title: Evidence for a radial SNARE super-complex mediating neurotransmitter release at the Drosophila neuromuscular junction.
abstract: The SNARE proteins VAMP/synaptobrevin, SNAP-25 and syntaxin are core components of the apparatus that mediates neurotransmitter release. They form a heterotrimeric complex, and an undetermined number of SNARE complexes assemble to form a super-complex. Here, we present a radial model of this nanomachine. Experiments performed with botulinum neurotoxins led to the identification of one arginine residue in SNAP-25 and one aspartate residue in syntaxin (R206 and D253 in Drosophila melanogaster). These residues are highly conserved and predicted to play a major role in the protein-protein interactions between SNARE complexes by forming an ionic couple. Accordingly, we generated transgenic Drosophila lines expressing SNAREs mutated in these residues and performed an electrophysiological analysis of their neuromuscular junctions. Our results indicate that SNAP-25-R206 and syntaxin-D253 play a major role in neuroexocytosis and support a radial assembly of several SNARE complexes interacting via the ionic couple formed by these two residues.
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 56 B, 35121 Padova, Italy.
authors.forename: Aram
authors.initials: A
authors.lastname: Megighian
authors.forename: Mauro
authors.initials: M
authors.lastname: Zordan
authors.forename: Sergio
authors.initials: S
authors.lastname: Pantano
authors.forename: Michele
authors.initials: M
authors.lastname: Scorzeto
authors.forename: Michela
authors.initials: M
authors.lastname: Rigoni
authors.forename: Damiano
authors.initials: D
authors.lastname: Zanini
authors.forename: Ornella
authors.initials: O
authors.lastname: Rossetto
authors.forename: Cesare
authors.initials: C
authors.lastname: Montecucco
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001905:Botulinum Toxins / Q000378:metabolism; D002478:Cells, Cultured; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000502:physiology*; D005818:Genetic Engineering; D007473:Ion Channels / Q000378:metabolism*; D007814:Larva; D008956:Models, Chemical; D009154:Mutation / Q000235:genetics; D009469:Neuromuscular Junction / Q000502:physiology*; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D055503:Protein Multimerization / Q000235:genetics; D050765:Qa-SNARE Proteins / Q000235:genetics / Q000378:metabolism*; D013237:Stereoisomerism; D009435:Synaptic Transmission; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D007473:Ion Channels; D050765:Qa-SNARE Proteins; C494207:Snap25 protein, Drosophila; D050825:Synaptosomal-Associated Protein 25; C578392:syntaxin, Drosophila; D001905:Botulinum Toxins
keywords: Drosophila melanogaster; Neuroexocytosis; SNARE; Synapse