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Compound vesicle fusion increases quantal size and potentiates synaptic transmission
Liming He1, Lei Xue, Jianhua Xu
1National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
Nature
|March 13, 2009
Summary
Compound fusion between synaptic vesicles occurs at conventional synapses, mediated by calcium and synaptotagmin. This process increases neurotransmitter release and synaptic strength, followed by bulk endocytosis for vesicle retrieval.
Area of Science:
- Neuroscience
- Cell Biology
- Synaptic Transmission
Background:
- Exocytosis is crucial for synaptic function, involving vesicle fusion with the plasma membrane.
- Compound fusion, where vesicles fuse with each other before fusing with the plasma membrane, has been proposed but not confirmed at conventional synapses.
Purpose of the Study:
- To investigate the existence, mechanism, and role of compound fusion at conventional synapses.
- To elucidate the molecular players involved in this process.
Main Methods:
- Electrophysiological recordings (capacitance measurements, mEPSC analysis) in rat and mouse nerve terminals.
- Electron microscopy to visualize vesicle structures.
- Investigating the role of calcium and synaptotagmin.
Main Results:
- High-intensity stimulation induced giant capacitance events and giant vesicle-like structures, indicating compound vesicle fusion.
- Calcium and synaptotagmin are essential for these giant fusion events.
- Compound vesicle exocytosis increased quantal size and contributed to post-tetanic potentiation, followed by bulk endocytosis.
Conclusions:
- Compound fusion is a novel exocytosis and endocytosis pathway at conventional synapses.
- This pathway involves calcium/synaptotagmin-mediated vesicle-vesicle fusion, increasing synaptic strength.
- This finding necessitates updating synaptic vesicle cycling models to include compound fusion.
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