Synaptic vesicle protein 2 and polysialylated ganglioside complex (SV2/Ganglioside complex)

The target is a dual-receptor complex consisting of Synaptic Vesicle Protein 2 (SV2) and polysialylated gangliosides (such as GT1b and GD1a) located on the presynaptic membranes of cholinergic neurons (Dong et al., 2006, Science). This complex is the primary entry point for Botulinum neurotoxin type A (BoNT/A). According to the "double-receptor model," gangliosides act as initial low-affinity anchors that concentrate the toxin on the neuronal surface, while SV2 serves as the high-affinity protein receptor that mediates endocytosis during synaptic vesicle recycling (Montecucco, 1986, TIBS). SV2 is a transmembrane glycoprotein with three isoforms (A, B, and C), all of which can function as receptors for BoNT/A. Once internalized, the toxin's light chain is released into the cytosol where it cleaves the SNARE protein SNAP-25, effectively blocking the release of the neurotransmitter acetylcholine (Pirazzini et al., 2017, Pharmacological Reviews). This interaction is the pharmacological basis for the therapeutic use of botulinum toxins in treating conditions like cervical dystonia, chronic migraine, and muscle spasticity. The specificity of this target for cholinergic neurons at the neuromuscular junction allows for localized muscle relaxation, though systemic spread remains a significant safety concern.

Other names

SV2ASV2BSV2CGT1bGD1aBotulinum neurotoxin type A receptorBoNT/A receptor

Botulinum neurotoxin type A (BoNT/A) utilizes a dual-binding mechanism: the heavy chain first binds to polysialylated gangliosides (like GT1b) on the presynaptic membrane, followed by high-affinity binding to the luminal domain of Synaptic Vesicle Protein 2 (SV2) isoforms A, B, or C (Dong et al., 2006). This binding facilitates receptor-mediated endocytosis of the toxin. Following acidification of the endosome, the toxin's light chain translocates into the cytosol, where it acts as a zinc-dependent endopeptidase to cleave SNAP-25. The cleavage of SNAP-25 prevents the assembly of the SNARE complex, thereby inhibiting the fusion of synaptic vesicles with the presynaptic membrane and blocking acetylcholine release (Rossetto et al., 2014).