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Joensuu M, Syed P, Saber SH, Lanoue V, Wallis TP, Rae J, Blum A, Gormal RS, Small C, Sanders S, Jiang A, Mahrhold S, Krez N, Cousin MA, Cooper‐White R, Cooper‐White JJ, Collins BM, Parton RG, Balistreri G, Rummel A, Meunier FA. Presynaptic targeting of botulinum neurotoxin type A requires a tripartite PSG-Syt1-SV2 plasma membrane nanocluster for synaptic vesicle entry. EMBO J 2023; 42:e112095. [PMID: 37226896 PMCID: PMC10308369 DOI: 10.15252/embj.2022112095] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 04/18/2023] [Accepted: 04/28/2023] [Indexed: 05/26/2023] Open
Abstract
The unique nerve terminal targeting of botulinum neurotoxin type A (BoNT/A) is due to its capacity to bind two receptors on the neuronal plasma membrane: polysialoganglioside (PSG) and synaptic vesicle glycoprotein 2 (SV2). Whether and how PSGs and SV2 may coordinate other proteins for BoNT/A recruitment and internalization remains unknown. Here, we demonstrate that the targeted endocytosis of BoNT/A into synaptic vesicles (SVs) requires a tripartite surface nanocluster. Live-cell super-resolution imaging and electron microscopy of catalytically inactivated BoNT/A wildtype and receptor-binding-deficient mutants in cultured hippocampal neurons demonstrated that BoNT/A must bind coincidentally to a PSG and SV2 to target synaptic vesicles. We reveal that BoNT/A simultaneously interacts with a preassembled PSG-synaptotagmin-1 (Syt1) complex and SV2 on the neuronal plasma membrane, facilitating Syt1-SV2 nanoclustering that controls endocytic sorting of the toxin into synaptic vesicles. Syt1 CRISPRi knockdown suppressed BoNT/A- and BoNT/E-induced neurointoxication as quantified by SNAP-25 cleavage, suggesting that this tripartite nanocluster may be a unifying entry point for selected botulinum neurotoxins that hijack this for synaptic vesicle targeting.
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Affiliation(s)
- Merja Joensuu
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQLDAustralia
| | - Parnayan Syed
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Saber H Saber
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQLDAustralia
| | - Vanessa Lanoue
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Tristan P Wallis
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - James Rae
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
| | - Ailisa Blum
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Rachel S Gormal
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Christopher Small
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Shanley Sanders
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Anmin Jiang
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Stefan Mahrhold
- Institut für ToxikologieMedizinische Hochschule HannoverHannoverGermany
| | - Nadja Krez
- Institut für ToxikologieMedizinische Hochschule HannoverHannoverGermany
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, Hugh Robson BuildingUniversity of EdinburghEdinburghUK
- Muir Maxwell Epilepsy CentreUniversity of EdinburghEdinburghUK
- Simons Initiative for the Developing BrainUniversity of EdinburghEdinburghUK
| | - Ruby Cooper‐White
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQLDAustralia
- School of Chemical EngineeringThe University of QueenslandBrisbaneQLDAustralia
| | - Justin J Cooper‐White
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQLDAustralia
- School of Chemical EngineeringThe University of QueenslandBrisbaneQLDAustralia
- UQ Centre for Stem Cell Ageing and Regenerative EngineeringThe University of QueenslandBrisbaneQLDAustralia
| | - Brett M Collins
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
| | - Robert G Parton
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
- Centre for Microscopy and MicroanalysisThe University of QueenslandBrisbaneQLDAustralia
| | - Giuseppe Balistreri
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Department of Virology, Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | - Andreas Rummel
- Institut für ToxikologieMedizinische Hochschule HannoverHannoverGermany
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- School of Biomedical SciencesThe University of QueenslandBrisbaneQLDAustralia
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2
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Ambrin G, Cai S, Singh BR. Critical analysis in the advancement of cell-based assays for botulinum neurotoxin. Crit Rev Microbiol 2023; 49:1-17. [PMID: 35212259 DOI: 10.1080/1040841x.2022.2035315] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The study on botulinum neurotoxins (BoNTs) has rapidly evolved for their structure and functions as opposed to them being poisons or cures. Since their discoveries, the scientific community has come a long way in understanding BoNTs' structure and biological activity. Given its current application as a tool for understanding neurocellular activity and as a drug against over 800 neurological disorders, relevant and sensitive assays have become critical for biochemical, physiological, and pharmacological studies. The natural entry of the toxin being ingestion, it has also become important to examine its mechanism while crossing the epithelial cell barrier. Several techniques and methodologies have been developed, for its entry, pharmacokinetics, and biological activity for identification, and drug efficacy both in vivo and in vitro conditions. However, each of them presents its own challenges. The cell-based assay is a platform that exceeds the sensitivity of mouse bioassay while encompassing all the steps of intoxication including cell binding, transcytosis, endocytosis, translocation and proteolytic activity. In this article we review in detail both the neuronal and nonneuronal based cellular interaction of BoNT involving its transportation, and interaction with the targeted cells, and intracellular activities.
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Affiliation(s)
- Ghuncha Ambrin
- Department of Biomedical Engineering and Biotechnology, University of Massachusetts, Dartmouth, MA, USA.,Department of Chemistry and Biochemistry, University of Massachusetts, Dartmouth, MA, USA
| | - Shuowei Cai
- Department of Chemistry and Biochemistry, University of Massachusetts, Dartmouth, MA, USA
| | - Bal Ram Singh
- Institute of Advanced Sciences, Botulinum Research Center, Dartmouth, MA, USA
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3
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Wang T, Meunier FA. Live-Cell Superresolution Imaging of Retrograde Axonal Trafficking Using Pulse-Chase Labeling in Cultured Hippocampal Neurons. Methods Mol Biol 2022; 2473:101-128. [PMID: 35819762 DOI: 10.1007/978-1-0716-2209-4_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The entanglement of long axons found in cultured dissociated hippocampal neurons restricts the analysis of the machinery underlying directed axonal trafficking. Further, hippocampal neurons exhibit "en passant" presynapses that may confound the analysis of long-range retrograde axonal transport. To solve these issues, we and others have developed microfluid-based methods to specifically follow the fates of the retrograde axonal cargoes following pulse-chase labeling by super-resolution live-cell imaging, and automatically tracking their directed transport and analyzing their kinetical properties. These methods have allowed us to visualize the trafficking of fluorescently tagged signaling endosomes and autophagosomes derived from axonal terminals and resolve their localizations and movements with high spatial and temporal accuracy. In this chapter, we describe how to use a commercially available microfluidic device to enable the labeling and tracking of retrograde axonal carriers, including (1) how to culture and transfect rat hippocampal neurons in the microfluidic device; (2) how to perform pulse-chase to label specific populations of retrograde axonal carriers; and (3) how to conduct the automatic tracking and data analysis using open-source software.
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Affiliation(s)
- Tong Wang
- Center for Brain Science, School of Life Science and Technology, Shanghaitech University, Shanghai, China.
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
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4
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Cai S, Kumar R, Singh BR. Clostridial Neurotoxins: Structure, Function and Implications to Other Bacterial Toxins. Microorganisms 2021; 9:2206. [PMID: 34835332 PMCID: PMC8618262 DOI: 10.3390/microorganisms9112206] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/19/2021] [Accepted: 10/19/2021] [Indexed: 01/20/2023] Open
Abstract
Gram-positive bacteria are ancient organisms. Many bacteria, including Gram-positive bacteria, produce toxins to manipulate the host, leading to various diseases. While the targets of Gram-positive bacterial toxins are diverse, many of those toxins use a similar mechanism to invade host cells and exert their functions. Clostridial neurotoxins produced by Clostridial tetani and Clostridial botulinum provide a classical example to illustrate the structure-function relationship of bacterial toxins. Here, we critically review the recent progress of the structure-function relationship of clostridial neurotoxins, including the diversity of the clostridial neurotoxins, the mode of actions, and the flexible structures required for the activation of toxins. The mechanism clostridial neurotoxins use for triggering their activity is shared with many other Gram-positive bacterial toxins, especially molten globule-type structures. This review also summarizes the implications of the molten globule-type flexible structures to other Gram-positive bacterial toxins. Understanding these highly dynamic flexible structures in solution and their role in the function of bacterial toxins not only fills in the missing link of the high-resolution structures from X-ray crystallography but also provides vital information for better designing antidotes against those toxins.
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Affiliation(s)
- Shuowei Cai
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, Dartmouth, MA 02747, USA
| | - Raj Kumar
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA; (R.K.); (B.R.S.)
| | - Bal Ram Singh
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA; (R.K.); (B.R.S.)
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5
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Solabre Valois L, Wilkinson KA, Nakamura Y, Henley JM. Endocytosis, trafficking and exocytosis of intact full-length botulinum neurotoxin type a in cultured rat neurons. Neurotoxicology 2020; 78:80-87. [PMID: 32088326 PMCID: PMC7225749 DOI: 10.1016/j.neuro.2020.02.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 02/17/2020] [Accepted: 02/19/2020] [Indexed: 01/08/2023]
Abstract
Botulinum toxin A (BoNT/A) is a potent neurotoxin that acts primarily by silencing synaptic transmission by blocking neurotransmitter release. BoNT/A comprises a light chain (LC/A) intracellular protease and a heavy chain (HC/A) composed of a receptor binding domain (HCC/A) and a translocation domain (HCN/A) that mediates cell entry. Following entry into the neuron, the disulphide bond linking the two peptide chains is reduced to release the LC/A. To gain better insight into the trafficking and fate of BoNT/A before dissociation we have used a catalytically inactive, non-toxic full-length BoNT/A(0) mutant. Our data confirm that BoNT/A(0) enters cortical neurons both in an activity-dependent manner and via a pathway dependent on fibroblast growth factor receptor 3 (Fgfr3) signalling. We demonstrate that both dynamin-dependent endocytosis and lipid rafts are involved in BoNT/A internalisation and that full-length BoNT/A(0) traffics to early endosomes. Furthermore, while a proportion of BoNT/A remains stable in neurons for 3 days, BoNT/A degradation is primarily mediated by the proteasome. Finally, we demonstrate that a fraction of the endocytosed full-length BoNT/A(0) is capable of exiting the cell to intoxicate other neurons. Together, our data shed new light on the entry routes, trafficking and degradation of BoNT/A, and confirm that trafficking properties previously described for the isolated HCC/A receptor binding domain of are also applicable to the intact, full-length toxin.
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Affiliation(s)
- Luis Solabre Valois
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK
| | - Kevin A Wilkinson
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK
| | - Yasuko Nakamura
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK
| | - Jeremy M Henley
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK.
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6
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Poulain B, Lemichez E, Popoff MR. Neuronal selectivity of botulinum neurotoxins. Toxicon 2020; 178:20-32. [PMID: 32094099 DOI: 10.1016/j.toxicon.2020.02.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 02/03/2020] [Accepted: 02/10/2020] [Indexed: 12/12/2022]
Abstract
Botulinum neurotoxins (BoNTs) are highly potent toxins responsible for a severe disease, called botulism. They are also efficient therapeutic tools with an increasing number of indications ranging from neuromuscular dysfunction to hypersecretion syndrome, pain release, depression as well as cosmetic application. BoNTs are known to mainly target the motor-neurons terminals and to induce flaccid paralysis. BoNTs recognize a specific double receptor on neuronal cells consisting of gangliosides and synaptic vesicle protein, SV2 or synaptotagmin. Using cultured neuronal cells, BoNTs have been established blocking the release of a wide variety of neurotransmitters. However, BoNTs are more potent in motor-neurons than in the other neuronal cell types. In in vivo models, BoNT/A impairs the cholinergic neuronal transmission at the motor-neurons but also at neurons controlling secretions and smooth muscle neurons, and blocks several neuronal pathways including excitatory, inhibitory, and sensitive neurons. However, only a few reports investigated the neuronal selectivity of BoNTs in vivo. In the intestinal wall, BoNT/A and BoNT/B target mainly the cholinergic neurons and to a lower extent the other non-cholinergic neurons including serotonergic, glutamatergic, GABAergic, and VIP-neurons. The in vivo effects induced by BoNTs on the non-cholinergic neurons remain to be precisely investigated. We report here a literature review of the neuronal selectivity of BoNTs.
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Affiliation(s)
- Bernard Poulain
- Université de Strasbourg, CNRS, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
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7
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Sethi A, Wands AM, Mettlen M, Krishnamurthy S, Wu H, Kohler JJ. Cell type and receptor identity regulate cholera toxin subunit B (CTB) internalization. Interface Focus 2019; 9:20180076. [PMID: 30842875 PMCID: PMC6388018 DOI: 10.1098/rsfs.2018.0076] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/09/2019] [Indexed: 12/21/2022] Open
Abstract
Cholera toxin (CT) is a secreted bacterial toxin that binds to glycoconjugate receptors on the surface of mammalian cells, enters mammalian cells through endocytic mechanisms and intoxicates mammalian cells by activating cytosolic adenylate cyclase. CT recognizes cell surface receptors through its B subunit (CTB). While the ganglioside GM1 has been historically described as the sole receptor, CTB is also capable of binding to fucosylated glycoconjugates, and fucosylated molecules have been shown to play a functional role in host cell intoxication by CT. Here, we use colonic epithelial and respiratory epithelial cell lines to examine how two types of CT receptors-gangliosides and fucosylated glycoconjugates-contribute to CTB internalization. We show that fucosylated glycoconjugates contribute to CTB binding to and internalization into host cells, even when the ganglioside GM1 is present. The contributions of the two classes of receptors to CTB internalization depend on cell type. Additionally, in a cell line that harbours both classes of receptors, gangliosides dictate the efficiency of CTB internalization. Together, the results lend support to the idea that fucosylated glycoconjugates play a functional role in CTB internalization, and suggest that CT internalization depends on both receptor identity and cell type.
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Affiliation(s)
- Anirudh Sethi
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Amberlyn M Wands
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Marcel Mettlen
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Soumya Krishnamurthy
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Han Wu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jennifer J Kohler
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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8
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Variability of Botulinum Toxins: Challenges and Opportunities for the Future. Toxins (Basel) 2018; 10:toxins10090374. [PMID: 30217070 PMCID: PMC6162648 DOI: 10.3390/toxins10090374] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 09/03/2018] [Accepted: 09/08/2018] [Indexed: 12/31/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are the most potent known toxins, and are therefore classified as extremely harmful biological weapons. However, BoNTs are therapeutic drugs that are widely used and have an increasing number of applications. BoNTs show a high diversity and are divided into multiple types and subtypes. Better understanding of the activity at the molecular and clinical levels of the natural BoNT variants as well as the development of BoNT-based chimeric molecules opens the door to novel medical applications such as silencing the sensory neurons at targeted areas and dermal restoration. This short review is focused on BoNTs’ variability and the opportunities or challenges posed for future clinical applications.
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9
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Grando SA, Zachary CB. The non-neuronal and nonmuscular effects of botulinum toxin: an opportunity for a deadly molecule to treat disease in the skin and beyond. Br J Dermatol 2018; 178:1011-1019. [PMID: 29086923 DOI: 10.1111/bjd.16080] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2017] [Indexed: 01/19/2023]
Abstract
There is growing evidence that botulinum neurotoxins (BoNTs) exhibit biological effects on various human cell types with a host of associated clinical implications. This review aims to provide an update on the non-neuronal and nonmuscular effects of botulinum toxin. We critically analysed recent reports on the structure and function of cellular signalling systems subserving biological effects of BoNTs. The BoNT receptors and intracellular targets are not unique for neurotransmission. They have been found in both neuronal and non-neuronal cells, but there are differences in how BoNT binds to, and acts on, neuronal vs. non-neuronal cells. The non-neuronal cells that express one or more BoNT/A-binding proteins, and/or cleavage target synaptosomal-associated protein 25, include: epidermal keratinocytes; mesenchymal stem cells from subcutaneous adipose; nasal mucosal cells; urothelial cells; intestinal, prostate and alveolar epithelial cells; breast cell lines; neutrophils; and macrophages. Serotype BoNT/A can also elicit specific biological effects in dermal fibroblasts, sebocytes and vascular endothelial cells. Nontraditional applications of BoNT have been reported for the treatment of the following dermatological conditions: hyperhidrosis, Hailey-Hailey disease, Darier disease, inversed psoriasis, aquagenic palmoplantar keratoderma, pachyonychia congenita, multiple eccrine hydrocystomas, eccrine angiomatous hamartoma, eccrine sweat gland naevi, congenital eccrine naevus, Raynaud phenomenon and cutaneous leiomyomas. Experimental studies have demonstrated the ability of BoNT/A to protect skin flaps, facilitate wound healing, decrease thickness of hypertrophic scars, produce an anti-ageing effect, improve a mouse model of psoriasiform dermatitis, and have also revealed extracutaneous effects of BoNT arising from its anti-inflammatory and anticancer properties. BoNTs have a much wider range of applications than originally understood, and the individual cellular responses to the cholinergic impacts of BoNTs could provide fertile ground for future studies.
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Affiliation(s)
- S A Grando
- Department of Dermatology, University of California, Irvine, Irvine, CA, U.S.A
| | - C B Zachary
- Department of Dermatology, University of California, Irvine, Irvine, CA, U.S.A
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10
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Pirazzini M, Rossetto O, Eleopra R, Montecucco C. Botulinum Neurotoxins: Biology, Pharmacology, and Toxicology. Pharmacol Rev 2017; 69:200-235. [PMID: 28356439 PMCID: PMC5394922 DOI: 10.1124/pr.116.012658] [Citation(s) in RCA: 410] [Impact Index Per Article: 58.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The study of botulinum neurotoxins (BoNT) is rapidly progressing in many aspects.
Novel BoNTs are being discovered owing to next generation sequencing, but their
biologic and pharmacological properties remain largely unknown. The molecular
structure of the large protein complexes that the toxin forms with accessory
proteins, which are included in some BoNT type A1 and B1 pharmacological
preparations, have been determined. By far the largest effort has been dedicated to
the testing and validation of BoNTs as therapeutic agents in an ever increasing
number of applications, including pain therapy. BoNT type A1 has been also exploited
in a variety of cosmetic treatments, alone or in combination with other agents, and
this specific market has reached the size of the one dedicated to the treatment of
medical syndromes. The pharmacological properties and mode of action of BoNTs have
shed light on general principles of neuronal transport and protein-protein
interactions and are stimulating basic science studies. Moreover, the wide array of
BoNTs discovered and to be discovered and the production of recombinant BoNTs endowed
with specific properties suggest novel uses in therapeutics with increasing
disease/symptom specifity. These recent developments are reviewed here to provide an
updated picture of the biologic mechanism of action of BoNTs, of their increasing use
in pharmacology and in cosmetics, and of their toxicology.
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Affiliation(s)
- Marco Pirazzini
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Ornella Rossetto
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Roberto Eleopra
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Cesare Montecucco
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
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11
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Connan C, Voillequin M, Chavez CV, Mazuet C, Leveque C, Vitry S, Vandewalle A, Popoff MR. Botulinum neurotoxin type B uses a distinct entry pathway mediated by CDC42 into intestinal cells versus neuronal cells. Cell Microbiol 2017; 19. [PMID: 28296078 DOI: 10.1111/cmi.12738] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/07/2017] [Accepted: 03/08/2017] [Indexed: 12/15/2022]
Abstract
Botulinum neurotoxins (BoNTs) are responsible for severe flaccid paralysis by inhibiting the release of acetylcholine at the neuromuscular junctions. BoNT type B (BoNT/B) most often induces mild forms of botulism with predominant dysautonomic symptoms. In food borne botulism and botulism by intestinal colonisation such as infant botulism, which are the most frequent naturally acquired forms of botulism, the digestive tract is the main entry route of BoNTs into the organism. We previously showed that BoNT/B translocates through mouse intestinal barrier by an endocytosis-dependent mechanism and subsequently targets neuronal cells, mainly cholinergic neurons, in the intestinal mucosa and musculosa. Here, we investigated the entry pathway of BoNT/B using fluorescent C-terminal domain of the heavy chain (HcB), which is involved in the binding to specific receptor(s) and entry process into target cells. While the combination of gangliosides GD1a /GD1b /GT1b and synaptotagmin I and to a greater extent synaptotagmin II constitutes the functional HcB receptor on NG108-15 neuronal cells, HcB only uses the gangliosides GD1a /GD1b /GT1b to efficiently bind to m-ICcl2 intestinal cells. HcB enters both cell types by a dynamin-dependent endocytosis, which is efficiently prevented by Dynasore, a dynamin inhibitor, and reaches a common early endosomal compartment labeled by early endosome antigen (EEA1). In contrast to neuronal cells, HcB uses a Cdc42-dependent pathway to enter intestinal cells. Then, HcB is transported to late endosomes in neuronal cells, whereas it exploits a nonacidified pathway from apical to basal lateral side of m-ICcl2 cells supporting a transcytotic route in epithelial intestinal cells.
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Affiliation(s)
- Chloé Connan
- Bactéries anaérobies et Toxines, Institut Pasteur, Paris, France
| | - Marie Voillequin
- Bactéries anaérobies et Toxines, Institut Pasteur, Paris, France
| | | | | | - Christian Leveque
- INSERM, UMR_S 1072 (UNIS), Faculté de Médecine -Secteur Nord, Aix Marseille Université, Marseille, France
| | - Sandrine Vitry
- Neuro-Immunologie Virale, Institut Pasteur, Paris, France
| | | | - Michel R Popoff
- Bactéries anaérobies et Toxines, Institut Pasteur, Paris, France
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12
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Connan C, Popoff MR. Uptake of Clostridial Neurotoxins into Cells and Dissemination. Curr Top Microbiol Immunol 2017; 406:39-78. [PMID: 28879524 DOI: 10.1007/82_2017_50] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Clostridial neurotoxins, botulinum neurotoxins (BoNT) and tetanus neurotoxin (TeNT), are potent toxins, which are responsible for severe neurological diseases in man and animals. BoNTs induce a flaccid paralysis (botulism) by inhibiting acetylcholine release at the neuromuscular junctions, whereas TeNT causes a spastic paralysis (tetanus) by blocking the neurotransmitter release (glycine, GABA) in inhibitory interneurons within the central nervous system. Clostridial neurotoxins recognize specific receptor(s) on the target neuronal cells and enter via a receptor-mediated endocytosis. They transit through an acidic compartment which allows the translocation of the catalytic chain into the cytosol, a prerequisite step for the intracellular activity of the neurotoxins. TeNT migrates to the central nervous system by using a motor neuron as transport cell. TeNT enters a neutral pH compartment and undergoes a retrograde axonal transport to the spinal cord or brain, where the whole undissociated toxin is delivered and interacts with target neurons. Botulism most often results from ingestion of food contaminated with BoNT. Thus, BoNT passes through the intestinal epithelial barrier mainly via a transcytotic mechanism and then diffuses or is transported to the neuromuscular junctions by the lymph or blood circulation. Indeed, clostridial neurotoxins are specific neurotoxins which transit through a transport cell to gain access to the target neuron, and use distinct trafficking pathways in both cell types.
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Affiliation(s)
- Chloé Connan
- Unité Des Bactéries Anaérobies et Toxines, Institut Pasteur, 25 Rue Du Dr Roux, 75724, Paris Cedex 15, France
| | - Michel R Popoff
- Unité Des Bactéries Anaérobies et Toxines, Institut Pasteur, 25 Rue Du Dr Roux, 75724, Paris Cedex 15, France.
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Ayyar BV, Atassi MZ. Effects of membrane properties on the binding activities of the H N and H C heavy-chain domains of botulinum neurotoxin A. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1678-1685. [PMID: 27596061 DOI: 10.1016/j.bbapap.2016.09.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 08/15/2016] [Accepted: 09/01/2016] [Indexed: 10/21/2022]
Abstract
Binding behaviors of the HN and the HC domains of BoNT/A were investigated individually to identify if there exist any differences in their interaction with the cell membrane. Recombinant fragments corresponding to both BoNT/A HN and HC regions were prepared (HN519-845 and HC967-1296) and their binding to synaptic proteins was verified. The binding behaviors of these heavy-chain domains were analyzed by treating the Neuro 2a, a murine neuroblastoma cell line, with compounds known to alter membrane properties. Cholesterol depletion and lipid raft inhibition increased the binding of HN519-845 to Neuro 2a cells without affecting HC967-1296-cell interaction. Sphingolipid depletion decreased the binding of cells to both HC967-1296 and HN519-845 whereas, loading exogenous GD1a, on to the Neuro 2a cells, increased the binding of both the peptides to cells. Microtubule disruption of the Neuro 2a cells by nocodazole decreased the binding of both HC967-1296 and HN519-845 to the treated cells. Inhibition of the clathrin-mediated endocytosis using dynasore, chlorpromazine or potassium (K+) depletion buffer lowered the binding of both HC967-1296 and HN519-845 to the cells, but seemed to exert a more pronounced effect on the binding of HC967-1296 than on the binding of HN519-845. Results indicate that while both the HN and HC domains are involved in the binding of the toxin to neuronal cells there are differences in their behavior which probably stem from their respective amino acid composition and structural location in the toxin three-dimensional structure along with their intended role in translocation and internalization into the cells.
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Affiliation(s)
- B Vijayalakshmi Ayyar
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - M Zouhair Atassi
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA.
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Harper CB, Papadopulos A, Martin S, Matthews DR, Morgan GP, Nguyen TH, Wang T, Nair D, Choquet D, Meunier FA. Botulinum neurotoxin type-A enters a non-recycling pool of synaptic vesicles. Sci Rep 2016; 6:19654. [PMID: 26805017 PMCID: PMC4726273 DOI: 10.1038/srep19654] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 11/20/2015] [Indexed: 02/03/2023] Open
Abstract
Neuronal communication relies on synaptic vesicles undergoing regulated exocytosis and recycling for multiple rounds of fusion. Whether all synaptic vesicles have identical protein content has been challenged, suggesting that their recycling ability may differ greatly. Botulinum neurotoxin type-A (BoNT/A) is a highly potent neurotoxin that is internalized in synaptic vesicles at motor nerve terminals and induces flaccid paralysis. Recently, BoNT/A was also shown to undergo retrograde transport, suggesting it might enter a specific pool of synaptic vesicles with a retrograde trafficking fate. Using high-resolution microscopy techniques including electron microscopy and single molecule imaging, we found that the BoNT/A binding domain is internalized within a subset of vesicles that only partially co-localize with cholera toxin B-subunit and have markedly reduced VAMP2 immunoreactivity. Synaptic vesicles loaded with pHrodo-BoNT/A-Hc exhibited a significantly reduced ability to fuse with the plasma membrane in mouse hippocampal nerve terminals when compared with pHrodo-dextran-containing synaptic vesicles and pHrodo-labeled anti-GFP nanobodies bound to VAMP2-pHluorin or vGlut-pHluorin. Similar results were also obtained at the amphibian neuromuscular junction. These results reveal that BoNT/A is internalized in a subpopulation of synaptic vesicles that are not destined to recycle, highlighting the existence of significant molecular and functional heterogeneity between synaptic vesicles.
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Affiliation(s)
- Callista B Harper
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Andreas Papadopulos
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Sally Martin
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Daniel R Matthews
- The University of Queensland, Queensland Brain Institute, Brisbane, Queensland 4072, Australia
| | - Garry P Morgan
- The University of Queensland, Centre for Microscopy and Microanalysis, Brisbane, Queensland 4072, Australia
| | - Tam H Nguyen
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Tong Wang
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Deepak Nair
- Interdisciplinary Institute for Neuroscience, The University of Bordeaux, Bordeaux, 33000, France.,Centre for Neuroscience, Indian Institute of Science, Bangalore, 560012, India
| | - Daniel Choquet
- Interdisciplinary Institute for Neuroscience, The University of Bordeaux, Bordeaux, 33000, France
| | - Frederic A Meunier
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
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Connan C, Varela-Chavez C, Mazuet C, Molgó J, Haustant GM, Disson O, Lecuit M, Vandewalle A, Popoff MR. Translocation and dissemination to target neurons of botulinum neurotoxin type B in the mouse intestinal wall. Cell Microbiol 2015; 18:282-301. [DOI: 10.1111/cmi.12502] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 08/18/2015] [Accepted: 08/18/2015] [Indexed: 12/19/2022]
Affiliation(s)
- Chloé Connan
- Unité des Bactéries anaérobies et Toxines; Institut Pasteur; Paris 75724 France
| | | | - Christelle Mazuet
- Unité des Bactéries anaérobies et Toxines; Institut Pasteur; Paris 75724 France
| | - Jordi Molgó
- Service d'Ingénierie Moléculaire des Protéines, Laboratoire de Toxinologie Moléculaire et Biotechnologies; CEA, iBiTec-S; bâtiment 152, courrier N° 24 Gif-sur-Yvette 91191 France
- Institut des Neurosciences Paris-Saclay, UMR 9197; CNRS; Gif-sur-Yvette 91190 France
| | | | - Olivier Disson
- Unité de Biologie des Infections; Institut Pasteur; Paris 75724 France
| | - Marc Lecuit
- Unité de Biologie des Infections; Institut Pasteur; Paris 75724 France
| | - Alain Vandewalle
- Centre de Recherche sur l'Inflammation (CRI), UMRS 1149; Université Paris 7-Denis Diderot; site Bichat Paris 75018 France
| | - Michel R. Popoff
- Unité des Bactéries anaérobies et Toxines; Institut Pasteur; Paris 75724 France
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16
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Rummel A. The long journey of botulinum neurotoxins into the synapse. Toxicon 2015; 107:9-24. [PMID: 26363288 DOI: 10.1016/j.toxicon.2015.09.009] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 08/27/2015] [Accepted: 09/08/2015] [Indexed: 01/09/2023]
Abstract
Botulinum neurotoxins (BoNT) cause the disease botulism, a flaccid paralysis of the muscle. They are also very effective, widely used medicines applied locally in sub-nanogram quantities. BoNTs are released together with several non-toxic, associated proteins as progenitor toxin complexes (PCT) by Clostridium botulinum to become highly potent oral poisons ingested via contaminated food. They block the neurotransmission in susceptible animals and humans already in nanogram quantities due to their specific ability to enter motoneurons and to cleave only selected neuronal proteins involved in neuroexocytosis. BoNTs have developed a sophisticated strategy to passage the gastrointestinal tract and to be absorbed in the intestine of the host to finally attack neurons. A non-toxic non-hemagglutinin (NTNHA) forms a binary complex with BoNT to protect it from gastrointestinal degradation. This binary M-PTC is one component of the bi-modular 14-subunit ∼760 kDa large progenitor toxin complex. The other component is the structurally and functionally independent dodecameric hemagglutinin (HA) complex which facilitates the absorption on the intestinal epithelium by glycan binding. Subsequent to its transcytosis the HA complex disrupts the tight junction of the intestinal barrier from the basolateral side by binding to E-cadherin. Now, the L-PTC can also enter the circulation by paracellular routes in much larger quantities. From here, the dissociated BoNTs reach the neuromuscular junction and accumulate via interaction with polysialo gangliosides, complex glycolipids, on motoneurons at the neuromuscular junction. Subsequently, additional specific binding to luminal segments of synaptic vesicles proteins like SV2 and synaptotagmin leads to their uptake. Finally, the neurotoxins shut down the synaptic vesicle cycle, which they had exploited before to enter their target cells, via specific cleavage of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, which constitute the core components of the cellular membrane fusion machinery.
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Affiliation(s)
- Andreas Rummel
- Institut für Toxikologie, Medizinische Hochschule Hannover, 30623 Hannover, Germany.
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Pellett S, Tepp WH, Scherf JM, Johnson EA. Botulinum Neurotoxins Can Enter Cultured Neurons Independent of Synaptic Vesicle Recycling. PLoS One 2015; 10:e0133737. [PMID: 26207366 PMCID: PMC4514655 DOI: 10.1371/journal.pone.0133737] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 06/15/2015] [Indexed: 11/25/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are the causative agent of the severe and long-lasting disease botulism. At least seven different serotypes of BoNTs (denoted A-G) have been described. All BoNTs enter human or animal neuronal cells via receptor mediated endocytosis and cleave cytosolic SNARE proteins, resulting in a block of synaptic vesicle exocytosis, leading to the flaccid paralysis characteristic of botulism. Previous data have indicated that once a neuronal cell has been intoxicated by a BoNT, further entry of the same or other BoNTs is prevented due to disruption of synaptic vesicle recycling. However, it has also been shown that cultured neurons exposed to BoNT/A are still capable of taking up BoNT/E. In this report we show that in general BoNTs can enter cultured human or mouse neuronal cells that have previously been intoxicated with another BoNT serotype. Quantitative analysis of cell entry by assessing SNARE cleavage revealed none or only a minor difference in the efficiency of uptake of BoNTs into previously intoxicated neurons. Examination of the endocytic entry pathway by specific endocytosis inhibitors indicated that BoNTs are taken up by clathrin coated pits in both non pre-exposed and pre-exposed neurons. LDH release assays indicated that hiPSC derived neurons exposed consecutively to two different BoNT serotypes remained viable and healthy except in the case of BoNT/E or combinations of BoNT/E with BoNT/B, /D, or /F. Overall, our data indicate that previous intoxication of neuronal cells with BoNT does not inhibit further uptake of BoNTs.
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Affiliation(s)
- Sabine Pellett
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, 53706, United States of America
| | - William H. Tepp
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, 53706, United States of America
| | - Jacob M. Scherf
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, 53706, United States of America
| | - Eric A. Johnson
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, 53706, United States of America
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18
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Kim DW, Lee SK, Ahnn J. Botulinum Toxin as a Pain Killer: Players and Actions in Antinociception. Toxins (Basel) 2015; 7:2435-53. [PMID: 26134255 PMCID: PMC4516922 DOI: 10.3390/toxins7072435] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 06/19/2015] [Accepted: 06/23/2015] [Indexed: 11/17/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) have been widely used to treat a variety of clinical ailments associated with pain. The inhibitory action of BoNTs on synaptic vesicle fusion blocks the releases of various pain-modulating neurotransmitters, including glutamate, substance P (SP), and calcitonin gene-related peptide (CGRP), as well as the addition of pain-sensing transmembrane receptors such as transient receptor potential (TRP) to neuronal plasma membrane. In addition, growing evidence suggests that the analgesic and anti-inflammatory effects of BoNTs are mediated through various molecular pathways. Recent studies have revealed that the detailed structural bases of BoNTs interact with their cellular receptors and SNAREs. In this review, we discuss the molecular and cellular mechanisms related to the efficacy of BoNTs in alleviating human pain and insights on engineering the toxins to extend therapeutic interventions related to nociception.
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Affiliation(s)
- Dong-Wan Kim
- Department of Life Science, School of Natural Science, Hanyang University, Seoul 133-791, Korea.
- BK21 PLUS Life Science for BioDefense Research (BDR) Team, Hanyang University, Seoul 133-791, Korea.
| | - Sun-Kyung Lee
- Department of Life Science, School of Natural Science, Hanyang University, Seoul 133-791, Korea.
- BK21 PLUS Life Science for BioDefense Research (BDR) Team, Hanyang University, Seoul 133-791, Korea.
- The Research Institute for Natural Science, Hanyang University, Seoul 133-791, Korea.
| | - Joohong Ahnn
- Department of Life Science, School of Natural Science, Hanyang University, Seoul 133-791, Korea.
- BK21 PLUS Life Science for BioDefense Research (BDR) Team, Hanyang University, Seoul 133-791, Korea.
- The Research Institute for Natural Science, Hanyang University, Seoul 133-791, Korea.
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Wang T, Martin S, Papadopulos A, Harper CB, Mavlyutov TA, Niranjan D, Glass NR, Cooper-White JJ, Sibarita JB, Choquet D, Davletov B, Meunier FA. Control of autophagosome axonal retrograde flux by presynaptic activity unveiled using botulinum neurotoxin type a. J Neurosci 2015; 35:6179-94. [PMID: 25878289 PMCID: PMC4787026 DOI: 10.1523/jneurosci.3757-14.2015] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 03/09/2015] [Accepted: 03/11/2015] [Indexed: 11/21/2022] Open
Abstract
Botulinum neurotoxin type A (BoNT/A) is a highly potent neurotoxin that elicits flaccid paralysis by enzymatic cleavage of the exocytic machinery component SNAP25 in motor nerve terminals. However, recent evidence suggests that the neurotoxic activity of BoNT/A is not restricted to the periphery, but also reaches the CNS after retrograde axonal transport. Because BoNT/A is internalized in recycling synaptic vesicles, it is unclear which compartment facilitates this transport. Using live-cell confocal and single-molecule imaging of rat hippocampal neurons cultured in microfluidic devices, we show that the activity-dependent uptake of the binding domain of the BoNT/A heavy chain (BoNT/A-Hc) is followed by a delayed increase in retrograde axonal transport of BoNT/A-Hc carriers. Consistent with a role of presynaptic activity in initiating transport of the active toxin, activity-dependent uptake of BoNT/A in the terminal led to a significant increase in SNAP25 cleavage detected in the soma chamber compared with nonstimulated neurons. Surprisingly, most endocytosed BoNT/A-Hc was incorporated into LC3-positive autophagosomes generated in the nerve terminals, which then underwent retrograde transport to the cell soma, where they fused with lysosomes both in vitro and in vivo. Blocking autophagosome formation or acidification with wortmannin or bafilomycin A1, respectively, inhibited the activity-dependent retrograde trafficking of BoNT/A-Hc. Our data demonstrate that both the presynaptic formation of autophagosomes and the initiation of their retrograde trafficking are tightly regulated by presynaptic activity.
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Affiliation(s)
- Tong Wang
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute
| | - Sally Martin
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute
| | | | - Callista B Harper
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute
| | | | - Dhevahi Niranjan
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Nick R Glass
- Australian Institute for Bioengineering and Nanotechnology, and
| | - Justin J Cooper-White
- Australian Institute for Bioengineering and Nanotechnology, and School of Chemical Engineering, University of Queensland, Brisbane, Queensland 4072, Australia, Materials Science and Engineering Division, Commonwealth Scientific and Industrial Research Organization, Clayton, Victoria 3169, Australia
| | - Jean-Baptiste Sibarita
- University of Bordeaux, Interdisciplinary Institute for Neuroscience, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5297, Bordeaux, France
| | - Daniel Choquet
- University of Bordeaux, Interdisciplinary Institute for Neuroscience, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5297, Bordeaux, France, Bordeaux Imaging Center, Unité Mixte de Service 3420, Centre National de la Recherche Scientifique, US4 INSERM, University of Bordeaux, France, and
| | - Bazbek Davletov
- Department of Biomedical Science, The University of Sheffield, Sheffield, S10 2TN, United Kingdom
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute,
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Botulinum toxin A complex exploits intestinal M cells to enter the host and exert neurotoxicity. Nat Commun 2015; 6:6255. [PMID: 25687350 PMCID: PMC4339894 DOI: 10.1038/ncomms7255] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 01/11/2015] [Indexed: 01/08/2023] Open
Abstract
To cause food-borne botulism, botulinum neurotoxin (BoNT) in the gastrointestinal lumen must traverse the intestinal epithelial barrier. However, the mechanism by which BoNT crosses the intestinal epithelial barrier remains unclear. BoNTs are produced along with one or more non-toxic components, with which they form progenitor toxin complexes (PTCs). Here we show that serotype A1 L-PTC, which has high oral toxicity and makes the predominant contribution to causing illness, breaches the intestinal epithelial barrier from microfold (M) cells via an interaction between haemagglutinin (HA), one of the non-toxic components, and glycoprotein 2 (GP2). HA strongly binds to GP2 expressed on M cells, which do not have thick mucus layers. Susceptibility to orally administered L-PTC is dramatically reduced in M-cell-depleted mice and GP2-deficient (Gp2−/−) mice. Our finding provides the basis for the development of novel antitoxin therapeutics and delivery systems for oral biologics. It is unclear how ingested botulinum neurotoxin invades the host to cause illness. Here, the authors show that the toxin complex containing neurotoxin, hemagglutinin (HA), and NTNHA proteins traverses the epithelial barrier via HA-glycoprotein 2 interaction and endocytosis by Peyer’s patch microfold cells.
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Pathogenesis of human enterovirulent bacteria: lessons from cultured, fully differentiated human colon cancer cell lines. Microbiol Mol Biol Rev 2014; 77:380-439. [PMID: 24006470 DOI: 10.1128/mmbr.00064-12] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Hosts are protected from attack by potentially harmful enteric microorganisms, viruses, and parasites by the polarized fully differentiated epithelial cells that make up the epithelium, providing a physical and functional barrier. Enterovirulent bacteria interact with the epithelial polarized cells lining the intestinal barrier, and some invade the cells. A better understanding of the cross talk between enterovirulent bacteria and the polarized intestinal cells has resulted in the identification of essential enterovirulent bacterial structures and virulence gene products playing pivotal roles in pathogenesis. Cultured animal cell lines and cultured human nonintestinal, undifferentiated epithelial cells have been extensively used for understanding the mechanisms by which some human enterovirulent bacteria induce intestinal disorders. Human colon carcinoma cell lines which are able to express in culture the functional and structural characteristics of mature enterocytes and goblet cells have been established, mimicking structurally and functionally an intestinal epithelial barrier. Moreover, Caco-2-derived M-like cells have been established, mimicking the bacterial capture property of M cells of Peyer's patches. This review intends to analyze the cellular and molecular mechanisms of pathogenesis of human enterovirulent bacteria observed in infected cultured human colon carcinoma enterocyte-like HT-29 subpopulations, enterocyte-like Caco-2 and clone cells, the colonic T84 cell line, HT-29 mucus-secreting cell subpopulations, and Caco-2-derived M-like cells, including cell association, cell entry, intracellular lifestyle, structural lesions at the brush border, functional lesions in enterocytes and goblet cells, functional and structural lesions at the junctional domain, and host cellular defense responses.
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Lee K, Lam KH, Kruel AM, Perry K, Rummel A, Jin R. High-resolution crystal structure of HA33 of botulinum neurotoxin type B progenitor toxin complex. Biochem Biophys Res Commun 2014; 446:568-73. [PMID: 24631690 DOI: 10.1016/j.bbrc.2014.03.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 03/03/2014] [Indexed: 12/13/2022]
Abstract
Botulinum neurotoxins (BoNTs) are produced as progenitor toxin complexes (PTCs) by Clostridium botulinum. The PTCs are composed of BoNT and non-toxic neurotoxin-associated proteins (NAPs), which serve to protect and deliver BoNT through the gastrointestinal tract in food borne botulism. HA33 is a key NAP component that specifically recognizes host carbohydrates and helps enrich PTC on the intestinal lumen preceding its transport across the epithelial barriers. Here, we report the crystal structure of HA33 of type B PTC (HA33/B) in complex with lactose at 1.46Å resolution. The structural comparisons among HA33 of serotypes A-D reveal two different HA33-glycan interaction modes. The glycan-binding pockets on HA33/A and B are more suitable to recognize galactose-containing glycans in comparison to the equivalent sites on HA33/C and D. On the contrary, HA33/C and D could potentially recognize Neu5Ac as an independent receptor, whereas HA33/A and B do not. These findings indicate that the different oral toxicity and host susceptibility observed among different BoNT serotypes could be partly determined by the serotype-specific interaction between HA33 and host carbohydrate receptors. Furthermore, we have identified a key structural water molecule that mediates the HA33/B-lactose interactions. It provides the structural basis for development of new receptor-mimicking compounds, which have enhanced binding affinity with HA33 through their water-displacing moiety.
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Affiliation(s)
- Kwangkook Lee
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
| | - Kwok-Ho Lam
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
| | | | - Kay Perry
- NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Argonne National Laboratory, Argonne, IL, USA
| | - Andreas Rummel
- Institut für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
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23
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Yao G, Lee K, Gu S, Lam KH, Jin R. Botulinum neurotoxin A complex recognizes host carbohydrates through its hemagglutinin component. Toxins (Basel) 2014; 6:624-35. [PMID: 24525478 PMCID: PMC3942755 DOI: 10.3390/toxins6020624] [Citation(s) in RCA: 13] [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: 12/24/2013] [Revised: 01/15/2014] [Accepted: 02/05/2014] [Indexed: 11/16/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are potent bacterial toxins. The high oral toxicity of BoNTs is largely attributed to the progenitor toxin complex (PTC), which is assembled from BoNT and nontoxic neurotoxin-associated proteins (NAPs) that are produced together with BoNT in bacteria. Here, we performed ex vivo studies to examine binding of the highly homogeneous recombinant NAPs to mouse small intestine. We also carried out the first comprehensive glycan array screening with the hemagglutinin (HA) component of NAPs. Our data confirmed that intestinal binding of the PTC is partly mediated by the HA moiety through multivalent interactions between HA and host carbohydrates. The specific HA-carbohydrate recognition could be inhibited by receptor-mimicking saccharides.
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Affiliation(s)
- Guorui Yao
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
| | - Kwangkook Lee
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
| | - Shenyan Gu
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
| | - Kwok-Ho Lam
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
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24
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Simpson L. The life history of a botulinum toxin molecule. Toxicon 2013; 68:40-59. [DOI: 10.1016/j.toxicon.2013.02.014] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 02/13/2013] [Accepted: 02/19/2013] [Indexed: 12/31/2022]
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25
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Meng J, Wang J, Lawrence GW, Dolly JO. Molecular components required for resting and stimulated endocytosis of botulinum neurotoxins by glutamatergic and peptidergic neurons. FASEB J 2013; 27:3167-80. [PMID: 23640057 DOI: 10.1096/fj.13-228973] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Proteins responsible for basal and stimulated endocytosis in nerves containing small clear synaptic vesicles (SCSVs) or large dense-core vesicles (LDCVs) are revealed herein, using probes that exploit surface-exposed vesicle proteins as acceptors for internalization. Basal uptake of botulinum neurotoxins (BoNTs) by both SCSV-releasing cerebellar granule neurons (CGNs) and LDCV-enriched trigeminal ganglionic neurons (TGNs) was found to require protein acceptors and acidic compartments. In addition, dynamin, clathrin, adaptor protein complex-2 (AP2), and amphiphysin contribute to the depolarization-evoked entry. For fast recycling of SCSVs, knockdown and knockout strategies demonstrated that CGNs use predominantly dynamin 1, whereas isoform 2 and, to a smaller extent, isoform 3 support a less rapid mode of stimulated endocytosis. Accordingly, proximity ligation assay confirmed that dynamin 1 and 2 colocalize with amphiphysin 1 in CGNs, and the latter copurified with both dynamins from cell extracts. In contrast, LDCV-releasing TGNs preferentially employ dynamins 2 and 3 and amphiphysin 1 for evoked endocytosis and lack the fast phase. Hence, stimulation recruits dynamin, clathrin, AP2, and amphiphysin to augment BoNT internalization, and neurons match endocytosis mediators to the different demands for locally recycling SCSVs or replenishing distally synthesized LDCVs.
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Affiliation(s)
- Jianghui Meng
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
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Harper CB, Popoff MR, McCluskey A, Robinson PJ, Meunier FA. Targeting membrane trafficking in infection prophylaxis: dynamin inhibitors. Trends Cell Biol 2013; 23:90-101. [DOI: 10.1016/j.tcb.2012.10.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 10/11/2012] [Accepted: 10/11/2012] [Indexed: 12/01/2022]
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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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Harper CB, Martin S, Nguyen TH, Daniels SJ, Lavidis NA, Popoff MR, Hadzic G, Mariana A, Chau N, McCluskey A, Robinson PJ, Meunier FA. Dynamin inhibition blocks botulinum neurotoxin type A endocytosis in neurons and delays botulism. J Biol Chem 2011; 286:35966-35976. [PMID: 21832053 DOI: 10.1074/jbc.m111.283879] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The botulinum neurotoxins (BoNTs) are di-chain bacterial proteins responsible for the paralytic disease botulism. Following binding to the plasma membrane of cholinergic motor nerve terminals, BoNTs are internalized into an endocytic compartment. Although several endocytic pathways have been characterized in neurons, the molecular mechanism underpinning the uptake of BoNTs at the presynaptic nerve terminal is still unclear. Here, a recombinant BoNT/A heavy chain binding domain (Hc) was used to unravel the internalization pathway by fluorescence and electron microscopy. BoNT/A-Hc initially enters cultured hippocampal neurons in an activity-dependent manner into synaptic vesicles and clathrin-coated vesicles before also entering endosomal structures and multivesicular bodies. We found that inhibiting dynamin with the novel potent Dynasore analog, Dyngo-4a(TM), was sufficient to abolish BoNT/A-Hc internalization and BoNT/A-induced SNAP25 cleavage in hippocampal neurons. Dyngo-4a also interfered with BoNT/A-Hc internalization into motor nerve terminals. Furthermore, Dyngo-4a afforded protection against BoNT/A-induced paralysis at the rat hemidiaphragm. A significant delay of >30% in the onset of botulism was observed in mice injected with Dyngo-4a. Dynamin inhibition therefore provides a therapeutic avenue for the treatment of botulism and other diseases caused by pathogens sharing dynamin-dependent uptake mechanisms.
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Affiliation(s)
- Callista B Harper
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Sally Martin
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Tam H Nguyen
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Shari J Daniels
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Nickolas A Lavidis
- School of Biomedical Sciences, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Michel R Popoff
- Unité des Bactéries anaérobies et Toxines, Institut Pasteur, 28 rue du Dr. Roux, 75724 Paris cedex, France
| | - Gordana Hadzic
- Centre for Chemical Biology, Chemistry Building, the University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Anna Mariana
- Children's Medical Research Institute, the University of Sydney, Sydney, New South Wales 2145, Australia
| | - Ngoc Chau
- Children's Medical Research Institute, the University of Sydney, Sydney, New South Wales 2145, Australia
| | - Adam McCluskey
- Centre for Chemical Biology, Chemistry Building, the University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Phillip J Robinson
- Children's Medical Research Institute, the University of Sydney, Sydney, New South Wales 2145, Australia
| | - Frederic A Meunier
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia.
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Elias M, Al-Saleem F, Ancharski DM, Singh A, Nasser Z, Olson RM, Simpson LL. Evidence that botulinum toxin receptors on epithelial cells and neuronal cells are not identical: implications for development of a non-neurotropic vaccine. J Pharmacol Exp Ther 2011; 336:605-12. [PMID: 21106906 PMCID: PMC3061530 DOI: 10.1124/jpet.110.175018] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 11/24/2010] [Indexed: 11/22/2022] Open
Abstract
Botulinum toxin typically interacts with two types of cells to cause the disease botulism. The toxin initially interacts with epithelial cells in the gut or airway to undergo binding, transcytosis, and delivery to the general circulation. The toxin then interacts with peripheral cholinergic nerve endings to undergo binding, endocytosis, and delivery to the cytosol. The receptors for botulinum toxin on nerve cells have been identified, but receptors on epithelial cells remain unknown. The initial toxin binding site on nerve cells is a polysialoganglioside, so experiments were performed to determine whether polysialogangliosides are also receptors on epithelial cells. A series of single mutant and dimutant forms of the botulinum toxin type A binding domain (HC₅₀) were cloned and expressed. One of these (dimutant HC₅₀ A(W₁₂₆₆L,Y₁₂₆₇S)) was shown to have lost its ability to bind nerve cells (phrenic nerve-hemidiaphragm preparation), yet it retained its ability to bind and cross human epithelial monolayers (T-84 cells). In addition, the wild-type HC₅₀ and the dimutant HC₅₀ displayed the same ability to undergo binding and transcytosis (absorption) in a mouse model. The fact that the dimutant retained the ability to cross epithelial barriers but did not possess the ability to bind to nerve cells was exploited to create a mucosal vaccine that was non-neurotropic. The wild-type HC₅₀ and non-neurotropic HC₅₀ proved to be comparable in their abilities to: 1) evoke a circulating IgA and IgG response and 2) evoke protection against a substantial challenge dose of botulinum toxin.
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Affiliation(s)
- Md Elias
- Department of Medicine, Jefferson Medical College, Philadelphia, PA 19107, USA
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Thirunavukkarasusx N, Ghosal KJ, Kukreja R, Zhou Y, Dombkowski A, Cai S, Singh BR. Microarray analysis of differentially regulated genes in human neuronal and epithelial cell lines upon exposure to type A botulinum neurotoxin. Biochem Biophys Res Commun 2011; 405:684-90. [PMID: 21291863 DOI: 10.1016/j.bbrc.2011.01.102] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 01/27/2011] [Indexed: 11/16/2022]
Abstract
Among the seven serotypes (A-G), type A botulinum neurotoxin (BoNT/A) is the most prevalent etiologic agent and the most potent serotype to cause foodborne botulism, characterized by flaccid muscle paralysis. Upon ingestion, BoNT/A crosses epithelial cell barriers to reach lymphatic and circulatory systems and blocks acetylcholine release at the pre-synaptic cholinergic nerve terminals of neuromuscular junctions (NMJs) resulting in paralysis. One of the unique features of BoNT/A intoxication is its neuroparalytic longevity due to its persistent catalytic activity. The persistent presence of the toxin inside the cell can induce host cell responses. To understand the pathophysiology and host response at the cellular level, gene expression changes upon exposure of human HT-29 colon carcinoma (epithelial) and SH-SY5Y neuroblastoma cell lines to BoNT/A complex were investigated using microarray analysis. In HT-29 cells, 167 genes were up-regulated while 60 genes were down-regulated, whereas in SH-SY5Y cells about 223 genes were up-regulated and 18 genes were down-regulated. Modulation of genes and pathways involved in neuroinflammatory, ubiquitin-proteasome degradation, phosphatidylinositol, calcium signaling in SH-SY5Y cells, and genes relevant to focal adhesion, cell adhesion molecules, adherens and gap junction related pathways in HT-29 cells suggest a massive host response to BoNT/A. A clear differential response in epithelial and neuronal cells indicates that the genes affected may play a distinct role in BoNTs cellular mode of action, involving these two types of host cells.
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Affiliation(s)
- Nagarajan Thirunavukkarasusx
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, Botulinum Research Center, 285 Old Westport Road, N Dartmouth, MA 02747, United States
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Interaction of botulinum toxin with the epithelial barrier. J Biomed Biotechnol 2010; 2010:974943. [PMID: 20169001 PMCID: PMC2822237 DOI: 10.1155/2010/974943] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 12/24/2009] [Indexed: 11/17/2022] Open
Abstract
Botulinum neurotoxin (BoNT) is a protein toxin (approximately 150 kDa), which possesses a metalloprotease activity. Food-borne botulism is manifested when BoNT is absorbed from the digestive tract to the blood stream and enters the peripheral nerves, where the toxin cleaves core proteins of the neuroexocytosis apparatus and elicits the inhibition of neurotransmitter release. The initial obstacle to orally ingested BoNT entering the body is the epithelial barrier of the digestive tract. Recent cell biology and molecular biology studies are beginning to elucidate the mechanism by which this large protein toxin crosses the epithelial barrier. In this review, we provide an overview of the structural features of botulinum toxins (BoNT and BoNT complex) and the interaction of these toxins with the epithelial barrier.
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Abstract
Clostridia produce the highest number of toxins of any type of bacteria and are involved in severe diseases in humans and other animals. Most of the clostridial toxins are pore-forming toxins responsible for gangrenes and gastrointestinal diseases. Among them, perfringolysin has been extensively studied and it is the paradigm of the cholesterol-dependent cytolysins, whereas Clostridium perfringens epsilon-toxin and Clostridium septicum alpha-toxin, which are related to aerolysin, are the prototypes of clostridial toxins that form small pores. Other toxins active on the cell surface possess an enzymatic activity, such as phospholipase C and collagenase, and are involved in the degradation of specific cell-membrane or extracellular-matrix components. Three groups of clostridial toxins have the ability to enter cells: large clostridial glucosylating toxins, binary toxins and neurotoxins. The binary and large clostridial glucosylating toxins alter the actin cytoskeleton by enzymatically modifying the actin monomers and the regulatory proteins from the Rho family, respectively. Clostridial neurotoxins proteolyse key components of neuroexocytosis. Botulinum neurotoxins inhibit neurotransmission at neuromuscular junctions, whereas tetanus toxin targets the inhibitory interneurons of the CNS. The high potency of clostridial toxins results from their specific targets, which have an essential cellular function, and from the type of modification that they induce. In addition, clostridial toxins are useful pharmacological and biological tools.
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Affiliation(s)
- Michel R Popoff
- Institut Pasteur, Bactéries Anaérobies et Toxines, 75724 Paris cedex 15, France.
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Abstract
Bacterial toxins damage the host at the site of bacterial infection or distant from the site. Bacterial toxins can be single proteins or oligomeric protein complexes that are organized with distinct AB structure-function properties. The A domain encodes a catalytic activity. ADP ribosylation of host proteins is the earliest post-translational modification determined to be performed by bacterial toxins; other modifications include glucosylation and proteolysis. Bacterial toxins also catalyze the non-covalent modification of host protein function or can modify host cell properties through direct protein-protein interactions. The B domain includes two functional domains: a receptor-binding domain, which defines the tropism of a toxin for a cell and a translocation domain that delivers the A domain across a lipid bilayer, either on the plasma membrane or the endosome. Bacterial toxins are often characterized based upon the secretion mechanism that delivers the toxin out of the bacterium, termed types I-VII. This review summarizes the major families of bacterial toxins and also describes the specific structure-function properties of the botulinum neurotoxins.
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Affiliation(s)
- James S Henkel
- Medical College of Wisconsin, Department of Microbiology and Molecular Genetics, Milwaukee, WI 53151, USA.
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