptotagmin 1 to the SNARE complex.
- Synaphin and synaptotagmin 1 act synergistically to mediate fast synaptic vesicle exocytosis.
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