title: Spontaneous Vesicle Release Is Not Tightly Coupled to Voltage-Gated Calcium Channel-Mediated Ca2+ Influx and Is Triggered by a Ca2+ Sensor Other Than Synaptotagmin-2 at the Juvenile Mice Calyx of Held Synapses.
abstract: It is well known that voltage-gated calcium channels (VGCCs)-mediated Ca(2+) influx triggers evoked synaptic vesicle release. However, the mechanisms of Ca(2+) regulation of spontaneous miniature vesicle release (mini) remain poorly understood. Here we show that blocking VGCCs at the juvenile mice (C57BL/6) calyx of Held synapse failed to cause an immediate change in minis. Instead, it resulted in a significant reduction (∼40%) of mini frequency several minutes after the blockage. By recording VGCC activity and single vesicle fusion events directly at the presynaptic terminal, we found that minis did not couple to VGCC-mediated Ca(2+) entry, arguing for a lack of direct correlation between mini and transient Ca(2+) influx. Moreover, mini frequencies displayed a lower apparent Ca(2+) cooperativity than those of evoked release. In agreement with this observation, abrogation of the Ca(2+) sensor synaptotagmin-2 had no effect on apparent Ca(2+) cooperativity of minis. Together, our study provides the first direct evidence that spontaneous minis are not mediated by transient Ca(2+) signals through VGCCs and are triggered by a Ca(2+)-sensing mechanism that is different from the evoked release at these microdomain VGCC-vesicle coupled synapses.
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China, University of Chinese Academy of Sciences, Beijing 100049, China, and.
authors.forename: Jinye
authors.initials: J
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China, Center of Parkinson's Disease, Beijing Institute for Brain Disorders, Beijing 100053, China.
authors.forename: Peihua
authors.initials: P
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China, University of Chinese Academy of Sciences, Beijing 100049, China, and.
authors.forename: Hao
authors.initials: H
authors.lastname: Tian
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China, University of Chinese Academy of Sciences, Beijing 100049, China, and Center of Parkinson's Disease, Beijing Institute for Brain Disorders, Beijing 100053, China jysun@ibp.ac.cn.
authors.forename: Jianyuan
authors.initials: J
authors.lastname: Sun
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001703:Biophysics; D001921:Brain / Q000166:cytology; D019256:Cadmium Chloride / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology; D018408:Patch-Clamp Techniques; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D050861:Synaptotagmin II / Q000235:genetics / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D050861:Synaptotagmin II; C494263:Syt2 protein, mouse; D019256:Cadmium Chloride; D002118:Calcium
keywords: Ca2+ sensor; VGCC; spontaneous vesicle release; synaptic plasticity