Molecular Neurobiology

, Volume 48, Issue 1, pp 120–127

Botulinum Neurotoxin Type A is Internalized and Translocated from Small Synaptic Vesicles at the Neuromuscular Junction

  • Cesare Colasante
  • Ornella Rossetto
  • Laura Morbiato
  • Marco Pirazzini
  • Jordi Molgó
  • Cesare Montecucco
Article

DOI: 10.1007/s12035-013-8423-9

Cite this article as:
Colasante, C., Rossetto, O., Morbiato, L. et al. Mol Neurobiol (2013) 48: 120. doi:10.1007/s12035-013-8423-9

Abstract

Botulinum neurotoxin type A (BoNT/A) is the most frequent cause of human botulism and, at the same time, is largely used in human therapy. Some evidence indicates that it enters inside nerve terminals via endocytosis of synaptic vesicles, though this has not been directly proven. The metalloprotease L chain of the neurotoxin then reaches the cytosol in a process driven by low pH, but the acidic compartment wherefrom it translocates has not been identified. Using immunoelectron microscope, we show that BoNT/A does indeed enter inside synaptic vesicles and that each vesicle contains either one or two toxin molecules. This finding indicates that it is the BoNT/A protein receptor synaptic vesicle protein 2, and not its polysialoganglioside receptor that determines the number of toxin molecules taken up by a single vesicle. In addition, by rapid quenching the vesicle trans-membrane pH gradient, we show that the neurotoxin translocation into the cytosol is a fast process. Taken together, these results strongly indicate that translocation of BoNT/A takes place from synaptic vesicles, and not from endosomal compartments, and that the translocation machinery is operated by no more than two neurotoxin molecules.

Keywords

Botulinum neurotoxin Electron microscopy Endocytosis Membrane translocation Neuromuscular junction Synaptic vesicles 

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Cesare Colasante
    • 1
  • Ornella Rossetto
    • 2
  • Laura Morbiato
    • 2
  • Marco Pirazzini
    • 2
  • Jordi Molgó
    • 1
  • Cesare Montecucco
    • 2
  1. 1.Laboratoire de Neurobiologie et Développement, Institut de Neurobiologie Alfred FessardCNRS-UPR 3294Gif-sur-Yvette CedexFrance
  2. 2.Dipartimento di Scienze Biomediche and Istituto CNR di NeuroscienzeUniversità di PadovaPadovaItaly

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