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Calcium-dependent transmitter secretion from fibroblasts: modulation by synaptotagmin I
T Morimoto1, S Popov, K M Buckley
1Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
Neuron
|September 1, 1995
Summary
Synaptotagmin I reduces spontaneous acetylcholine release in CHO fibroblasts but enhances calcium-evoked release. This protein improves excitation-secretion coupling by regulating vesicular exocytosis.
Area of Science:
- Cell Biology
- Neuroscience
- Biochemistry
Background:
- CHO fibroblasts release acetylcholine (ACh) spontaneously and upon depolarization.
- This release is calcium (Ca2+)-dependent and can be detected electrophysiologically.
- Synaptic vesicle proteins play crucial roles in regulating neurotransmitter release.
Purpose of the Study:
- To investigate the role of synaptotagmin I in regulating acetylcholine release from CHO fibroblasts.
- To determine how synaptotagmin I affects both spontaneous and evoked ACh release.
- To elucidate the mechanism by which synaptotagmin I influences excitation-secretion coupling.
Main Methods:
- Whole-cell voltage-clamp electrophysiology to measure ACh release.
- Transfection of CHO fibroblasts with synaptotagmin I.
- Biochemical and ultrastructural studies using horseradish peroxidase (HPP) as an endocytic marker.
Main Results:
- Synaptotagmin I expression reduced spontaneous quantal ACh release.
- Synaptotagmin I enhanced Ca2+-evoked ACh release compared to control cells.
- Synaptotagmin I inhibited exocytosis at resting Ca2+ levels and was relieved by depolarization-induced Ca2+ influx.
Conclusions:
- Synaptotagmin I acts as a negative regulator of spontaneous ACh release.
- Synaptotagmin I enhances the efficiency of excitation-secretion coupling by modulating Ca2+-dependent exocytosis.
- These findings highlight synaptotagmin I's critical role in precise control of vesicular release.