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Garrigós M, Garrido M, Morales-Yuste M, Martínez-de la Puente J, Veiga J. Survival effects of antibiotic exposure during the larval and adult stages in the West Nile virus vector Culex pipiens. INSECT SCIENCE 2024; 31:542-550. [PMID: 37559499 DOI: 10.1111/1744-7917.13259] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/26/2023] [Accepted: 07/15/2023] [Indexed: 08/11/2023]
Abstract
The ability of mosquitoes to transmit a pathogen is affected, among other factors, by their survival rate, which is partly modulated by their microbiota. Mosquito microbiota is acquired during the larval phase and modified during their development and adult feeding behavior, being highly dependent on environmental factors. Pharmaceutical residues including antibiotics are widespread pollutants potentially being present in mosquito breeding waters likely affecting their microbiota. Here, we used Culex pipiens mosquitoes to assess the impact of antibiotic exposure during the larval and adult stages on the survival rate of adult mosquitoes. Wild-collected larvae were randomly assigned to two treatments: larvae maintained in water supplemented with antibiotics and control larvae. Emerged adults were subsequently assigned to each of two treatments, fed with sugar solution with antibiotics and fed only with sugar solution (controls). Larval exposure to antibiotics significantly increased the survival rate of adult females that received a control diet. In addition, the effect of adult exposure to antibiotics on the survival rate of both male and female mosquitoes depended on the number of days that larvae fed ad libitum in the laboratory before emergence. In particular, shorter larval ad libitum feeding periods reduced the survival rate of antibiotic-treated adult mosquitoes compared with those that emerged after a longer larval feeding period. These differences were not found in control adult mosquitoes. Our results extend the current understanding of the impact of antibiotic exposure of mosquitoes on a key component of vectorial capacity, that is the vector survival rate.
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Affiliation(s)
- Marta Garrigós
- Faculty of Pharmacy, Department of Parasitology, University of Granada, Granada, Spain
| | - Mario Garrido
- Faculty of Pharmacy, Department of Parasitology, University of Granada, Granada, Spain
| | - Manuel Morales-Yuste
- Faculty of Pharmacy, Department of Parasitology, University of Granada, Granada, Spain
| | - Josué Martínez-de la Puente
- Faculty of Pharmacy, Department of Parasitology, University of Granada, Granada, Spain
- CIBER de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Jesús Veiga
- Faculty of Pharmacy, Department of Parasitology, University of Granada, Granada, Spain
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2
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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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3
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Košenina S, Škerlová J, Zhang S, Dong M, Stenmark P. The cryo-EM structure of the BoNT/Wo-NTNH complex reveals two immunoglobulin-like domains. FEBS J 2024; 291:676-689. [PMID: 37746829 DOI: 10.1111/febs.16964] [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: 07/03/2023] [Revised: 09/07/2023] [Accepted: 09/20/2023] [Indexed: 09/26/2023]
Abstract
The botulinum neurotoxin-like toxin from Weissella oryzae (BoNT/Wo) is one of the BoNT-like toxins recently identified outside of the Clostridium genus. We show that, like the canonical BoNTs, BoNT/Wo forms a complex with its non-toxic non-hemagglutinin (NTNH) partner, which in traditional BoNT serotypes protects the toxin from proteases and the acidic environment of the hosts' guts. We here report the cryo-EM structure of the 300 kDa BoNT/Wo-NTNH/Wo complex together with pH stability studies of the complex. The structure reveals molecular details of the toxin's interactions with its protective partner. The overall structural arrangement is similar to other reported BoNT-NTNH complexes, but NTNH/Wo uniquely contains two extra bacterial immunoglobulin-like (Big) domains on the C-terminus. Although the function of these Big domains is unknown, they are structurally most similar to bacterial proteins involved in adhesion to host cells. In addition, the BoNT/Wo protease domain contains an internal disulfide bond not seen in other BoNTs. Mass photometry analysis revealed that the BoNT/Wo-NTNH/Wo complex is stable under acidic conditions and may dissociate at neutral to basic pH. These findings established that BoNT/Wo-NTNH/Wo shares the general fold of canonical BoNT-NTNH complexes. The presence of unique structural features suggests that it may have an alternative mode of activation, translocation and recognition of host cells, raising interesting questions about the activity and the mechanism of action of BoNT/Wo as well as about its target environment, receptors and substrates.
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Affiliation(s)
- Sara Košenina
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| | - Jana Škerlová
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - Sicai Zhang
- Department of Urology, Boston Children's Hospital, MA, USA
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Min Dong
- Department of Urology, Boston Children's Hospital, 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, Sweden
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4
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Gao L, Jin R. NTNH protein: more than a bodyguard for botulinum neurotoxins. FEBS J 2024; 291:672-675. [PMID: 38009421 PMCID: PMC10922118 DOI: 10.1111/febs.17004] [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: 11/01/2023] [Accepted: 11/14/2023] [Indexed: 11/28/2023]
Abstract
As one of the most fatal substances, botulinum neurotoxins (BoNTs) have never acted solo to accomplish their formidable missions. Most notably, nontoxic nonhemagglutinin (NTNH), a protein co-secreted with BoNT by bacteria, plays critical roles to stabilize and protect BoNT by tightly associating with it to form the minimal progenitor toxin complex (M-PTC). A new cryo-EM structure of the M-PTC of a BoNT-like toxin from Weissella oryzae (BoNT/Wo) reveals similar assembly modes between M-PTC/Wo and that of other BoNTs, yet also reveals some unique structural features of NTNH/Wo. These findings shed new light on the potential versatile roles of NTNH during BoNT intoxication.
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Affiliation(s)
- Linfeng Gao
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
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5
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Leka O, Wu Y, Zanetti G, Furler S, Reinberg T, Marinho J, Schaefer JV, Plückthun A, Li X, Pirazzini M, Kammerer RA. A DARPin promotes faster onset of botulinum neurotoxin A1 action. Nat Commun 2023; 14:8317. [PMID: 38110403 PMCID: PMC10728214 DOI: 10.1038/s41467-023-44102-4] [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: 12/24/2022] [Accepted: 11/30/2023] [Indexed: 12/20/2023] Open
Abstract
In this study, we characterize Designed Ankyrin Repeat Proteins (DARPins) as investigative tools to probe botulinum neurotoxin A1 (BoNT/A1) structure and function. We identify DARPin-F5 that completely blocks SNAP25 substrate cleavage by BoNT/A1 in vitro. X-ray crystallography reveals that DARPin-F5 inhibits BoNT/A1 activity by interacting with a substrate-binding region between the α- and β-exosite. This DARPin does not block substrate cleavage of BoNT/A3, indicating that DARPin-F5 is a subtype-specific inhibitor. BoNT/A1 Glu-171 plays a critical role in the interaction with DARPin-F5 and its mutation to Asp, the residue found in BoNT/A3, results in a loss of inhibition of substrate cleavage. In contrast to the in vitro results, DARPin-F5 promotes faster substrate cleavage of BoNT/A1 in primary neurons and muscle tissue by increasing toxin translocation. Our findings could have important implications for the application of BoNT/A1 in therapeutic areas requiring faster onset of toxin action combined with long persistence.
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Affiliation(s)
- Oneda Leka
- Laboratory of Biomolecular Research, Division of Biology, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Yufan Wu
- Laboratory of Biomolecular Research, Division of Biology, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Giulia Zanetti
- Department of Biomedical Sciences, University of Padova, 35121, Padova, Italy
| | - Sven Furler
- Department of Biochemistry, University of Zurich, 8057, Zurich, Switzerland
| | - Thomas Reinberg
- Department of Biochemistry, University of Zurich, 8057, Zurich, Switzerland
| | - Joana Marinho
- Department of Biochemistry, University of Zurich, 8057, Zurich, Switzerland
| | - Jonas V Schaefer
- Department of Biochemistry, University of Zurich, 8057, Zurich, Switzerland
| | - Andreas Plückthun
- Department of Biochemistry, University of Zurich, 8057, Zurich, Switzerland
| | - Xiaodan Li
- Laboratory of Biomolecular Research, Division of Biology, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Marco Pirazzini
- Department of Biomedical Sciences, University of Padova, 35121, Padova, Italy
| | - Richard A Kammerer
- Laboratory of Biomolecular Research, Division of Biology, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland.
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6
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Cai X, Peng Y, Yang G, Feng L, Tian X, Huang P, Mao Y, Xu L. Populational genomic insights of Paraclostridium bifermentans as an emerging human pathogen. Front Microbiol 2023; 14:1293206. [PMID: 38029151 PMCID: PMC10665999 DOI: 10.3389/fmicb.2023.1293206] [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: 09/12/2023] [Accepted: 10/26/2023] [Indexed: 12/01/2023] Open
Abstract
Paraclostridium bifermentans (P.b) is an emerging human pathogen that is phylogenomically close to Paeniclostridium sordellii (P.s), while their populational genomic features and virulence capacity remain understudied. Here, we performed comparative genomic analyses of P.b and compared their pan-genomic features and virulence coding profiles to those of P.s. Our results revealed that P.b has a more plastic pangenome, a larger genome size, and a higher GC content than P.s. Interestingly, the P.b and P.s share similar core-genomic functions, but P.b encodes more functions in nutrient metabolism and energy conversion and fewer functions in host defense in their accessory-genomes. The P.b may initiate extracellular infection processes similar to those of P.s and Clostridium perfringens by encoding three toxin homologs (i.e., microbial collagenase, thiol-activated cytolysin, phospholipase C, which are involved in extracellular matrices degradation and membrane damaging) in their core-genomes. However, P.b is less toxic than the P.s by encoding fewer secretion toxins in the core-genome and fewer lethal toxins in the accessory-genome. Notably, P.b carries more toxins genes in their accessory-genomes, particularly those of plasmid origin. Moreover, three within-species and highly conserved plasmid groups, encoding virulence, gene acquisition, and adaptation, were carried by 25-33% of P.b strains and clustered by isolation source rather than geography. This study characterized the pan-genomic virulence features of P.b for the first time, and revealed that P. bifermentans is an emerging pathogen that can threaten human health in many aspects, emphasizing the importance of phenotypic and genomic characterizations of in situ clinical isolates.
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Affiliation(s)
- Xunchao Cai
- Department of Gastroenterology and Hepatology, Shenzhen University General Hospital, Shenzhen University, Shenzhen, Guangdong, China
- Marshall Laboratory of Biomedical Engineering, Shenzhen University, Shenzhen, Guangdong, China
| | - Yao Peng
- Department of Gastroenterology and Hepatology, Shenzhen University General Hospital, Shenzhen University, Shenzhen, Guangdong, China
| | - Gongli Yang
- Department of Gastroenterology and Hepatology, Shenzhen University General Hospital, Shenzhen University, Shenzhen, Guangdong, China
| | - Lijuan Feng
- Department of Gastroenterology and Hepatology, Shenzhen University General Hospital, Shenzhen University, Shenzhen, Guangdong, China
| | - Xiaojuan Tian
- Department of Gastroenterology and Hepatology, Shenzhen University General Hospital, Shenzhen University, Shenzhen, Guangdong, China
| | - Ping Huang
- Department of Gastroenterology and Hepatology, Shenzhen University General Hospital, Shenzhen University, Shenzhen, Guangdong, China
| | - Yanping Mao
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, China
| | - Long Xu
- Department of Gastroenterology and Hepatology, Shenzhen University General Hospital, Shenzhen University, Shenzhen, Guangdong, China
- Marshall Laboratory of Biomedical Engineering, Shenzhen University, Shenzhen, Guangdong, China
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7
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Antonucci F, Bozzi Y. Action of Botulinum Neurotoxin E Type in Experimental Epilepsies. Toxins (Basel) 2023; 15:550. [PMID: 37755976 PMCID: PMC10536604 DOI: 10.3390/toxins15090550] [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: 07/21/2023] [Revised: 08/09/2023] [Accepted: 08/26/2023] [Indexed: 09/28/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) are zinc endopeptidases produced by the Clostridium genus of anerobic bacteria, largely known for their ability to cleave synaptic proteins, leading to neuromuscular paralysis. In the central nervous system, BoNTs are known to block the release of glutamate neurotransmitter, and for this reason, researchers explored the possible therapeutic action in disorders characterized by neuronal hyperactivity, such as epilepsy. Thus, using multidisciplinary approaches and models of experimental epilepsy, we investigated the pharmacological potential of BoNT/E serotype. In this review, written in memory of Prof. Matteo Caleo, a pioneer in these studies, we go back over the hypotheses and experimental approaches that led us to the conclusion that intrahippocampal administration of BoNT/E (i) displays anticonvulsant effects if prophylactically delivered in a model of acute generalized seizures; (ii) does not have any antiepileptogenic action after the induction of status epilepticus; (iii) reduces frequency of spontaneous seizures in a model of recurrent seizures if delivered during the chronic phase but in a transient manner. Indeed, the control on spontaneous seizures stops when BoNT/E effects are off (few days), thus limiting its pharmacological potential in humans.
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Affiliation(s)
- Flavia Antonucci
- Department of Medical Biotechnology and Translational Medicine (BIOMETRA), University of Milan, via Fratelli Cervi 93, 20054 Milan, Italy
- CNR Institute of Neuroscience, via Raoul Follereau 3, 20854 Vedano al Lambro, Italy
- CIMeC-Center for Mind/Brain Sciences, University of Trento, Piazza della Manifattura 1, 38068 Rovereto, Italy
| | - Yuri Bozzi
- CIMeC-Center for Mind/Brain Sciences, University of Trento, Piazza della Manifattura 1, 38068 Rovereto, Italy
- CNR Institute of Neuroscience, via Giuseppe Moruzzi 1, 56124 Pisa, Italy
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8
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Katak RDM, Cintra AM, Burini BC, Marinotti O, Souza-Neto JA, Rocha EM. Biotechnological Potential of Microorganisms for Mosquito Population Control and Reduction in Vector Competence. INSECTS 2023; 14:718. [PMID: 37754686 PMCID: PMC10532289 DOI: 10.3390/insects14090718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 08/11/2023] [Accepted: 08/19/2023] [Indexed: 09/28/2023]
Abstract
Mosquitoes transmit pathogens that cause human diseases such as malaria, dengue fever, chikungunya, yellow fever, Zika fever, and filariasis. Biotechnological approaches using microorganisms have a significant potential to control mosquito populations and reduce their vector competence, making them alternatives to synthetic insecticides. Ongoing research has identified many microorganisms that can be used effectively to control mosquito populations and disease transmission. However, the successful implementation of these newly proposed approaches requires a thorough understanding of the multipronged microorganism-mosquito-pathogen-environment interactions. Although much has been achieved in discovering new entomopathogenic microorganisms, antipathogen compounds, and their mechanisms of action, only a few have been turned into viable products for mosquito control. There is a discrepancy between the number of microorganisms with the potential for the development of new insecticides and/or antipathogen products and the actual available products, highlighting the need for investments in the intersection of basic research and biotechnology.
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Affiliation(s)
- Ricardo de Melo Katak
- Malaria and Dengue Laboratory, Instituto Nacional de Pesquisas da Amazônia-INPA, Manaus 69060-001, AM, Brazil;
| | - Amanda Montezano Cintra
- Multiuser Central Laboratory, Department of Bioprocesses and Biotechnology, School of Agricultural Sciences, São Paulo State University (UNESP), Botucatu 18610-034, SP, Brazil; (A.M.C.); (J.A.S.-N.)
| | - Bianca Correa Burini
- Florida Medical Entomology Laboratory, University of Florida, Vero Beach, FL 32962, USA;
| | - Osvaldo Marinotti
- Department of Biology, Indiana University, Bloomington, IN 47405, USA;
| | - Jayme A. Souza-Neto
- Multiuser Central Laboratory, Department of Bioprocesses and Biotechnology, School of Agricultural Sciences, São Paulo State University (UNESP), Botucatu 18610-034, SP, Brazil; (A.M.C.); (J.A.S.-N.)
| | - Elerson Matos Rocha
- Multiuser Central Laboratory, Department of Bioprocesses and Biotechnology, School of Agricultural Sciences, São Paulo State University (UNESP), Botucatu 18610-034, SP, Brazil; (A.M.C.); (J.A.S.-N.)
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9
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Košenina S, Stenmark P. Crystal structure of the OrfX1-OrfX3 complex from the PMP1 neurotoxin gene cluster. FEBS Lett 2023; 597:515-523. [PMID: 36403098 DOI: 10.1002/1873-3468.14542] [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: 10/28/2022] [Accepted: 11/10/2022] [Indexed: 11/21/2022]
Abstract
Paraclostridial mosquitocidal protein 1 (PMP1) is a member of the clostridial neurotoxin (CNT) family, which includes botulinum and tetanus neurotoxins. PMP1 has unique selectivity for anopheline mosquitos and is the only known member of the family that targets insects. PMP1 is encoded in an orfX gene cluster, which in addition to the toxin, consists of OrfX1, OrfX2, OrfX3, P47 and NTNH, which have been shown to aid in PMP1 toxicity. We here show that OrfX1 and OrfX3 form a complex and present its structure at 2.7 Å. The OrfX1-OrfX3 complex mimics the structure of full-length OrfX2 and belongs to the lipid-binding TULIP protein superfamily. With this report, the structures of all proteins encoded in the orfX gene cluster of CNTs are now determined.
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Affiliation(s)
- Sara Košenina
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
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10
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Gao L, Lam KH, Liu S, Przykopanski A, Lübke J, Qi R, Krüger M, Nowakowska MB, Selby K, Douillard FP, Dorner MB, Perry K, Lindström M, Dorner BG, Rummel A, Jin R. Crystal structures of OrfX1, OrfX2 and the OrfX1-OrfX3 complex from the orfX gene cluster of botulinum neurotoxin E1. FEBS Lett 2023; 597:524-537. [PMID: 36653893 PMCID: PMC10019085 DOI: 10.1002/1873-3468.14576] [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: 12/07/2022] [Accepted: 12/12/2022] [Indexed: 01/20/2023]
Abstract
Botulinum neurotoxins (BoNTs) are among the most lethal toxins known to humans, comprising seven established serotypes termed BoNT/A-G encoded in two types of gene clusters (ha and orfX) in BoNT-producing clostridia. The ha cluster encodes four non-toxic neurotoxin-associated proteins (NAPs) that assemble with BoNTs to protect and enhance their oral toxicity. However, the structure and function of the orfX-type NAPs remain largely unknown. Here, we report the crystal structures for OrfX1, OrfX2, and an OrfX1-OrfX3 complex, which are encoded in the orfX cluster of a BoNT/E1-producing Clostridium botulinum strain associated with human foodborne botulism. These structures lay the foundation for future studies on the potential roles of OrfX proteins in oral intoxication and pathogenesis of BoNTs.
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Affiliation(s)
- Linfeng Gao
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
| | - Kwok-ho Lam
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
| | - Shun Liu
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
| | - Adina Przykopanski
- Institute of Toxicology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Johanna Lübke
- Institute of Toxicology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Ruifeng Qi
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
| | - Maren Krüger
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Seestrasse 10, 13353 Berlin, Germany
| | - Maria B. Nowakowska
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, P. O. Box 66, 00014 University of Helsinki, Finland
| | - Katja Selby
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, P. O. Box 66, 00014 University of Helsinki, Finland
| | - François P. Douillard
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, P. O. Box 66, 00014 University of Helsinki, Finland
| | - Martin B. Dorner
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Seestrasse 10, 13353 Berlin, Germany
| | - Kay Perry
- NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Miia Lindström
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, P. O. Box 66, 00014 University of Helsinki, Finland
| | - Brigitte G. Dorner
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Seestrasse 10, 13353 Berlin, Germany
| | - Andreas Rummel
- Institute of Toxicology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
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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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12
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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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13
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Complete Genome Sequence of Paraclostridium bifermentans DSM 14991. Microbiol Resour Announc 2022; 11:e0010322. [PMID: 35758721 PMCID: PMC9302108 DOI: 10.1128/mra.00103-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The complete genome sequence of Paraclostridium bifermentans was obtained by assembly of Illumina and Oxford Nanopore (ONT) reads. The sequence will enable study into the organism’s ability to biohydrogenate unsaturated acyl chains in the transformation of C20 polyunsaturated fatty acids (PUFAs) into the corresponding bioactive non-methylene-interrupted fatty acids (NMIFAs).
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14
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In-Depth Analysis of an Obligate Anaerobe Paraclostridium bifermentans Isolated from Uterus of Bubalus bubalis. Animals (Basel) 2022; 12:ani12141765. [PMID: 35883312 PMCID: PMC9311886 DOI: 10.3390/ani12141765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 05/12/2022] [Accepted: 05/18/2022] [Indexed: 11/17/2022] Open
Abstract
Simple Summary Non-specific uterine infections in bovine (uterine line inflammation) are a significant issue for the dairy industry. These infections are responsible for significant financial losses all over the world. Paraclostridium bifermentans is an obligate anaerobe, gram-positive rod-shaped bacteria belonging to the Clostridia class and the Peptostreptococcaceae family produces endospores. This bacterium has the ability to infiltrate bovine uterine endometrial epithelial cells and cause infection in the endometrium epithelial cells. Our study found that an examination of a buffalo uterus with yellowish purulent discharge reported the presence of pathogenic bacteria Paraclostridium bifermentans, where its genomic characterization, substrate utilization, and antibiotic susceptibility potentiality was studied. This discovery indicates the presence of virulence genes as well as pathogenic features. This is the first report of P. bifermentans from the bovine uterus environment. Abstract Chronic non-specific contamination of the reproductive tract in animals is a major issue during early postpartum, natural coitus, or artificial insemination. Uterine infection is one of the major concerns reducing fertility, production loss, and early culling of the animals. Therefore, the aim of this study was to identify any novel bacterium if present in the uterine environment of Bubalus bubalis causing infections. A strictly anaerobic bacterial strain designated as Paraclostridium bifermentans GBRC was isolated and characterized. Bacterium was found to be Gram positive moderate rod with motility. The optimum growth was observed at 40 ± 2 °C. The pathogenic characteristics of the GBRC strain, such as hemolysis, gelatin hydrolysis, and the production of volatile sulfur compounds, were similar to those seen in the epithelial layer invading pathogenic strains. Assembled genome size was 3.6 MB, with 78 contigs, and a G + C content of 28.10%. Furthermore, the whole genome sequence analysis confirmed the presence of genes encoding virulence factors and provided genomic insights on adaptation of the strain in the uterine environment. Based on the phenotypic and genetic differences with phylogenetic relatives, strain GBRC is proposed to represent a first reported species of the genus Paraclostridium with potential pathogenic character, from the buffalo uterine environment. This study analysis of the GBRC strain serves as a key reference point for the investigation of potential pathogenic strains that may cause endometritis and metritis in bovine.
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15
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Regulatory Networks Controlling Neurotoxin Synthesis in Clostridium botulinum and Clostridium tetani. Toxins (Basel) 2022; 14:toxins14060364. [PMID: 35737025 PMCID: PMC9229411 DOI: 10.3390/toxins14060364] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 05/16/2022] [Accepted: 05/21/2022] [Indexed: 12/30/2022] Open
Abstract
Clostridium botulinum and Clostridium tetani are Gram-positive, spore-forming, and anaerobic bacteria that produce the most potent neurotoxins, botulinum toxin (BoNT) and tetanus toxin (TeNT), responsible for flaccid and spastic paralysis, respectively. The main habitat of these toxigenic bacteria is the environment (soil, sediments, cadavers, decayed plants, intestinal content of healthy carrier animals). C. botulinum can grow and produce BoNT in food, leading to food-borne botulism, and in some circumstances, C. botulinum can colonize the intestinal tract and induce infant botulism or adult intestinal toxemia botulism. More rarely, C. botulinum colonizes wounds, whereas tetanus is always a result of wound contamination by C. tetani. The synthesis of neurotoxins is strictly regulated by complex regulatory networks. The highest levels of neurotoxins are produced at the end of the exponential growth and in the early stationary growth phase. Both microorganisms, except C. botulinum E, share an alternative sigma factor, BotR and TetR, respectively, the genes of which are located upstream of the neurotoxin genes. These factors are essential for neurotoxin gene expression. C. botulinum and C. tetani share also a two-component system (TCS) that negatively regulates neurotoxin synthesis, but each microorganism uses additional distinct sets of TCSs. Neurotoxin synthesis is interlocked with the general metabolism, and CodY, a master regulator of metabolism in Gram-positive bacteria, is involved in both clostridial species. The environmental and nutritional factors controlling neurotoxin synthesis are still poorly understood. The transition from amino acid to peptide metabolism seems to be an important factor. Moreover, a small non-coding RNA in C. tetani, and quorum-sensing systems in C. botulinum and possibly in C. tetani, also control toxin synthesis. However, both species use also distinct regulatory pathways; this reflects the adaptation of C. botulinum and C. tetani to different ecological niches.
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16
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Gregory KS, Mahadeva TB, Liu SM, Acharya KR. Structural Features of Clostridium botulinum Neurotoxin Subtype A2 Cell Binding Domain. Toxins (Basel) 2022; 14:toxins14050356. [PMID: 35622602 PMCID: PMC9146395 DOI: 10.3390/toxins14050356] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 05/17/2022] [Accepted: 05/18/2022] [Indexed: 12/14/2022] Open
Abstract
Botulinum neurotoxins (BoNT) are a group of clostridial toxins that cause the potentially fatal neuroparalytic disease botulism. Although highly toxic, BoNTs are utilized as therapeutics to treat a range of neuromuscular conditions. Several serotypes (BoNT/A-/G, /X) have been identified with vastly differing toxicological profiles. Each serotype can be further sub-categorised into subtypes due to subtle variations in their protein sequence. These minor changes have been attributed to differences in both the duration of action and potency for BoNT/A subtypes. BoNTs are composed of three domains—a cell-binding domain, a translocation domain, and a catalytic domain. In this paper, we present the crystal structures of the botulinum neurotoxin A2 cell binding domain, both alone and in complex with its receptor ganglioside GD1a at 1.63 and 2.10 Å, respectively. The analysis of these structures reveals a potential redox-dependent Lys-O-Cys bridge close to the ganglioside binding site and a hinge motion between the HCN and HCC subdomains. Furthermore, we make a detailed comparison with the previously reported HC/A2:SV2C structure for a comprehensive structural analysis of HC/A2 receptor binding.
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Affiliation(s)
- Kyle S. Gregory
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (T.B.M.)
| | - Tejaswini B. Mahadeva
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (T.B.M.)
| | - Sai Man Liu
- Protein Sciences Department, Ipsen Bioinnovation Limited, 102 Park Drive, Milton Park, Abingdon OX14 4RY, UK;
| | - K. Ravi Acharya
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (T.B.M.)
- Correspondence: ; Tel.: +44-(0)1225-386238
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17
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Rasetti-Escargueil C, Popoff MR. Recent Developments in Botulinum Neurotoxins Detection. Microorganisms 2022; 10:microorganisms10051001. [PMID: 35630444 PMCID: PMC9145529 DOI: 10.3390/microorganisms10051001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 04/29/2022] [Accepted: 05/03/2022] [Indexed: 02/04/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) are produced as protein complexes by bacteria of the genus Clostridium that are Gram-positive, anaerobic and spore forming (Clostridium botulinum, C. butyricum, C. baratii and C. argentinense spp.). BoNTs show a high immunological and genetic diversity. Therefore, fast, precise, and more reliable detection methods are still required to monitor outbreaks and ensure surveillance of botulism. The botulinum toxin field also comprises therapeutic uses, basic research studies and biodefense issues. This review presents currently available detection methods, and new methods offering the potential of enhanced precision and reproducibility. While the immunological methods offer a range of benefits, such as rapid analysis time, reproducibility and high sensitivity, their implementation is subject to the availability of suitable tools and reagents, such as specific antibodies. Currently, the mass spectrometry approach is the most sensitive in vitro method for a rapid detection of active or inactive forms of BoNTs. However, these methods require inter-laboratory validation before they can be more widely implemented in reference laboratories. In addition, these surrogate in vitro models also require full validation before they can be used as replacement bioassays of potency. Cell-based assays using neuronal cells in culture recapitulate all functional steps of toxin activity, but are still at various stages of development; they are not yet sufficiently robust, due to high batch-to-batch cell variability. Cell-based assays have a strong potential to replace the mouse bioassay (MBA) in terms of BoNT potency determination in pharmaceutical formulations; they can also help to identify suitable inhibitors while reducing the number of animals used. However, the development of safe countermeasures still requires the use of in vivo studies to complement in vitro immunological or cell-based approaches.
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18
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Pirazzini M, Montecucco C, Rossetto O. Toxicology and pharmacology of botulinum and tetanus neurotoxins: an update. Arch Toxicol 2022; 96:1521-1539. [PMID: 35333944 PMCID: PMC9095541 DOI: 10.1007/s00204-022-03271-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 02/28/2022] [Indexed: 12/27/2022]
Abstract
Tetanus and botulinum neurotoxins cause the neuroparalytic syndromes of tetanus and botulism, respectively, by delivering inside different types of neurons, metalloproteases specifically cleaving the SNARE proteins that are essential for the release of neurotransmitters. Research on their mechanism of action is intensively carried out in order to devise improved therapies based on antibodies and chemical drugs. Recently, major results have been obtained with human monoclonal antibodies and with single chain antibodies that have allowed one to neutralize the metalloprotease activity of botulinum neurotoxin type A1 inside neurons. In addition, a method has been devised to induce a rapid molecular evolution of the metalloprotease domain of botulinum neurotoxin followed by selection driven to re-target the metalloprotease activity versus novel targets with respect to the SNARE proteins. At the same time, an intense and wide spectrum clinical research on novel therapeutics based on botulinum neurotoxins is carried out, which are also reviewed here.
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Affiliation(s)
- Marco Pirazzini
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131, Padova, Italy.,Centro Interdipartimentale di Ricerca di Miologia, CIR-Myo, University of Padova, Via U. Bassi 58/B, 35131, Padova, Italy
| | - Cesare Montecucco
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131, Padova, Italy. .,Institute of Neuroscience, National Research Council, Via Ugo Bassi 58/B, 35131, Padova, Italy.
| | - Ornella Rossetto
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131, Padova, Italy.,Centro Interdipartimentale di Ricerca di Miologia, CIR-Myo, University of Padova, Via U. Bassi 58/B, 35131, Padova, Italy.,Institute of Neuroscience, National Research Council, Via Ugo Bassi 58/B, 35131, Padova, Italy
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19
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Wentz TG, Tremblay BJM, Bradshaw M, Doxey AC, Sharma SK, Sauer JD, Pellett S. Endogenous CRISPR-Cas Systems in Group I Clostridium botulinum and Clostridium sporogenes Do Not Directly Target the Botulinum Neurotoxin Gene Cluster. Front Microbiol 2022; 12:787726. [PMID: 35222299 PMCID: PMC8865420 DOI: 10.3389/fmicb.2021.787726] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 12/27/2021] [Indexed: 12/28/2022] Open
Abstract
Most strains of proteolytic group I Clostridium botulinum (G1 C. botulinum) and some strains of Clostridium sporogenes possess genes encoding botulinum neurotoxin (BoNT), a potent neuroparalytic agent. Within G1 C. botulinum, conserved bont gene clusters of three major toxin serotypes (bont/A/B/F) can be found on conjugative plasmids and/or within chromosomal pathogenicity islands. CRISPR-Cas systems enable site-specific targeting of previously encountered mobile genetic elements (MGE) such as plasmids and bacteriophage through the creation of a spacer library complementary to protospacers within the MGEs. To examine whether endogenous CRISPR-Cas systems restrict the transfer of bont gene clusters across strains we conducted a bioinformatic analysis profiling endogenous CRISPR-Cas systems from 241 G1 C. botulinum and C. sporogenes strains. Approximately 6,200 CRISPR spacers were identified across the strains and Type I-B, III-A/B/D cas genes and CRISPR array features were identified in 83% of the strains. Mapping the predicted spacers against the masked strain and RefSeq plasmid dataset identified 56,000 spacer-protospacer matches. While spacers mapped heavily to targets within bont(+) plasmids, no protospacers were identified within the bont gene clusters. These results indicate the toxin is not a direct target of CRISPR-Cas but the plasmids predominantly responsible for its mobilization are. Finally, while the presence of a CRISPR-Cas system did not reliably indicate the presence or absence of a bont gene cluster, comparative genomics across strains indicates they often occupy the same hypervariable loci common to both species, potentially suggesting similar mechanisms are involved in the acquisition and curation of both genomic features.
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Affiliation(s)
- Travis G. Wentz
- Microbiology Doctoral Training Program, University of Wisconsin–Madison, Madison, WI, United States,Division of Microbiology, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD, United States,Department of Bacteriology, University of Wisconsin–Madison, Madison, WI, United States
| | | | - Marite Bradshaw
- Department of Bacteriology, University of Wisconsin–Madison, Madison, WI, United States
| | - Andrew C. Doxey
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Shashi K. Sharma
- Division of Microbiology, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD, United States
| | - John-Demian Sauer
- Department of Medical Microbiology and Immunology, University of Wisconsin–Madison, Madison, WI, United States
| | - Sabine Pellett
- Department of Bacteriology, University of Wisconsin–Madison, Madison, WI, United States,*Correspondence: Sabine Pellett,
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20
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Gregory KS, Mojanaga OO, Liu SM, Acharya KR. Crystal Structures of Botulinum Neurotoxin Subtypes A4 and A5 Cell Binding Domains in Complex with Receptor Ganglioside. Toxins (Basel) 2022; 14:toxins14020129. [PMID: 35202156 PMCID: PMC8876736 DOI: 10.3390/toxins14020129] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 02/02/2022] [Accepted: 02/05/2022] [Indexed: 02/04/2023] Open
Abstract
Botulinum neurotoxins (BoNT) cause the potentially fatal neuroparalytic disease botulism that arises due to proteolysis of a SNARE protein. Each BoNT is comprised of three domains: a cell binding domain (HC), a translocation domain (HN), and a catalytic (Zn2+ endopeptidase) domain (LC). The HC is responsible for neuronal specificity by targeting both a protein and ganglioside receptor at the neuromuscular junction. Although highly toxic, some BoNTs are commercially available as therapeutics for the treatment of a range of neuromuscular conditions. Here we present the crystal structures of two BoNT cell binding domains, HC/A4 and HC/A5, in a complex with the oligosaccharide of ganglioside, GD1a and GM1b, respectively. These structures, along with a detailed comparison with the previously reported apo-structures, reveal the conformational changes that occur upon ganglioside binding and the interactions involved.
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Affiliation(s)
- Kyle S. Gregory
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (O.O.M.)
| | - Otsile O. Mojanaga
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (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 Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK; (K.S.G.); (O.O.M.)
- Correspondence: ; Tel.: +44-(0)1225-386238
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21
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A Deep Learning Approach with Data Augmentation to Predict Novel Spider Neurotoxic Peptides. Int J Mol Sci 2021; 22:ijms222212291. [PMID: 34830173 PMCID: PMC8619404 DOI: 10.3390/ijms222212291] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/09/2021] [Accepted: 11/11/2021] [Indexed: 11/17/2022] Open
Abstract
As major components of spider venoms, neurotoxic peptides exhibit structural diversity, target specificity, and have great pharmaceutical potential. Deep learning may be an alternative to the laborious and time-consuming methods for identifying these peptides. However, the major hurdle in developing a deep learning model is the limited data on neurotoxic peptides. Here, we present a peptide data augmentation method that improves the recognition of neurotoxic peptides via a convolutional neural network model. The neurotoxic peptides were augmented with the known neurotoxic peptides from UniProt database, and the models were trained using a training set with or without the generated sequences to verify the augmented data. The model trained with the augmented dataset outperformed the one with the unaugmented dataset, achieving accuracy of 0.9953, precision of 0.9922, recall of 0.9984, and F1 score of 0.9953 in simulation dataset. From the set of all RNA transcripts of Callobius koreanus spider, we discovered neurotoxic peptides via the model, resulting in 275 putative peptides of which 252 novel sequences and only 23 sequences showing homology with the known peptides by Basic Local Alignment Search Tool. Among these 275 peptides, four were selected and shown to have neuromodulatory effects on the human neuroblastoma cell line SH-SY5Y. The augmentation method presented here may be applied to the identification of other functional peptides from biological resources with insufficient data.
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22
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Knockin mouse models demonstrate differential contributions of synaptotagmin-1 and -2 as receptors for botulinum neurotoxins. PLoS Pathog 2021; 17:e1009994. [PMID: 34662366 PMCID: PMC8553082 DOI: 10.1371/journal.ppat.1009994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 10/28/2021] [Accepted: 09/30/2021] [Indexed: 12/11/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are the most potent toxins known and are also utilized to treat a wide range of disorders including muscle spasm, overactive bladder, and pain. BoNTs' ability to target neurons determines their specificity, potency, and therapeutic efficacy. Homologous synaptic vesicle membrane proteins synaptotagmin-1 (Syt1) and synaptotagmin-2 (Syt2) have been identified as receptors for BoNT family members including BoNT/B, DC, and G, but their contributions at physiologically relevant toxin concentrations in vivo have yet to be validated and established. Here we generated two knockin mutant mouse models containing three designed point-mutations that specifically disrupt BoNT binding in endogenous Syt1 or Syt2, respectively. Utilizing digit abduction score assay by injecting toxins into the leg muscle, we found that Syt1 mutant mice showed similar sensitivity as the wild type mice, whereas Syt2 mutant mice showed reduced sensitivity to BoNT/B, DC, and G, demonstrating that Syt2 is the dominant receptor at skeletal neuromuscular junctions. We further developed an in vivo bladder injection assay for analyzing BoNT action on bladder tissues and demonstrated that Syt1 is the dominant toxin receptor in autonomic nerves controlling bladder tissues. These findings establish the critical role of protein receptors for the potency and specificity of BoNTs in vivo and demonstrate the differential contributions of Syt1 and Syt2 in two sets of clinically relevant target tissues.
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23
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Miyashita SI, Zhang J, Zhang S, Shoemaker CB, Dong M. Delivery of single-domain antibodies into neurons using a chimeric toxin-based platform is therapeutic in mouse models of botulism. Sci Transl Med 2021; 13:13/575/eaaz4197. [PMID: 33408184 DOI: 10.1126/scitranslmed.aaz4197] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 05/01/2020] [Indexed: 12/15/2022]
Abstract
Efficient penetration of cell membranes and specific targeting of a cell type represent major challenges for developing therapeutics toward intracellular targets. One example facing these hurdles is to develop post-exposure treatment for botulinum neurotoxins (BoNTs), a group of bacterial toxins (BoNT/A to BoNT/G) that are major potential bioterrorism agents. BoNTs enter motor neurons, block neurotransmitter release, and cause a paralytic disease botulism. Members of BoNTs such as BoNT/A exhibit extremely long half-life within neurons, resulting in persistent paralysis for months, yet there are no therapeutics that can inhibit BoNTs once they enter neurons. Here, we developed a chimeric toxin-based delivery platform by fusing the receptor-binding domain of a BoNT, which targets neurons, with the membrane translocation domain and inactivated protease domain of the recently discovered BoNT-like toxin BoNT/X, which can deliver cargoes across endosomal membranes into the cytosol. A therapeutic protein was then created by fusing a single-domain antibody (nanobody) against BoNT/A with the delivery platform. In vitro characterization demonstrated that nanobodies were delivered into cultured neurons and neutralized BoNT/A in neurons. Administration of this protein in mice shortened duration of local muscle paralysis, restoring muscle function within hours, and rescued mice from systemic toxicity of lethal doses of BoNT/A. Fusion of two nanobodies, one against BoNT/A and the other against BoNT/B, created a multivalent therapeutic protein able to neutralize both BoNT/A and BoNT/B in mice. These studies provide an effective post-exposure treatment for botulism and establish a platform for intracellular delivery of therapeutics targeting cytosolic proteins and processes.
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Affiliation(s)
- Shin-Ichiro Miyashita
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Jie Zhang
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Sicai Zhang
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Charles B Shoemaker
- Department of Infectious Diseases and Global Health, Cummings School of Veterinary Medicine at Tufts University, North Grafton, MA 01536, USA
| | - Min Dong
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA. .,Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
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Abstract
Large clostridial toxins (LCTs) are a family of bacterial exotoxins that infiltrate and destroy target cells. Members of the LCT family include Clostridioides difficile toxins TcdA and TcdB, Paeniclostridium sordellii toxins TcsL and TcsH, Clostridium novyi toxin TcnA, and Clostridium perfringens toxin TpeL. Since the 19th century, LCT-secreting bacteria have been isolated from the blood, organs, and wounds of diseased individuals, and LCTs have been implicated as the primary virulence factors in a variety of infections, including C. difficile infection and some cases of wound-associated gas gangrene. Clostridia express and secrete LCTs in response to various physiological signals. LCTs invade host cells by binding specific cell surface receptors, ultimately leading to internalization into acidified vesicles. Acidic pH promotes conformational changes within LCTs, which culminates in translocation of the N-terminal glycosyltransferase and cysteine protease domain across the endosomal membrane and into the cytosol, leading first to cytopathic effects and later to cytotoxic effects. The focus of this review is on the role of LCTs in infection and disease, the mechanism of LCT intoxication, with emphasis on recent structural work and toxin subtyping analysis, and the genomic discovery and characterization of LCT homologues. We provide a comprehensive review of these topics and offer our perspective on emerging questions and future research directions for this enigmatic family of toxins.
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25
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Leka O, Wu Y, Li X, Kammerer RA. Crystal structure of the catalytic domain of botulinum neurotoxin subtype A3. J Biol Chem 2021; 296:100684. [PMID: 33891946 PMCID: PMC8135040 DOI: 10.1016/j.jbc.2021.100684] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 04/08/2021] [Accepted: 04/19/2021] [Indexed: 10/28/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are among the most widely used therapeutic proteins; however, only two subtypes within the seven serotypes, BoNT/A1 and BoNT/B1, are currently used for medical and cosmetic applications. Distinct catalytic properties, substrate specificities, and duration of enzymatic activities potentially make other subtypes very attractive candidates to outperform conventional BoNTs in particular therapeutic applications. For example, BoNT/A3 has a significantly shorter duration of action than other BoNT/A subtypes. Notably, BoNT/A3 is the subtype with the least conserved catalytic domain among BoNT/A subtypes. This suggests that the sequence differences, many of which concern the α-exosite, contribute to the observed functional differences in toxin persistence by affecting the binding of the substrate SNAP-25 and/or the stability of the catalytic domain fold. To identify the molecular determinants accounting for the differences in the persistence observed for BoNT/A subtypes, we determined the crystal structure of the catalytic domain of BoNT/A3 (LC/A3). The structure of LC/A3 was found to be very similar to that of LC/A1, suggesting that the overall mode of SNAP-25 binding is common between these two proteins. However, circular dichroism (CD) thermal unfolding experiments demonstrated that LC/A3 is significantly less stable than LC/A1, implying that this might contribute to the reduced toxin persistence of BoNT/A3. These findings could be of interest in developing next-generation therapeutic toxins.
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Affiliation(s)
- Oneda Leka
- The Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Yufan Wu
- The Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Xiaodan Li
- The Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Richard A Kammerer
- The Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI, Switzerland.
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Rasetti-Escargueil C, Popoff MR. Engineering Botulinum Neurotoxins for Enhanced Therapeutic Applications and Vaccine Development. Toxins (Basel) 2020; 13:1. [PMID: 33374954 PMCID: PMC7821915 DOI: 10.3390/toxins13010001] [Citation(s) in RCA: 12] [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: 11/10/2020] [Revised: 12/16/2020] [Accepted: 12/17/2020] [Indexed: 02/07/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) show increasing therapeutic applications ranging from treatment of locally paralyzed muscles to cosmetic benefits. At first, in the 1970s, BoNT was used for the treatment of strabismus, however, nowadays, BoNT has multiple medical applications including the treatment of muscle hyperactivity such as strabismus, dystonia, movement disorders, hemifacial spasm, essential tremor, tics, cervical dystonia, cerebral palsy, as well as secretory disorders (hyperhidrosis, sialorrhea) and pain syndromes such as chronic migraine. This review summarizes current knowledge related to engineering of botulinum toxins, with particular emphasis on their potential therapeutic applications for pain management and for retargeting to non-neuronal tissues. Advances in molecular biology have resulted in generating modified BoNTs with the potential to act in a variety of disorders, however, in addition to the modifications of well characterized toxinotypes, the diversity of the wild type BoNT toxinotypes or subtypes, provides the basis for innovative BoNT-based therapeutics and research tools. This expanding BoNT superfamily forms the foundation for new toxins candidates in a wider range of therapeutic options.
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Potential for Bacillus thuringiensis and Other Bacterial Toxins as Biological Control Agents to Combat Dipteran Pests of Medical and Agronomic Importance. Toxins (Basel) 2020; 12:toxins12120773. [PMID: 33291447 PMCID: PMC7762171 DOI: 10.3390/toxins12120773] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 11/24/2020] [Accepted: 12/03/2020] [Indexed: 11/16/2022] Open
Abstract
The control of dipteran pests is highly relevant to humans due to their involvement in the transmission of serious diseases including malaria, dengue fever, Chikungunya, yellow fever, zika, and filariasis; as well as their agronomic impact on numerous crops. Many bacteria are able to produce proteins that are active against insect species. These bacteria include Bacillus thuringiensis, the most widely-studied pesticidal bacterium, which synthesizes proteins that accumulate in crystals with insecticidal properties and which has been widely used in the biological control of insects from different orders, including Lepidoptera, Coleoptera, and Diptera. In this review, we summarize all the bacterial proteins, from B. thuringiensis and other entomopathogenic bacteria, which have described insecticidal activity against dipteran pests, including species of medical and agronomic importance.
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The 25 kDa H CN Domain of Clostridial Neurotoxins Is Indispensable for Their Neurotoxicity. Toxins (Basel) 2020; 12:toxins12120743. [PMID: 33255952 PMCID: PMC7760224 DOI: 10.3390/toxins12120743] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 11/13/2020] [Accepted: 11/20/2020] [Indexed: 11/17/2022] Open
Abstract
The extraordinarily potent clostridial neurotoxins (CNTs) comprise tetanus neurotoxin (TeNT) and the seven established botulinum neurotoxin serotypes (BoNT/A-G). They are composed of four structurally independent domains: the roles of the catalytically active light chain, the translocation domain HN, and the C-terminal receptor binding domain HCC are largely resolved, but that of the HCN domain sandwiched between HN and HCC has remained unclear. Here, mutants of BoNT/A, BoNT/B, and TeNT were generated by deleting their HCN domains or swapping HCN domains between each other. Both deletion and replacement of TeNT HCN domain by HCNA and HCNB reduced the biological activity similarly, by ~95%, whereas BoNT/A and B deletion mutants displayed >500-fold reduced activity in the mouse phrenic nerve hemidiaphragm assay. Swapping HCN domains between BoNT/A and B hardly impaired their biological activity, but substitution with HCNT did. Binding assays revealed that in the absence of HCN, not all receptor binding sites are equally well accessible. In conclusion, the presence of HCN is vital for CNTs to exert their neurotoxicity. Although structurally similar, the HCN domain of TeNT cannot equally substitute those of BoNT and vice versa, leaving the possibility that HCNT plays a different role in the intoxication mechanism of TeNT.
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Toxemia in Human Naturally Acquired Botulism. Toxins (Basel) 2020; 12:toxins12110716. [PMID: 33202855 PMCID: PMC7697460 DOI: 10.3390/toxins12110716] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/07/2020] [Accepted: 11/10/2020] [Indexed: 12/18/2022] Open
Abstract
Human botulism is a severe disease characterized by flaccid paralysis and inhibition of certain gland secretions, notably salivary secretions, caused by inhibition of neurotransmitter release. Naturally acquired botulism occurs in three main forms: food-borne botulism by ingestion of preformed botulinum neurotoxin (BoNT) in food, botulism by intestinal colonization (infant botulism and intestinal toxemia botulism in infants above one year and adults), and wound botulism. A rapid laboratory confirmation of botulism is required for the appropriate management of patients. Detection of BoNT in the patient's sera is the most direct way to address the diagnosis of botulism. Based on previous published reports, botulinum toxemia was identified in about 70% of food-borne and wound botulism cases, and only in about 28% of infant botulism cases, in which the diagnosis is mainly confirmed from stool sample investigation. The presence of BoNT in serum depends on the BoNT amount ingested with contaminated food or produced locally in the intestine or wound, and the timeframe between serum sampling and disease onset. BoNT levels in patient's sera are most frequently low, requiring a highly sensitive method of detection. Mouse bioassay is still the most used method of botulism identification from serum samples. However, in vitro methods based on BoNT endopeptidase activity with detection by mass spectrometry or immunoassay have been developed and depending on BoNT type, are more sensitive than the mouse bioassay. These new assays show high specificity for individual BoNT types and allow more accurate differentiation between positive toxin sera from botulism and autoimmune neuropathy patients.
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Ursino E, Albertini AM, Fiorentino G, Gabrieli P, Scoffone VC, Pellegrini A, Gasperi G, Di Cosimo A, Barbieri G. Bacillus subtilis as a host for mosquitocidal toxins production. Microb Biotechnol 2020; 13:1972-1982. [PMID: 32864888 PMCID: PMC7533320 DOI: 10.1111/1751-7915.13648] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 07/23/2020] [Indexed: 02/05/2023] Open
Abstract
Aedes albopictus transmits several arboviral infections. In the absence of vaccines, control of mosquito populations is the only strategy to prevent vector-borne diseases. As part of the search for novel, biological and environmentally friendly strategies for vector control, the isolation of new bacterial species with mosquitocidal activity represents a promising approach. However, new bacterial isolates may be difficult to grow and genetically manipulate. To overcome these limits, here we set up a system allowing the expression of mosquitocidal bacterial toxins in the well-known genetic background of Bacillus subtilis. As a proof of this concept, the ability of B. subtilis to express individual or combinations of toxins of Bacillus thuringiensis israelensis (Bti) was studied. Different expression systems in which toxin gene expression was driven by IPTG-inducible, auto-inducible or toxin gene-specific promoters were developed. The larvicidal activity of the resulting B. subtilis strains against second-instar Ae. albopictus larvae allowed studying the activity of individual toxins or the synergistic interaction among Cry and Cyt toxins. The expression systems here presented lay the foundation for a better improved system to be used in the future to characterize the larvicidal activity of toxin genes from new environmental isolates.
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Affiliation(s)
- Emanuela Ursino
- Department of Biology and BiotechnologyUniversità degli Studi di PaviaPaviaItaly
| | | | - Giulia Fiorentino
- Department of Biology and BiotechnologyUniversità degli Studi di PaviaPaviaItaly
| | - Paolo Gabrieli
- Department of Biology and BiotechnologyUniversità degli Studi di PaviaPaviaItaly
- Present address:
Department of BiosciencesUniversità degli Studi di MilanoMilanoItaly
| | | | - Angelica Pellegrini
- Department of Biology and BiotechnologyUniversità degli Studi di PaviaPaviaItaly
| | - Giuliano Gasperi
- Department of Biology and BiotechnologyUniversità degli Studi di PaviaPaviaItaly
| | - Alessandro Di Cosimo
- Department of Biology and BiotechnologyUniversità degli Studi di PaviaPaviaItaly
| | - Giulia Barbieri
- Department of Biology and BiotechnologyUniversità degli Studi di PaviaPaviaItaly
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Kumar V, Tyagi I, Tyagi K, Chandra K. Diversity and Structure of Bacterial Communities in the Gut of Spider: Thomisidae and Oxyopidae. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.588102] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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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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Yin L, Masuyer G, Zhang S, Zhang J, Miyashita SI, Burgin D, Lovelock L, Coker SF, Fu TM, Stenmark P, Dong M. Characterization of a membrane binding loop leads to engineering botulinum neurotoxin B with improved therapeutic efficacy. PLoS Biol 2020; 18:e3000618. [PMID: 32182233 PMCID: PMC7077807 DOI: 10.1371/journal.pbio.3000618] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 02/12/2020] [Indexed: 11/25/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are a family of bacterial toxins with seven major serotypes (BoNT/A–G). The ability of these toxins to target and bind to motor nerve terminals is a key factor determining their potency and efficacy. Among these toxins, BoNT/B is one of the two types approved for medical and cosmetic uses. Besides binding to well-established receptors, an extended loop in the C-terminal receptor-binding domain (HC) of BoNT/B (HC/B) has been proposed to also contribute to toxin binding to neurons by interacting with lipid membranes (termed lipid-binding loop [LBL]). Analogous loops exist in the HCs of BoNT/C, D, G, and a chimeric toxin DC. However, it has been challenging to detect and characterize binding of LBLs to lipid membranes. Here, using the nanodisc system and biolayer interferometry assays, we find that HC/DC, C, and G, but not HC/B and HC/D, are capable of binding to receptor-free lipids directly, with HC/DC having the highest level of binding. Mutagenesis studies demonstrate the critical role of consecutive aromatic residues at the tip of the LBL for binding of HC/DC to lipid membranes. Taking advantage of this insight, we then create a “gain-of-function” mutant HC/B by replacing two nonaromatic residues at the tip of its LBL with tryptophan. Cocrystallization studies confirm that these two tryptophan residues do not alter the structure of HC/B or the interactions with its receptors. Such a mutated HC/B gains the ability to bind receptor-free lipid membranes and shows enhanced binding to cultured neurons. Finally, full-length BoNT/B containing two tryptophan mutations in its LBL, together with two additional mutations (E1191M/S1199Y) that increase binding to human receptors, is produced and evaluated in mice in vivo using Digit Abduction Score assays. This mutant toxin shows enhanced efficacy in paralyzing local muscles at the injection site and lower systemic diffusion, thus extending both safety range and duration of paralysis compared with the control BoNT/B. These findings establish a mechanistic understanding of LBL–lipid interactions and create a modified BoNT/B with improved therapeutic efficacy. Botulinum neurotoxins are a family of bacterial toxins, some of which are approved for medical and cosmetic uses. This study shows that introducing aromatic residues to a lipid binding loop improved therapeutic efficacy of botulinum neurotoxin B by enhancing its ability to bind to lipid membranes at motor nerve terminals.
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Affiliation(s)
- Linxiang Yin
- Department of Urology, Boston Children’s Hospital, Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Geoffrey Masuyer
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Sicai Zhang
- Department of Urology, Boston Children’s Hospital, Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jie Zhang
- Department of Urology, Boston Children’s Hospital, Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Shin-Ichiro Miyashita
- Department of Urology, Boston Children’s Hospital, Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
| | | | | | | | - Tian-min Fu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, Massachusetts, United States of America
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- * E-mail: (PS); (MD)
| | - Min Dong
- Department of Urology, Boston Children’s Hospital, Department of Microbiology and Department of Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (PS); (MD)
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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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Potency and stability of a trivalent, catalytically inactive vaccine against botulinum neurotoxin serotypes C, E and F (triCEF). Toxicon 2020; 176:67-76. [PMID: 32032587 DOI: 10.1016/j.toxicon.2020.02.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 01/18/2020] [Accepted: 02/03/2020] [Indexed: 01/13/2023]
Abstract
Botulism is an acute neuroparalytic affliction of the motor and autonomic neurons caused by the toxins produced from Clostridium botulinum and related bacterial strains. The botulinum neurotoxins, or BoNTs, consist of a phylogenetically diverse group of highly potent protein toxins. Current medical interventions for confirmed cases of botulism are limited to immediate administration of antitoxins and respiratory support. There is currently no licensed vaccine against botulism in the United States. The most widely distributed botulism vaccine was a pentavalent BoNT toxoid (PBT) against serotypes A-E administered until 2011 under an investigational new drug license. A binary vaccine composed of the recombinant, non-toxic, receptor binding domains (RBD) of serotypes/A1 and/B1 has completed a phase II clinical trial, but has yet to attain full licensure. We have previously published data demonstrating catalytically inactive, full length botulinum neurotoxin holoproteins (ciBoNT HPs) against serotypes/A1,/B1,/C1,/E1 and/F1 provide equivalent or superior potency against parental and dissimilar subtype toxins as compared the RBD vaccines. Here we describe the consistent potencies of the three independent lots each of ciBoNT/C1,/E1, and/F1 HPs against substantial monovalent challenges of the parental toxins. We also present data that a trivalent formulation of ciBoNT/C1,/E1 and/F1 (triCEF) maintains potency against both monovalent and polyvalent toxin challenges when stored as an adjuvanted vaccine at 4-8 °C for up to 2 years.
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36
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Gao H, Cui C, Wang L, Jacobs-Lorena M, Wang S. Mosquito Microbiota and Implications for Disease Control. Trends Parasitol 2020; 36:98-111. [PMID: 31866183 PMCID: PMC9827750 DOI: 10.1016/j.pt.2019.12.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2019] [Revised: 12/02/2019] [Accepted: 12/02/2019] [Indexed: 01/11/2023]
Abstract
Mosquito-transmitted diseases account for about 500 000 deaths every year. Blocking these pathogens in the mosquito vector before they are transmitted to humans is an effective strategy to prevent mosquito-borne diseases. Like most higher organisms, mosquitoes harbor a highly diverse and dynamic microbial flora that can be explored for prevention of pathogen transmission. Here we review the structure and function of the mosquito microbiota, including bacteria, fungi, and viruses, and discuss the potential of using components of the microbiota to thwart pathogen transmission.
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Affiliation(s)
- Han Gao
- CAS key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China,These authors contributed equally to this work
| | - Chunlai Cui
- CAS key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China,These authors contributed equally to this work
| | - Lili Wang
- CAS key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China,These authors contributed equally to this work
| | - Marcelo Jacobs-Lorena
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA,Correspondence: ,
| | - Sibao Wang
- CAS key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China,Correspondence: ,
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Harris RA, Anniballi F, Austin JW. Adult Intestinal Toxemia Botulism. Toxins (Basel) 2020; 12:E81. [PMID: 31991691 PMCID: PMC7076759 DOI: 10.3390/toxins12020081] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 01/20/2020] [Accepted: 01/22/2020] [Indexed: 12/30/2022] Open
Abstract
Intoxication with botulinum neurotoxin can occur through various routes. Foodborne botulism results after consumption of food in which botulinum neurotoxin-producing clostridia (i.e., Clostridium botulinum or strains of Clostridiumbutyricum type E or Clostridiumbaratii type F) have replicated and produced botulinum neurotoxin. Infection of a wound with C. botulinum and in situ production of botulinum neurotoxin leads to wound botulism. Colonization of the intestine by neurotoxigenic clostridia, with consequent production of botulinum toxin in the intestine, leads to intestinal toxemia botulism. When this occurs in an infant, it is referred to as infant botulism, whereas in adults or children over 1 year of age, it is intestinal colonization botulism. Predisposing factors for intestinal colonization in children or adults include previous bowel or gastric surgery, anatomical bowel abnormalities, Crohn's disease, inflammatory bowel disease, antimicrobial therapy, or foodborne botulism. Intestinal colonization botulism is confirmed by detection of botulinum toxin in serum and/or stool, or isolation of neurotoxigenic clostridia from the stool, without finding a toxic food. Shedding of neurotoxigenic clostridia in the stool may occur for a period of several weeks. Adult intestinal botulism occurs as isolated cases, and may go undiagnosed, contributing to the low reported incidence of this rare disease.
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Affiliation(s)
- Richard A. Harris
- Botulism Reference Service for Canada, Microbiology Research Division, Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch, Ottawa, ON K1A 0K9, Canada;
| | - Fabrizio Anniballi
- National Reference Centre for Botulism, Microbiological Foodborne Hazard Unit, Department of Food Safety, Nutrition and Veterinary Public Health, Istituto Superiore di Sanità, viale Regina Elena, 29900161 Rome, Italy;
| | - John W. Austin
- Botulism Reference Service for Canada, Microbiology Research Division, Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch, Ottawa, ON K1A 0K9, Canada;
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38
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Amatsu S, Fujinaga Y. Botulinum Hemagglutinin: Critical Protein for Adhesion and Absorption of Neurotoxin Complex in Host Intestine. Methods Mol Biol 2020; 2132:183-190. [PMID: 32306327 DOI: 10.1007/978-1-0716-0430-4_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Botulinum hemagglutinin (HA) is one of the auxiliary protein components of the botulinum neurotoxin (BoNT) complex, the most lethal toxin known. HA promotes the intestinal absorption of BoNT by at least two mechanisms, resulting in high oral toxicity. One of the mechanisms is the attachment of large progenitor toxin complexes (L-PTCs) to the cell surface of the intestinal epithelium by the carbohydrate-binding activity of HA. The other is epithelial barrier disruption by the E-cadherin-binding activity of HA. The carbohydrate-binding activity of HA also promotes attachment to the basolateral cell surface, which increases the frequency of contact between HA and E-cadherin. Together, the carbohydrate-binding activity of HA is critical for the intestinal absorption of BoNTs. The trimeric triskelion-shaped structure of HA confers the multivalent binding to its ligands and increases the pathogenic biological activities of HA.
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Affiliation(s)
- Sho Amatsu
- Department of Bacteriology, Graduate School of Medical Sciences, Kanazawa University, Ishikawa, Japan.,Department of Forensic Medicine and Pathology, Graduate School of Medical Sciences, Kanazawa University, Ishikawa, Japan
| | - Yukako Fujinaga
- Department of Bacteriology, Graduate School of Medical Sciences, Kanazawa University, Ishikawa, Japan.
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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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40
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Looking for the X Factor in Bacterial Pathogenesis: Association of orfX- p47 Gene Clusters with Toxin Genes in Clostridial and Non-Clostridial Bacterial Species. Toxins (Basel) 2019; 12:toxins12010019. [PMID: 31906154 PMCID: PMC7020563 DOI: 10.3390/toxins12010019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 12/23/2019] [Accepted: 12/29/2019] [Indexed: 12/13/2022] Open
Abstract
The botulinum neurotoxin (BoNT) has been extensively researched over the years in regard to its structure, mode of action, and applications. Nevertheless, the biological roles of four proteins encoded from a number of BoNT gene clusters, i.e., OrfX1-3 and P47, are unknown. Here, we investigated the diversity of orfX-p47 gene clusters using in silico analytical tools. We show that the orfX-p47 cluster was not only present in the genomes of BoNT-producing bacteria but also in a substantially wider range of bacterial species across the bacterial phylogenetic tree. Remarkably, the orfX-p47 cluster was consistently located in proximity to genes coding for various toxins, suggesting that OrfX1-3 and P47 may have a conserved function related to toxinogenesis and/or pathogenesis, regardless of the toxin produced by the bacterium. Our work also led to the identification of a putative novel BoNT-like toxin gene cluster in a Bacillus isolate. This gene cluster shares striking similarities to the BoNT cluster, encoding a bont/ntnh-like gene and orfX-p47, but also differs from it markedly, displaying additional genes putatively encoding the components of a polymorphic ABC toxin complex. These findings provide novel insights into the biological roles of OrfX1, OrfX2, OrfX3, and P47 in toxinogenesis and pathogenesis of BoNT-producing and non-producing bacteria.
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Rasetti-Escargueil C, Lemichez E, Popoff MR. Public Health Risk Associated with Botulism as Foodborne Zoonoses. Toxins (Basel) 2019; 12:E17. [PMID: 31905908 PMCID: PMC7020394 DOI: 10.3390/toxins12010017] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 12/23/2019] [Accepted: 12/25/2019] [Indexed: 12/03/2022] Open
Abstract
Botulism is a rare but severe neurological disease in man and animals that is caused by botulinum neurotoxins (BoNTs) produced by Clostridium botulinum and atypical strains from other Clostridium and non-Clostridium species. BoNTs are divided into more than seven toxinotypes based on neutralization with specific corresponding antisera, and each toxinotype is subdivided into subtypes according to amino acid sequence variations. Animal species show variable sensitivity to the different BoNT toxinotypes. Thereby, naturally acquired animal botulism is mainly due to BoNT/C, D and the mosaic variants CD and DC, BoNT/CD being more prevalent in birds and BoNT/DC in cattle, whereas human botulism is more frequently in the types A, B and E, and to a lower extent, F. Botulism is not a contagious disease, since there is no direct transmission from diseased animals or man to a healthy subject. Botulism occurs via the environment, notably from food contaminated with C. botulinum spores and preserved in conditions favorable for C. botulinum growth and toxin production. The high prevalence of botulism types C, D and variants DC and CD in farmed and wild birds, and to a lower extent in cattle, raises the risk of transmission to human beings. However, human botulism is much rarer than animal botulism, and botulism types C and D are exceptional in humans. Only 15 cases or suspected cases of botulism type C and one outbreak of botulism type D have been reported in humans to date. In contrast, animal healthy carriers of C. botulinum group II, such as C. botulinum type E in fish of the northern hemisphere, and C. botulinum B4 in pigs, represent a more prevalent risk of botulism transmission to human subjects. Less common botulism types in animals but at risk of transmission to humans, can sporadically be observed, such as botulism type E in farmed chickens in France (1998-2002), botulism type B in cattle in The Netherlands (1977-1979), botulism types A and B in horses, or botulism type A in dairy cows (Egypt, 1976). In most cases, human and animal botulisms have distinct origins, and cross transmissions between animals and human beings are rather rare, accidental events. But, due to the severity of this disease, human and animal botulism requires a careful surveillance.
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Affiliation(s)
| | | | - Michel R. Popoff
- Institut Pasteur, Département de Microbiologie, Unité des Toxines Bactériennes, CNRS ERL6002, 75724 Paris, France; (C.R.-E.); (E.L.)
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Structural insights into the interaction of botulinum neurotoxin a with its neuronal receptor SV2C. Toxicon 2019; 175:36-43. [PMID: 31783045 DOI: 10.1016/j.toxicon.2019.11.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 11/08/2019] [Accepted: 11/25/2019] [Indexed: 11/23/2022]
Abstract
A dual-receptor interaction with a polysialoganglioside and synaptic vesicle glycoprotein 2 (SV2) is required for botulinum neurotoxin A (BoNT) toxicity. Here, we review what is currently known about the BoNT/A-SV2 interaction based on structural studies. Currently, five crystal structures of the receptor-binding domain (Hc) of BoNT subtypes A1 and A2 complexed to the large luminal domain (LD4) of SV2C have been determined. On the basis of the available structures, we will discuss the importance of protein-protein and protein-carbohydrate interactions for BoNT/A toxicity as well as the high plasticity of BoNT/A for receptor recognition by tolerating a variety of side-chain interactions at the interface. A plausible explanation how receptor-binding specificity of BoNT/A may be achieved without an extensive and conserved side chain-side chain interaction network will be provided.
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Tables of Toxicity of Botulinum and Tetanus Neurotoxins. Toxins (Basel) 2019; 11:toxins11120686. [PMID: 31771110 PMCID: PMC6950492 DOI: 10.3390/toxins11120686] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 11/17/2022] Open
Abstract
Tetanus and botulinum neurotoxins are the most poisonous substances known, so much so as to be considered for a possible terrorist use. At the same time, botulinum neurotoxin type A1 is successfully used to treat a variety of human syndromes characterized by hyperactive cholinergic nerve terminals. The extreme toxicity of these neurotoxins is due to their neurospecificity and to their metalloprotease activity, which results in the deadly paralysis of tetanus and botulism. Recently, many novel botulinum neurotoxins and some botulinum-like toxins have been discovered. This large number of toxins differs in terms of toxicity and biological activity, providing a potential goldmine for novel therapeutics and for new molecular tools to dissect vesicular trafficking, fusion, and exocytosis. The scattered data on toxicity present in the literature require a systematic organization to be usable by scientists and clinicians. We have assembled here the data available in the literature on the toxicity of these toxins in different animal species. The internal comparison of these data provides insights on the biological activity of these toxins.
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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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