title: Hsp90 is involved in the entry of clostridial neurotoxins into the cytosol of nerve terminals.
abstract: Botulinum and tetanus neurotoxins are the most toxic substances known and form the growing family of clostridial neurotoxins. They are composed of a metalloprotease light chain (L), linked via a disulfide bond to a heavy chain (H). H mediates the binding to nerve terminals and the membrane translocation of L into the cytosol where their substrates, the three SNARE proteins, are localised. L translocation is accompanied by unfolding, and it has to be reduced and reacquire the native fold to exert its neurotoxicity. The Thioredoxin reductase-Thioredoxin system is responsible for the reduction, but it is unknown whether the refolding of L is spontaneous or aided by host chaperones. Here we report that geldanamycin, a specific inhibitor of heat shock protein 90, hampers the refolding of L after membrane translocation and completely prevents the cleavage of SNAREs. We also found that geldanamycin strongly synergises with PX-12, an inhibitor of thioredoxin, suggesting that the processes of L chain refolding and interchain disulfide reduction are strictly coupled. Indeed we found that the heat shock protein 90 and the Thioredoxin reductase-Thioredoxin system physically interact on synaptic vesicle where they orchestrate a chaperone-redox machinery which is exploited by clostridial neurotoxins to deliver their catalytic part into the cytosol.
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35121, Padova, Italy.
authors.forename: Domenico
authors.identifier: 0000-0001-8955-7240
authors.initials: D
authors.lastname: Azarnia Tehran
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35121, Padova, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Pirazzini
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35121, Padova, Italy.
authors.forename: Oneda
authors.initials: O
authors.lastname: Leka
authors.affiliation: Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131, Padova, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Mattarei
authors.affiliation: Histology and Molecular Biology Section, Army Medical and Veterinary Research Center, Via Santo Stefano Rotondo 4, 00184, Rome, Italy.
authors.forename: Florigio
authors.initials: F
authors.lastname: Lista
authors.affiliation: Medizinische Hochschule Hannover, Institut für Physiologische Chemie OE4310, 30625, Hannover, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Binz
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35121, Padova, Italy.
authors.forename: Ornella
authors.initials: O
authors.lastname: Rossetto
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35121, Padova, Italy.|National Research Institute of Neuroscience, University of Padova, Via Ugo Bassi 58/B, 35121, Padova, Italy.
authors.forename: Cesare
authors.initials: C
authors.lastname: Montecucco
mesh_terms: D003600:Cytosol / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D017510:Protein Folding; D021381:Protein Transport; D059748:Proteolysis; D050600:SNARE Proteins / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism; D013744:Tetanus Toxin / Q000378:metabolism*; D013880:Thioredoxin-Disulfide Reductase / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism
chemical_list: D018841:HSP90 Heat-Shock Proteins; D050600:SNARE Proteins; D013744:Tetanus Toxin; D013879:Thioredoxins; D013880:Thioredoxin-Disulfide Reductase