title: Microsecond dissection of neurotransmitter release: SNARE-complex assembly dictates speed and Ca²⁺ sensitivity.
abstract: SNARE-complex assembly mediates synaptic vesicle fusion during neurotransmitter release and requires that the target-SNARE protein syntaxin-1 switches from a closed to an open conformation. Although many SNARE proteins are available per vesicle, only one to three SNARE complexes are minimally needed for a fusion reaction. Here, we use high-resolution measurements of synaptic transmission in the calyx-of-Held synapse from mutant mice in which syntaxin-1 is rendered constitutively open and SNARE-complex assembly is enhanced to examine the relation between SNARE-complex assembly and neurotransmitter release. We show that enhancing SNARE-complex assembly dramatically increases the speed of evoked release, potentiates the Ca(2+)-affinity of release, and accelerates fusion-pore expansion during individual vesicle fusion events. Our data indicate that the number of assembled SNARE complexes per vesicle during fusion determines the presynaptic release probability and fusion kinetics and suggest a mechanism whereby proteins (Munc13 or RIM) may control presynaptic plasticity by regulating SNARE-complex assembly.
authors.affiliation: Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, 265 Campus Drive, Stanford, CA 94305-5453, USA. Electronic address: claudioa@stanford.edu.
authors.forename: Claudio
authors.initials: C
authors.lastname: Acuna
authors.affiliation: Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China.
authors.forename: Qingchen
authors.initials: Q
authors.lastname: Guo
authors.affiliation: Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, 265 Campus Drive, Stanford, CA 94305-5453, USA.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Burré
authors.affiliation: Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, 265 Campus Drive, Stanford, CA 94305-5453, USA.
authors.forename: Manu
authors.initials: M
authors.lastname: Sharma
authors.affiliation: Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China; Center of Parkinson's Disease, Beijing Institute for Brain Disorders, 15 Datun Road, Chaoyang District, Beijing 100101, China.
authors.forename: Jianyuan
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, 265 Campus Drive, Stanford, CA 94305-5453, USA. Electronic address: tcs1@stanford.edu.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Südhof
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008561:Membrane Fusion / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000502:physiology; D050600:SNARE Proteins / Q000378:metabolism*; D009435:Synaptic Transmission; D013572:Synaptic Vesicles / Q000378:metabolism*; D050827:Syntaxin 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D050600:SNARE Proteins; D050827:Syntaxin 1; D018698:Glutamic Acid; D002118:Calcium