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Zhang CM, Imoto Y, Hikima T, Inoue T. Structural flexibility of the tetanus neurotoxin revealed by crystallographic and solution scattering analyses. JOURNAL OF STRUCTURAL BIOLOGY-X 2021; 5:100045. [PMID: 33598655 PMCID: PMC7868712 DOI: 10.1016/j.yjsbx.2021.100045] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Although the tetanus neurotoxin (TeNT) delivers its protease domain (LC) across the synaptic vesicle lumen into the cytosol via its receptor binding domain (HC) and translocation domain (HN), the molecular mechanism coordinating this membrane translocation remains unresolved. Here, we report the high-resolution crystal structures of full-length reduced TeNT (rTeNT, 2.3 Å), TeNT isolated HN (TeNT/iHN, 2.3 Å), TeNT isolated HC (TeNT/iHC, 1.5 Å), together with the solution structures of TeNT/iHN and beltless TeNT/iHN (TeNT/blHN). TeNT undergoes significant domains rotation of the HN and LC were demonstrated by structural comparison of rTeNT and non-reduced-TeNT (nrTeNT). A linker loop connects the HN and HC is essential for the self-domain rotation of TeNT. The TeNT-specific C869-C1093 disulfide bond is sensitive to the redox environment and its disruption provides linker loop flexibility, which enables domain arrangement of rTeNT distinct from that of nrTeNT. Furthermore, the mobility of C869 in the linker loop and the sensitivity to redox condition of C1093 were confirmed by crystal structure analysis of TeNT/iHC. On the other hand, the structural flexibility of HN was investigated by crystallographic and solution scattering analyses. It was found that the region (residues 698-769), which follows the translocation region had remarkable change in TeNT/iHN. Besides, the so-called belt region has a high propensity to swing around the upper half of TeNT/iHN at acidic pH. It provides the first overview of the dynamics of the Belt in solution. These newly obtained structural information that shed light on the transmembrane mechanism of TeNT.
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Affiliation(s)
- Chun-Ming Zhang
- Graduate School of Pharmaceutical Science, Osaka University, Suita, 565-0871 Osaka, Japan
| | - Yoshihiro Imoto
- Graduate School of Pharmaceutical Science, Osaka University, Suita, 565-0871 Osaka, Japan
| | - Takaaki Hikima
- Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo-gun, 679-6148, Japan
| | - Tsuyoshi Inoue
- Graduate School of Pharmaceutical Science, Osaka University, Suita, 565-0871 Osaka, Japan
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2
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Pirazzini M, Azarnia Tehran D, Zanetti G, Rossetto O, Montecucco C. Hsp90 and Thioredoxin-Thioredoxin Reductase enable the catalytic activity of Clostridial neurotoxins inside nerve terminals. Toxicon 2017; 147:32-37. [PMID: 29111118 DOI: 10.1016/j.toxicon.2017.10.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 10/21/2017] [Accepted: 10/23/2017] [Indexed: 12/12/2022]
Abstract
Botulinum (BoNTs) and tetanus (TeNT) neurotoxins are the most toxic substances known and form the growing family of Clostridial neurotoxins (CNT), the etiologic agents of botulism and tetanus. CNT 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 its substrates, the three SNARE proteins, are localized. L translocation is accompanied by unfolding and, once delivered on the cytosolic side of the endosome membrane, it has to be reduced and reacquire the native fold to be active. The Thioredoxin-Thioredoxin Reductase system (Trx-TrxR) specifically reduces the interchain disulfide bond while the cytosolic chaperone protein Hsp90 mediates L refolding. Both steps are essential for CNT activity and their inhibition efficiently blocks the neurotoxicity in cultured neurons and mice. Trx and its reductase physically interact with Hsp90 and are loosely bound to the cytosolic side of synaptic vesicles, the organelle exploited by CNT to enter nerve terminals and wherefrom L is translocated into the cytosol. Therefore, Trx, TrxR and Hsp90 orchestrate a chaperone-redox molecular machinery that enables the catalytic activity of the L inside nerve terminals. Given the fundamental role of L reduction and refolding, this machinery represents a rational target for the development of mechanism-based antitoxins.
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Affiliation(s)
- Marco Pirazzini
- Dipartimento di Scienze Biomediche, Università di Padova, Via U. Bassi 58/B, 35121 Padova, Italy.
| | - Domenico Azarnia Tehran
- Dipartimento di Scienze Biomediche, Università di Padova, Via U. Bassi 58/B, 35121 Padova, Italy
| | - Giulia Zanetti
- Dipartimento di Scienze Biomediche, Università di Padova, Via U. Bassi 58/B, 35121 Padova, Italy
| | - Ornella Rossetto
- Dipartimento di Scienze Biomediche, Università di Padova, Via U. Bassi 58/B, 35121 Padova, Italy
| | - Cesare Montecucco
- Dipartimento di Scienze Biomediche, Università di Padova, Via U. Bassi 58/B, 35121 Padova, Italy; Istituto CNR di Neuroscienze, Università di Padova, Via U. Bassi 58/B, 35121 Padova, Italy
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3
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Tyagi P, Kashyap M, Yoshimura N, Chancellor M, Chermansky CJ. Past, Present and Future of Chemodenervation with Botulinum Toxin in the Treatment of Overactive Bladder. J Urol 2016; 197:982-990. [PMID: 27871929 DOI: 10.1016/j.juro.2016.11.092] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2016] [Indexed: 12/13/2022]
Abstract
PURPOSE We systematically reviewed preclinical and clinical studies on bladder chemodenervation with onabotulinumtoxin A to highlight current limitations and future drug delivery approaches. MATERIALS AND METHODS We identified peer reviewed basic and clinical research studies of onabotulinumtoxin A in the treatment of neurogenic bladder and refractory idiopathic overactive bladder published between March 2000 and March 2016. Paired investigators independently screened 125 English language articles to identify controlled studies on onabotulinumtoxin A administration in the MEDLINE® database and abstracts presented at annual American Urological Association meetings. The review yielded an evidence base of more than 50 articles relevant to the approach of injection-free onabotulinumtoxin A chemodenervation. RESULTS The efficacy and safety of intradetrusor injection of onabotulinumtoxin A for the treatment of overactive bladder are sensitive to injection volume and depth, and this issue has motivated researchers to study injection-free modes of drug delivery into the bladder. Urothelial denudation with protamine sulfate or dimethyl sulfoxide, liposome encapsulated onabotulinumtoxin A and other physical approaches are being studied to increase toxin permeability and avoid intradetrusor injections. Liposome encapsulated onabotulinumtoxin A enhances toxin activity while reducing its toxin degradation. The safety and efficacy of liposome encapsulated onabotulinumtoxin A were tested in a multicenter, placebo controlled study. Although this treatment successfully reduced urinary frequency and urgency, it did not significantly reduce urgency urinary incontinence episodes. CONCLUSIONS Intradetrusor injection of onabotulinumtoxin A is a safe and effective treatment as reported in several large multicenter, randomized controlled trials. Injection of the toxin into the bladder wall impairs afferent and efferent nerves, but injection-free drug delivery approaches only impair the bladder afferent nerves. Further studies are needed to develop better drug delivery platforms that overcome the drawbacks of intradetrusor injection, increase patient acceptance and reduce treatment costs.
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Affiliation(s)
- Pradeep Tyagi
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania.
| | - Mahendra Kashyap
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Naoki Yoshimura
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Michael Chancellor
- Department of Urology, William Beaumont School of Medicine, Royal Oak, Michigan
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Bomba-Warczak E, Vevea JD, Brittain JM, Figueroa-Bernier A, Tepp WH, Johnson EA, Yeh FL, Chapman ER. Interneuronal Transfer and Distal Action of Tetanus Toxin and Botulinum Neurotoxins A and D in Central Neurons. Cell Rep 2016; 16:1974-87. [PMID: 27498860 DOI: 10.1016/j.celrep.2016.06.104] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 06/07/2016] [Accepted: 07/13/2016] [Indexed: 10/21/2022] Open
Abstract
Recent reports suggest that botulinum neurotoxin (BoNT) A, which is widely used clinically to inhibit neurotransmission, can spread within networks of neurons to have distal effects, but this remains controversial. Moreover, it is not known whether other members of this toxin family are transferred between neurons. Here, we investigate the potential distal effects of BoNT/A, BoNT/D, and tetanus toxin (TeNT), using central neurons grown in microfluidic devices. Toxins acted upon the neurons that mediated initial entry, but all three toxins were also taken up, via an alternative pathway, into non-acidified organelles that mediated retrograde transport to the somato-dendritic compartment. Toxins were then released into the media, where they entered and exerted their effects upon upstream neurons. These findings directly demonstrate that these agents undergo transcytosis and interneuronal transfer in an active form, resulting in long-distance effects.
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Affiliation(s)
- Ewa Bomba-Warczak
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, WI 53705, USA
| | - Jason D Vevea
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, WI 53705, USA
| | - Joel M Brittain
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, WI 53705, USA
| | - Annette Figueroa-Bernier
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, WI 53705, USA
| | - William H Tepp
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706, USA
| | - Eric A Johnson
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706, USA
| | - Felix L Yeh
- Department of Neuroscience, Genentech Inc., South San Francisco, CA 94080, USA
| | - Edwin R Chapman
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, WI 53705, USA.
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Azarnia Tehran D, Pirazzini M, Leka O, Mattarei A, Lista F, Binz T, Rossetto O, Montecucco C. Hsp90 is involved in the entry of clostridial neurotoxins into the cytosol of nerve terminals. Cell Microbiol 2016; 19. [DOI: 10.1111/cmi.12647] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Revised: 07/06/2016] [Accepted: 07/08/2016] [Indexed: 12/31/2022]
Affiliation(s)
- Domenico Azarnia Tehran
- Department of Biomedical Sciences; University of Padova; Via Ugo Bassi 58/B 35121 Padova Italy
| | - Marco Pirazzini
- Department of Biomedical Sciences; University of Padova; Via Ugo Bassi 58/B 35121 Padova Italy
| | - Oneda Leka
- Department of Biomedical Sciences; University of Padova; Via Ugo Bassi 58/B 35121 Padova Italy
| | - Andrea Mattarei
- Department of Chemical Sciences; University of Padova; Via F. Marzolo 1 35131 Padova Italy
| | - Florigio Lista
- Histology and Molecular Biology Section; Army Medical and Veterinary Research Center; Via Santo Stefano Rotondo 4 00184 Rome Italy
| | - Thomas Binz
- Medizinische Hochschule Hannover; Institut für Physiologische Chemie OE4310; 30625 Hannover Germany
| | - Ornella Rossetto
- Department of Biomedical Sciences; University of Padova; Via Ugo Bassi 58/B 35121 Padova Italy
| | - Cesare Montecucco
- 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
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Araye A, Goudet A, Barbier J, Pichard S, Baron B, England P, Pérez J, Zinn-Justin S, Chenal A, Gillet D. The Translocation Domain of Botulinum Neurotoxin A Moderates the Propensity of the Catalytic Domain to Interact with Membranes at Acidic pH. PLoS One 2016; 11:e0153401. [PMID: 27070312 PMCID: PMC4829238 DOI: 10.1371/journal.pone.0153401] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 03/29/2016] [Indexed: 01/23/2023] Open
Abstract
Botulinum neurotoxin A (BoNT/A) is composed of three domains: a catalytic domain (LC), a translocation domain (HN) and a receptor-binding domain (HC). Like most bacterial toxins BoNT/A is an amphitropic protein, produced in a soluble form that is able to interact, penetrate and/or cross a membrane to achieve its toxic function. During intoxication BoNT/A is internalized by the cell by receptor-mediated endocytosis. Then, LC crosses the membrane of the endocytic compartment and reaches the cytosol. This translocation is initiated by the low pH found in this compartment. It has been suggested that LC passes in an unfolded state through a transmembrane passage formed by HN. We report here that acidification induces no major conformational change in either secondary or tertiary structures of LC and HN of BoNT/A in solution. GdnHCl-induced denaturation experiments showed that the stability of LC and HN increases as pH drops, and that HN further stabilizes LC. Unexpectedly we found that LC has a high propensity to interact with and permeabilize anionic lipid bilayers upon acidification without the help of HN. This property is downplayed when LC is linked to HN. HN thus acts as a chaperone for LC by enhancing its stability but also as a moderator of the membrane interaction of LC.
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Affiliation(s)
- Anne Araye
- CEA, iBiTec-S/SIMOPRO, CEA-Saclay, Paris Saclay University, LabEx LERMIT, F-91191 Gif-sur-Yvette, France
| | - Amélie Goudet
- CEA, iBiTec-S/SIMOPRO, CEA-Saclay, Paris Saclay University, LabEx LERMIT, F-91191 Gif-sur-Yvette, France
| | - Julien Barbier
- CEA, iBiTec-S/SIMOPRO, CEA-Saclay, Paris Saclay University, LabEx LERMIT, F-91191 Gif-sur-Yvette, France
| | - Sylvain Pichard
- CEA, iBiTec-S/SIMOPRO, CEA-Saclay, Paris Saclay University, LabEx LERMIT, F-91191 Gif-sur-Yvette, France
| | - Bruno Baron
- Institut Pasteur, Proteopole, Plateforme de Biophysique des Macromolécules et de leurs Interactions (PFBMI), 25–28 rue du Dr Roux, F-75724 Paris cedex 15, France
| | - Patrick England
- Institut Pasteur, Proteopole, Plateforme de Biophysique des Macromolécules et de leurs Interactions (PFBMI), 25–28 rue du Dr Roux, F-75724 Paris cedex 15, France
| | - Javier Pérez
- Synchrotron Soleil, BP 48, F-91192 Gif-sur-Yvette Cedex, France
| | | | - Alexandre Chenal
- Institut Pasteur, Unité de Biochimie des Interactions Macromoléculaires, UMR 3528, 25–28 rue du Dr Roux, F-75724 Paris cedex 15, France
| | - Daniel Gillet
- CEA, iBiTec-S/SIMOPRO, CEA-Saclay, Paris Saclay University, LabEx LERMIT, F-91191 Gif-sur-Yvette, France
- * E-mail:
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7
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On the translocation of botulinum and tetanus neurotoxins across the membrane of acidic intracellular compartments. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:467-74. [PMID: 26307528 DOI: 10.1016/j.bbamem.2015.08.014] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 08/04/2015] [Accepted: 08/17/2015] [Indexed: 01/25/2023]
Abstract
Tetanus and botulinum neurotoxins are produced by anaerobic bacteria of the genus Clostridium and are the most poisonous toxins known, with 50% mouse lethal dose comprised within the range of 0.1-few nanograms per Kg, depending on the individual toxin. Botulinum neurotoxins are similarly toxic to humans and can therefore be considered for potential use in bioterrorism. At the same time, their neurospecificity and reversibility of action make them excellent therapeutics for a growing and heterogeneous number of human diseases that are characterized by a hyperactivity of peripheral nerve terminals. The complete crystallographic structure is available for some botulinum toxins, and reveals that they consist of four domains functionally related to the four steps of their mechanism of neuron intoxication: 1) binding to specific receptors of the presynaptic membrane; 2) internalization via endocytic vesicles; 3) translocation across the membrane of endocytic vesicles into the neuronal cytosol; 4) catalytic activity of the enzymatic moiety directed towards the SNARE proteins. Despite the many advances in understanding the structure-mechanism relationship of tetanus and botulinum neurotoxins, the molecular events involved in the translocation step have been only partially elucidated. Here we will review recent advances that have provided relevant insights on the process and discuss possible models that can be experimentally tested. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
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Chellappan G, Kumar R, Santos E, Goyal D, Cai S, Singh BR. Structural and functional analysis of botulinum neurotoxin subunits for pH-dependent membrane channel formation and translocation. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1510-6. [PMID: 26012869 DOI: 10.1016/j.bbapap.2015.05.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2015] [Revised: 04/29/2015] [Accepted: 05/18/2015] [Indexed: 10/23/2022]
Abstract
The structure-function relationship of Botulinum Neurotoxin (BoNT) proteins is greatly influenced by pH. While the low pH of endosome favors membrane interaction of the heavy chain (HC) for the formation of a membrane channel and translocation of the light chain (LC), the catalytic activity of the LC requires a neutral pH for cleavage of the soluble NSF attachment protein receptor (SNARE) complex in the cytosol. In this study, we monitored secondary structural characteristics of LC, HC and holotoxin at individual pHs 4.5 and 7.2 and at the transition pH4.5 to 7.2 to identify the structural signatures underlying their function. The HC showed higher thermal stability at pH4.5 with a melting temperature (Tm) of 60.4°C. The structural analysis of HC in the presence of liposomes showed no difference in ellipticity with that of HC at pH7.2 at 208 and 222 nm but a 25.2% decrease in ellipticity at 208 nm at acidic pH, indicating low pH-induced structural changes that might facilitate interaction with the membrane. Further, HC showed 18% release of K+ ions from liposomes at pH4.5 as against 6% at neutral pH, reinforcing its role in membrane channel formation. LC on the other hand, showed maximum ellipticity at pH7.2, a condition that is relevant to its endopeptidase activity in the cytosol of the neurons. Also, the similarity in the structures at pH7.2 and transition pH4.5 to 7.2 suggested that the flexibility acquired by the protein at low pH was reversible upon exposure to neutral pH for cleavage of SNARE proteins.
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Affiliation(s)
- Gowri Chellappan
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA
| | - Raj Kumar
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA; Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA
| | - Erin Santos
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA
| | - Dipak Goyal
- Department of Chemistry and Biochemistry, University of Massachusetts Lowell, Lowell, MA 01854, USA
| | - Shuowei Cai
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA
| | - Bal Ram Singh
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA; Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA; Prime Bio, Inc., Dartmouth, MA 02747, USA.
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9
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Rossetto O, Pirazzini M, Montecucco C. Botulinum neurotoxins: genetic, structural and mechanistic insights. Nat Rev Microbiol 2014; 12:535-49. [PMID: 24975322 DOI: 10.1038/nrmicro3295] [Citation(s) in RCA: 378] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Botulinum neurotoxins (BoNTs) are produced by anaerobic bacteria of the genus Clostridium and cause a persistent paralysis of peripheral nerve terminals, which is known as botulism. Neurotoxigenic clostridia belong to six phylogenetically distinct groups and produce more than 40 different BoNT types, which inactivate neurotransmitter release owing to their metalloprotease activity. In this Review, we discuss recent studies that have improved our understanding of the genetics and structure of BoNT complexes. We also describe recent insights into the mechanisms of BoNT entry into the general circulation, neuronal binding, membrane translocation and neuroparalysis.
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Affiliation(s)
- Ornella Rossetto
- 1] Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy. [2] National Research Council Institute of Neuroscience, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy. [3]
| | - Marco Pirazzini
- 1] Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy. [2] National Research Council Institute of Neuroscience, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy. [3]
| | - Cesare Montecucco
- 1] Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy. [2] National Research Council Institute of Neuroscience, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy
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10
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Burns JR, Baldwin MR. Tetanus neurotoxin utilizes two sequential membrane interactions for channel formation. J Biol Chem 2014; 289:22450-8. [PMID: 24973217 DOI: 10.1074/jbc.m114.559302] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tetanus neurotoxin (TeNT) causes neuroparalytic disease by entering the neuronal soma to block the release of neurotransmitters. However, the mechanism by which TeNT translocates its enzymatic domain (light chain) across endosomal membranes remains unclear. We found that TeNT and a truncated protein devoid of the receptor binding domain (TeNT-LHN) associated with membranes enriched in acidic phospholipids in a pH-dependent manner. Thus, in contrast to diphtheria toxin, the formation of a membrane-competent state of TeNT requires the membrane interface and is modulated by the bilayer composition. Channel formation is further enhanced by tethering of TeNT to the membrane through ganglioside co-receptors prior to acidification. Thus, TeNT channel formation can be resolved into two sequential steps: 1) interaction of the receptor binding domain (heavy chain receptor binding domain) with ganglioside co-receptors orients the translocation domain (heavy chain translocation domain) as the lumen of the endosome is acidified and 2) low pH, in conjunction with acidic lipids within the membrane drives the conformational changes in TeNT necessary for channel formation.
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Affiliation(s)
- Joshua R Burns
- From the Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri 65212
| | - Michael R Baldwin
- From the Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri 65212
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11
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Fischer A. Synchronized Chaperone Function of Botulinum Neurotoxin Domains Mediates Light Chain Translocation into Neurons. Curr Top Microbiol Immunol 2012. [DOI: 10.1007/978-3-662-45790-0_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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12
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Pirazzini M, Rossetto O, Bolognese P, Shone CC, Montecucco C. Double anchorage to the membrane and intact inter-chain disulfide bond are required for the low pH induced entry of tetanus and botulinum neurotoxins into neurons. Cell Microbiol 2011; 13:1731-43. [PMID: 21790947 DOI: 10.1111/j.1462-5822.2011.01654.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Tetanus and botulinum neurotoxins are di-chain proteins that cause paralysis by inhibiting neuroexocytosis. These neurotoxins enter into nerve terminals via endocytosis inside synaptic vesicles, whose acidic pH induces a structural change of the neurotoxin molecule that becomes capable of translocating its L chain into the cytosol, via a transmembrane protein-conducting channel made by the H chain. This is the least understood step of the intoxication process primarily because it takes place inside vesicles within the cytosol. In the present study, we describe how this passage was made accessible to investigation by making it to occur at the surface of neurons. The neurotoxin, bound to the plasma membrane in the cold, was exposed to a warm low pH extracellular medium and the entry of the L chain was monitored by measuring its specific metalloprotease activity with a ratiometric method. We found that the neurotoxin has to be bound to the membrane via at least two anchorage sites in order for a productive low-pH induced structural change to take place. In addition, this process can only occur if the single inter-chain disulfide bond is intact. The pH dependence of the conformational change of tetanus neurotoxin and botulinum neurotoxin B, C and D is similar and take places in the same slightly acidic range, which comprises that present inside synaptic vesicles. Based on these and previous findings, we propose a stepwise sequence of molecular events that lead from toxin binding to membrane insertion.
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Affiliation(s)
- Marco Pirazzini
- Dipartimento di Scienze Biomediche and Istituto CNR di Neuroscienze, Università di Padova, Viale G. Colombo 3, 35131 Padova, Italy
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Mushrush DJ, Koteiche HA, Sammons MA, Link AJ, McHaourab HS, Lacy DB. Studies of the mechanistic details of the pH-dependent association of botulinum neurotoxin with membranes. J Biol Chem 2011; 286:27011-8. [PMID: 21652698 DOI: 10.1074/jbc.m111.256982] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Botulinum neurotoxin (BoNT) belongs to a large class of toxic proteins that act by enzymatically modifying cytosolic substrates within eukaryotic cells. The process by which a catalytic moiety is transferred across a membrane to enter the cytosol is not understood for any such toxin. BoNT is known to form pH-dependent pores important for the translocation of the catalytic domain into the cytosol. As a first step toward understanding this process, we investigated the mechanism by which the translocation domain of BoNT associates with a model liposome membrane. We report conditions that allow pH-dependent proteoliposome formation and identify a sequence at the translocation domain C terminus that is protected from proteolytic degradation in the context of the proteoliposome. Fluorescence quenching experiments suggest that residues within this sequence move to a hydrophobic environment upon association with liposomes. EPR analyses of spin-labeled mutants reveal major conformational changes in a distinct region of the structure upon association and indicate the formation of an oligomeric membrane-associated intermediate. Together, these data support a model of how BoNT orients with membranes in response to low pH.
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Affiliation(s)
- Darren J Mushrush
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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14
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Low pH-induced pore formation by the T domain of botulinum toxin type A is dependent upon NaCl concentration. J Membr Biol 2010; 236:191-201. [PMID: 20711775 DOI: 10.1007/s00232-010-9292-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 07/19/2010] [Indexed: 10/19/2022]
Abstract
Botulinum neurotoxins (BoNTs) undergo low pH-triggered membrane insertion, resulting in the translocation of their light (catalytic) chains into the cytoplasm. The T (translocation) domain of the BoNT heavy chain is believed to carry out translocation. Here, the behavior of isolated T domain from BoNT type A has been characterized, both in solution and when associated with model membranes. When BoNT T domain prepared in the detergent dodecylmaltoside was diluted into aqueous solution, it exhibited a low pH-dependent conformational change below pH 6. At low pH the T domain associated with, and formed pores within, model membrane vesicles composed of 30 mol% dioleoylphosphatidylglycerol/70 mol% dioleoylphosphatidylcholine. Although T domain interacted with vesicles at low (50 mM) and high (400 mM) NaCl concentrations, the interaction required much less lipid at low salt. However, even at high lipid concentrations pore formation was much more pronounced at low NaCl concentrations than at high NaCl concentration. Increasing salt concentration after insertion in the presence of 50 mM NaCl did not decrease pore formation. A similar effect of NaCl concentration upon pore formation was observed in vesicles composed solely of dioleoylphosphatidylcholine, showing that the effect of NaCl did not solely involve modulation of electrostatic interactions between protein and anionic lipids. These results indicate that some feature of membrane-bound T domain tertiary structure critical for pore formation is highly dependent upon salt concentration.
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Protein Domain Analysis of C. botulinum Type A Neurotoxin and Its Relationship with Other Botulinum Serotypes. Toxins (Basel) 2009; 2:1-9. [PMID: 22069543 PMCID: PMC3206622 DOI: 10.3390/toxins2010001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 12/23/2009] [Accepted: 12/23/2009] [Indexed: 11/16/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are highly potent poisons produced by seven serotypes of Clostridium botulinum. The mechanism of neurotoxin action is a multistep process which leads to the cleavage of one of three different SNARE proteins essential for synaptic vesicle fusion and transmission of the nerve signals to muscles: synaptobrevin, syntaxin, or SNAP-25. In order to understand the precise mechanism of neurotoxin in a host, the domain structure of the neurotoxin was analyzed among different serotypes of C. botulinum. The results indicate that neurotoxins type A, C, D, E and F contain a coiled-coil domain while types B and type G neurotoxin do not. Interestingly, phylogenetic analysis based on neurotoxin sequences has further confirmed that serotypes B and G are closely related. These results suggest that neurotoxin has multi-domain structure, and coiled-coil domain plays an important role in oligomerisation of the neurotoxin. Domain analysis may help to identify effective antibodies to treat Botulinum toxin intoxication.
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Drug Insight: biological effects of botulinum toxin A in the lower urinary tract. ACTA ACUST UNITED AC 2008; 5:319-28. [PMID: 18461049 DOI: 10.1038/ncpuro1124] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 03/26/2008] [Indexed: 12/29/2022]
Abstract
Botulinum toxins can effectively and selectively disrupt and modulate neurotransmission in striated muscle. Recently, urologists have become interested in the use of these toxins in patients with detrusor overactivity and other urological disorders. In both striated and smooth muscle, botulinum toxin A (BTX-A) is internalized by presynaptic neurons after binding to an extracellular receptor (ganglioside and presumably synaptic vesicle protein 2C). In the neuronal cytosol, BTX-A disrupts fusion of the acetylcholine-containing vesicle with the neuronal wall by cleaving the SNAP-25 protein in the synaptic fusion complex. The net effect is selective paralysis of the low-grade contractions of the unstable detrusor, while still allowing high-grade contraction that initiates micturition. Additionally, BTX-A seems to have effects on afferent nerve activity by modulating the release of ATP in the urothelium, blocking the release of substance P, calcitonin gene-related peptide and glutamate from afferent nerves, and reducing levels of nerve growth factor. These effects on sensory feedback loops might not only help to explain the mechanism of BTX-A in relieving symptoms of overactive bladder, but also suggest a potential role for BTX-A in the relief of hyperalgesia associated with lower urinary tract disorders.
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Abstract
In an effort to compare the molecular basis of differential toxic activity of botulinum neurotoxin A (BoNT/A) and BoNT/E, we have analyzed their membrane channel activity by measuring calcein release from liposomes. Both BoNT/A and /E showed a same level of membrane channel activity that was specifically blocked by IgG specific to the neurotoxins. With the use of fluorescein-labeled dextran, we determined that the size of the channel is at least 24.2 A which is appropriate for the translocation of a protein of 50 kDa (the light chain of BoNT). These findings would suggest that the difference in the toxicity level of the two BoNT serotypes might reflect differences in either endopeptidase activity or their binding to receptor(s).
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Affiliation(s)
- Sweta Parikh
- Botulinum Research Center, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA, 02747, USA
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Singh BR. Botulinum neurotoxin structure, engineering, and novel cellular trafficking and targeting. Neurotox Res 2006; 9:73-92. [PMID: 16785103 DOI: 10.1007/bf03033925] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Botulinum neurotoxins are multifaceted molecules, which are truly unique not only in their mode of action, but also their utility as a drug carrier either across the gut wall or to the nerve terminals. The molecule is divided in clear functional domains that can operate independently. This feature can be used to employ them as cargo carrier by linking other drugs or vaccines with the binding and translocation domains of BoNT. While the domain structures are largely independent of each other, the dynamic structure of these domains, especially that of the enzymatic domain (L chain), is quite different from the reported crystal structures for several BoNT serotypes and their enzymatic domain. This review discusses the comparative structures of BoNT in crystal and solution for their relevance to the molecular mechanism of BoNT action, especially in view of our recent discovery that the enzymatically active structure of the BoNT exists as a molten-globule and that of the endopeptidase domain as a novel PRIME conformation. Finally, a non-exhaustive discussion has been included to explain the long-lasting biological effects of certain serotypes of BoNT, based on the current knowledge of the structure-function of different serotypes of botulinum neurotoxins.
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Affiliation(s)
- B R Singh
- Botulinum Research Center, and Department of Chemistry and Biochemistry, University of Massachusetts, Dartmouth, 02747, USA.
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