Structural basis for antiepileptic drugs and botulinum neurotoxin recognition of SV2A

Abstract

More than one percent of people have epilepsy worldwide. Levetiracetam (LEV) is a successful new-generation antiepileptic drug (AED), and its derivative, brivaracetam (BRV), shows improved efficacy. Synaptic vesicle glycoprotein 2a (SV2A), a putative membrane transporter in the synaptic vesicles (SVs), has been identified as a target of LEV and BRV. SV2A also serves as a receptor for botulinum neurotoxin (BoNT), which is the most toxic protein and has paradoxically emerged as a potent reagent for therapeutic and cosmetic applications. Nevertheless, no structural analysis on AEDs and BoNT recognition by full-length SV2A has been available. Here we describe the cryo-electron microscopy structures of the full-length SV2A in complex with the BoNT receptor-binding domain, BoNT/A2 HC, and either LEV or BRV. The large fourth luminal domain of SV2A binds to BoNT/A2 HC through protein-protein and protein-glycan interactions. LEV and BRV occupy the putative substrate-binding site in an outward-open conformation. A propyl group in BRV creates additional contacts with SV2A, explaining its higher binding affinity than that of LEV, which was further supported by label-free spectral shift assay. Numerous LEV derivatives have been developed as AEDs and positron emission tomography (PET) tracers for neuroimaging. Our work provides a structural framework for AEDs and BoNT recognition of SV2A and a blueprint for the rational design of additional AEDs and PET tracers.

Structures of native SV2A reveal the binding mode for tetanus neurotoxin and anti-epileptic racetams

“…Higher resolution structures will be needed alongside with mutagenesis studies to resolve the exact conformation of the butyl-amide group of LEV when bound to SV2A. We note further that the published structure differs with respect to the disulfide-bridge between Cys198 and Cys583 that we can clearly resolve in the map but that seems to be not formed in the protein overexpressed in insect cells 64 . This could have impact for the mobility of the LD4.…”

“…During the writing of this manuscript, another research group has provided a structure of SV2A with bound LEV 64 . We note that the LEV molecule was placed differently from our study with respect to the rotamer of the butyl-amide as the authors placed the ethyl-group pointing to Cys297.…”