title: Arg206 of SNAP-25 is essential for neuroexocytosis at the Drosophila melanogaster neuromuscular junction.
abstract: An analysis of SNAP-25 isoform sequences indicates that there is a highly conserved arginine residue (198 in vertebrates, 206 in the genus Drosophila) within the C-terminal region, which is cleaved by botulinum neurotoxin A, with consequent blockade of neuroexocytosis. The possibility that it may play an important role in the function of the neuroexocytosis machinery was tested at neuromuscular junctions of Drosophila melanogaster larvae expressing SNAP-25 in which Arg206 had been replaced by alanine. Electrophysiological recordings of spontaneous and evoked neurotransmitter release under different conditions as well as testing for the assembly of the SNARE complex indicate that this residue, which is at the P(1)' position of the botulinum neurotoxin A cleavage site, plays an essential role in neuroexocytosis. Computer graphic modelling suggests that this arginine residue mediates protein-protein contacts within a rosette of SNARE complexes that assembles to mediate the fusion of synaptic vesicles with the presynaptic plasma membrane.
authors.affiliation: Department of Human Anatomy and Physiology, Section of Physiology, University of Padova, 35131, Italy.
authors.forename: Aram
authors.initials: A
authors.lastname: Megighian
authors.forename: Michele
authors.initials: M
authors.lastname: Scorzeto
authors.forename: Damiano
authors.initials: D
authors.lastname: Zanini
authors.forename: Sergio
authors.initials: S
authors.lastname: Pantano
authors.forename: Michela
authors.initials: M
authors.lastname: Rigoni
authors.forename: Clara
authors.initials: C
authors.lastname: Benna
authors.forename: Ornella
authors.initials: O
authors.lastname: Rossetto
authors.forename: Cesare
authors.initials: C
authors.lastname: Montecucco
authors.forename: Mauro
authors.initials: M
authors.lastname: Zordan
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001120:Arginine / Q000235:genetics; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D020013:Calcium Signaling; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004331:Drosophila melanogaster / Q000502:physiology*; D004594:Electrophysiology; D005071:Evoked Potentials / Q000235:genetics; D005089:Exocytosis / Q000235:genetics; D007814:Larva; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000235:genetics / Q000378:metabolism*; D009435:Synaptic Transmission / Q000235:genetics; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism*
chemical_list: D050505:Mutant Proteins; D050825:Synaptosomal-Associated Protein 25; D001120:Arginine