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Martínez-Carranza M, Škerlová J, Lee PG, Zhang J, Krč A, Sirohiwal A, Burgin D, Elliott M, Philippe J, Donald S, Hornby F, Henriksson L, Masuyer G, Kaila VRI, Beard M, Dong M, Stenmark P. Activity of botulinum neurotoxin X and its structure when shielded by a non-toxic non-hemagglutinin protein. Commun Chem 2024; 7:179. [PMID: 39138288 PMCID: PMC11322297 DOI: 10.1038/s42004-024-01262-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2024] [Accepted: 07/29/2024] [Indexed: 08/15/2024] Open
Abstract
Botulinum neurotoxins (BoNTs) are the most potent toxins known and are used to treat an increasing number of medical disorders. All BoNTs are naturally co-expressed with a protective partner protein (NTNH) with which they form a 300 kDa complex, to resist acidic and proteolytic attack from the digestive tract. We have previously identified a new botulinum neurotoxin serotype, BoNT/X, that has unique and therapeutically attractive properties. We present the cryo-EM structure of the BoNT/X-NTNH/X complex and the crystal structure of the isolated NTNH protein. Unexpectedly, the BoNT/X complex is stable and protease-resistant at both neutral and acidic pH and disassembles only in alkaline conditions. Using the stabilizing effect of NTNH, we isolated BoNT/X and showed that it has very low potency both in vitro and in vivo. Given the high catalytic activity and translocation efficacy of BoNT/X, low activity of the full toxin is likely due to the receptor-binding domain, which presents very weak ganglioside binding and exposed hydrophobic surfaces.
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Affiliation(s)
| | - Jana Škerlová
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Pyung-Gang Lee
- Department of Urology, Boston Children's Hospital, Boston, MA, USA
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Jie Zhang
- Department of Urology, Boston Children's Hospital, Boston, MA, USA
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Ajda Krč
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Abhishek Sirohiwal
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | | | | | | | | | | | - Linda Henriksson
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Geoffrey Masuyer
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Ville R I Kaila
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | | | - Min Dong
- Department of Urology, Boston Children's Hospital, Boston, MA, USA.
- Department of Microbiology, Harvard Medical School, Boston, MA, USA.
- Department of Surgery, Harvard Medical School, Boston, MA, USA.
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
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2
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Rasetti-Escargueil C, Palea S. Embracing the Versatility of Botulinum Neurotoxins in Conventional and New Therapeutic Applications. Toxins (Basel) 2024; 16:261. [PMID: 38922155 PMCID: PMC11209287 DOI: 10.3390/toxins16060261] [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] [Received: 04/15/2024] [Revised: 05/26/2024] [Accepted: 05/27/2024] [Indexed: 06/27/2024] Open
Abstract
Botulinum neurotoxins (BoNTs) have been used for almost half a century in the treatment of excessive muscle contractility. BoNTs are routinely used to treat movement disorders such as cervical dystonia, spastic conditions, blepharospasm, and hyperhidrosis, as well as for cosmetic purposes. In addition to the conventional indications, the use of BoNTs to reduce pain has gained increased recognition, giving rise to an increasing number of indications in disorders associated with chronic pain. Furthermore, BoNT-derived formulations are benefiting a much wider range of patients suffering from overactive bladder, erectile dysfunction, arthropathy, neuropathic pain, and cancer. BoNTs are categorised into seven toxinotypes, two of which are in clinical use, and each toxinotype is divided into multiple subtypes. With the development of bioinformatic tools, new BoNT-like toxins have been identified in non-Clostridial organisms. In addition to the expanding indications of existing formulations, the rich variety of toxinotypes or subtypes in the wild-type BoNTs associated with new BoNT-like toxins expand the BoNT superfamily, forming the basis on which to develop new BoNT-based therapeutics as well as research tools. An overview of the diversity of the BoNT family along with their conventional therapeutic uses is presented in this review followed by the engineering and formulation opportunities opening avenues in therapy.
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Affiliation(s)
| | - Stefano Palea
- Humana Biosciences-Prologue Biotech, 516 Rue Pierre et Marie Curie, 31670 Labège, France;
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3
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Gregg BM, Matsumura T, Wentz TG, Tepp WH, Bradshaw M, Stenmark P, Johnson EA, Fujinaga Y, Pellett S. Botulinum neurotoxin X lacks potency in mice and in human neurons. mBio 2024; 15:e0310623. [PMID: 38347673 PMCID: PMC10936432 DOI: 10.1128/mbio.03106-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 01/16/2024] [Indexed: 03/14/2024] Open
Abstract
Botulinum neurotoxins (BoNTs) are a class of toxins produced by Clostridium botulinum (C. botulinum) and other species of Clostridia. BoNT/X is a putative novel botulinum neurotoxin identified through genome sequencing and capable of SNARE cleavage, but its neurotoxic potential in humans and vertebrates remained unclear. The C. botulinum strain producing BoNT/X, Strain 111, encodes both a plasmid-borne bont/b2 as well as the chromosomal putative bont/x. This study utilized C. botulinum Strain 111 from Japan as well as recombinantly produced full-length BoNT/X to more fully analyze this putative pathogenic toxin. We confirmed production of full-length, catalytically active native BoNT/X by C. botulinum Strain 111, produced as a disulfide-bonded dichain polypeptide similar to other BoNTs. Both the purified native and the recombinant BoNT/X had high enzymatic activity in vitro but displayed very low potency in human-induced pluripotent stem cell-derived neuronal cells and in mice. Intraperitoneal injection of up to 50 µg of native BoNT/X in mice did not result in botulism; however, mild local paralysis was observed after injection of 2 μg into the gastrocnemius muscle. We further demonstrate that the lack of toxicity by BoNT/X is due to inefficient neuronal cell association and entry, which can be rescued by replacing the receptor binding domain of BoNT/X with that of BoNT/A. These data demonstrate that BoNT/X is not a potent vertebrate neurotoxin like the classical seven serotypes of BoNTs. IMPORTANCE The family of botulinum neurotoxins comprises the most potent toxins known to humankind. New members of this family of protein toxins as well as more distantly related homologs are being identified. The discovery of BoNT/X via bioinformatic screen in 2017 as a putative new BoNT serotype raised concern about its potential as a pathogenic agent with no available countermeasures. This study for the first time assessed both recombinantly produced and native purified BoNT/X for its vertebrate neurotoxicity.
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Affiliation(s)
- Brieana M. Gregg
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, USA
| | - Takuhiro Matsumura
- Department of Bacteriology, Kanazawa University, Kanazawa, Ishikawa, Japan
| | - Travis G. Wentz
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, USA
| | - William H. Tepp
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, USA
| | - Marite Bradshaw
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, USA
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Eric A. Johnson
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, USA
| | - Yukako Fujinaga
- Department of Bacteriology, Kanazawa University, Kanazawa, Ishikawa, Japan
| | - Sabine Pellett
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, USA
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4
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Gregory KS, Hall PR, Onuh JP, Mojanaga OO, Liu SM, Acharya KR. Crystal Structure of the Catalytic Domain of a Botulinum Neurotoxin Homologue from Enterococcus faecium: Potential Insights into Substrate Recognition. Int J Mol Sci 2023; 24:12721. [PMID: 37628902 PMCID: PMC10454453 DOI: 10.3390/ijms241612721] [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] [Received: 06/28/2023] [Revised: 07/25/2023] [Accepted: 08/10/2023] [Indexed: 08/27/2023] Open
Abstract
Clostridium botulinum neurotoxins (BoNTs) are the most potent toxins known, causing the deadly disease botulism. They function through Zn2+-dependent endopeptidase cleavage of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, preventing vesicular fusion and subsequent neurotransmitter release from motor neurons. Several serotypes of BoNTs produced by Clostridium botulinum (BoNT/A-/G and/X) have been well-characterised over the years. However, a BoNT-like gene (homologue of BoNT) was recently identified in the non-clostridial species, Enterococcus faecium, which is the leading cause of hospital-acquired multi-drug resistant infections. Here, we report the crystal structure of the catalytic domain of a BoNT homologue from Enterococcus faecium (LC/En) at 2.0 Å resolution. Detailed structural analysis in comparison with the full-length BoNT/En AlphaFold2-predicted structure, LC/A (from BoNT/A), and LC/F (from BoNT/F) revealed putative subsites and exosites (including loops 1-5) involved in recognition of LC/En substrates. LC/En also appears to possess a conserved autoproteolytic cleavage site whose function is yet to be established.
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Affiliation(s)
- Kyle S. Gregory
- Department of Life Sciences, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (P.-R.H.); (J.P.O.); (O.O.M.)
| | - Peter-Rory Hall
- Department of Life Sciences, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (P.-R.H.); (J.P.O.); (O.O.M.)
| | - Jude Prince Onuh
- Department of Life Sciences, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (P.-R.H.); (J.P.O.); (O.O.M.)
| | - Otsile O. Mojanaga
- Department of Life Sciences, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (P.-R.H.); (J.P.O.); (O.O.M.)
| | - Sai Man Liu
- Protein Sciences Department, Ipsen Bioinnovation Limited, 102 Park Drive, Milton Park, Abingdon OX14 4RY, UK;
| | - K. Ravi Acharya
- Department of Life Sciences, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (P.-R.H.); (J.P.O.); (O.O.M.)
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Mastrorilli V, De Angelis F, Vacca V, Pavone F, Luvisetto S, Marinelli S. Xeomin®, a Commercial Formulation of Botulinum Neurotoxin Type A, Promotes Regeneration in a Preclinical Model of Spinal Cord Injury. Toxins (Basel) 2023; 15:toxins15040248. [PMID: 37104185 PMCID: PMC10142820 DOI: 10.3390/toxins15040248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 03/17/2023] [Accepted: 03/27/2023] [Indexed: 03/31/2023] Open
Abstract
Xeomin® is a commercial formulation of botulinum neurotoxin type A (BoNT/A) clinically authorized for treating neurological disorders, such as blepharospasm, cervical dystonia, limb spasticity, and sialorrhea. We have previously demonstrated that spinal injection of laboratory purified 150 kDa BoNT/A in paraplegic mice, after undergoing traumatic spinal cord injury (SCI), was able to reduce excitotoxic phenomena, glial scar, inflammation, and the development of neuropathic pain and facilitate regeneration and motor recovery. In the present study, as proof of concept in view of a possible clinical application, we studied the efficacy of Xeomin® in the same preclinical SCI model in which we highlighted the positive effects of lab-purified BoNT/A. Data comparison shows that Xeomin® induces similar pharmacological and therapeutic effects, albeit with less efficacy, to lab-purified BoNT/A. This difference, which can be improved by adjusting the dose, can be attributable to the different formulation and pharmacodynamics. Although the mechanism by which Xeomin® and laboratory purified BoNT/A induce functional improvement in paraplegic mice is still far from being understood, these results open a possible new scenario in treatment of SCI and are a stimulus for further research.
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6
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Xi Y, Zhao T, Liu R, Song F, Deng J, Ai N. Assessing Sensory Attributes and Properties of Infant Formula Milk Powder Driving Consumers' Preference. Foods 2023; 12:foods12050997. [PMID: 36900514 PMCID: PMC10000600 DOI: 10.3390/foods12050997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 02/18/2023] [Accepted: 02/24/2023] [Indexed: 03/03/2023] Open
Abstract
Infant formula milk powder (IFMP) is an excellent substitute for breast milk. It is known that the composition of maternal food during pregnancy and lactation and exposure level to food during infancy highly influence taste development in early infancy. However, little is known about the sensory aspects of infant formula. Herein, the sensory characteristics of 14 brands of infant formula segment 1 marketed in China were evaluated, and differences in preferences for IFMPs were determined. Descriptive sensory analysis was performed by well-trained panelists to determine the sensory characteristics of evaluated IFMPs. The brands S1 and S3 had significantly lower astringency and fishy flavor compared to the other brands. Moreover, it was found that S6, S7 and S12 had lower milk flavor scores but higher butter scores. Furthermore, internal preference mapping revealed that the attributes fatty flavor, aftertaste, saltiness, astringency, fishy flavor and sourness negatively contributed to consumer preference in all three clusters. Considering that the majority of consumers prefer milk powders rich in aroma, sweet and steamed flavors, these attributes could be considered for enhancement by the food industry.
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Affiliation(s)
- Yanmei Xi
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, School of Food and Health, Beijing Technology & Business University, Beijing 100048, China
| | - Tong Zhao
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, School of Food and Health, Beijing Technology & Business University, Beijing 100048, China
| | - Ruirui Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, School of Food and Health, Beijing Technology & Business University, Beijing 100048, China
| | - Fuhang Song
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, School of Food and Health, Beijing Technology & Business University, Beijing 100048, China
| | - Jianjun Deng
- State Key Laboratory of Vegetable Biobreeding, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
- Correspondence: (J.D.); (N.A.)
| | - Nasi Ai
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, School of Food and Health, Beijing Technology & Business University, Beijing 100048, China
- Correspondence: (J.D.); (N.A.)
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7
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Panditrao MV, Chung CH, Khouri JM, Barash JR, Motter RN, Dover N, Arnon SS. Dual-Toxin ("Bivalent") Infant Botulism in California, 1976-2020: Epidemiologic, Clinical, and Laboratory Aspects. J Pediatr 2023; 253:8-13. [PMID: 35977619 DOI: 10.1016/j.jpeds.2022.08.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/05/2022] [Accepted: 08/11/2022] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To assess the consequences of infant botulism that result from Clostridium botulinum strains that produce 2 botulinum toxin serotypes, termed "bivalent." STUDY DESIGN Epidemiologic investigations used a standard questionnaire. Clostridium botulinum strains were isolated by standard methods. Botulinum neurotoxin (BoNT) serotypes and the relative amounts of toxins produced were identified using the standard mouse bioassay. BoNT subtypes and genomic locations were identified by DNA nucleotide sequencing. RESULTS Thirty bivalent cases of infant botulism occurred in the 45 years (1976-2020), representing 2.0% of all California infant botulism cases, in the 3 geographic regions of southern California, the southern Central Valley, and mid-northern California. Toxin serotype combinations were Ba (n = 22), Bf (n = 7), and Ab (n = 1). More patients with illness caused by bivalent C botulinum Ba and Bf strains needed endotracheal intubation at hospital admission, 60.0% (18/30), than did patients with illness caused by monovalent BoNT/B strains, 34.3% (152/443). The Cbotulinum Ba and Bf strains produced BoNT/B5 and either BoNT/A4 or /F2. The Ab strain produced BoNT/A2 and /B1. All toxin gene clusters were on plasmids. CONCLUSIONS Infant botulism caused by bivalent Cbotulinum strains occurs sporadically and in diverse locations in California. Affected patients with bivalent Ba and Bf strains lacked distinguishing epidemiological features but appeared to be more severely paralyzed at hospital presentation than patients with illness caused by only BoNT/B. These bivalent strains produced BoNT subtypes A2, A4, B1, B5, and F2, and all toxin gene clusters were on plasmids.
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Affiliation(s)
- Mayuri V Panditrao
- Epidemiology, Surveillance, and Modeling Branch, COVID-19 Response California Department of Public Health, Richmond, CA
| | - Connie H Chung
- Infant Botulism Treatment and Prevention Program, Infectious Diseases Laboratory Branch, Center for Infectious Diseases, California Department of Public Health, Richmond, CA
| | - Jessica M Khouri
- Infant Botulism Treatment and Prevention Program, Infectious Diseases Laboratory Branch, Center for Infectious Diseases, California Department of Public Health, Richmond, CA.
| | - Jason R Barash
- Infant Botulism Treatment and Prevention Program, Infectious Diseases Laboratory Branch, Center for Infectious Diseases, California Department of Public Health, Richmond, CA
| | - Ruth N Motter
- Infant Botulism Treatment and Prevention Program, Infectious Diseases Laboratory Branch, Center for Infectious Diseases, California Department of Public Health, Richmond, CA
| | - Nir Dover
- Infant Botulism Treatment and Prevention Program, Infectious Diseases Laboratory Branch, Center for Infectious Diseases, California Department of Public Health, Richmond, CA
| | - Stephen S Arnon
- Infant Botulism Treatment and Prevention Program, Infectious Diseases Laboratory Branch, Center for Infectious Diseases, California Department of Public Health, Richmond, CA
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8
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Fang Y, Chang AY, Verma D, Miyashita SI, Eszterhas S, Lee PG, Shen Y, Davis LR, Dong M, Bailey-Kellogg C, Griswold KE. Functional Deimmunization of Botulinum Neurotoxin Protease Domain via Computationally Driven Library Design and Ultrahigh-Throughput Screening. ACS Synth Biol 2023; 12:153-163. [PMID: 36623275 PMCID: PMC9872818 DOI: 10.1021/acssynbio.2c00426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Indexed: 01/11/2023]
Abstract
Botulinum neurotoxin serotype A (BoNT/A) is a widely used cosmetic agent that also has diverse therapeutic applications; however, adverse antidrug immune responses and associated loss of efficacy have been reported in clinical uses. Here, we describe computational design and ultrahigh-throughput screening of a massive BoNT/A light-chain (BoNT/A-LC) library optimized for reduced T cell epitope content and thereby dampened immunogenicity. We developed a functional assay based on bacterial co-expression of BoNT/A-LC library members with a Förster resonance energy transfer (FRET) sensor for BoNT/A-LC enzymatic activity, and we employed high-speed fluorescence-activated cell sorting (FACS) to identify numerous computationally designed variants having wild-type-like enzyme kinetics. Many of these variants exhibited decreased immunogenicity in humanized HLA transgenic mice and manifested in vivo paralytic activity when incorporated into full-length toxin. One variant achieved near-wild-type paralytic potency and a 300% reduction in antidrug antibody response in vivo. Thus, we have achieved a striking level of BoNT/A-LC functional deimmunization by combining computational library design and ultrahigh-throughput screening. This strategy holds promise for deimmunizing other biologics with complex superstructures and mechanisms of action.
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Affiliation(s)
- Yongliang Fang
- Thayer
School of Engineering, Dartmouth, Hanover, New Hampshire 03755, United States
- Department
of Urology, Boston Children’s Hospital, Boston, Massachusetts 02115, United States
- Department
of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Andrew Y. Chang
- Thayer
School of Engineering, Dartmouth, Hanover, New Hampshire 03755, United States
| | - Deeptak Verma
- Department
of Computer Science, Dartmouth, Hanover, New Hampshire 03755, United States
| | - Shin-Ichiro Miyashita
- Department
of Urology, Boston Children’s Hospital, Boston, Massachusetts 02115, United States
- Department
of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115, United States
- Department
of Food, Aroma and Cosmetic Chemistry, Tokyo
University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan
| | - Susan Eszterhas
- Thayer
School of Engineering, Dartmouth, Hanover, New Hampshire 03755, United States
| | - Pyung-Gang Lee
- Department
of Urology, Boston Children’s Hospital, Boston, Massachusetts 02115, United States
- Department
of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Yi Shen
- Department
of Urology, Boston Children’s Hospital, Boston, Massachusetts 02115, United States
- Department
of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Lydia R. Davis
- Thayer
School of Engineering, Dartmouth, Hanover, New Hampshire 03755, United States
| | - Min Dong
- Department
of Urology, Boston Children’s Hospital, Boston, Massachusetts 02115, United States
- Department
of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Chris Bailey-Kellogg
- Department
of Computer Science, Dartmouth, Hanover, New Hampshire 03755, United States
| | - Karl E. Griswold
- Thayer
School of Engineering, Dartmouth, Hanover, New Hampshire 03755, United States
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9
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A Comprehensive Structural Analysis of Clostridium botulinum Neurotoxin A Cell-Binding Domain from Different Subtypes. Toxins (Basel) 2023; 15:toxins15020092. [PMID: 36828407 PMCID: PMC9966434 DOI: 10.3390/toxins15020092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/11/2023] [Accepted: 01/16/2023] [Indexed: 01/20/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) cause flaccid neuromuscular paralysis by cleaving one of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex proteins. BoNTs display high affinity and specificity for neuromuscular junctions, making them one of the most potent neurotoxins known to date. There are seven serologically distinct BoNTs (serotypes BoNT/A to BoNT/G) which can be further divided into subtypes (e.g., BoNT/A1, BoNT/A2…) based on small changes in their amino acid sequence. Of these, BoNT/A1 and BoNT/B1 have been utilised to treat various diseases associated with spasticity and hypersecretion. There are potentially many more BoNT variants with differing toxicological profiles that may display other therapeutic benefits. This review is focused on the structural analysis of the cell-binding domain from BoNT/A1 to BoNT/A6 subtypes (HC/A1 to HC/A6), including features such as a ganglioside binding site (GBS), a dynamic loop, a synaptic vesicle glycoprotein 2 (SV2) binding site, a possible Lys-Cys/Cys-Cys bridge, and a hinge motion between the HCN and HCC subdomains. Characterising structural features across subtypes provides a better understanding of how the cell-binding domain functions and may aid the development of novel therapeutics.
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10
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Structure and activity of botulinum neurotoxin X. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.11.523524. [PMID: 36712025 PMCID: PMC9882044 DOI: 10.1101/2023.01.11.523524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Botulinum neurotoxins (BoNTs) are the most potent toxins known and are used to treat an increasing number of medical disorders. All BoNTs are naturally co-expressed with a protective partner protein (NTNH) with which they form a 300 kDa complex, to resist acidic and proteolytic attack from the digestive tract. We have previously identified a new botulinum neurotoxin serotype, BoNT/X, that has unique and therapeutically attractive properties. We present the cryo-EM structure of the BoNT/X-NTNH/X complex at 3.1 Å resolution. Unexpectedly, the BoNT/X complex is stable and protease resistant at both neutral and acidic pH and disassembles only in alkaline conditions. Using the stabilizing effect of NTNH, we isolated BoNT/X and showed that it has very low potency both in vitro and in vivo . Given the high catalytic activity and translocation efficacy of BoNT/X, low activity of the full toxin is likely due to the receptor-binding domain, which presents weak ganglioside binding and exposed hydrophobic surfaces.
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11
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Shikhkerimov RK, Istomina EV. Recombinant botulinum toxin as a new stage in the development of botulinum toxin therapy. Possibilities and perspectives of use in neurological practice. NEUROLOGY, NEUROPSYCHIATRY, PSYCHOSOMATICS 2022. [DOI: 10.14412/2074-2711-2022-6-103-109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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12
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Liu J, Xu S, Huang C, Shen J, Yu S, Yu Y, Sun Q, Dai Q. Synthesis and activity evaluation of selenazole-coupled CPI-1 irreversible bifunctional inhibitors for botulinum toxin A light chain. Bioorg Med Chem Lett 2022; 73:128913. [PMID: 35914651 DOI: 10.1016/j.bmcl.2022.128913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 07/21/2022] [Accepted: 07/26/2022] [Indexed: 11/02/2022]
Abstract
A series of novel conjugates of benzoselenazole or selenazole and CPI-1 were designed, synthesized, and evaluated for inhibitory activities against the botulinum neurotoxin A (BoNT/A) light chain (LC) and BoNT/A in vivo. The results show that these compounds exhibit potent inhibitory activities to the LC with IC50 of 0.5-4.1 µM. The reaction kinetics and the mass spectra of the reaction products of LC with benzoselenazole- or selenazole- coupled CPI-1 demonstrate that the benzoselenazole group of most inhibitors is coupled to the LC of BoNT/A. These data indicate that the CPI-1 conjugates can inhibit both the active center of BoNT/A LC as well as Cys165, therefore functioning as irreversible bifunctional inhibitors. The detoxification activities in vivo show that one of the benzoselenazole-CPI-1 compounds prolongs the survival time of mice challenged by 2 × LD50 of BoNT/A. This work provides a new strategy to design potent antidotes of BoNT/A.
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13
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Structure-Functional Characteristics of the Svx Protein—The Virulence Factor of the Phytopathogenic Bacterium Pectobacterium atrosepticum. Int J Mol Sci 2022; 23:ijms23136914. [PMID: 35805920 PMCID: PMC9266454 DOI: 10.3390/ijms23136914] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/17/2022] [Accepted: 06/20/2022] [Indexed: 11/17/2022] Open
Abstract
The Svx proteins are virulence factors of phytopathogenic bacteria of the Pectobacterium genus. The specific functions of these proteins are unknown. Here we show that most of the phytopathogenic species of Pectobacterium, Dickeya, and Xanthomonas genera have genes encoding Svx proteins, as well as some plant-non-associated species of different bacterial genera. As such, the Svx-like proteins of phytopathogenic species form a distinct clade, pointing to the directed evolution of these proteins to provide effective interactions with plants. To get a better insight into the structure and functions of the Svx proteins, we analyzed the Svx of Pectobacterium atrosepticum (Pba)—an extracellular virulence factor secreted into the host plant cell wall (PCW). Using in silico analyses and by obtaining and analyzing the recombinant Pba Svx and its mutant forms, we showed that this protein was a gluzincin metallopeptidase. The 3D structure model of the Pba Svx was built and benchmarked against the experimental overall secondary structure content. Structure-based substrate specificity analysis using molecular docking revealed that the Pba Svx substrate-binding pocket might accept α-glycosylated proteins represented in the PCW by extensins—proteins that strengthen the PCW. Thus, these results elucidate the way in which the Pba Svx may contribute to the Pba virulence.
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14
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Nowakowska MB, Selby K, Przykopanski A, Krüger M, Krez N, Dorner BG, Dorner MB, Jin R, Minton NP, Rummel A, Lindström M. Construction and validation of safe Clostridium botulinum Group II surrogate strain producing inactive botulinum neurotoxin type E toxoid. Sci Rep 2022; 12:1790. [PMID: 35110559 PMCID: PMC8810926 DOI: 10.1038/s41598-022-05008-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 12/24/2021] [Indexed: 01/05/2023] Open
Abstract
Botulinum neurotoxins (BoNTs), produced by the spore-forming bacterium Clostridium botulinum, cause botulism, a rare but fatal illness affecting humans and animals. Despite causing a life-threatening disease, BoNT is a multipurpose therapeutic. Nevertheless, as the most potent natural toxin, BoNT is classified as a Select Agent in the US, placing C. botulinum research under stringent governmental regulations. The extreme toxicity of BoNT, its impact on public safety, and its diverse therapeutic applications urge to devise safe solutions to expand C. botulinum research. Accordingly, we exploited CRISPR/Cas9-mediated genome editing to introduce inactivating point mutations into chromosomal bont/e gene of C. botulinum Beluga E. The resulting Beluga Ei strain displays unchanged physiology and produces inactive BoNT (BoNT/Ei) recognized in serological assays, but lacking biological activity detectable ex- and in vivo. Neither native single-chain, nor trypsinized di-chain form of BoNT/Ei show in vivo toxicity, even if isolated from Beluga Ei sub-cultured for 25 generations. Beluga Ei strain constitutes a safe alternative for the BoNT research necessary for public health risk management, the development of food preservation strategies, understanding toxinogenesis, and for structural BoNT studies. The example of Beluga Ei generation serves as template for future development of C. botulinum producing different inactive BoNT serotypes.
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Affiliation(s)
- Maria B Nowakowska
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Katja Selby
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Adina Przykopanski
- Institut Für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Maren Krüger
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Nadja Krez
- Institut Für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Brigitte G Dorner
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Martin B Dorner
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Nigel P Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham, UK
| | - Andreas Rummel
- Institut Für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Miia Lindström
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
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15
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Silva-Andrade C, Martin AJ, Garrido D. Comparative Genomics of Clostridium baratii Reveals Strain-Level Diversity in Toxin Abundance. Microorganisms 2022; 10:microorganisms10020213. [PMID: 35208668 PMCID: PMC8879937 DOI: 10.3390/microorganisms10020213] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/29/2021] [Accepted: 11/10/2021] [Indexed: 01/27/2023] Open
Abstract
Clostridium baratii strains are rare opportunistic pathogens associated with botulism intoxication. They have been isolated from foods, soil and be carried asymptomatically or cause botulism outbreaks. Is not taxonomically related to Clostridium botulinum, but some strains are equipped with BoNT/F7 cluster. Despite their relationship with diseases, our knowledge regarding the genomic features and phylogenetic characteristics is limited. We analyzed the pangenome of C. baratii to understand the diversity and genomic features of this species. We compared existing genomes in public databases, metagenomes, and one newly sequenced strain isolated from an asymptomatic subject. The pangenome was open, indicating it comprises genetically diverse organisms. The core genome contained 28.49% of the total genes of the pangenome. Profiling virulence factors confirmed the presence of phospholipase C in some strains, a toxin capable of disrupting eukaryotic cell membranes. Furthermore, the genomic analysis indicated significant horizontal gene transfer (HGT) events as defined by the presence of prophage genomes. Seven strains were equipped with BoNT/F7 cluster. The active site was conserved in all strains, identifying a missing 7-aa region upstream of the active site in C. baratii genomes. This analysis could be important to advance our knowledge regarding opportunistic clostridia and better understand their contribution to disease.
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Affiliation(s)
- Claudia Silva-Andrade
- Laboratorio de Biología de Redes, Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago 8580000, Chile;
- Department of Chemical and Bioprocess Engineering, School of Engineering, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
| | - Alberto J. Martin
- Laboratorio de Biología de Redes, Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago 8580000, Chile;
- Correspondence: (A.J.M.); (D.G.)
| | - Daniel Garrido
- Department of Chemical and Bioprocess Engineering, School of Engineering, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
- Correspondence: (A.J.M.); (D.G.)
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16
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O'Neil PT, Vasquez-Montes V, Swint-Kruse L, Baldwin MR, Ladokhin AS. Spectroscopic evidence of tetanus toxin translocation domain bilayer-induced refolding and insertion. Biophys J 2021; 120:4763-4776. [PMID: 34555358 PMCID: PMC8595737 DOI: 10.1016/j.bpj.2021.09.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/03/2021] [Accepted: 09/16/2021] [Indexed: 12/21/2022] Open
Abstract
Tetanus neurotoxin (TeNT) is an A-B toxin with three functional domains: endopeptidase, translocation (HCT), and receptor binding. Endosomal acidification triggers HCT to interact with and insert into the membrane, translocating the endopeptidase across the bilayer. Although the function of HCT is well defined, the mechanism by which it accomplishes this task is unknown. To gain insight into the HCT membrane interaction on both local and global scales, we utilized an isolated, beltless HCT variant (bHCT), which retained the ability to release potassium ions from vesicles. To examine which bHCT residues interact with the membrane, we widely sampled the surface of bHCT using 47 single-cysteine variants labeled with the environmentally sensitive fluorophore NBD. At neutral pH, no interaction was observed for any variant. In contrast, all NBD-labeled positions reported environmental change in the presence of acidic pH and membranes containing anionic lipids. We then examined the conformation of inserted bHCT using circular dichroism and intrinsic fluorescence. Upon entering the membrane, bHCT retained predominantly α-helical secondary structure, whereas the tertiary structure exhibited substantial refolding. The use of lipid-attached quenchers revealed that at least one of the three tryptophan residues penetrated deep into the hydrocarbon core of the membrane, suggesting formation of a bHCT transmembrane conformation. The possible conformational topology was further explored with the hydropathy analysis webtool MPEx, which identified a large, potential α-helical transmembrane region. Altogether, the spectroscopic evidence supports a model in which, upon acidification, the majority of TeNT bHCT entered the membrane with a concurrent change in tertiary structure.
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Affiliation(s)
- Pierce T O'Neil
- Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas
| | - Victor Vasquez-Montes
- Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas
| | - Liskin Swint-Kruse
- Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas
| | - Michael R Baldwin
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri
| | - Alexey S Ladokhin
- Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas.
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17
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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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18
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Duchesne de Lamotte J, Perrier A, Martinat C, Nicoleau C. Emerging Opportunities in Human Pluripotent Stem-Cells Based Assays to Explore the Diversity of Botulinum Neurotoxins as Future Therapeutics. Int J Mol Sci 2021; 22:7524. [PMID: 34299143 PMCID: PMC8308099 DOI: 10.3390/ijms22147524] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/02/2021] [Accepted: 07/07/2021] [Indexed: 02/07/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) are produced by Clostridium botulinum and are responsible for botulism, a fatal disorder of the nervous system mostly induced by food poisoning. Despite being one of the most potent families of poisonous substances, BoNTs are used for both aesthetic and therapeutic indications from cosmetic reduction of wrinkles to treatment of movement disorders. The increasing understanding of the biology of BoNTs and the availability of distinct toxin serotypes and subtypes offer the prospect of expanding the range of indications for these toxins. Engineering of BoNTs is considered to provide a new avenue for improving safety and clinical benefit from these neurotoxins. Robust, high-throughput, and cost-effective assays for BoNTs activity, yet highly relevant to the human physiology, have become indispensable for a successful translation of engineered BoNTs to the clinic. This review presents an emerging family of cell-based assays that take advantage of newly developed human pluripotent stem cells and neuronal function analyses technologies.
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Affiliation(s)
- Juliette Duchesne de Lamotte
- IPSEN Innovation, 91940 Les Ulis, France;
- I-STEM, INSERM UMR861, Université Evry-Paris Saclay, 91100 Corbeil-Essonne, France
| | - Anselme Perrier
- I-STEM, INSERM UMR861, Université Evry-Paris Saclay, 91100 Corbeil-Essonne, France
- Laboratoire des Maladies Neurodégénératives: Mécanismes, Thérapies, Imagerie, CEA/CNRS UMR9199, Université Paris Saclay, 92265 Fontenay-aux-Roses, France
| | - Cécile Martinat
- I-STEM, INSERM UMR861, Université Evry-Paris Saclay, 91100 Corbeil-Essonne, France
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19
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Blum TR, Liu H, Packer MS, Xiong X, Lee PG, Zhang S, Richter M, Minasov G, Satchell KJF, Dong M, Liu DR. Phage-assisted evolution of botulinum neurotoxin proteases with reprogrammed specificity. Science 2021; 371:803-810. [PMID: 33602850 DOI: 10.1126/science.abf5972] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 12/24/2020] [Indexed: 12/14/2022]
Abstract
Although bespoke, sequence-specific proteases have the potential to advance biotechnology and medicine, generation of proteases with tailor-made cleavage specificities remains a major challenge. We developed a phage-assisted protease evolution system with simultaneous positive and negative selection and applied it to three botulinum neurotoxin (BoNT) light-chain proteases. We evolved BoNT/X protease into separate variants that preferentially cleave vesicle-associated membrane protein 4 (VAMP4) and Ykt6, evolved BoNT/F protease to selectively cleave the non-native substrate VAMP7, and evolved BoNT/E protease to cleave phosphatase and tensin homolog (PTEN) but not any natural BoNT protease substrate in neurons. The evolved proteases display large changes in specificity (218- to >11,000,000-fold) and can retain their ability to form holotoxins that self-deliver into primary neurons. These findings establish a versatile platform for reprogramming proteases to selectively cleave new targets of therapeutic interest.
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Affiliation(s)
- Travis R Blum
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
| | - Hao Liu
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
| | - Michael S Packer
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
| | - Xiaozhe Xiong
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
| | - Pyung-Gang Lee
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
| | - Sicai Zhang
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
| | - Michelle Richter
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
| | - George Minasov
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Min Dong
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA. .,Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA. .,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
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20
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Lin L, Olson ME, Sugane T, Turner LD, Tararina MA, Nielsen AL, Kurbanov EK, Pellett S, Johnson EA, Cohen SM, Allen KN, Janda KD. Catch and Anchor Approach To Combat Both Toxicity and Longevity of Botulinum Toxin A. J Med Chem 2020; 63:11100-11120. [PMID: 32886509 PMCID: PMC7581224 DOI: 10.1021/acs.jmedchem.0c01006] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Botulinum neurotoxins have remarkable persistence (∼weeks to months in cells), outlasting the small-molecule inhibitors designed to target them. To address this disconnect, inhibitors bearing two pharmacophores-a zinc binding group and a Cys-reactive warhead-were designed to leverage both affinity and reactivity. A series of first-generation bifunctional inhibitors was achieved through structure-based inhibitor design. Through X-ray crystallography, engagement of both the catalytic Zn2+ and Cys165 was confirmed. A second-generation series improved on affinity by incorporating known reversible inhibitor pharmacophores; the mechanism was confirmed by exhaustive dialysis, mass spectrometry, and in vitro evaluation against the C165S mutant. Finally, a third-generation inhibitor was shown to have good cellular activity and low toxicity. In addition to our findings, an alternative method of modeling time-dependent inhibition that simplifies assay setup and allows comparison of inhibition models is discussed.
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Affiliation(s)
- Lucy Lin
- Departments of Chemistry and Immunology, The Skaggs Institute for Chemical Biology, Worm Institute of Research and Medicine (WIRM), Scripps Research, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Margaret E. Olson
- Departments of Chemistry and Immunology, The Skaggs Institute for Chemical Biology, Worm Institute of Research and Medicine (WIRM), Scripps Research, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Takashi Sugane
- Departments of Chemistry and Immunology, The Skaggs Institute for Chemical Biology, Worm Institute of Research and Medicine (WIRM), Scripps Research, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Lewis D. Turner
- Departments of Chemistry and Immunology, The Skaggs Institute for Chemical Biology, Worm Institute of Research and Medicine (WIRM), Scripps Research, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Margarita A. Tararina
- Program in Biomolecular Pharmacology, Boston University School of Medicine, Boston, Massachusetts 02118, United States
| | - Alexander L. Nielsen
- Departments of Chemistry and Immunology, The Skaggs Institute for Chemical Biology, Worm Institute of Research and Medicine (WIRM), Scripps Research, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Elbek K. Kurbanov
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, United States
| | - Sabine Pellett
- Department of Bacteriology, University of Wisconsin, 1550 Linden Drive, Madison, Wisconsin 53706, United States
| | - Eric A. Johnson
- Department of Bacteriology, University of Wisconsin, 1550 Linden Drive, Madison, Wisconsin 53706, United States
| | - Seth M. Cohen
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, United States
| | - Karen N. Allen
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Kim D. Janda
- Departments of Chemistry and Immunology, The Skaggs Institute for Chemical Biology, Worm Institute of Research and Medicine (WIRM), Scripps Research, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
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21
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Abstract
How protein toxins translocate their catalytic domain across a cell membrane is the least understood step in toxin action. This study utilized a reporter, β-lactamase, that was genetically fused to full-length, nontoxic tetanus toxin (βlac-TT) in discovery-based live-cell assays to study LC translocation. Directed mutagenesis identified a role for K768 in LC translocation. K768 was located between α15 and α16 (termed the cis-loop). Cellular assays showed that K768 did not interfere with other toxin functions, including cell binding, intracellular trafficking, and pore formation. The equivalent K768 is conserved among the clostridial neurotoxin family of proteins as a conserved structural motif. The cis-loop appears to contribute to LC translocation. The clostridial neurotoxins (CNTs) comprise tetanus toxin (TT) and botulinum neurotoxin (BoNT [BT]) serotypes (A to G and X) and several recently identified CNT-like proteins, including BT/En and the mosquito BoNT-like toxin Pmp1. CNTs are produced as single proteins cleaved to a light chain (LC) and a heavy chain (HC) connected by an interchain disulfide bond. LC is a zinc metalloprotease (cleaving soluble N-ethylmaleimide-sensitive factor attachment protein receptors [SNAREs]), while HC contains an N-terminal translocation domain (HCN) and a C-terminal receptor binding domain (HCC). HCN-mediated LC translocation is the least understood function of CNT action. Here, β-lactamase (βlac) was used as a reporter in discovery-based live-cell assays to characterize TT-mediated LC translocation. Directed mutagenesis identified a role for a charged loop (767DKE769) connecting α15 and α16 (cis-loop) within HCN in LC translocation; aliphatic substitution inhibited LC translocation but not other toxin functions such as cell binding, intracellular trafficking, or HCN-mediated pore formation. K768 was conserved among the CNTs. In molecular simulations of the HCN with a membrane, the cis-loop did not bind with the cell membrane. Taken together, the results of these studies implicate the cis-loop in LC translocation, independently of pore formation. IMPORTANCE How protein toxins translocate their catalytic domain across a cell membrane is the least understood step in toxin action. This study utilized a reporter, β-lactamase, that was genetically fused to full-length, nontoxic tetanus toxin (βlac-TT) in discovery-based live-cell assays to study LC translocation. Directed mutagenesis identified a role for K768 in LC translocation. K768 was located between α15 and α16 (termed the cis-loop). Cellular assays showed that K768 did not interfere with other toxin functions, including cell binding, intracellular trafficking, and pore formation. The equivalent K768 is conserved among the clostridial neurotoxin family of proteins as a conserved structural motif. The cis-loop appears to contribute to LC translocation.
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22
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Steward L, Brin MF, Brideau-Andersen A. Novel Native and Engineered Botulinum Neurotoxins. Handb Exp Pharmacol 2020; 263:63-89. [PMID: 32274579 DOI: 10.1007/164_2020_351] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Botulinum neurotoxins (BoNTs), produced by Clostridia and other bacteria, are the most potent toxins known. Their cleavage of the soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins in neurons prevents the release of neurotransmitters, thus resulting in the muscle paralysis that is characteristic of botulism. This mechanism of action has been exploited for a variety of therapeutic and cosmetic applications of BoNTs. This chapter provides an overview of the native BoNTs, including the classical serotypes and their clinical use, mosaic BoNTs, and novel BoNTs that have been recently identified in clostridial and non-clostridial strains. In addition, the modular structure of native BoNTs, which are composed of a light chain and a heavy chain, is amenable to a multitude of novel fusions and mutations using molecular biology techniques. These novel recombinant BoNTs have been used or are being developed to further characterize the biology of toxins, to assist in vaccine production, to serve as delivery vehicles to neurons, and to be utilized as novel therapeutics for both neuronal and non-neuronal cells.
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Affiliation(s)
| | - Mitchell F Brin
- Allergan plc, Irvine, CA, USA.,University of California, Irvine, CA, USA
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23
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Martínez-Carranza M, Blasco P, Gustafsson R, Dong M, Berntsson RPA, Widmalm G, Stenmark P. Synaptotagmin Binding to Botulinum Neurotoxins. Biochemistry 2019; 59:491-498. [PMID: 31809018 DOI: 10.1021/acs.biochem.9b00554] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Botulinum neurotoxins (BoNTs) are exceptionally toxic proteins that cause paralysis but are also extensively used as treatment for various medical conditions. Most BoNTs bind two receptors on neuronal cells, namely, a ganglioside and a protein receptor. Differences in the sequence between the protein receptors from different species can impact the binding affinity and toxicity of the BoNTs. Here we have investigated how BoNT/B, /DC, and /G, all three toxins that utilize synaptotagmin I and II (Syt-I and Syt-II, respectively) as their protein receptors, bind to Syt-I and -II of mouse/rat, bovine, and human origin by isothermal titration calorimetry analysis. BoNT/G had the highest affinity for human Syt-I, and BoNT/DC had the highest affinity for bovine Syt-II. As expected, BoNT/B, /DC, and /G showed very low levels of binding to human Syt-II. Furthermore, we carried out saturation transfer difference (STD) and STD-TOCSY NMR experiments that revealed the region of the Syt peptide in direct contact with BoNT/G, which demonstrate that BoNT/G recognizes the Syt peptide in a model similar to that in the established BoNT/B-Syt-II complex. Our analyses also revealed that regions outside the Syt peptide's toxin-binding region are important for the helicity of the peptide and, therefore, the binding affinity.
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Affiliation(s)
| | - Pilar Blasco
- Department of Organic Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Robert Gustafsson
- Department of Biochemistry and Biophysics , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Min Dong
- Department of Urology, Boston's Children Hospital, and Department of Microbiology and Immunology and Department of Surgery , Harvard Medical School , Boston , Massachusetts 02115 , United States
| | - Ronnie Per-Arne Berntsson
- Department of Medical Biochemistry and Biophysics , Umeå University , SE-90187 Umeå , Sweden.,Wallenberg Centre for Molecular Medicine , Umeå University , SE-90187 Umeå , Sweden
| | - Göran Widmalm
- Department of Organic Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Pål Stenmark
- Department of Biochemistry and Biophysics , Stockholm University , SE-106 91 Stockholm , Sweden.,Department of Experimental Medical Science , Lund University , SE-221 00 Lund , Sweden
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von Berg L, Stern D, Weisemann J, Rummel A, Dorner MB, Dorner BG. Optimization of SNAP-25 and VAMP-2 Cleavage by Botulinum Neurotoxin Serotypes A-F Employing Taguchi Design-of-Experiments. Toxins (Basel) 2019; 11:toxins11100588. [PMID: 31614566 PMCID: PMC6832249 DOI: 10.3390/toxins11100588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 10/01/2019] [Accepted: 10/09/2019] [Indexed: 11/17/2022] Open
Abstract
The detection of catalytically active botulinum neurotoxins (BoNTs) can be achieved by monitoring the enzymatic cleavage of soluble NSF (N-ethylmaleimide-sensitive-factor) attachment protein receptor (SNARE) proteins by the toxins’ light chains (LC) in cleavage-based assays. Thus, for sensitive BoNT detection, optimal cleavage conditions for the clinically relevant A–F serotypes are required. Until now, a systematic evaluation of cleavage conditions for the different BoNT serotypes is still lacking. To address this issue, we optimized cleavage conditions for BoNT/A–F using the Taguchi design-of-experiments (DoE) method. To this aim, we analyzed the influence of buffer composition (pH, Zn2+, DTT (dithiothreitol), NaCl) as well as frequently used additives (BSA (bovine serum albumin), Tween 20, trimethylamine N-oxide (TMAO)) on BoNT substrate cleavage. We identified major critical factors (DTT, Zn2+, TMAO) and were able to increase the catalytic efficiency of BoNT/B, C, E, and F when compared to previously described buffers. Moreover, we designed a single consensus buffer for the optimal cleavage of all tested serotypes. Our optimized buffers are instrumental to increase the sensitivity of cleavage-based assays for BoNT detection. Furthermore, the application of the Taguchi DoE approach shows how the method helps to rationally improve enzymatic assays.
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Affiliation(s)
- Laura von Berg
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Seestr. 10, 13353 Berlin, Germany.
| | - Daniel Stern
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Seestr. 10, 13353 Berlin, Germany.
| | - Jasmin Weisemann
- Institut für Toxikologie, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
| | - Andreas Rummel
- Institut für Toxikologie, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
| | - Martin Bernhard Dorner
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Seestr. 10, 13353 Berlin, Germany.
| | - Brigitte Gertrud Dorner
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Seestr. 10, 13353 Berlin, Germany.
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25
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Košenina S, Masuyer G, Zhang S, Dong M, Stenmark P. Crystal structure of the catalytic domain of the Weissella oryzae botulinum-like toxin. FEBS Lett 2019; 593:1403-1410. [PMID: 31111466 DOI: 10.1002/1873-3468.13446] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 05/15/2019] [Accepted: 05/16/2019] [Indexed: 11/10/2022]
Abstract
Botulinum neurotoxins (BoNTs) are the most potent toxins known. So far, eight serotypes have been identified that all act as zinc-dependent endopeptidases targeting SNARE proteins and inhibiting the release of neurotransmitters. Recently, the first botulinum toxin-like protein was identified outside the Clostridial genus, designated BoNT/Wo in the genome of Weissella oryzae. Here, we report the 1.6 Å X-ray crystal structure of the light chain of BoNT/Wo (LC/Wo). LC/Wo presents the core fold common to BoNTs but has an unusually wide, open and negatively charged catalytic pocket, with an additional Ca2+ ion besides the zinc ion and a unique ß-hairpin motif. The structural information will help establish the substrate profile of BoNT/Wo and help our understanding of how BoNT evolved.
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Affiliation(s)
- Sara Košenina
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| | - Geoffrey Masuyer
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| | - Sicai Zhang
- Department of Urology, Boston Children's Hospital, Boston, MA, USA.,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Min Dong
- Department of Urology, Boston Children's Hospital, Boston, MA, USA.,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Sweden.,Department of Experimental Medical Science, Lund University, Sweden
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26
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Abstract
Botulinum neurotoxins (BoNTs) are a family of bacterial protein toxins produced by various Clostridium species. They are traditionally classified into seven major serotypes (BoNT/A-G). Recent progress in sequencing microbial genomes has led to an ever-growing number of subtypes, chimeric toxins, BoNT-like toxins, and remotely related BoNT homologs, constituting an expanding BoNT superfamily. Recent structural studies of BoNTs, BoNT progenitor toxin complexes, tetanus neurotoxin (TeNT), toxin-receptor complexes, and toxin-substrate complexes have provided mechanistic understandings of toxin functions and the molecular basis for their variations. The growing BoNT superfamily of toxins present a natural repertoire that can be explored to develop novel therapeutic toxins, and the structural understanding of their variations provides a knowledge basis for engineering toxins to improve therapeutic efficacy and expand their clinical applications.
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Affiliation(s)
- Min Dong
- Department of Urology, Boston Children's Hospital, Boston, MA, USA.
- Department of Microbiology, Harvard Medical School, Boston, MA, USA.
- Department of Surgery, Harvard Medical School, Boston, MA, USA.
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
- Department of Experimental Medical Science, Lund University, Lund, Sweden.
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27
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Davies JR, Liu SM, Acharya KR. Variations in the Botulinum Neurotoxin Binding Domain and the Potential for Novel Therapeutics. Toxins (Basel) 2018; 10:toxins10100421. [PMID: 30347838 PMCID: PMC6215321 DOI: 10.3390/toxins10100421] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 10/11/2018] [Accepted: 10/18/2018] [Indexed: 01/23/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) are categorised into immunologically distinct serotypes BoNT/A to /G). Each serotype can also be further divided into subtypes based on differences in amino acid sequence. BoNTs are ~150 kDa proteins comprised of three major functional domains: an N-terminal zinc metalloprotease light chain (LC), a translocation domain (HN), and a binding domain (HC). The HC is responsible for targeting the BoNT to the neuronal cell membrane, and each serotype has evolved to bind via different mechanisms to different target receptors. Most structural characterisations to date have focussed on the first identified subtype within each serotype (e.g., BoNT/A1). Subtype differences within BoNT serotypes can affect intoxication, displaying different botulism symptoms in vivo, and less emphasis has been placed on investigating these variants. This review outlines the receptors for each BoNT serotype and describes the basis for the highly specific targeting of neuronal cell membranes. Understanding receptor binding is of vital importance, not only for the generation of novel therapeutics but also for understanding how best to protect from intoxication.
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Affiliation(s)
- Jonathan R Davies
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
| | - Sai Man Liu
- Ipsen Bioinnovation Limited, Abingdon OX14 4RY, UK.
| | - K Ravi Acharya
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
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28
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Fonfria E, Elliott M, Beard M, Chaddock JA, Krupp J. Engineering Botulinum Toxins to Improve and Expand Targeting and SNARE Cleavage Activity. Toxins (Basel) 2018; 10:toxins10070278. [PMID: 29973505 PMCID: PMC6071219 DOI: 10.3390/toxins10070278] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 06/29/2018] [Accepted: 07/01/2018] [Indexed: 12/14/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are highly successful protein therapeutics. Over 40 naturally occurring BoNTs have been described thus far and, of those, only 2 are commercially available for clinical use. Different members of the BoNT family present different biological properties but share a similar multi-domain structure at the molecular level. In nature, BoNTs are encoded by DNA in producing clostridial bacteria and, as such, are amenable to recombinant production through insertion of the coding DNA into other bacterial species. This, in turn, creates possibilities for protein engineering. Here, we review the production of BoNTs by the natural host and also recombinant production approaches utilised in the field. Applications of recombinant BoNT-production include the generation of BoNT-derived domain fragments, the creation of novel BoNTs with improved performance and enhanced therapeutic potential, as well as the advancement of BoNT vaccines. In this article, we discuss site directed mutagenesis, used to affect the biological properties of BoNTs, including approaches to alter their binding to neurons and to alter the specificity and kinetics of substrate cleavage. We also discuss the target secretion inhibitor (TSI) platform, in which the neuronal binding domain of BoNTs is substituted with an alternative cellular ligand to re-target the toxins to non-neuronal systems. Understanding and harnessing the potential of the biological diversity of natural BoNTs, together with the ability to engineer novel mutations and further changes to the protein structure, will provide the basis for increasing the scope of future BoNT-based therapeutics.
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Affiliation(s)
- Elena Fonfria
- Ipsen Bioinnovation, 102 Park Drive, Milton Park, Abingdon OX14 4RY, UK.
| | - Mark Elliott
- Ipsen Bioinnovation, 102 Park Drive, Milton Park, Abingdon OX14 4RY, UK.
| | - Matthew Beard
- Ipsen Bioinnovation, 102 Park Drive, Milton Park, Abingdon OX14 4RY, UK.
| | - John A Chaddock
- Ipsen Bioinnovation, 102 Park Drive, Milton Park, Abingdon OX14 4RY, UK.
| | - Johannes Krupp
- Ipsen Innovation, 5 Avenue du Canada, 91940 Les Ulis, France.
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Light Chain Diversity among the Botulinum Neurotoxins. Toxins (Basel) 2018; 10:toxins10070268. [PMID: 30004421 PMCID: PMC6070880 DOI: 10.3390/toxins10070268] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 06/19/2018] [Accepted: 06/21/2018] [Indexed: 12/30/2022] Open
Abstract
Botulinum neurotoxins (BoNT) are produced by several species of clostridium. There are seven immunologically unique BoNT serotypes (A⁻G). The Centers for Disease Control classifies BoNTs as 'Category A' select agents and are the most lethal protein toxins for humans. Recently, BoNT-like proteins have also been identified in several non-clostridia. BoNTs are di-chain proteins comprised of an N-terminal zinc metalloprotease Light Chain (LC) and a C-terminal Heavy Chain (HC) which includes the translocation and receptor binding domains. The two chains are held together by a disulfide bond. The LC cleaves Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). The cleavage of SNAREs inhibits the fusion of synaptic vesicles to the cell membrane and the subsequent release of acetylcholine, which results in flaccid paralysis. The LC controls the catalytic properties and the duration of BoNT action. This review discusses the mechanism for LC catalysis, LC translocation, and the basis for the duration of LC action. Understanding these properties of the LC may expand the applications of BoNT as human therapies.
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30
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Tehran DA, Pirazzini M. Novel Botulinum Neurotoxins: Exploring Underneath the Iceberg Tip. Toxins (Basel) 2018; 10:toxins10050190. [PMID: 29748471 PMCID: PMC5983246 DOI: 10.3390/toxins10050190] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 05/05/2018] [Accepted: 05/08/2018] [Indexed: 12/26/2022] Open
Abstract
Botulinum neurotoxins (BoNTs), the etiological agents of botulism, are the deadliest toxins known to humans. Yet, thanks to their biological and toxicological features, BoNTs have become sophisticated tools to study neuronal physiology and valuable therapeutics for an increasing number of human disorders. BoNTs are produced by multiple bacteria of the genus Clostridium and, on the basis of their different immunological properties, were classified as seven distinct types of toxin. BoNT classification remained stagnant for the last 50 years until, via bioinformatics and high-throughput sequencing techniques, dozens of BoNT variants, novel serotypes as well as BoNT-like toxins within non-clostridial species have been discovered. Here, we discuss how the now “booming field” of botulinum neurotoxin may shed light on their evolutionary origin and open exciting avenues for future therapeutic applications.
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Affiliation(s)
- Domenico Azarnia Tehran
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy.
| | - Marco Pirazzini
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy.
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