Glycosylated SV2 and gangliosides as dual receptors for botulinum neurotoxin serotype F

Biochemistry. 2009 Jun 23;48(24):5631-41. doi: 10.1021/bi9002138.

Abstract

Botulinum neurotoxin causes rapid flaccid paralysis through the inhibition of acetylcholine release at the neuromuscular junction. The seven BoNT serotypes (A-G) have been proposed to bind motor neurons via ganglioside-protein dual receptors. To date, the structure-function properties of BoNT/F host receptor interactions have not been resolved. Here, we report the crystal structures of the receptor binding domains (HCR) of BoNT/A and BoNT/F and the characterization of the dual receptors for BoNT/F. The overall polypeptide fold of HCR/A is essentially identical to the receptor binding domain of the BoNT/A holotoxin, and the structure of HCR/F is very similar to that of HCR/A, except for two regions implicated in neuronal binding. Solid phase array analysis identified two HCR/F binding glycans: ganglioside GD1a and oligosaccharides containing an N-acetyllactosamine core. Using affinity chromatography, HCR/F bound native synaptic vesicle glycoproteins as part of a protein complex. Deglycosylation of glycoproteins using alpha(1-3,4)-fucosidase, endo-beta-galactosidase, and PNGase F disrupted the interaction with HCR/F, while the binding of HCR/B to its cognate receptor, synaptotagmin I, was unaffected. These data indicate that the HCR/F binds synaptic vesicle glycoproteins through the keratan sulfate moiety of SV2. The interaction of HCR/F with gangliosides was also investigated. HCR/F bound specifically to gangliosides that contain alpha2,3-linked sialic acid on the terminal galactose of a neutral saccharide core (binding order GT1b = GD1a >> GM3; no binding to GD1b and GM1a). Mutations within the putative ganglioside binding pocket of HCR/F decreased binding to gangliosides, synaptic vesicle protein complexes, and primary rat hippocampal neurons. Thus, BoNT/F neuronal discrimination involves the recognition of ganglioside and protein (glycosylated SV2) carbohydrate moieties, providing a structural basis for the high affinity and specificity of BoNT/F for neurons.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Binding Sites
  • Botulinum Toxins / chemistry*
  • Botulinum Toxins / metabolism*
  • Botulinum Toxins, Type A / chemistry
  • Botulinum Toxins, Type A / metabolism
  • Gangliosides / chemistry
  • Gangliosides / metabolism*
  • Glycosylation
  • Membrane Glycoproteins / chemistry
  • Membrane Glycoproteins / metabolism*
  • Models, Molecular
  • Nerve Tissue Proteins / chemistry
  • Nerve Tissue Proteins / metabolism
  • Neurons / metabolism
  • Protein Conformation
  • Rats
  • Rats, Sprague-Dawley
  • Synaptic Vesicles / metabolism

Substances

  • Gangliosides
  • Membrane Glycoproteins
  • Nerve Tissue Proteins
  • Sv2a protein, rat
  • Botulinum Toxins
  • Botulinum Toxins, Type A
  • botulinum toxin type F

Associated data

  • PDB/3FUO
  • PDB/3FUQ