Botulinum Neurotoxin D Uses Synaptic Vesicle Protein SV2 and Gangliosides as Receptors

Lisheng Peng,Min Dong,William H Tepp,Eric A Johnson,Theresa Koehler

doi:10.1371/journal.ppat.1002008

Abstract

Botulinum neurotoxins (BoNTs) include seven bacterial toxins (BoNT/A-G) that target presynaptic terminals and act as proteases cleaving proteins required for synaptic vesicle exocytosis. Here we identified synaptic vesicle protein SV2 as the protein receptor for BoNT/D. BoNT/D enters cultured hippocampal neurons via synaptic vesicle recycling and can bind SV2 in brain detergent extracts. BoNT/D failed to bind and enter neurons lacking SV2, which can be rescued by expressing one of the three SV2 isoforms (SV2A/B/C). Localization of SV2 on plasma membranes mediated BoNT/D binding in both neurons and HEK293 cells. Furthermore, chimeric receptors containing the binding sites for BoNT/A and E, two other BoNTs that use SV2 as receptors, failed to mediate the entry of BoNT/D suggesting that BoNT/D binds SV2 via a mechanism distinct from BoNT/A and E. Finally, we demonstrated that gangliosides are essential for the binding and entry of BoNT/D into neurons and for its toxicity in vivo, supporting a double-receptor model for this toxin.

Highlights

Botulinum neurotoxins (BoNTs), one of the six Category A potential bioterrorism agents, are a family of bacterial toxins that cause the fatal disease botulism in humans and animals [1,2,3]
Previous studies have suggested that BoNT/D does not need a protein receptor nor ganglioside co-receptor, in contrast to all other BoNTs
We demonstrate that BoNT/D uses synaptic vesicle protein SV2 as its protein receptor and gangliosides as coreceptor, supporting the ‘‘double-receptor’’ model as a central theme for this class of toxins

Summary

Introduction

Botulinum neurotoxins (BoNTs), one of the six Category A potential bioterrorism agents, are a family of bacterial toxins that cause the fatal disease botulism in humans and animals [1,2,3]. These toxins target and enter presynaptic nerve terminals by receptor-mediated endocytosis. Once inside neurons, they act as proteases to cleave host proteins essential for synaptic vesicle exocytosis. These three proteins are known as soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNARE) that form the basic machinery mediating the fusion of synaptic vesicle membranes to plasma membranes [24,25,26,27,28]

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