Botulinum neurotoxins C, E and F bind gangliosides via a conserved binding site prior to stimulation-dependent uptake with botulinum neurotoxin F utilising the three isoforms of SV2 as second receptor

J Neurochem. 2009 Sep;110(6):1942-54. doi: 10.1111/j.1471-4159.2009.06298.x. Epub 2009 Jul 23.

Abstract

The high toxicity of clostridial neurotoxins primarily results from their specific binding and uptake into neurons. At motor neurons, the seven botulinum neurotoxin serotypes A-G (BoNT/A-G) inhibit acetylcholine release, leading to flaccid paralysis, while tetanus neurotoxin blocks neurotransmitter release in inhibitory neurons, resulting in spastic paralysis. Uptake of BoNT/A, B, E and G requires a dual interaction with gangliosides and the synaptic vesicle (SV) proteins synaptotagmin or SV2, whereas little is known about the entry mechanisms of the remaining serotypes. Here, we demonstrate that BoNT/F as wells depends on the presence of gangliosides, by employing phrenic nerve hemidiaphragm preparations derived from mice expressing GM3, GM2, GM1 and GD1a or only GM3. Subsequent site-directed mutagenesis based on homology models identified the ganglioside binding site at a conserved location in BoNT/E and F. Using the mice phrenic nerve hemidiaphragm assay as a physiological model system, cross-competition of full-length neurotoxin binding by recombinant binding fragments, plus accelerated neurotoxin uptake upon increased electrical stimulation, indicate that BoNT/F employs SV2 as protein receptor, whereas BoNT/C and D utilise different SV receptor structures. The co-precipitation of SV2A, B and C from Triton-solubilised SVs by BoNT/F underlines this conclusion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites / drug effects
  • Binding Sites / genetics
  • Binding, Competitive / drug effects
  • Binding, Competitive / genetics
  • Botulinum Toxins / metabolism*
  • Botulinum Toxins / pharmacology
  • Diaphragm / drug effects
  • Diaphragm / physiology
  • Dose-Response Relationship, Drug
  • Electric Stimulation / methods
  • Gangliosides / chemistry
  • Gangliosides / deficiency
  • Gangliosides / metabolism*
  • Isometric Contraction / drug effects
  • Isometric Contraction / physiology
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Models, Molecular
  • Mutagenesis, Site-Directed / methods
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Phrenic Nerve / physiology
  • Protein Binding / drug effects
  • Protein Binding / physiology
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism*
  • Rats
  • Synaptic Vesicles / metabolism

Substances

  • Gangliosides
  • Membrane Glycoproteins
  • Nerve Tissue Proteins
  • Protein Isoforms
  • Sv2a protein, mouse
  • botulinum toxin type G
  • Botulinum Toxins
  • botulinum toxin type C
  • botulinum toxin type F