Structural basis for botulinum neurotoxin E recognition of synaptic vesicle protein 2

Area of Science:

• Neuroscience
• Structural Biology
• Toxicology

Background:

• Botulinum neurotoxin E (BoNT/E) is a significant cause of human botulism.
• BoNT/E also holds promise as a therapeutic agent.
• Understanding its mechanism of action is crucial for both preventing and treating botulism.

Purpose of the Study:

• To determine the co-crystal structures of the BoNT/E receptor-binding domain (H_CE) with its neuronal receptor SV2A.
• To elucidate the molecular interactions governing BoNT/E binding and cell entry.
• To provide a structural basis for engineering BoNT/E variants for clinical applications.

Main Methods:

• Co-crystallography of H_CE with SV2A and a nanobody.
• Structure-based mutagenesis.
• Functional assays to assess cell entry and neurotoxicity.

Main Results:

• The co-crystal structures reveal dual binding interactions: protein-protein with SV2A/SV2B and protein-glycan via a sialic acid-binding pocket.
• BoNT/E specifically recognizes SV2A and SV2B, but not SV2C, through protein-protein interactions.
• Both protein-protein and protein-glycan interactions are critical for SV2A-mediated cell entry and neurotoxicity.

Conclusions:

• The study establishes the structural basis for BoNT/E receptor specificity.
• Dual binding mechanisms are essential for BoNT/E neurotoxicity and cell entry.
• These findings can guide the engineering of BoNT/E for novel therapeutic strategies.