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Visualizing Intracellular SNARE Trafficking by Fluorescence Lifetime Imaging Microscopy
Published on: December 29, 2017
Synaptotagmin 1 and SNAREs form a complex that is structurally heterogeneous.
Alex L Lai1, Hao Huang, Dawn Z Herrick
1Department of Chemistry, Biophysics Program and Center for Membrane Biology at the University of Virginia, Charlottesville, VA 22904-4319, USA.
Journal of Molecular Biology
|November 20, 2010
Summary
Synaptotagmin 1 (syt1) is a calcium sensor for neuronal exocytosis. It interacts with the SNARE complex, adopting a flexible structure that may facilitate membrane binding.
Area of Science:
- Neuroscience
- Biochemistry
- Structural Biology
Background:
- Synaptotagmin 1 (syt1) is a key calcium (Ca2+) sensor regulating neuronal exocytosis.
- The core soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex is essential for membrane fusion during exocytosis.
Purpose of the Study:
- To investigate the structural interactions between the C2 domains of syt1 and the core SNARE complex.
- To determine the conformational flexibility of syt1 when bound to the SNARE complex.
Main Methods:
- Site-directed spin labeling coupled with electron paramagnetic resonance (EPR) spectroscopy.
- Double electron-electron resonance (DEER) to measure distances between syt1 domains.
- Simulated annealing using EPR-derived distance restraints.
Main Results:
- The assembled core SNARE complex contacts syt1's C2A and C2B domains in multiple regions.
- Distances between syt1's C2 domains show broad distributions, indicating structural heterogeneity.
- Syt1 does not adopt a single, well-defined structure when associated with the SNARE complex.
Conclusions:
- Syt1, when bound to SNAREs, is structurally flexible and samples multiple conformational states.
- This flexibility suggests syt1 is configured to bind opposing bilayers, facilitating membrane fusion.
- The syt1/SNARE complex exhibits dynamic behavior crucial for exocytosis regulation.
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