Translocation domain of botulinum neurotoxin A subtype 2 potently induces entry into neuronal cells

Botulinum neurotoxin (BoNT) is the causative agent of botulism in humans and animals. Only BoNT serotype A subtype 1 (BoNT/A1) is used clinically because of its high potency and long duration of action. BoNT/A1 and BoNT/A subtype 2 (BoNT/A2) have a high degree of amino acid sequence similarity in th...

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Published in:Microbiology and immunology 2020-07, Vol.64 (7), p.502-511
Main Authors: Kohda, Tomoko, Tsukamoto, Kentaro, Torii, Yasushi, Kozaki, Shunji, Mukamoto, Masafumi
Format: Article
Language:English
Subjects:
Amino acid sequence
Animals
botulinum neurotoxin
Botulinum toxin type A
Botulinum Toxins, Type A - chemistry
Botulinum Toxins, Type A - genetics
Botulism
Cells, Cultured
Clostridium botulinum - metabolism
Endopeptidases
Escherichia coli - metabolism
Mice
Neurons - metabolism
Neurotoxicity
potency
Protein Binding
Protein Domains
Recombinant Proteins - chemistry
Recombinant Proteins - genetics
SNAP‐25
subtypes
translocation domain
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Summary:Botulinum neurotoxin (BoNT) is the causative agent of botulism in humans and animals. Only BoNT serotype A subtype 1 (BoNT/A1) is used clinically because of its high potency and long duration of action. BoNT/A1 and BoNT/A subtype 2 (BoNT/A2) have a high degree of amino acid sequence similarity in the light chain (LC) (96%), whereas their N‐and C‐terminal heavy chain (HN and HC) differ by 13%. The LC acts as a zinc‐dependent endopeptidase, HN as the translocation domain, and HC as the receptor‐binding domain. BoNT/A2 and BoNT/A1 had similar potency in the mouse bioassay, but BoNT/A2 entered faster and more efficiently into neuronal cells. To identify the domains responsible for these characteristics, HN of BoNT/A1 and BoNT/A2 was exchanged to construct chimeric BoNT/A121 and BoNT/A212. After expression in Escherichia coli, chimeric and wild‐type BoNT/As were purified as single‐chain proteins and activated by conversion to disulfide‐linked dichains. The toxicities of recombinant wild‐type and chimeric BoNT/As were similar, but dropped to 60% compared with the values of native BoNT/As. The relative orders of SNAP‐25 cleavage activity in neuronal cells and toxicity differed. BoNT/A121 and recombinant BoNT/A2 have similar SNAP‐25 cleavage activity. BoNT/A2 HN is possibly responsible for the higher potency of BoNT/A2 than BoNT/A1.
ISSN:0385-5600
1348-0421
DOI:10.1111/1348-0421.12796