1
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Kempher ML, Shadid TM, Larabee JL, Ballard JD. A sequence invariable region in TcdB2 is required for toxin escape from Clostridioides difficile. J Bacteriol 2024:e0009624. [PMID: 38888328 DOI: 10.1128/jb.00096-24] [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: 03/06/2024] [Accepted: 05/23/2024] [Indexed: 06/20/2024] Open
Abstract
Sequence differences among the subtypes of Clostridioides difficile toxin TcdB (2,366 amino acids) are broadly distributed across the entire protein, with the notable exception of 76 residues at the protein's carboxy terminus. This sequence invariable region (SIR) is identical at the DNA and protein level among the TcdB variants, suggesting this string of amino acids has undergone selective pressure to prevent alterations. The functional role of the SIR domain in TcdB has not been determined. Analysis of a recombinantly constructed TcdB mutant lacking the SIR domain did not identify changes in TcdB's enzymatic or cytopathic activities. To further assess the SIR region, we constructed a C. difficile strain with the final 228 bp deleted from the tcdB gene, resulting in the production of a truncated form of TcdB lacking the SIR (TcdB2∆2291-2366). Using a combination of approaches, we found in the absence of the SIR sequence TcdB2∆2291-2366 retained cytotoxic activity but was not secreted from C. difficile. TcdB2∆2291-2366 was not released from the cell under autolytic conditions, indicating the SIR is involved in a more discrete step in toxin escape from the bacterium. Fractionation experiments combined with antibody detection found that TcdB2∆2291-2366 accumulates at the cell membrane but is unable to complete steps in secretion beyond this point. These data suggest conservation of the SIR domain across variants of TcdB could be influenced by the sequence's role in efficient escape of the toxin from C. difficile. IMPORTANCE Clostridioides difficile is a leading cause of antibiotic associated disease in the United States. The primary virulence factors produced by C. difficile are two large glucosylating toxins TcdA and TcdB. To date, several sequence variants of TcdB have been identified that differ in various functional properties. Here, we identified a highly conserved region among TcdB subtypes that is required for release of the toxin from C. difficile. This study reveals a putative role for the longest stretch of invariable sequence among TcdB subtypes and provides new details regarding toxin release into the extracellular environment. Improving our understanding of the functional roles of the conserved regions of TcdB variants aids in the development of new, broadly applicable strategies to treat CDI.
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Affiliation(s)
- Megan L Kempher
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Tyler M Shadid
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Jason L Larabee
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Jimmy D Ballard
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
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2
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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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3
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Pan Z, Zhang Y, Luo J, Li D, Zhou Y, He L, Yang Q, Dong M, Tao L. Functional analyses of epidemic Clostridioides difficile toxin B variants reveal their divergence in utilizing receptors and inducing pathology. PLoS Pathog 2021; 17:e1009197. [PMID: 33507919 PMCID: PMC7842947 DOI: 10.1371/journal.ppat.1009197] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 11/30/2020] [Indexed: 02/06/2023] Open
Abstract
Clostridioides difficile toxin B (TcdB) is a key virulence factor that causes C. difficile associated diseases (CDAD) including diarrhea and pseudomembranous colitis. TcdB can be divided into multiple subtypes/variants based on their sequence variations, of which four (TcdB1-4) are dominant types found in major epidemic isolates. Here, we find that these variants are highly diverse in their receptor preference: TcdB1 uses two known receptors CSPG4 and Frizzled (FZD) proteins, TcdB2 selectively uses CSPG4, TcdB3 prefers to use FZDs, whereas TcdB4 uses neither CSPG4 nor FZDs. By creating chimeric toxins and systematically switching residues between TcdB1 and TcdB3, we determine that regions in the N-terminal cysteine protease domain (CPD) are involved in CSPG4-recognition. We further evaluate the pathological effects induced by TcdB1-4 with a mouse intrarectal installation model. TcdB1 leads to the most severe overall symptoms, followed by TcdB2 and TcdB3. When comparing the TcdB2 and TcdB3, TcdB2 causes stronger oedema while TcdB3 induces severer inflammatory cell infiltration. These findings together demonstrate divergence in the receptor preference and further lead to colonic pathology for predominant TcdB subtypes. Clostridioides difficile is a major cause of nosocomial and community-associated gastrointestinal infections. The bacterium produces three exotoxins including TcdA, TcdB, and CDT, of which TcdB is known as a key virulence factor causing the diseases. Since C. difficile was first linked to antibiotic-associated infections in 1978, a large number of clinically relevant strains were characterized and many of them were found to harbor some variant forms of TcdB. In this study, we examined four predominant TcdB variants from epidemic C. difficile strains. We found that these variants are highly diverse in preference to the known receptors, CSPG4 and Frizzled proteins. By conducting a systematically designed mutagenesis study, we determined that TcdB interacts with CSPG4 via regions across multiple domains. We also found that TcdB variants could induce distinguishable pathological phenotypes in a mouse model, suggesting C. difficile strains harboring divergent TcdB variants might exhibit different disease progression. Our study provides new insights into the toxicology and pathology of C. difficile toxin variants.
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Affiliation(s)
- Zhenrui Pan
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Yuanyuan Zhang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Jianhua Luo
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Danyang Li
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Yao Zhou
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Liuqing He
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Qi Yang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Min Dong
- Department of Urology, Boston Children’s Hospital, Boston, Massechusetts, United States of America
- Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, Massechusetts, United States of America
- * E-mail: (MD); (LT)
| | - Liang Tao
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
- * E-mail: (MD); (LT)
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4
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Shen E, Zhu K, Li D, Pan Z, Luo Y, Bian Q, He L, Song X, Zhen Y, Jin D, Tao L. Subtyping analysis reveals new variants and accelerated evolution of Clostridioides difficile toxin B. Commun Biol 2020; 3:347. [PMID: 32620855 PMCID: PMC7335066 DOI: 10.1038/s42003-020-1078-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 06/16/2020] [Indexed: 02/06/2023] Open
Abstract
Clostridioides difficile toxins (TcdA and TcdB) are major exotoxins responsible for C. difficile infection (CDI) associated diseases. The previously reported TcdB variants showed distinct biological features, immunoactivities, and potential pathogenicity in disease progression. Here, we performed global comparisons of amino acid sequences of both TcdA and TcdB from 3,269 C. difficile genomes and clustered them according to the evolutionary relatedness. We found that TcdB was much diverse and could be divided into eight subtypes, of which four were first described. Further analysis indicates that the tcdB gene undergoes accelerated evolution to maximize diversity. By tracing TcdB subtypes back to their original isolates, we found that the distribution of TcdB subtypes was not completely aligned with the phylogeny of C. difficile. These findings suggest that the tcdB genes not only frequently mutate, but also continuously transfer and exchange among C. difficile strains. Shen et al. compare the amino acid sequences of bacterial toxins TcdA and TcdB from 3,269 Clostridioides difficile genomes to identify four new TcdB subtypes. They find that TcdB was more diverse in amino acid sequence than TcdA. This study suggests that the tcdB genes not only frequently mutate, but they also continuously transfer and exchange among C. difficile strains.
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Affiliation(s)
- Enhui Shen
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Kangli Zhu
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Danyang Li
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Zhenrui Pan
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Yun Luo
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, 310051, China.,School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Qiao Bian
- School of Medicine, Ningbo University, Ningbo, Zhejiang, 315211, China
| | - Liuqing He
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Xiaojun Song
- Centre of Laboratory Medicine, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, Zhejiang, 310014, China
| | - Ying Zhen
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Dazhi Jin
- Centre of Laboratory Medicine, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, Zhejiang, 310014, China.,School of Laboratory Medicine, Hangzhou Medical College, Hangzhou, Zhejiang, 310053, China
| | - Liang Tao
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China. .,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China.
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5
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Chen P, Lam KH, Liu Z, Mindlin FA, Chen B, Gutierrez CB, Huang L, Zhang Y, Hamza T, Feng H, Matsui T, Bowen ME, Perry K, Jin R. Structure of the full-length Clostridium difficile toxin B. Nat Struct Mol Biol 2019; 26:712-719. [PMID: 31308519 PMCID: PMC6684407 DOI: 10.1038/s41594-019-0268-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 06/07/2019] [Indexed: 01/07/2023]
Abstract
Clostridium difficile is an opportunistic pathogen that establishes in the colon when the gut microbiota are disrupted by antibiotics or disease. C. difficile infection (CDI) is largely caused by two virulence factors, TcdA and TcdB. Here, we report a 3.87-Å-resolution crystal structure of TcdB holotoxin that captures a unique conformation of TcdB at endosomal pH. Complementary biophysical studies suggest that the C-terminal combined repetitive oligopeptides (CROPs) domain of TcdB is dynamic and can sample open and closed conformations that may facilitate modulation of TcdB activity in response to environmental and cellular cues during intoxication. Furthermore, we report three crystal structures of TcdB-antibody complexes that reveal how antibodies could specifically inhibit the activities of individual TcdB domains. Our studies provide novel insight into the structure and function of TcdB holotoxin and identify intrinsic vulnerabilities that could be exploited to develop new therapeutics and vaccines for the treatment of CDI.
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Affiliation(s)
- Peng Chen
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Kwok-Ho Lam
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Zheng Liu
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Frank A Mindlin
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Baohua Chen
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Craig B Gutierrez
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Lan Huang
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Yongrong Zhang
- Department of Microbial Pathogenesis, University of Maryland Baltimore, Baltimore, MD, USA
| | - Therwa Hamza
- Department of Microbial Pathogenesis, University of Maryland Baltimore, Baltimore, MD, USA
| | - Hanping Feng
- Department of Microbial Pathogenesis, University of Maryland Baltimore, Baltimore, MD, USA
| | - Tsutomu Matsui
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, USA
| | - Mark E Bowen
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Kay Perry
- NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Argonne National Laboratory, Argonne, IL, USA
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA.
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6
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López-Ureña D, Orozco-Aguilar J, Chaves-Madrigal Y, Ramírez-Mata A, Villalobos-Jimenez A, Ost S, Quesada-Gómez C, Rodríguez C, Papatheodorou P, Chaves-Olarte E. Toxin B Variants from Clostridium difficile Strains VPI 10463 and NAP1/027 Share Similar Substrate Profile and Cellular Intoxication Kinetics but Use Different Host Cell Entry Factors. Toxins (Basel) 2019; 11:toxins11060348. [PMID: 31212980 PMCID: PMC6628394 DOI: 10.3390/toxins11060348] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 05/14/2019] [Indexed: 02/07/2023] Open
Abstract
Clostridium difficile induces antibiotic-associated diarrhea due to the release of toxin A (TcdA) and toxin B (TcdB), the latter being its main virulence factor. The epidemic strain NAP1/027 has an increased virulence attributed to different factors. We compared cellular intoxication by TcdBNAP1 with that by the reference strain VPI 10463 (TcdBVPI). In a mouse ligated intestinal loop model, TcdBNAP1 induced higher neutrophil recruitment, cytokine release, and epithelial damage than TcdBVPI. Both toxins modified the same panel of small GTPases and exhibited similar in vitro autoprocessing kinetics. On the basis of sequence variations in the frizzled-binding domain (FBD), we reasoned that TcdBVPI and TcdBNAP1 might have different receptor specificities. To test this possibility, we used a TcdB from a NAP1 variant strain (TcdBNAP1v) unable to glucosylate RhoA but with the same receptor-binding domains as TcdBNAP1. Cells were preincubated with TcdBNAP1v to block cellular receptors, prior to intoxication with either TcdBVPI or TcdBNAP1. Preincubation with TcdBNAP1v blocked RhoA glucosylation by TcdBNAP1 but not by TcdBVPI, indicating that the toxins use different host factors for cell entry. This crucial difference might explain the increased biological activity of TcdBNAP1 in the intestine, representing a contributing factor for the increased virulence of the NAP1/027 strain.
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Affiliation(s)
- Diana López-Ureña
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Josué Orozco-Aguilar
- Facultad de Farmacia and Laboratorio de Ensayos Biológicos, Escuela de Medicina, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Yendry Chaves-Madrigal
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Andrea Ramírez-Mata
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Amanda Villalobos-Jimenez
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Stefan Ost
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany.
| | - Carlos Quesada-Gómez
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - César Rodríguez
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | | | - Esteban Chaves-Olarte
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
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Ivarsson ME, Durantie E, Huberli C, Huwiler S, Hegde C, Friedman J, Altamura F, Lu J, Verdu EF, Bercik P, Logan SM, Chen W, Leroux JC, Castagner B. Small-Molecule Allosteric Triggers of Clostridium difficile Toxin B Auto-proteolysis as a Therapeutic Strategy. Cell Chem Biol 2019; 26:17-26.e13. [DOI: 10.1016/j.chembiol.2018.10.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 06/27/2018] [Accepted: 09/28/2018] [Indexed: 01/19/2023]
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8
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Chung SY, Schöttelndreier D, Tatge H, Fühner V, Hust M, Beer LA, Gerhard R. The Conserved Cys-2232 in Clostridioides difficile Toxin B Modulates Receptor Binding. Front Microbiol 2018; 9:2314. [PMID: 30416488 PMCID: PMC6212469 DOI: 10.3389/fmicb.2018.02314] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/11/2018] [Indexed: 12/14/2022] Open
Abstract
Clostridioides difficile toxins TcdA and TcdB are large clostridial glucosyltransferases which are the main pathogenicity factors in C. difficile-associated diseases. Four highly conserved cysteines are present in all large clostridial glucosyltransferases. In this study we focused on the conserved cysteine 2232 within the combined repetitive oligopeptide domain of TcdB from reference strain VPI10463 (clade I). Cysteine 2232 is not present in TcdB from hypervirulent strain R20291 (clade II), where a tyrosine is found instead. Replacement of cysteine 2232 by tyrosine in TcdBV PI10463 reduced binding to the soluble fragments of the two known TcdB receptors, frizzled-2 (FZD2) and poliovirus receptor-like protein-3/nectin-3 (PVRL3). In line with this, TcdBR20291 showed weak binding to PVRL3 in pull-down assays which was increased when tyrosine 2232 was exchanged for cysteine. Surprisingly, we did not observe binding of TcdBR20291 to FZD2, indicating that this receptor is less important for this toxinotype. Competition assay with the receptor binding fragments (aa 1101–1836) of TcdBV PI10463 and TcdBR20291, as well as antibodies newly developed by antibody phage display, revealed different characteristics of the yet poorly described delivery domain of TcdB harboring the second receptor binding region. In summary, we found that conserved Cys-2232 in TcdB indirectly contributes to toxin–receptor interaction.
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Affiliation(s)
- Soo-Young Chung
- Institute of Toxicology, Hannover Medical School, Hanover, Germany
| | | | - Helma Tatge
- Institute of Toxicology, Hannover Medical School, Hanover, Germany
| | - Viola Fühner
- Department of Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Michael Hust
- Department of Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | | | - Ralf Gerhard
- Institute of Toxicology, Hannover Medical School, Hanover, Germany
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9
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Chen X, Kelly CP. On and Off: A Dual Role for Cysteine Protease Autoprocessing of C difficile Toxin B on Cytotoxicity vs Proinflammatory Toxin Actions? Cell Mol Gastroenterol Hepatol 2018; 5:654-655. [PMID: 29713672 PMCID: PMC5924747 DOI: 10.1016/j.jcmgh.2018.02.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Affiliation(s)
| | - Ciaran P. Kelly
- Correspondence Address correspondence to: Ciaran P. Kelly, MD, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Dana 601, Boston, Massachusetts 02215.
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10
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Zhang Y, Li S, Yang Z, Shi L, Yu H, Salerno-Goncalves R, Saint Fleur A, Feng H. Cysteine Protease-Mediated Autocleavage of Clostridium difficile Toxins Regulates Their Proinflammatory Activity. Cell Mol Gastroenterol Hepatol 2018; 5:611-625. [PMID: 29930981 PMCID: PMC6009800 DOI: 10.1016/j.jcmgh.2018.01.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 01/30/2018] [Indexed: 02/04/2023]
Abstract
BACKGROUND & AIMS Clostridium difficile toxin A (TcdA) and C difficile toxin toxin B (TcdB), the major virulence factors of the bacterium, cause intestinal tissue damage and inflammation. Although the 2 toxins are homologous and share a similar domain structure, TcdA is generally more inflammatory whereas TcdB is more cytotoxic. The functional domain of the toxins that govern the proinflammatory activities of the 2 toxins is unknown. METHODS Here, we investigated toxin domain functions that regulate the proinflammatory activity of C difficile toxins. By using a mouse ilea loop model, human tissues, and immune cells, we examined the inflammatory responses to a series of chimeric toxins or toxin mutants deficient in specific domain functions. RESULTS Blocking autoprocessing of TcdB by mutagenesis or chemical inhibition, while reducing cytotoxicity of the toxin, significantly enhanced its proinflammatory activities in the animal model. Furthermore, a noncleavable mutant TcdB was significantly more potent than the wild-type toxin in the induction of proinflammatory cytokines in human colonic tissues and immune cells. CONCLUSIONS In this study, we identified a novel mechanism of regulating the biological activities of C difficile toxins in that cysteine protease-mediated autoprocessing regulates toxins' proinflammatory activities. Our findings provide new insight into the pathogenesis of C difficile infection and the design of therapeutics against the disease.
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Key Words
- 3D, 3-dimensional
- ACPD, CPD domain of TcdA
- Autoprocessing
- Bgt, GTD of TcdB
- Br, RBD of TcdB
- C difficile
- CDI, Clostridium difficile infection
- CPD, cysteine protease domain
- Cysteine Protease
- GT, glucosyltransferase
- GTD, glucosyltransferase domain
- IL, interleukin
- Inflammation
- InsP6, inositol hexakisphosphate
- MPO, myeloperoxidase
- PBMC, peripheral blood mononuclear cell
- PBS, phosphate-buffered saline
- PCR, polymerase chain reaction
- RBD, receptor binding domain
- TER, transepithelial electrical resistance
- TcdA, Clostridium difficile toxin A
- TcdB, Clostridium difficile toxin B
- Toxins
- aTcdA, GTD deficient TcdA
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Affiliation(s)
- Yongrong Zhang
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland
| | - Shan Li
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland
| | - Zhiyong Yang
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland
| | - Lianfa Shi
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland
| | - Hua Yu
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland
| | - Rosangela Salerno-Goncalves
- Department of Pediatrics and Center for Vaccine Development, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Ashley Saint Fleur
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland
| | - Hanping Feng
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland,Correspondence Address correspondence to: Hanping Feng, PhD, 650 W Baltimore Street, Room 7211, Baltimore, Maryland 21201. fax: (410) 706-6511.
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11
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Kroh HK, Chandrasekaran R, Zhang Z, Rosenthal K, Woods R, Jin X, Nyborg AC, Rainey GJ, Warrener P, Melnyk RA, Spiller BW, Lacy DB. A neutralizing antibody that blocks delivery of the enzymatic cargo of Clostridium difficile toxin TcdB into host cells. J Biol Chem 2017; 293:941-952. [PMID: 29180448 DOI: 10.1074/jbc.m117.813428] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 11/08/2017] [Indexed: 12/14/2022] Open
Abstract
Clostridium difficile infection is the leading cause of hospital-acquired diarrhea and is mediated by the actions of two toxins, TcdA and TcdB. The toxins perturb host cell function through a multistep process of receptor binding, endocytosis, low pH-induced pore formation, and the translocation and delivery of an N-terminal glucosyltransferase domain that inactivates host GTPases. Infection studies with isogenic strains having defined toxin deletions have established TcdB as an important target for therapeutic development. Monoclonal antibodies that neutralize TcdB function have been shown to protect against C. difficile infection in animal models and reduce recurrence in humans. Here, we report the mechanism of TcdB neutralization by PA41, a humanized monoclonal antibody capable of neutralizing TcdB from a diverse array of C. difficile strains. Through a combination of structural, biochemical, and cell functional studies, involving X-ray crystallography and EM, we show that PA41 recognizes a single, highly conserved epitope on the TcdB glucosyltransferase domain and blocks productive translocation and delivery of the enzymatic cargo into the host cell. Our study reveals a unique mechanism of C. difficile toxin neutralization by a monoclonal antibody, which involves targeting a process that is conserved across the large clostridial glucosylating toxins. The PA41 antibody described here provides a valuable tool for dissecting the mechanism of toxin pore formation and translocation across the endosomal membrane.
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Affiliation(s)
- Heather K Kroh
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363
| | - Ramyavardhanee Chandrasekaran
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363
| | - Zhifen Zhang
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | | | - Rob Woods
- MedImmune LLC, Gaithersburg, Maryland 20878-2204
| | - Xiaofang Jin
- MedImmune LLC, Gaithersburg, Maryland 20878-2204
| | | | | | | | - Roman A Melnyk
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Benjamin W Spiller
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363.,Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232-6600, and
| | - D Borden Lacy
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363, .,Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee 37212-2637
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12
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Abt MC, McKenney PT, Pamer EG. Clostridium difficile colitis: pathogenesis and host defence. Nat Rev Microbiol 2016; 14:609-20. [PMID: 27573580 DOI: 10.1038/nrmicro.2016.108] [Citation(s) in RCA: 331] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Clostridium difficile is a major cause of intestinal infection and diarrhoea in individuals following antibiotic treatment. Recent studies have begun to elucidate the mechanisms that induce spore formation and germination and have determined the roles of C. difficile toxins in disease pathogenesis. Exciting progress has also been made in defining the role of the microbiome, specific commensal bacterial species and host immunity in defence against infection with C. difficile. This Review will summarize the recent discoveries and developments in our understanding of C. difficile infection and pathogenesis.
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Affiliation(s)
- Michael C Abt
- Immunology Program, Lucille Castori Center for Microbes, Inflammation and Cancer, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA
| | - Peter T McKenney
- Immunology Program, Lucille Castori Center for Microbes, Inflammation and Cancer, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA
| | - Eric G Pamer
- Immunology Program, Lucille Castori Center for Microbes, Inflammation and Cancer, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA
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13
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Abstract
Infection of the colon with the Gram-positive bacterium Clostridium difficile is potentially life threatening, especially in elderly people and in patients who have dysbiosis of the gut microbiota following antimicrobial drug exposure. C. difficile is the leading cause of health-care-associated infective diarrhoea. The life cycle of C. difficile is influenced by antimicrobial agents, the host immune system, and the host microbiota and its associated metabolites. The primary mediators of inflammation in C. difficile infection (CDI) are large clostridial toxins, toxin A (TcdA) and toxin B (TcdB), and, in some bacterial strains, the binary toxin CDT. The toxins trigger a complex cascade of host cellular responses to cause diarrhoea, inflammation and tissue necrosis - the major symptoms of CDI. The factors responsible for the epidemic of some C. difficile strains are poorly understood. Recurrent infections are common and can be debilitating. Toxin detection for diagnosis is important for accurate epidemiological study, and for optimal management and prevention strategies. Infections are commonly treated with specific antimicrobial agents, but faecal microbiota transplants have shown promise for recurrent infections. Future biotherapies for C. difficile infections are likely to involve defined combinations of key gut microbiota.
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Affiliation(s)
- Wiep Klaas Smits
- Section Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands
| | - Dena Lyras
- Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Victoria, Australia
| | - D. Borden Lacy
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, and The Veterans Affairs Tennessee Valley Healthcare System, Nashville Tennessee, USA
| | - Mark H. Wilcox
- Institute of Biomedical and Clinical Sciences, University of Leeds, Leeds, UK
| | - Ed J. Kuijper
- Section Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands
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14
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Janoir C. Virulence factors of Clostridium difficile and their role during infection. Anaerobe 2016; 37:13-24. [DOI: 10.1016/j.anaerobe.2015.10.009] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 10/16/2015] [Accepted: 10/21/2015] [Indexed: 02/08/2023]
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15
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Carlson PE, Kaiser AM, McColm SA, Bauer JM, Young VB, Aronoff DM, Hanna PC. Variation in germination of Clostridium difficile clinical isolates correlates to disease severity. Anaerobe 2015; 33:64-70. [PMID: 25681667 PMCID: PMC4467518 DOI: 10.1016/j.anaerobe.2015.02.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 02/02/2015] [Accepted: 02/10/2015] [Indexed: 01/05/2023]
Abstract
Over the past two decades, Clostridium difficile infections have been increasing in both number and severity throughout the world. As with other spore forming bacteria, germination is a vital step in the life cycle of this pathogen. Studies have examined differences in sporulation and toxin production among a number of C. difficile clinical isolates; however, few have examined differences in germination and the relationship between this phenotype and disease severity. Here, over 100 C. difficile isolates from the University of Michigan Health System were examined for overall germination in response to various combinations of known germinants (taurocholate) and co-germinants (glycine and histidine). Significant variation was observed among isolates under all conditions tested. Isolates representing ribotype 014-020, which was the most frequently isolated ribotype at our hospital, exhibited increased germination in the presence of taurocholate and glycine when compared to isolates representing other ribotypes. Interestingly, isolates that caused severe disease exhibited significantly lower germination in response to minimal germination conditions (taurocholate only), indicating increased control over germination in these isolates. These data provide a broad picture of C. difficile isolate germination and indicate a role for precise control of germination in disease severity.
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Affiliation(s)
- Paul E Carlson
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Alyssa M Kaiser
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sarah A McColm
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jessica M Bauer
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Vincent B Young
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Internal Medicine, Division of Infectious Diseases, University of Michigan, Ann Arbor, MI 48109, USA
| | - David M Aronoff
- Division of Infectious Diseases, Department of Medicine, Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Philip C Hanna
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA.
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16
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Zhang Y, Hamza T, Gao S, Feng H. Masking autoprocessing of Clostridium difficile toxin A by the C-terminus combined repetitive oligo peptides. Biochem Biophys Res Commun 2015; 459:259-263. [PMID: 25725153 DOI: 10.1016/j.bbrc.2015.02.095] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 02/17/2015] [Indexed: 10/23/2022]
Abstract
Clostridium difficile toxin A and B (TcdA and TcdB) are the major virulence factors of the bacterium, both of which consist of two enzymatic domains: an effector glucosyltransferase domain (GTD) and a cysteine protease domain (CPD) responsible for autocleavage and release of GTD. Although the CPDs from both toxins share a similar structure and mechanism of hexakisphosphate (InsP6)-induced activation, TcdA is substantially less sensitive to the autocleavage as compared with TcdB. In this study, we provided evidence of inter-domain regulation of CPD activity of TcdA and its autoprocessing. The C-terminus combined repetitive oligo peptides (CROPs) of TcdA reduced the accessibility of TcdB CPD to its substrate in a chimeric toxin TxB-Ar, consequently blocking autoprocessing. Moreover, interference of antibodies with the CROPs of full-length TcdA efficiently enhanced its GTD release. In conclusion, by utilizing chimeric toxins and specific antibodies, we identified that the CROPs of TcdA plays a crucial role in controlling the InsP6-mediated activation of CPD and autocleavage of GTD. Our data provides insights on the molecular mode of action of the C. difficile toxins.
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Affiliation(s)
- Yongrong Zhang
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, MD 21201, USA
| | - Therwa Hamza
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, MD 21201, USA
| | - Si Gao
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, MD 21201, USA
| | - Hanping Feng
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, MD 21201, USA.
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17
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Larabee JL, Krumholz A, Hunt JJ, Lanis JM, Ballard JD. Exposure of neutralizing epitopes in the carboxyl-terminal domain of TcdB is altered by a proximal hypervariable region. J Biol Chem 2015; 290:6975-85. [PMID: 25614625 DOI: 10.1074/jbc.m114.612184] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The sequence, activity, and antigenicity of TcdB varies between different strains of Clostridium difficile. As a result, ribotype-specific forms of TcdB exhibit different toxicities and are not strongly cross-neutralized. Using a combination of biochemical and immunological approaches, we compared two important variants of TcdB (TcdB012 and TcdB027) to identify the mechanisms through which sequence differences alter epitopes and activity of the toxin. These analyses led to the discovery of a critical variation in the 1753-1851 (B2') region of TcdB, which affects the exposure of neutralizing epitopes in the toxin. Sequence comparisons found that the B2' region exhibits only 77% identity and is the most variable sequence between the two forms of TcdB. A combination of biochemical, analytical, and mutagenesis experiments revealed that the B2' region promotes protein-protein interactions. These interactions appear to shield neutralizing epitopes that would otherwise be exposed in the toxin, an event found to be less prominent in TcdB012 due to sequence differences in the 1773-1780 and 1791-1798 regions of the B2' domain. When the carboxyl-terminal domains of TcdB012 and TcdB027 are swapped, neutralization experiments suggest that the amino terminus of TcdB interacts with the B2' region and impacts the exposure of neutralizing epitopes in the carboxyl terminus. Collectively, these data suggest that variations in the B2' region affect protein-protein interactions within TcdB and that these interactions influence the exposure of neutralizing epitopes.
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Affiliation(s)
- Jason L Larabee
- From the Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Aleze Krumholz
- From the Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Jonathan J Hunt
- From the Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Jordi M Lanis
- From the Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Jimmy D Ballard
- From the Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
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18
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Critical roles of Clostridium difficile toxin B enzymatic activities in pathogenesis. Infect Immun 2014; 83:502-13. [PMID: 25404023 DOI: 10.1128/iai.02316-14] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
TcdB is one of the key virulence factors of Clostridium difficile that is responsible for causing serious and potentially fatal colitis. The toxin contains at least two enzymatic domains: an effector glucosyltransferase domain for inactivating host Rho GTPases and a cysteine protease domain for the delivery of the effector domain into host cytosol. Here, we describe a novel intrabody approach to examine the role of these enzymes of TcdB in cellular intoxication. By screening a single-domain heavy chain (V(H)H) library raised against TcdB, we identified two V(H)H antibodies, 7F and E3, that specifically inhibit TcdB cysteine protease and glucosyltransferase activities, respectively. Cytoplasmic expression of 7F intrabody in Vero cells inhibited TcdB autoprocessing and delayed cellular intoxication, whereas E3 intrabody completely blocked the cytopathic effects of TcdB holotoxin. These data also demonstrate for the first time that toxin autoprocessing occurs after cysteine protease and glucosyltransferase domains translocate into the cytosol of target cells. We further determined the role of the enzymatic activities of TcdB in in vivo toxicity using a sensitive systemic challenge model in mice. Consistent with these in vitro results, a cysteine protease noncleavable mutant, TcdB-L543A, delayed toxicity in mice, whereas glycosyltransferase-deficient TcdB demonstrated no toxicity up to 500-fold of the 50% lethal dose (LD50) when it was injected systemically. Thus, glucosyltransferase but not cysteine protease activity is critical for TcdB-mediated cytopathic effects and TcdB systemic toxicity, highlighting the importance of targeting toxin glucosyltransferase activity for future therapy.
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19
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Luciano JA, Zuckerbraun BS. Clostridium difficile infection: prevention, treatment, and surgical management. Surg Clin North Am 2014; 94:1335-49. [PMID: 25440127 DOI: 10.1016/j.suc.2014.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Clostridium difficile is increasing in both incidence and severity. Although metronidazole and vancomycin remain the gold standard for medical management, and surgical colectomy the gold standard for surgical management, new treatment alternatives, including the creation of a diverting loop ileostomy along with colonic lavage and vancomycin enemas, are being investigated that may lead to changes in the current treatment algorithms. The most exciting development in the treatment options for C difficile infection, however, is likely to be novel immunologic agents, which hold the potential to reduce the incidence, mortality, and costs associated with C difficile.
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Affiliation(s)
- Jason A Luciano
- Department of Surgery, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA 15213, USA
| | - Brian S Zuckerbraun
- Department of Surgery, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA 15213, USA; Department of Surgery, VA Pittsburgh Healthcare System, University Drive, Pittsburgh, PA 15240, USA.
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20
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Variations in virulence and molecular biology among emerging strains of Clostridium difficile. Microbiol Mol Biol Rev 2014; 77:567-81. [PMID: 24296572 DOI: 10.1128/mmbr.00017-13] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Clostridium difficile is a Gram-positive, spore-forming organism which infects and colonizes the large intestine, produces potent toxins, triggers inflammation, and causes significant systemic complications. Treating C. difficile infection (CDI) has always been difficult, because the disease is both caused and resolved by antibiotic treatment. For three and a half decades, C. difficile has presented a treatment challenge to clinicians, and the situation took a turn for the worse about 10 years ago. An increase in epidemic outbreaks related to CDI was first noticed around 2003, and these outbreaks correlated with a sudden increase in the mortality rate of this illness. Further studies discovered that these changes in CDI epidemiology were associated with the rapid emergence of hypervirulent strains of C. difficile, now collectively referred to as NAP1/BI/027 strains. The discovery of new epidemic strains of C. difficile has provided a unique opportunity for retrospective and prospective studies that have sought to understand how these strains have essentially replaced more historical strains as a major cause of CDI. Moreover, detailed studies on the pathogenesis of NAP1/BI/027 strains are leading to new hypotheses on how this emerging strain causes severe disease and is more commonly associated with epidemics. In this review, we provide an overview of CDI, discuss critical mechanisms of C. difficile virulence, and explain how differences in virulence-associated factors between historical and newly emerging strains might explain the hypervirulence exhibited by this pathogen during the past decade.
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21
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Abstract
Clostridium difficile infections (CDI) have emerged as a major cause of healthcare associated disease, and recent epidemiological evidence also suggests an important role in community-acquired diarrhea. This increase is associated with specific types, especially PCR ribotypes 027 and 078, which are sometimes referred to as “hypervirulent”. Over the past years major advances have been made in our understanding of C. difficile pathogenicity, with the identification and characterization of the major clostridial toxins TcdA and TcdB. However, the relation between the toxins, their regulation, and “hypervirulence” remain unclear. Here I review our current understanding of C. difficile pathogenicity and argue that “hypervirulent” is an inadequate term to describe PCR ribotypes 027 and 078, that the ability of C. difficile to cause problematic infections is a consequence of a multifactorial process that extends beyond toxins, sporulation, and antimicrobial resistance, and that vigilance is in order toward types that are closely related to ribotypes 027 and 078, but are currently not considered problematic.
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Affiliation(s)
- Wiep Klaas Smits
- Department of Medical Microbiology; Leiden University Medical Center; Leiden, the Netherlands
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22
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Puri AW, Bogyo M. Applications of small molecule probes in dissecting mechanisms of bacterial virulence and host responses. Biochemistry 2013; 52:5985-96. [PMID: 23937332 DOI: 10.1021/bi400854d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Elucidating the molecular and biochemical details of bacterial infections can be challenging because of the many complex interactions that exist between a pathogen and its host. Consequently, many tools have been developed to aid the study of bacterial pathogenesis. Small molecules are a valuable complement to traditional genetic techniques because they can be used to rapidly perturb genetically intractable systems and to monitor post-translationally regulated processes. Activity-based probes are a subset of small molecules that covalently label an enzyme of interest based on its catalytic mechanism. These tools allow monitoring of enzyme activation within the context of a native biological system and can be used to dissect the biochemical details of enzyme function. This review describes the development and application of activity-based probes for examining aspects of bacterial infection on both sides of the host-pathogen interface.
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Affiliation(s)
- Aaron W Puri
- Department of Chemical and Systems Biology, ‡Department of Microbiology and Immunology, and §Department of Pathology, Stanford University School of Medicine , 300 Pasteur Drive, Stanford, California 94305, United States
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23
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Lanis JM, Heinlen LD, James JA, Ballard JD. Clostridium difficile 027/BI/NAP1 encodes a hypertoxic and antigenically variable form of TcdB. PLoS Pathog 2013; 9:e1003523. [PMID: 23935501 PMCID: PMC3731247 DOI: 10.1371/journal.ppat.1003523] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 06/11/2013] [Indexed: 12/18/2022] Open
Abstract
The Clostridium difficile exotoxin, TcdB, which is a major virulence factor, varies between strains of this pathogen. Herein, we show that TcdB from the epidemic BI/NAP1/027 strain of C. difficile is more lethal, causes more extensive brain hemorrhage, and is antigenically variable from TcdB produced by previously studied strains of this pathogen (TcdB003). In mouse intoxication assays, TcdB from a ribotype 027 strain (TcdB027) was at least four fold more lethal than TcdB003. TcdB027 caused a previously undescribed brain hemorrhage in mice and this correlated with a heightened sensitivity of brain microvascular endothelial cells to the toxin. TcdB003 and TcdB027 also differed in their antigenic profiles and did not share cross-neutralizing epitopes in a major immunogenic region of the protein. Solid phase humoral mapping of epitopes in the carboxy-terminal domains (CTD) of TcdB027 and TcdB003 identified 11 reactive epitopes that varied between the two forms of TcdB, and 13 epitopes that were shared or overlapping. Despite the epitope differences and absence of neutralizing epitopes in the CTD of TcdB027, a toxoid form of this toxin primed a strong protective response. These findings indicate TcdB027 is a more potent toxin than TcdB003 as measured by lethality assays and pathology, moreover the sequence differences between the two forms of TcdB alter antigenic epitopes and reduce cross-neutralization by antibodies targeting the CTD. During the past decade, the C. difficile BI/NAP1/027 strain has emerged and in some settings predominated as the cause of C. difficile infection. Moreover, in some reports C. difficile BI/NAP1/027 has been associated with more severe disease. The reasons for association of this strain with more severe disease and relapse are poorly understood. We compared the toxicity and antigenic profiles of the major C. difficile virulence factor, TcdB, from a previously studied reference strain and a BI/NAP1/027 strain. The results indicate TcdB027, the toxin from the BI/NAP1/027 strain, is more lethal and causes more extensive brain hemorrhaging than TcdB003, the toxin produced by a reference strain of C. difficile. Furthermore, the results show that the antigenic carboxy-terminal domain (CTD) encodes at least 11 epitopes that differ between the two forms of TcdB. In line with this, experiments demonstrate that antiserum against the CTD does not cross-neutralize TcdB003 and TcdB027 toxicity against CHO cells, and TcdB027 appears to be devoid of neutralizing epitopes in this domain. These findings indicate differences in TcdB003 and TcdB027 contribute to increased virulence of C. difficile BI/NAP1/027 and reduce the likelihood of acquired immunity providing cross-protection against infection by these strains.
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Affiliation(s)
- Jordi M. Lanis
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Latisha D. Heinlen
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- Department of Medicine, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Judith A. James
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- Department of Medicine, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States of America
| | - Jimmy D. Ballard
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- * E-mail:
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24
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Using phenotype microarrays to determine culture conditions that induce or repress toxin production by Clostridium difficile and other microorganisms. PLoS One 2013; 8:e56545. [PMID: 23437164 PMCID: PMC3577869 DOI: 10.1371/journal.pone.0056545] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 01/11/2013] [Indexed: 12/18/2022] Open
Abstract
Toxin production is a central issue in the pathogenesis of Clostridium difficile and many other pathogenic microorganisms. Toxin synthesis is influenced by a variety of known and unknown factors of genetics, physiology, and environment. To facilitate the study of toxin production by C. difficile, we have developed a new, reliable, quantitative, and robust cell-based cytotoxicity assay. Then we combined this new assay with Phenotype MicroArrays (PM) technology which provides high throughput testing of culture conditions. This allowed us to quantitatively measure toxin production by C. difficile type strain ATCC 9689 under 768 culture conditions. The culture conditions include different carbon, nitrogen, phosphorus, and sulfur sources. Among these, 89 conditions produced strong toxin induction and 31 produced strong toxin repression. Strong toxin inducers included adenine, guanosine, arginine dipeptides, γ-D-Glu-Gly, methylamine, and others. Some leucine dipeptides and the triple-leucine tripeptide were among the strongest toxin repressors. While some results are consistent with previous observations, others are new observations that provide insights into toxin regulation and pathogenesis of C. difficile. Additionally, we have demonstrated that this combined assay technology can be applied broadly to a wide range of toxin producing microorganisms. This study is the first demonstration of simultaneous assessment of a large number of culture conditions influencing bacterial toxin production. The new functional cytotoxin quantitation method developed provides a valuable tool for studying toxigenic microorganisms and may also find applications in clinical and epidemiological research.
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25
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Clostridium difficile in foods and animals: history and measures to reduce exposure. Anim Health Res Rev 2013; 14:11-29. [PMID: 23324529 DOI: 10.1017/s1466252312000229] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Many articles have summarized the changing epidemiology of Clostridium difficile infections (CDI) in humans, but the emerging presence of C. difficile in foods and animals and possible measures to reduce human exposure to this important pathogen have been infrequently addressed. CDIs have traditionally been assumed to be restricted to health-care settings. However, recent molecular studies indicate that this is no longer the case; animals and foods might be involved in the changing epidemiology of CDIs in humans; and genome sequencing is disproving person-to-person transmission in hospitals. Although zoonotic and foodborne transmission have not been confirmed, it is evident that susceptible people can be inadvertently exposed to C. difficile from foods, animals, or their environment. Strains of epidemic clones present in humans are common in companion and food animals, raw meats, poultry products, vegetables, and ready-to-eat foods, including salads. In order to develop science-based prevention strategies, it is critical to understand how C. difficile reaches foods and humans. This review contextualizes the current understanding of CDIs in humans, animals, and foods. Based on available information, we propose a list of educational measures that could reduce the exposure of susceptible people to C. difficile. Enhanced educational efforts and behavior change targeting medical and non-medical personnel are needed.
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26
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Li S, Shi L, Yang Z, Feng H. Cytotoxicity of Clostridium difficile toxin B does not require cysteine protease-mediated autocleavage and release of the glucosyltransferase domain into the host cell cytosol. Pathog Dis 2013; 67:11-8. [PMID: 23620115 DOI: 10.1111/2049-632x.12016] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 11/26/2012] [Accepted: 11/29/2012] [Indexed: 01/05/2023] Open
Abstract
Clostridium difficile virulence requires secretion of two exotoxins: TcdA and TcdB. The precise mechanism of toxin uptake and delivery is undefined, but current models predict that the cysteine protease domain (CPD)-mediated autocleavage and release of glucosyltransferase domain (GTD) are crucial for intoxication. To determine the importance of CPD-mediated cleavage to TcdB cytotoxicity, we generated two mutant toxins--TcdB-C698S and TcdB-H653A--and assayed their abilities to intoxicate cells. The CPD mutants include an intact GTD but lack the cysteine protease activity. The mutants had reduced potency in that their effect on cells was delayed and required higher concentrations than wild-type TcdB. They did eventually cause cell rounding, glucosylation of Rho GTPases, and apoptosis that was indistinguishable from that caused by TcdB. Although the mutant toxins caused a complete cell rounding, they failed to release their GTD into cytosol, whereas wild-type TcdB displayed significant autocleavage and release of GTD. We conclude that the cysteine protease-mediated autocleavage and release of GTD is not a prerequisite for the cytotoxic activity of TcdB, but rather limits the potency and speed of Rho GTPase glucosylation. Our findings revise and refine the current model for the mode of the action and cellular trafficking of TcdB.
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Affiliation(s)
- Shan Li
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, MD 21201, USA
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Chumbler NM, Farrow MA, Lapierre LA, Franklin JL, Haslam D, Goldenring JR, Lacy DB. Clostridium difficile Toxin B causes epithelial cell necrosis through an autoprocessing-independent mechanism. PLoS Pathog 2012; 8:e1003072. [PMID: 23236283 PMCID: PMC3516567 DOI: 10.1371/journal.ppat.1003072] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 10/22/2012] [Indexed: 01/21/2023] Open
Abstract
Clostridium difficile is the most common cause of antibiotic-associated nosocomial infection in the United States. C. difficile secretes two homologous toxins, TcdA and TcdB, which are responsible for the symptoms of C. difficile associated disease. The mechanism of toxin action includes an autoprocessing event where a cysteine protease domain (CPD) releases a glucosyltransferase domain (GTD) into the cytosol. The GTD acts to modify and inactivate Rho-family GTPases. The presumed importance of autoprocessing in toxicity, and the apparent specificity of the CPD active site make it, potentially, an attractive target for small molecule drug discovery. In the course of exploring this potential, we have discovered that both wild-type TcdB and TcdB mutants with impaired autoprocessing or glucosyltransferase activities are able to induce rapid, necrotic cell death in HeLa and Caco-2 epithelial cell lines. The concentrations required to induce this phenotype correlate with pathology in a porcine colonic explant model of epithelial damage. We conclude that autoprocessing and GTD release is not required for epithelial cell necrosis and that targeting the autoprocessing activity of TcdB for the development of novel therapeutics will not prevent the colonic tissue damage that occurs in C. difficile – associated disease. Clostridium difficile is an anaerobic spore-forming bacterium that infects the human colon and causes diarrhea, pseudomembranous colitis, and toxic megacolon. Most people that develop disease symptoms have undergone antibiotic treatment, which alters the normal gut flora and allows C. difficile to flourish. C. difficile secretes two toxins, TcdA and TcdB, that are responsible for the fluid secretion, inflammation, and colonic tissue damage associated with disease. The emergence of hypervirulent strains of C. difficile that are linked to increased morbidity and mortality highlights the need for new therapeutic strategies. One strategy is to inhibit the function of the toxins, thereby decreasing damage to the colon while the patient clears the infection with antibiotics. Toxin function is thought to depend on an autoprocessing event that releases a catalytic ‘effector’ portion of the toxin into the host cell. In the course of trying to identify small molecules that would inhibit such a function, we found that TcdB induces a rapid necrosis in epithelial cells that is not dependent on autoprocessing. The physiological relevance of this observation is confirmed in colonic explants and suggests that inhibiting TcdB autoprocessing will not prevent the colonic tissue damage observed in C. difficile associated diseases.
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Affiliation(s)
- Nicole M. Chumbler
- Chemical and Physical Biology Program, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Melissa A. Farrow
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Lynne A. Lapierre
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Jeffrey L. Franklin
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Cell and Developmental Biology and the Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - David Haslam
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - James R. Goldenring
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Cell and Developmental Biology and the Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - D. Borden Lacy
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail:
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Swett R, Cisneros GA, Feig AL. Conformational analysis of Clostridium difficile toxin B and its implications for substrate recognition. PLoS One 2012; 7:e41518. [PMID: 22844485 PMCID: PMC3402401 DOI: 10.1371/journal.pone.0041518] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 06/21/2012] [Indexed: 01/02/2023] Open
Abstract
Clostridium difficile (C. difficile) is an opportunistic pathogen that can cause potentially lethal hospital-acquired infections. The cellular damage that it causes is the result of two large clostridial cytotoxins: TcdA and TcdB which act by glucosylating cytosolic G-proteins, mis-regulation of which induces apoptosis. TcdB is a large flexible protein that appears to undergo significant structural rearrangement upon accommodation of its substrates: UDP-glucose and a Rho-family GTPase. To characterize the conformational space of TcdB, we applied normal mode and hinge-region analysis, followed by long-timescale unbiased molecular dynamics. In order to examine the TcdB and RhoA interaction, macromolecular docking and simulation of the TcdB/RhoA complex was performed. Generalized Masked Delaunay analysis of the simulations determined the extent of significant motions. This combination of methods elucidated a wide range of motions within TcdB that are reiterated in both the low-cost normal mode analysis and the extensive MD simulation. Of particular interest are the coupled motions between a peripheral 4-helix bundle and a small loop in the active site that must rearrange to allow RhoA entry to the catalytic site. These extensive coupled motions are indicative of TcdB using a conformational capture mechanism for substrate accommodation.
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Affiliation(s)
- Rebecca Swett
- Department of Chemistry, Wayne State University, Detroit, Michigan, United States of America
| | - G. Andrés Cisneros
- Department of Chemistry, Wayne State University, Detroit, Michigan, United States of America
| | - Andrew L. Feig
- Department of Chemistry, Wayne State University, Detroit, Michigan, United States of America
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