title: N-terminal domain of complexin independently activates calcium-triggered fusion.
abstract: Complexin activates Ca(2+)-triggered neurotransmitter release and regulates spontaneous release in the presynaptic terminal by cooperating with the neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and the Ca(2+)-sensor synaptotagmin. The N-terminal domain of complexin is important for activation, but its molecular mechanism is still poorly understood. Here, we observed that a split pair of N-terminal and central domain fragments of complexin is sufficient to activate Ca(2+)-triggered release using a reconstituted single-vesicle fusion assay, suggesting that the N-terminal domain acts as an independent module within the synaptic fusion machinery. The N-terminal domain can also interact independently with membranes, which is enhanced by a cooperative interaction with the neuronal SNARE complex. We show by mutagenesis that membrane binding of the N-terminal domain is essential for activation of Ca(2+)-triggered fusion. Consistent with the membrane-binding property, the N-terminal domain can be substituted by the influenza virus hemagglutinin fusion peptide, and this chimera also activates Ca(2+)-triggered fusion. Membrane binding of the N-terminal domain of complexin therefore cooperates with the other fusogenic elements of the synaptic fusion machinery during Ca(2+)-triggered release.
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94304; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94304; Department of Structural Biology, Stanford University, Stanford, CA 94304; Department of Photon Science, Stanford University, Stanford, CA 94304; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304.
authors.forename: Ying
authors.initials: Y
authors.lastname: Lai
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94304; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94304; Department of Structural Biology, Stanford University, Stanford, CA 94304; Department of Photon Science, Stanford University, Stanford, CA 94304; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304.
authors.forename: Ucheor B
authors.initials: UB
authors.lastname: Choi
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94304; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94304; Department of Structural Biology, Stanford University, Stanford, CA 94304; Department of Photon Science, Stanford University, Stanford, CA 94304; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304.
authors.forename: Yunxiang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94304; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94304; Department of Structural Biology, Stanford University, Stanford, CA 94304; Department of Photon Science, Stanford University, Stanford, CA 94304; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304.
authors.forename: Minglei
authors.initials: M
authors.lastname: Zhao
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94304; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94304; Department of Structural Biology, Stanford University, Stanford, CA 94304; Department of Photon Science, Stanford University, Stanford, CA 94304; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Pfuetzner
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94304; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94304; Department of Structural Biology, Stanford University, Stanford, CA 94304; Department of Photon Science, Stanford University, Stanford, CA 94304; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304.
authors.forename: Austin L
authors.initials: AL
authors.lastname: Wang
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94304; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94304; Department of Structural Biology, Stanford University, Stanford, CA 94304; Department of Photon Science, Stanford University, Stanford, CA 94304; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304 brunger@stanford.edu diaojj@gmail.com.
authors.forename: Jiajie
authors.identifier: 0000-0003-4288-3203
authors.initials: J
authors.lastname: Diao
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94304; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94304; Department of Structural Biology, Stanford University, Stanford, CA 94304; Department of Photon Science, Stanford University, Stanford, CA 94304; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304 brunger@stanford.edu diaojj@gmail.com.
authors.forename: Axel T
authors.initials: AT
authors.lastname: Brunger
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D006801:Humans; D008561:Membrane Fusion; D000072417:Protein Domains; D050600:SNARE Proteins / Q000502:physiology; D013572:Synaptic Vesicles / Q000502:physiology; D050863:Synaptotagmin I / Q000502:physiology
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D050600:SNARE Proteins; D050863:Synaptotagmin I; D002118:Calcium
keywords: SNAREs; membrane fusion; synaptic vesicle fusion; synaptotagmin; virus fusion