Botulinum neurotoxin A selectively cleaves the synaptic protein SNAP-25

Abstract

Neurotransmitter release is potently blocked by a group of structurally related toxin proteins produced by Clostridium botulinum. Botulinum neurotoxin type B (BoNT/B) and tetanus toxin (TeTx) are zinc-dependent proteases that specifically cleave synaptobrevin (VAMP), a membrane protein of synaptic vesicles. Here we report that inhibition of transmitter release from synaptosomes caused by botulinum neurotoxin A (BoNT/A) is associated with the selective proteolysis of the synaptic protein SNAP-25. Furthermore, isolated or recombinant L chain of BoNT/A cleaves SNAP-25 in vitro. Cleavage occurred near the carboxyterminus and was sensitive to divalent cation chelators. In addition, a glutamate residue in the BoNT/A L chain, presumably required to stabilize a water molecule in the zinc-containing catalytic centre, was required for proteolytic activity. These findings demonstrate that BoNT/A acts as a zinc-dependent protease that selectively cleaves SNAP-25. Thus, a second component of the putative fusion complex mediating synaptic vesicle exocytosis is targeted by a clostridial neurotoxin.

Sensing the Deadliest Toxin: Technologies for Botulinum Neurotoxin Detection

“…Finally, inside the cytosol, the LC acts as zinc-dependent metallo¬protease and cleaves proteins of the SNARE complex, which are the part of exocytosis apparatus, effectively destroying this apparatus and leading to inhibition of neurotransmitter release [3]. In this last step of SNARE complex protein cleavage, each of the seven different BoNT serotypes cleaves a unique peptide bond located on one of the SNARE proteins [16,17,18]. BoNT/A, /C and /E cleave synaptosomal associated protein of 25 kDa (SNAP-25), at positions 197-198, 198-199 and 180-181, respectively.…”

Adrenal chromaffin cells contain functionally different SNAP‐25 monomers and SNAP‐25/syntaxin heterodimers

“…1). In neurons blockade of transmitter release by BoNT/A is associated with cleavage of SNAP-25 [33,34]. In order to examine whether SNAP-25 is also cleaved by BoNT/ A in adrenal chromaffin cells we analyzed SNAP-25 in permeabilized cells by immunoblotting.…”

Development of vaccines for prevention of botulism

“…The light chains are zinc-dependent endoproteases that selectively inactivate three essential proteins involved in the docking and fusion of acetylcholinecontaining synaptic vesicles to the plasma membrane. The light chains of BoNT serotypes A, C 1 , and E cleave SNAP-25 (synaptosomal-associated protein of 25 kDa) [27][28][29][30]; serotypes B, D, F, and G cleave VAMP/ synaptobrevin (synaptic vesicle-associated membrane protein) [31]; and serotype C 1 cleaves syntaxin [32]. Inactivation of SNAP-25, VAMP, or syntaxin by BoNT leads to an inability of the nerve cells to release acetylcholine, resulting in neuromuscular paralysis.…”