How Botulinum Neurotoxin Light Chain A1 Maintains Stable Association with the Intracellular Neuronal Plasma Membrane

Abstract

Botulinum neurotoxin serotype A (BoNT/A) is the most potent protein toxin for humans and is utilized as a therapy for numerous neurologic diseases. BoNT/A comprises a catalytic Light Chain (LC/A) and a Heavy Chain (HC/A) and includes eight subtypes (BoNT/A1-/A8). Previously we showed BoNT/A potency positively correlated with stable localization on the intracellular plasma membrane and identified a low homology domain (amino acids 268–357) responsible for LC/A1 stable co-localization with SNAP-25 on the plasma membrane, while LC/A3 was present in the cytosol of Neuro2A cells. In the present study, steady-state- and live-imaging of a cytosolic LC/A3 derivative (LC/A3V) engineered to contain individual structural elements of the A1 LDH showed that a 59 amino acid region (275–334) termed the MLD was sufficient to direct LC/A3V from the cytosol to the plasma membrane co-localized with SNAP-25. Informatics and experimental validation of the MLD-predicted R1 region (an α-helix, residues 275–300) and R2 region (a loop, α-helix, loop, residues 302–334) both contribute independent steps to the stable co-localization of LC/A1 with SNAP-25 on the plasma membrane of Neuro-2A cells. Understanding how these structural elements contribute to the overall association of LC/A1 on the plasma membrane may identify the molecular basis for the LC contribution of BoNT/A1 to high potency.

A Comprehensive Structural Analysis of Clostridium botulinum Neurotoxin A Cell-Binding Domain from Different Subtypes

“…Cleavage of any one of these SNARE proteins at the NMJ prevents release of acetylcholine [ 64 ]. The precise mechanisms underpinning post-translocation trafficking of BoNT LC are yet to be established, however, recent evidence suggests LC/A1 is co-localised to the plasma membrane along with SNAP-25 [ 65 ].…”

Toxina botulínica. ¿Por qué dura menos? Una revisión desde nuestra experiencia

“…La cadena ligera escinde las proteínas SNARE (soluble N-ethylmaleimide sensitive attachment protein receptor), que intervienen en el transporte de vesículas de acetilcolina y su acoplamiento a la membrana presináptica antes, impidiendo la liberación de acetilcolina en la hendidura sináptica [8]. Esto da como resultado una parálisis temporal y reversible de los músculos [9][10][11].…”