Identification of the SV2-Protein Receptor Binding Site of Botulinum Neurotoxin Type E.

Biochemical Journal (Impact Factor: 4.4). 04/2013; 453(1). DOI: 10.1042/BJ20130391
Source: PubMed


The highly specific binding and uptake of botulinum neurotoxins (BoNT/A-G) into peripheral cholinergic motoneurons turns them into the most poisonous substances known. Interaction with gangliosides accumulates the neurotoxins on the plasma membrane and binding to a synaptic vesicle membrane protein leads to neurotoxin endocytosis. The synaptic vesicle (glyco-)protein 2 (SV2) mediates the uptake of BoNT/A and E, whereas synaptotagmin (Syt) is responsible for the endocytosis of BoNT/B and G. The Syt-binding site of the former was identified by co-crystallization and mutational analyses. Here we report the identification of the SV2‑binding interface of BoNT/E. Mutations interfering with SV2‑binding were located at a site that corresponds to the Syt‑binding site of BoNT/B and at an extended surface area located on the back side of the conserved ganglioside binding site, comprising the N- and C‑terminal half of the BoNT/E binding domain. Mutations impairing the affinity also reduced the neurotoxicity of full-length BoNT/E at mouse phrenic nerve hemidiaphragm preparations demonstrating the crucial role of the identified binding interface. Furthermore, we show that a monoclonal antibody neutralizes BoNT/E activity because it directly interferes with the BoNT/E-SV2 interaction. The data obtained suggest a novel mode of binding for BoNTs that exploit SV2 as cell surface receptor.

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    • "Similar to the serotype-specific BoNT binding to Syt discussed above, various BoNTs seem to develop different mechanisms recognizing three isoforms of SV2. For example, BoNT/A has the highest affinity to SV2C followed by SV2A and 2B (Dong et al., 2006); BoNT/D preferentially binds SV2B, and to a lesser extent, SV2A and 2C (Peng et al., 2011); BoNT/E exhibits higher binding affinity to SV2A over 2B but does not bind SV2C (Dong et al., 2008; Mahrhold et al., 2013; Peng et al., 2011). The binding-sites for BoNT/A and BoNT/E have been mapped to the large luminal domain 4 (LD4) of SV2, which is necessary and sufficient to mediate the entry of both toxins (Dong et al., 2008, 2006). "
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