title: Syntaxin-1 N-peptide and Habc-domain perform distinct essential functions in synaptic vesicle fusion.
abstract: Among SNARE proteins mediating synaptic vesicle fusion, syntaxin-1 uniquely includes an N-terminal peptide ('N-peptide') that binds to Munc18-1, and a large, conserved H(abc)-domain that also binds to Munc18-1. Previous in vitro studies suggested that the syntaxin-1 N-peptide is functionally important, whereas the syntaxin-1 H(abc)-domain is not, but limited information is available about the in vivo functions of these syntaxin-1 domains. Using rescue experiments in cultured syntaxin-deficient neurons, we now show that the N-peptide and the H(abc)-domain of syntaxin-1 perform distinct and independent roles in synaptic vesicle fusion. Specifically, we found that the N-peptide is essential for vesicle fusion as such, whereas the H(abc)-domain regulates this fusion, in part by forming the closed syntaxin-1 conformation. Moreover, we observed that deletion of the H(abc)-domain but not deletion of the N-peptide caused a loss of Munc18-1 which results in a decrease in the readily releasable pool of vesicles at a synapse, suggesting that Munc18 binding to the H(abc)-domain stabilizes Munc18-1. Thus, the N-terminal syntaxin-1 domains mediate different functions in synaptic vesicle fusion, probably via formation of distinct Munc18/SNARE-protein complexes.
authors.affiliation: Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhou
authors.forename: Zhiping P
authors.initials: ZP
authors.lastname: Pang
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Yang
authors.forename: Yingsha
authors.initials: Y
authors.lastname: Zhang
authors.forename: Christian
authors.initials: C
authors.lastname: Rosenmund
authors.forename: Taulant
authors.initials: T
authors.lastname: Bacaj
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Südhof
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D055785:Gene Knockdown Techniques; D008561:Membrane Fusion; D051379:Mice; D008969:Molecular Sequence Data; D051938:Munc18 Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D013569:Synapses / Q000235:genetics / Q000378:metabolism*; D009435:Synaptic Transmission; D013572:Synaptic Vesicles / Q000235:genetics / Q000378:metabolism; D050827:Syntaxin 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D051938:Munc18 Proteins; D010455:Peptides; C497938:Stxbp1 protein, mouse; D050827:Syntaxin 1