title: Bimodal modulation of the botulinum neurotoxin protein-conducting channel.
abstract: Clostridium botulinum neurotoxin (BoNT) is the causative agent of botulism, a neuroparalytic disease. We describe here a semisynthetic strategy to identify inhibitors based on toosendanin, a traditional Chinese medicine reported to protect from BoNT intoxication. Using a single molecule assay of BoNT serotypes A and E light chain (LC) translocation through the heavy chain (HC) channel in neurons, we discovered that toosendanin and its tetrahydrofuran analog selectively arrest the LC translocation step of intoxication with subnanomolar potency, and increase the unoccluded HC channel propensity to open with micromolar efficacy. The inhibitory profile on LC translocation is accurately recapitulated in 2 different BoNT intoxication assays, namely the mouse protection and the primary rat spinal cord cell assays. Toosendanin has an unprecedented dual mode of action on the protein-conducting channel acting as a cargo-dependent inhibitor of translocation and as cargo-free channel activator. These results imply that the bimodal modulation by toosendanin depends on the dynamic interactions between channel and cargo, highlighting their tight interplay during the progression of LC transit across endosomes.
authors.affiliation: Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA.
authors.forename: Audrey
authors.initials: A
authors.lastname: Fischer
authors.forename: Yuya
authors.initials: Y
authors.lastname: Nakai
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Eubanks
authors.forename: Colin M
authors.initials: CM
authors.lastname: Clancy
authors.forename: William H
authors.initials: WH
authors.lastname: Tepp
authors.forename: Sabine
authors.initials: S
authors.lastname: Pellett
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Dickerson
authors.forename: Eric A
authors.initials: EA
authors.lastname: Johnson
authors.forename: Kim D
authors.initials: KD
authors.lastname: Janda
authors.forename: Mauricio
authors.initials: M
authors.lastname: Montal
mesh_terms: D000818:Animals; D001905:Botulinum Toxins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002478:Cells, Cultured; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000494:pharmacology; D005260:Female; D051379:Mice; D018408:Patch-Clamp Techniques; D021381:Protein Transport; D051381:Rats; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D014315:Triterpenes
chemical_list: D001905:Botulinum Toxins; D004365:Drugs, Chinese Herbal; C036454:toosendanin; D014315:Triterpenes