The Cytoplasmic Domain of Rat Synaptotagmin I Enhances Synaptic Transmission
Synaptotagmin, an integral membrane protein of synaptic vesicles, functions as a calcium sensor in the temporal control of neurotransmitter release. Although synaptotagmin facilitates lipid membrane fusion in biochemical experiments, overexpression of synaptotagmin inhibits neurotransmission. A facilitatory effect of synaptotagmin on synaptic transmission was never observed. To determine whether synaptotagmin may accelerate synaptic transmission in vivo, we injected the cytoplasmic domain of rat synaptotagmin I (CD-syt) into crayfish motor axons and tested the effect of CD-syt on synaptic response. We confirmed that CD-syt accelerates neuromuscular transmission. The injected preparation had larger synaptic potentials with shorter rise time. Experiments with varying calcium concentrations showed that CD-syt increased the maximum synaptic response of the neuromuscular synapses. Further tests on short-term plasticity of neuromuscular synapses revealed that CD-syt increases the release probability of the release-ready vesicles.
KeywordsNeurotransmitter release Synaptic vesicle fusion Synaptic plasticity
We thank Dr. James Mohler and Dr. Claudio G. Giraudo for their kind help in protein expression. This study was supported by Graduate Research Technology Incentive Program of York College, The City University of New York.
Conflict of interest
The authors declare no competing financial interests.
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