Entry of Botulinum Neurotoxin Subtypes A1 and A2 into Neurons

• Published in: Infection and immunity 2017-01, Vol.85 (1)
• Main Authors: Kroken, Abby R, Blum, Faith C, Zuverink, Madison, Barbieri, Joseph T
• Format: Article
• Language: English
• Subjects: Animals; Botulinum Toxins, Type A - metabolism; Botulism - metabolism; Botulism - microbiology; Cells, Cultured; Cellular Microbiology: Pathogen-Host Cell Molecular Interactions; Clostridium botulinum; Clostridium botulinum - pathogenicity; Gangliosides - metabolism; Mice; Neurons - metabolism; Neurons - microbiology; Protein Binding - physiology; Rats; Synaptic Vesicles - metabolism; Synaptic Vesicles - microbiology
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.00795-16

Botulinum neurotoxins (BoNTs) are the most toxic proteins for humans but also are common therapies for neurological diseases. BoNTs are dichain toxins, comprising an N-terminal catalytic domain (LC) disulfide bond linked to a C-terminal heavy chain (HC) which includes a translocation domain (H ) and a receptor binding domain (H ). Recently, the BoNT serotype A (BoNT/A) subtypes A1 and A2 were reported to possess similar potencies but different rates of cellular intoxication and pathology in a mouse model of botulism. The current study measured H A1 and H A2 entry into rat primary neurons and cultured Neuro2A cells. We found that there were two sequential steps during the association of BoNT/A with neurons. The initial step was ganglioside dependent, while the subsequent step involved association with synaptic vesicles. H A1 and H A2 entered the same population of synaptic vesicles and entered cells at similar rates. The primary difference was that H A2 had a higher degree of receptor occupancy for cells and neurons than HcA1. Thus, H A2 and H A1 share receptors and entry pathway but differ in their affinity for receptor. The initial interaction of H A1 and H A2 with neurons may contribute to the unique pathologies of BoNT/A1 and BoNT/A2 in mouse models.