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Tamaki Y, Harakuni T, Arakawa T. Shiga toxin type 2 B subunit protects mice against toxin challenge when leashed and bundled by a stable pentameric coiled-coil molecule. Vaccine 2024; 42:1757-1767. [PMID: 38365487 DOI: 10.1016/j.vaccine.2024.01.102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 11/27/2023] [Accepted: 01/30/2024] [Indexed: 02/18/2024]
Abstract
Vaccines against Shiga toxin (Stx)-producing Escherichia coli (STEC) have not yet been developed. Two immunologically distinct serotypes of Stx (Stx1 and Stx2) are the main virulence factors of STEC. Thus, blocking their B subunits (StxB) from binding to the cell surface receptor globotriaosylceramide (Gb3) efficiently prevents the action of these toxins. We expressed Stx1B and Stx2B in E. coli inclusion bodies and reassembled them into pentamers by a stepwise dialysis. Stx1B pentamer fully protected mice against Stx1 challenge, but Stx2B pentamer failed to protect mice against Stx2 challenge. To explain those observations, we proposed that the pentamer of Stx2B readily dissociates into its constituent monomers, especially under in vivo conditions, thus being unable to induce pentamer-specific immunity. To increase pentamer stability, we fused the B subunit to a pentameric coiled-coil domain of the cartilage oligomeric matrix protein (COMP). This "five-to-five" fusion hybrid molecule (Stx2B-COMP) was shown to be protective against Stx2 challenge, demonstrating that the Stx2B subunit when leashed and bundled by a rigid pentameric coiled-coil domain mount a pentamer-specific immune response and efficiently neutralize the toxin both in vitro and in vivo. Our data strongly suggest that the Stx2B subunit moiety fluctuates between a pentameric and monomeric state within the fusion protein, which may increase the likelihood of the immune system recognizing the pentameric conformation for toxin neutralization.
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Affiliation(s)
- Yukihiro Tamaki
- Laboratory of Vaccine Research and Development, Center of Molecular Biosciences, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
| | - Tetsuya Harakuni
- Laboratory of Vaccine Research and Development, Center of Molecular Biosciences, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
| | - Takeshi Arakawa
- Laboratory of Vaccine Research and Development, Center of Molecular Biosciences, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
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2
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Fagerquist CK, Shi Y, Park J. Unusual modifications of protein biomarkers expressed by plasmid, prophage, and bacterial host of pathogenic Escherichia coli identified using top-down proteomic analysis. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2024; 38:e9667. [PMID: 38073204 DOI: 10.1002/rcm.9667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 10/04/2023] [Accepted: 10/05/2023] [Indexed: 12/18/2023]
Abstract
RATIONALE Pathogenic bacteria often carry prophage (bacterial viruses) and plasmids (small circular pieces of DNA) that may harbor toxin, antibacterial, and antibiotic resistance genes. Proteomic characterization of pathogenic bacteria should include the identification of host proteins and proteins produced by prophage and plasmid genomes. METHODS Protein biomarkers of two strains of Shiga toxin-producing Escherichia coli (STEC) were identified using antibiotic induction, matrix-assisted laser desorption/ionization tandem time-of-flight (MALDI-TOF-TOF) tandem mass spectrometry (MS/MS) with post-source decay (PSD), top-down proteomic (TDP) analysis, and plasmid sequencing. Alphafold2 was also used to compare predicted in silico structures of the identified proteins to prominent fragment ions generated using MS/MS-PSD. Strain samples were also analyzed with and without chemical reduction treatment to detect the attachment of pendant groups bound by thioester or disulfide bonds. RESULTS Shiga toxin was detected and/or identified in both STEC strains. For the first time, we also identified the osmotically inducible protein (OsmY) whose sequence unexpectedly had two forms: a full and a truncated sequence. The truncated OsmY terminates in the middle of an α-helix as determined by Alphafold2. A plasmid-encoded colicin immunity protein was also identified with and without attachment of an unidentified cysteine-bound pendant group (~307 Da). Plasmid sequencing confirmed top-down analysis and the identification of a promoter upstream of the immunity gene that is activated by antibiotic induction, that is, SOS box. CONCLUSIONS TDP analysis, coupled with other techniques (e.g., antibiotic induction, chemical reduction, plasmid sequencing, and in silico protein modeling), is a powerful tool to identify proteins (and their modifications), including prophage- and plasmid-encoded proteins, produced by pathogenic microorganisms.
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Affiliation(s)
- Clifton K Fagerquist
- Produce Safety and Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service, US Department of Agriculture, Albany, California, USA
| | - Yanlin Shi
- Produce Safety and Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service, US Department of Agriculture, Albany, California, USA
| | - Jihyun Park
- Produce Safety and Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service, US Department of Agriculture, Albany, California, USA
- Oak Ridge Institute for Science and Education, US Department of Energy, Oak Ridge, Tennessee, USA
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Pasupuleti R, Riedl S, Saltor Núñez L, Karava M, Kumar V, Kourist R, Turnbull WB, Zweytick D, Wiltschi B. Lectin-anticancer peptide fusion demonstrates a significant cancer-cell-selective cytotoxic effect and inspires the production of "clickable" anticancer peptide in Escherichia coli. Protein Sci 2023; 32:e4830. [PMID: 37916438 PMCID: PMC10682692 DOI: 10.1002/pro.4830] [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: 07/13/2023] [Revised: 10/30/2023] [Accepted: 10/31/2023] [Indexed: 11/03/2023]
Abstract
Targeted killing of tumor cells while protecting healthy cells is the pressing priority in cancer treatment. Lectins that target a specific glycan marker abundant in cancer cells can be valuable new tools for selective cancer cell killing. The lectin Shiga-like toxin 1 B subunit (Stx1B) is an example that specifically binds globotriaosylceramide (CD77 or Gb3), which is overexpressed in certain cancers. In this study, a human lactoferricin-derived synthetic retro di-peptide R-DIM-P-LF11-215 with antitumor efficacy was fused to the lectin Stx1B to selectively target and kill Gb3+ cancer cells. We produced lectin-peptide fusion proteins in Escherichia coli, isolated them by Gb3-affinity chromatography, and assessed their ability to selectively kill Gb3+ cancer cells in a Calcein AM assay. Furthermore, to expand the applications of R-DIM-P-LF11-215 in developing therapeutic bioconjugates, we labeled R-DIM-P-LF11-215 with the unique reactive non-canonical amino acid Nε -((2-azidoethoxy)carbonyl)-L-lysine (AzK) at a selected position by amber stop codon suppression. The R-DIM-P-LF11-215 20AzK and the unlabeled R-DIM-P-LF11-215 parent peptide were produced as GST-fusion proteins for soluble expression in E. coli for the first time. We purified both variants by size-exclusion chromatography and analyzed their peptide masses. Finally, a cyanin 3 fluorophore was covalently conjugated to R-DIM-P-LF11-215 20AzK by strain-promoted alkyne-azide cycloaddition. Our results showed that the recombinant lectin-peptide fusion R-DIM-P-LF11-215-Stx1B killed >99% Gb3+ HeLa cells while Gb3-negative cells were unaffected. The peptides R-DIM-P-LF11-215 and R-DIM-P-LF11-215 20AzK were produced recombinantly in E. coli in satisfactory amounts and were tested functional by cytotoxicity and cell-binding assays, respectively.
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Affiliation(s)
- Rajeev Pasupuleti
- acib ‐ Austrian Centre of Industrial BiotechnologyGrazAustria
- Institute of Molecular BiotechnologyGraz University of TechnologyGrazAustria
| | - Sabrina Riedl
- Institute of Molecular Biosciences, Biophysics DivisionUniversity of GrazGrazAustria
- BioHealthUniversity of GrazGrazAustria
- BioTechMed‐GrazGrazAustria
| | - Laia Saltor Núñez
- School of Chemistry and Astbury Centre for Structural Molecular BiologyUniversity of LeedsLeedsUK
| | - Marianna Karava
- Institute of Molecular BiotechnologyGraz University of TechnologyGrazAustria
| | - Vajinder Kumar
- School of Chemistry and Astbury Centre for Structural Molecular BiologyUniversity of LeedsLeedsUK
| | - Robert Kourist
- Institute of Molecular BiotechnologyGraz University of TechnologyGrazAustria
| | - W. Bruce Turnbull
- School of Chemistry and Astbury Centre for Structural Molecular BiologyUniversity of LeedsLeedsUK
| | - Dagmar Zweytick
- Institute of Molecular Biosciences, Biophysics DivisionUniversity of GrazGrazAustria
- BioHealthUniversity of GrazGrazAustria
- BioTechMed‐GrazGrazAustria
| | - Birgit Wiltschi
- acib ‐ Austrian Centre of Industrial BiotechnologyGrazAustria
- Institute of Molecular BiotechnologyGraz University of TechnologyGrazAustria
- BioTechMed‐GrazGrazAustria
- Institute of Bioprocess Science and Engineering, Department of BiotechnologyUniversity of Natural Resources and Life SciencesViennaAustria
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Heinisch L, Krause M, Roth A, Barth H, Schmidt H. Cytotoxic Effects of Recombinant StxA2-His in the Absence of Its Corresponding B-Subunit. Toxins (Basel) 2021; 13:toxins13050307. [PMID: 33925951 PMCID: PMC8145687 DOI: 10.3390/toxins13050307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/22/2021] [Accepted: 04/23/2021] [Indexed: 11/16/2022] Open
Abstract
AB5 protein toxins are produced by certain bacterial pathogens and are composed of an enzymatically active A-subunit and a B-subunit pentamer, the latter being responsible for cell receptor recognition, cellular uptake, and transport of the A-subunit into the cytosol of eukaryotic target cells. Two members of the AB5 toxin family were described in Shiga toxin-producing Escherichia coli (STEC), namely Shiga toxin (Stx) and subtilase cytotoxin (SubAB). The functional paradigm of AB toxins includes the B-subunit being mandatory for the uptake of the toxin into its target cells. Recent studies have shown that this paradigm cannot be maintained for SubAB, since SubA alone was demonstrated to intoxicate human epithelial cells in vitro. In the current study, we raised the hypothesis that this may also be true for the A-subunit of the most clinically relevant Stx-variant, Stx2a. After separate expression and purification, the recombinant Stx2a subunits StxA2a-His and StxB2a-His were applied either alone or in combination in a 1:5 molar ratio to Vero B4, HeLa, and HCT-116 cells. For all cell lines, a cytotoxic effect of StxA2a-His alone was detected. Competition experiments with Stx and SubAB subunits in combination revealed that the intoxication of StxA2a-His was reduced by addition of SubB1-His. This study showed that the enzymatic subunit StxA2a alone was active on different cells and might therefore play a yet unknown role in STEC disease development.
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Affiliation(s)
- Laura Heinisch
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (L.H.); (M.K.); (A.R.)
| | - Maike Krause
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (L.H.); (M.K.); (A.R.)
| | - Astrid Roth
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (L.H.); (M.K.); (A.R.)
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany;
| | - Herbert Schmidt
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (L.H.); (M.K.); (A.R.)
- Correspondence: ; Tel.: +49-711-459-22305
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Sadri Najafabadi Z, Nazarian S, Kargar M, Kafilzadeh F. Designing of a chimeric protein contains StxB, intimin and EscC against toxicity and adherence of enterohemorrhagic Escherichia coli O157:H7 and evaluation of serum antibody titers against it. Mol Immunol 2021; 134:218-227. [PMID: 33823320 DOI: 10.1016/j.molimm.2021.03.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 02/08/2021] [Accepted: 03/15/2021] [Indexed: 10/21/2022]
Abstract
Enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain is known as one of the major human foodborne pathogens. Lack of effective clinical treatment for human diarrheal diseases confirms the need for vaccine production against enteric bacteria such as E.coli O157:H7. Shiga-like toxin (Stx), EscC, and Intimin are the main important virulent factors of this enteric pathogen. In the present study, a comparative Omics analysis was conducted to identify most invasion EHEC antigenic factors as a potential immunogen. SEI (Stx-EscC-Intimin) trivalent chimeric protein was designed from the exposed and epitope rich part of these virulence factors. Sequence optimization, physicochemical properties, mRNA folding, three-dimensional structure and immunoinformatics data were investigated. The chimeric gene was synthesized with codon bias of E. coli. Recombinant protein was expressed and confirmed by western blot analysis. To evaluate the immunogenicity of the designed protein, the protein was administered to BALB/c mice and the serum IgG was determined by ELISA. Based on the Ramachandran plot, the validation data showed that 90.1 % of residues lie in the favored region. The high antigenicity of the multimeric protein was predicted by the immunoinformatic analysis. Epitope prediction had shown the proper distribution of linear and conformational B-cell epitopes and the competition of T-cell epitopes to bind MHC molecules too. Recombinant ESI Protein with 74.5 kDa was expressed in E. coli. Western blot analysis by anti-Stx antibody, confirmed a single band of chimeric protein. Consequently, the chimeric gene was designed and constructed after assessments. From in silico approach, the protein deduced from this cassette can be an immunogen candidate, and act against toxicity and adherence of EHEC.
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Affiliation(s)
| | - Shahram Nazarian
- Department of Biological Sciences, Faculty of Science, Imam Hossein University, Tehran, Iran.
| | - Mohammad Kargar
- Department of Microbiology, Jahrom Branch, Islamic Azad University, Jahrom, Iran
| | - Farshid Kafilzadeh
- Department of Biology, Jahrom Branch, Islamic Azad University, Jahrom, Iran
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Lingwood C. Verotoxin Receptor-Based Pathology and Therapies. Front Cell Infect Microbiol 2020; 10:123. [PMID: 32296648 PMCID: PMC7136409 DOI: 10.3389/fcimb.2020.00123] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 03/05/2020] [Indexed: 12/22/2022] Open
Abstract
Verotoxin, VT (aka Shiga toxin,Stx) is produced by enterohemorrhagic E. coli (EHEC) and is the key pathogenic factor in EHEC-induced hemolytic uremic syndrome (eHUS-hemolytic anemia/thrombocytopenia/glomerular infarct) which can follow gastrointestinal EHEC infection, particularly in children. This AB5 subunit toxin family bind target cell globotriaosyl ceramide (Gb3), a glycosphingolipid (GSL) (aka CD77, pk blood group antigen) of the globoseries of neutral GSLs, initiating lipid raft-dependent plasma membrane Gb3 clustering, membrane curvature, invagination, scission, endosomal trafficking, and retrograde traffic via the TGN to the Golgi, and ER. In the ER, A/B subunits separate and the A subunit hijacks the ER reverse translocon (dislocon-used to eliminate misfolded proteins-ER associated degradation-ERAD) for cytosolic access. This property has been used to devise toxoid-based therapy to temporarily block ERAD and rescue the mutant phenotype of several genetic protein misfolding diseases. The A subunit avoids cytosolic proteosomal degradation, to block protein synthesis via its RNA glycanase activity. In humans, Gb3 is primarily expressed in the kidney, particularly in the glomerular endothelial cells. Here, Gb3 is in lipid rafts (more ordered membrane domains which accumulate GSLs/cholesterol) whereas renal tubular Gb3 is in the non-raft membrane fraction, explaining the basic pathology of eHUS (glomerular endothelial infarct). Females are more susceptible and this correlates with higher renal Gb3 expression. HUS can be associated with encephalopathy, more commonly following verotoxin 2 exposure. Gb3 is expressed in the microvasculature of the brain. All members of the VT family bind Gb3, but with varying affinity. VT2e (pig edema toxin) binds Gb4 preferentially. Verotoxin-specific therapeutics based on chemical analogs of Gb3, though effective in vitro, have failed in vivo. While some analogs are effective in animal models, there are no good rodent models of eHUS since Gb3 is not expressed in rodent glomeruli. However, the mouse mimics the neurological symptoms more closely and provides an excellent tool to assess therapeutics. In addition to direct cytotoxicity, other factors including VT–induced cytokine release and aberrant complement cascade, are now appreciated as important in eHUS. Based on atypical HUS therapy, treatment of eHUS patients with anticomplement antibodies has proven effective in some cases. A recent switch using stem cells to try to reverse, rather than prevent VT induced pathology may prove a more effective methodology.
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Affiliation(s)
- Clifford Lingwood
- Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto, ON, Canada
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7
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Silva CJ. Food Forensics: Using Mass Spectrometry To Detect Foodborne Protein Contaminants, as Exemplified by Shiga Toxin Variants and Prion Strains. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:8435-8450. [PMID: 29860833 DOI: 10.1021/acs.jafc.8b01517] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Food forensicists need a variety of tools to detect the many possible food contaminants. As a result of its analytical flexibility, mass spectrometry is one of those tools. Use of the multiple reaction monitoring (MRM) method expands its use to quantitation as well as detection of infectious proteins (prions) and protein toxins, such as Shiga toxins. The sample processing steps inactivate prions and Shiga toxins; the proteins are digested with proteases to yield peptides suitable for MRM-based analysis. Prions are detected by their distinct physicochemical properties and differential covalent modification. Shiga toxin analysis is based on detecting peptides derived from the five identical binding B subunits comprising the toxin. 15N-labeled internal standards are prepared from cloned proteins. These examples illustrate the power of MRM, in that the same instrument can be used to safely detect and quantitate protein toxins, prions, and small molecules that might contaminate our food.
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Affiliation(s)
- Christopher J Silva
- Produce Safety and Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service , United States Department of Agriculture , Albany , California 94710 , United States
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8
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AB5 Preassembly Is Not Required for Shiga Toxin Activity. J Bacteriol 2016; 198:1621-1630. [PMID: 27002129 DOI: 10.1128/jb.00918-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 03/15/2016] [Indexed: 01/19/2023] Open
Abstract
UNLABELLED Shiga toxin (Stx)-producing Escherichia coli (STEC) is a major cause of foodborne illness, including the life-threatening complication hemolytic-uremic syndrome. The German outbreak in 2011 resulted in nearly 4,000 cases of infection, with 54 deaths. Two forms of Stx, Stx1 and Stx2, differ in potency, and subtype Stx2a is most commonly associated with fatal human disease. Stx is considered to be an AB5 toxin. The single A (enzymatically active) subunit inhibits protein synthesis by cleaving a catalytic adenine from the eukaryotic rRNA. The B (binding) subunit forms a homopentamer and mediates cellular association and toxin internalization by binding to the glycolipid globotriaosylceramide (Gb3). Both subunits are essential for toxicity. Here we report that unlike other AB5 toxin family members, Stx is produced by STEC as unassembled A and B subunits. A preformed AB5 complex is not required for cellular toxicity or in vivo toxicity to mice, and toxin assembly likely occurs at the cell membrane. We demonstrate that disruption of A- and B-subunit association by use of A-subunit peptides that lack enzymatic activity can protect mice from lethal doses of toxin. Currently, no treatments have been proven to be effective for hemolytic-uremic syndrome. Our studies demonstrate that agents that interfere with A- and B-subunit assembly may have therapeutic potential. Shiga toxin (Stx) produced by pathogenic Escherichia coli is considered to be an AB5 heterohexamer; however, no known mechanisms ensure AB5 assembly. Stx released by E. coli is not in the AB5 conformation and assembles at the receptor interface. Thus, unassembled Stx can impart toxicity. This finding shows that preventing AB5 assembly is a potential treatment for Stx-associated illnesses. IMPORTANCE Complications due to Shiga toxin are frequently fatal, and at present, supportive care is the only treatment option. Furthermore, antibiotic treatment is contraindicated due to the ability of antibiotics to amplify bacterial expression of Shiga toxin. We report, contrary to prevailing assumptions, that Shiga toxin produced by STEC circulates as unassembled A and B subunits at concentrations that are lethal to mice. Similar to the case for anthrax toxin, assembly occurs on receptors expressed on the surfaces of mammalian target cells. Disruption of Shiga toxin assembly by use of A-subunit peptides that lack enzymatic activity protects mice from lethal challenge with Shiga toxin, suggesting a new approach for development of therapeutics.
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Shiga Toxins as Multi-Functional Proteins: Induction of Host Cellular Stress Responses, Role in Pathogenesis and Therapeutic Applications. Toxins (Basel) 2016; 8:toxins8030077. [PMID: 26999205 PMCID: PMC4810222 DOI: 10.3390/toxins8030077] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 02/25/2016] [Accepted: 02/29/2016] [Indexed: 12/17/2022] Open
Abstract
Shiga toxins (Stxs) produced by Shiga toxin-producing bacteria Shigella dysenteriae serotype 1 and select serotypes of Escherichia coli are primary virulence factors in the pathogenesis of hemorrhagic colitis progressing to potentially fatal systemic complications, such as hemolytic uremic syndrome and central nervous system abnormalities. Current therapeutic options to treat patients infected with toxin-producing bacteria are limited. The structures of Stxs, toxin-receptor binding, intracellular transport and the mode of action of the toxins have been well defined. However, in the last decade, numerous studies have demonstrated that in addition to being potent protein synthesis inhibitors, Stxs are also multifunctional proteins capable of activating multiple cell stress signaling pathways, which may result in apoptosis, autophagy or activation of the innate immune response. Here, we briefly present the current understanding of Stx-activated signaling pathways and provide a concise review of therapeutic applications to target tumors by engineering the toxins.
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10
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Silva CJ, Erickson-Beltran ML, Skinner CB, Patfield SA, He X. Mass Spectrometry-Based Method of Detecting and Distinguishing Type 1 and Type 2 Shiga-Like Toxins in Human Serum. Toxins (Basel) 2015; 7:5236-53. [PMID: 26633510 PMCID: PMC4690125 DOI: 10.3390/toxins7124875] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 10/28/2015] [Accepted: 11/09/2015] [Indexed: 01/18/2023] Open
Abstract
Shiga-like toxins (verotoxins) are responsible for the virulence associated with a variety of foodborne bacterial pathogens. Direct detection of toxins requires a specific and sensitive technique. In this study, we describe a mass spectrometry-based method of analyzing the tryptic decapeptides derived from the non-toxic B subunits. A gene encoding a single protein that yields a set of relevant peptides upon digestion with trypsin was designed. The (15)N-labeled protein was prepared by growing the expressing bacteria in minimal medium supplemented with (15)NH₄Cl. Trypsin digestion of the (15)N-labeled protein yields a set of (15)N-labeled peptides for use as internal standards to identify and quantify Shiga or Shiga-like toxins. We determined that this approach can be used to detect, quantify and distinguish among the known Shiga toxins (Stx) and Shiga-like toxins (Stx1 and Stx2) in the low attomole range (per injection) in complex media, including human serum. Furthermore, Stx1a could be detected and distinguished from the newly identified Stx1e in complex media. As new Shiga-like toxins are identified, this approach can be readily modified to detect them. Since intact toxins are digested with trypsin prior to analysis, the handling of intact Shiga toxins is minimized. The analysis can be accomplished within 5 h.
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Affiliation(s)
- Christopher J Silva
- Western Regional Research Center, United States Department of Agriculture, Albany, CA 94710, USA.
| | | | - Craig B Skinner
- Western Regional Research Center, United States Department of Agriculture, Albany, CA 94710, USA.
| | - Stephanie A Patfield
- Western Regional Research Center, United States Department of Agriculture, Albany, CA 94710, USA.
| | - Xiaohua He
- Western Regional Research Center, United States Department of Agriculture, Albany, CA 94710, USA.
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11
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Frey SL, Todd J, Wurtzler E, Strelez CR, Wendell D. A non-foaming proteosurfactant engineered from Ranaspumin-2. Colloids Surf B Biointerfaces 2015; 133:239-45. [PMID: 26117804 DOI: 10.1016/j.colsurfb.2015.05.043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 05/20/2015] [Accepted: 05/22/2015] [Indexed: 11/20/2022]
Abstract
Advances in biological surfactant proteins have already yielded a diverse range of benefits from dramatically improved survival rates for premature births to artificial photosynthesis. Presented here is the design, development, and analysis of a novel biosurfactant protein we call Surfactant Resisting Foam formatioN (SRFN). Starting with the Tungara frog's foam forming protein Ranaspumin-2, we have engineered a new surfactant protein with a destabilized hinge region to alter the kinetics and equilibrium of the protein structural transition from aqueous globular form to an extended surfactant structure at the air/water interface. SRFN is capable of approximately the same total surface tension reduction, but with the unique property of forming quickly collapsible foams. The difference in foam formation is attributed to the destabilizing glycine substitutions engineered into the hinge region. Surfactants used specifically to increase wettability, such as those used in agricultural applications would benefit from this new proteosurfactant since foamed liquid has greater wind resistance and decreased dispersal. Indeed, given growing concern of organsilicone surfactant effects on declining bee populations, biological surfactant proteins have several unique advantages over more common amphiphiles in that they can be renewably sourced, are environmentally friendly, degrade readily into non-toxic byproducts, and reduce surface tension without deleterious effects on cell membranes.
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Affiliation(s)
- Shelli L Frey
- Department of Chemistry, Gettysburg College, Gettysburg, PA 17325, United States
| | - Jacob Todd
- Department of Biomedical, Chemical and Environmental Engineering, Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221, United States
| | - Elizabeth Wurtzler
- Department of Biomedical, Chemical and Environmental Engineering, Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221, United States
| | - Carly R Strelez
- Department of Chemistry, Gettysburg College, Gettysburg, PA 17325, United States
| | - David Wendell
- Department of Biomedical, Chemical and Environmental Engineering, Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221, United States.
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12
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Kato T, Oizumi T, Ogata M, Murakawa A, Usui T, Park EY. Novel enzymatic synthesis of spacer-linked Pk trisaccharide targeting for neutralization of Shiga toxin. J Biotechnol 2015; 209:50-7. [DOI: 10.1016/j.jbiotec.2015.06.403] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 06/10/2015] [Accepted: 06/16/2015] [Indexed: 01/17/2023]
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Abstract
Shiga toxin (Stx) is one of the most potent bacterial toxins known. Stx is found in Shigella dysenteriae 1 and in some serogroups of Escherichia coli (called Stx1 in E. coli). In addition to or instead of Stx1, some E. coli strains produce a second type of Stx, Stx2, that has the same mode of action as Stx/Stx1 but is antigenically distinct. Because subtypes of each toxin have been identified, the prototype toxin for each group is now designated Stx1a or Stx2a. The Stxs consist of two major subunits, an A subunit that joins noncovalently to a pentamer of five identical B subunits. The A subunit of the toxin injures the eukaryotic ribosome and halts protein synthesis in target cells. The function of the B pentamer is to bind to the cellular receptor, globotriaosylceramide, Gb3, found primarily on endothelial cells. The Stxs traffic in a retrograde manner within the cell, such that the A subunit of the toxin reaches the cytosol only after the toxin moves from the endosome to the Golgi and then to the endoplasmic reticulum. In humans infected with Stx-producing E. coli, the most serious manifestation of the disease, hemolytic-uremic syndrome, is more often associated with strains that produce Stx2a rather than Stx1a, and that relative toxicity is replicated in mice and baboons. Stx1a and Stx2a also exhibit differences in cytotoxicity to various cell types, bind dissimilarly to receptor analogs or mimics, induce differential chemokine responses, and have several distinctive structural characteristics.
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Affiliation(s)
- Angela R. Melton-Celsa
- Department of Microbiology & Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814,
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14
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Karve SS, Weiss AA. Glycolipid binding preferences of Shiga toxin variants. PLoS One 2014; 9:e101173. [PMID: 24983355 PMCID: PMC4077739 DOI: 10.1371/journal.pone.0101173] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 06/03/2014] [Indexed: 11/18/2022] Open
Abstract
The major virulence factor of Shiga toxin producing E. coli, is Shiga toxin (Stx), an AB5 toxin that consists of a ribosomal RNA-cleaving A-subunit surrounded by a pentamer of receptor-binding B subunits. The two major isoforms, Stx1 and Stx2, and Stx2 variants (Stx2a-h) significantly differ in toxicity. The exact reason for this toxicity difference is unknown, however different receptor binding preferences are speculated to play a role. Previous studies used enzyme linked immunosorbent assay (ELISA) to study binding of Stx1 and Stx2a toxoids to glycolipid receptors. Here, we studied binding of holotoxin and B-subunits of Stx1, Stx2a, Stx2b, Stx2c and Stx2d to glycolipid receptors globotriaosylceramide (Gb3) and globotetraosylceramide (Gb4) in the presence of cell membrane components such as phosphatidylcholine (PC), cholesterol (Ch) and other neutral glycolipids. In the absence of PC and Ch, holotoxins of Stx2 variants bound to mixtures of Gb3 with other glycolipids but not to Gb3 or Gb4 alone. Binding of all Stx holotoxins significantly increased in the presence of PC and Ch. Previously, Stx2a has been shown to form a less stable B-pentamer compared to Stx1. However, its effect on glycolipid receptor binding is unknown. In this study, we showed that even in the absence of the A-subunit, the B-subunits of both Stx1 and Stx2a were able to bind to the glycolipids and the more stable B-pentamer formed by Stx1 bound better than the less stable pentamer of Stx2a. B-subunit mutant of Stx1 L41Q, which shows similar stability as Stx2a B-subunits, lacked glycolipid binding, suggesting that pentamerization is more critical for binding of Stx1 than Stx2a.
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Affiliation(s)
- Sayali S. Karve
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Alison A. Weiss
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, United States of America
- * E-mail:
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15
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Lassabe G, Rossotti M, González-Techera A, González-Sapienza G. Shiga-like toxin B subunit of Escherichia coli as scaffold for high-avidity display of anti-immunocomplex peptides. Anal Chem 2014; 86:5541-6. [PMID: 24797274 PMCID: PMC4045326 DOI: 10.1021/ac500926f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
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Small
compounds cannot bind simultaneously to two antibodies, and
thus, their immunodetection is limited to competitive formats in which
the analyte is indirectly quantitated by measuring the unoccupied
antibody binding sites using a competing reporter. This limitation
can be circumvented by using phage-borne peptides selected for their
ability to specifically react with the analyte–antibody immunocomplex,
which allows the detection of these small molecules in a noncompetitive
format (PHAIA) with increased sensitivity and a positive readout.
In an effort to find substitutes for the phage particles in PHAIA,
we explore the use of the B subunit of the Shiga-like toxin of Escherichia coli, also known as verotoxin (VTX),
as a scaffold for multivalent display of anti-immunocomplex peptides.
Using the herbicides molinate and clomazone as model compounds, we
built peptide–VTX recombinant chimeras that were produced in
the periplasmic space of E. coli as
soluble pentamers, as confirmed by multiangle light scattering analysis.
These multivalent constructs, which we termed nanopeptamers, were
conjugated to a tracer enzyme and used to detect the herbicide–antibody
complex in an ELISA format. The VTX–nanopeptamer assays performed
with over a 10-fold increased sensitivity and excellent recovery from
spiked surface and mineral water samples. The carbon black-labeled
peptide–VTX nanopeptamers showed great potential for the development
of a lateral-flow test for small molecules with a visual positive
readout that allowed the detection of up to 2.5 ng/mL of clomazone.
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Affiliation(s)
- Gabriel Lassabe
- Cátedra de Inmunología, Facultad de Química, Instituto de Higiene, UDELAR , Montevideo, Uruguay
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16
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Silva CJ, Erickson-Beltran ML, Skinner CB, Dynin I, Hui C, Patfield SA, Carter JM, He X. Safe and Effective Means of Detecting and Quantitating Shiga-Like Toxins in Attomole Amounts. Anal Chem 2014; 86:4698-706. [DOI: 10.1021/ac402930r] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Christopher J. Silva
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Melissa L. Erickson-Beltran
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Craig B. Skinner
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Irina Dynin
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Colleen Hui
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Stephanie A. Patfield
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - John Mark Carter
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Xiaohua He
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
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17
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A Poly-N-acetylglucosamine-Shiga toxin broad-spectrum conjugate vaccine for Shiga toxin-producing Escherichia coli. mBio 2014; 5:e00974-14. [PMID: 24667709 PMCID: PMC3977355 DOI: 10.1128/mbio.00974-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Many pathogens produce the β-(1-6)-linked poly-N-acetylglucosamine (PNAG) surface polysaccharide that is being developed as a broadly protective antimicrobial vaccine. However, it is unknown whether systemically injected PNAG vaccines or antibodies would provide protective immunity against pathogens confined to the gastrointestinal tract such as Shiga toxin (Stx)-producing Escherichia coli (STEC), an important group of gastrointestinal (GI) pathogens for which effective immunotherapeutics are lacking. To ascertain whether systemic IgG antibody to PNAG impacts this infectious situation, a vaccine consisting of a synthetic nonamer of nonacetylated PNAG, 9GlcNH2, conjugated to the Shiga toxin 1b subunit (9GlcNH2-Stx1b) was produced. Rabbit antibodies raised to the conjugate vaccine were tested for bacterial killing and toxin neutralization in vitro and protection against infection in infant mice. Cell surface PNAG was detected on all 9 STEC isolates tested, representing 6 STEC serogroups, including E. coli O157:H7. Antibody to the 9GlcNH2-Stx1b conjugate neutralized Stx1 potently and Stx2 modestly. For O157:H7 and O104:H4 STEC strains, antibodies elicited by the 9GlcNH2-Stx1b conjugate possessed opsonic killing and bactericidal activity. Following intraperitoneal injection, antibodies to both PNAG and Stx were needed for infant mouse protection against O157 STEC. These antibodies also mediated protection against the Stx2-producing O104:H4 strain that was the cause of a recent outbreak in Germany, although sufficient doses of antibody to PNAG alone were protective against this strain in infant mice. Our observations suggest that vaccination against both PNAG and Stx, using a construct such as the 9GlcNH2-Stx1b conjugate vaccine, would be protective against a broad range of STEC serogroups. IMPORTANCE The presence of poly-N-acetylglucosamine (PNAG) on many pathogens presents an opportunity to target this one structure with a multispecies vaccine. Whether antibodies to PNAG can protect against pathogens confined to the gastrointestinal tract is not known. As Shiga toxin (Stx)-producing Escherichia coli (STEC) bacteria are serious causes of infection whose virulence is dependent on elaboration of Stx, we prepared a vaccine containing a synthetic nonamer of PNAG (9GlcNH2) conjugated to Shiga toxin 1b subunit (9GlcNH2-Stx1b) to evaluate bacterial killing, toxin neutralization, and protective efficacy in infant mice. All nine (100%) clinical strains of STEC from different serogroups expressed PNAG. Vaccine-induced antibody mediated in vitro killing of STEC and neutralization of both Stx1 and Stx2. Passive administration of antibody to the conjugate showed protection requiring immunity to both PNAG and Stx for O157 strains, although for an O104 strain, antibody to PNAG alone was protective. Immunity to PNAG may contribute to protection against STEC infections.
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18
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Binding of Pk-trisaccharide analogs of globotriaosylceramide to Shiga toxin variants. Infect Immun 2013; 81:2753-60. [PMID: 23690406 DOI: 10.1128/iai.00274-13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The two major forms of Shiga toxin, Stx1 and Stx2, use the glycolipid globotriaosylceramide (Gb3) as their cellular receptor. Stx1 primarily recognizes the Pk-trisaccharide portion and has three Pk binding sites per B monomer. The Stx2a subtype requires glycolipid residues in addition to Pk. We synthesized analogs of Pk to examine the binding preferences of Stx1 and Stx2 subtypes a to d. Furthermore, to determine how many binding sites must be engaged, the Pk analogues were conjugated to biotinylated mono- and biantennary platforms, allowing for the display of two to four Pk analogues per streptavidin molecule. Stx binding to Pk analogues immobilized on streptavidin-coated plates was assessed by enzyme-linked immunosorbent assay (ELISA). Stx1, but not the Stx2 subtypes, bound to native Pk. Stx2a and Stx2c bound to the Pk analog with a terminal GalNAc (NAc-Pk), while Stx1, Stx2b, and Stx2d did not bind to this analog. Interestingly, the purified Stx2d B subunit bound to NAc-Pk, suggesting that the A subunit of Stx2d interferes with binding. Disaccharide analogs (Galα1-4Gal, GalNAcα1-4Gal, and Galα1-4GalNAc) did not support the binding of any of the Stx forms, indicating that the trisaccharide is necessary for binding. Studies with monoantennary and biantennary analogs and mixtures suggest that Stx1, Stx2a, and Stx2c need to engage at least three Pk analogues for effective binding. To our knowledge, this is the first study examining the minimum number of Pk analogs required for effective binding and the first report documenting the role of the A subunit in influencing Stx2 binding.
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Bergan J, Dyve Lingelem AB, Simm R, Skotland T, Sandvig K. Shiga toxins. Toxicon 2012; 60:1085-107. [PMID: 22960449 DOI: 10.1016/j.toxicon.2012.07.016] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 06/19/2012] [Accepted: 07/25/2012] [Indexed: 02/03/2023]
Abstract
Shiga toxins are virulence factors produced by the bacteria Shigella dysenteriae and certain strains of Escherichia coli. There is currently no available treatment for disease caused by these toxin-producing bacteria, and understanding the biology of the Shiga toxins might be instrumental in addressing this issue. In target cells, the toxins efficiently inhibit protein synthesis by inactivating ribosomes, and they may induce signaling leading to apoptosis. To reach their cytoplasmic target, Shiga toxins are endocytosed and transported by a retrograde pathway to the endoplasmic reticulum, before the enzymatically active moiety is translocated to the cytosol. The toxins thereby serve as powerful tools to investigate mechanisms of intracellular transport. Although Shiga toxins are a serious threat to human health, the toxins may be exploited for medical purposes such as cancer therapy or imaging.
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Affiliation(s)
- Jonas Bergan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway
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20
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Analyzing of expression of novel polypeptide complexes consisting of Shiga toxin B subunit and Adherence Fimbriae of Escherichia coli based on in silico modeling. J Mol Model 2012; 18:4131-9. [PMID: 22527278 DOI: 10.1007/s00894-012-1414-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 03/26/2012] [Indexed: 10/28/2022]
Abstract
Enterohemorrhagic (EHEC) and enteroaggregative (EAEC) are two pathotypes of diarrheagenic Escherichia coli. EAEC strains express adhesins called aggregate adherence fimbriae (AAFs) which the bacteria use to adhere to intestinal mucosa. EHEC virulence factor is Shiga toxin which belongs to the AB5 toxin family. B subunit, the nontoxic part of Shiga toxin (StxB), forms a homo pentamer and is responsible for binding to target cells. StxB has recently been proven to have adjuvant activity. In the current study we fused StxB encoding gene to 3' end of genes encoding two variants of AAFs, i.e., AAF/I and AAF/II. The in silico studies on tertiary structure and biochemical characteristics of Shiga toxin A subunit (StxA) revealed more resemblance to AAF/II than AAF/I. The constructs were prepared in a way that StxB could imitate its natural structure (pentamer formation) and its position (C-terminus) in the native toxin complex. The expression of these constructs showed the formation of AAF/II-B as a protein complex but with lower molecular mass than its expected size. In contrast, the AAF/I-B complex was not formed. Overall, the results of in silico studies and expression experiments together revealed that despite AAF/II-B expression, StxB failed to form pentamer. Therefore the observed protein complex has lower molecular mass. Since StxB is bound to AAF/II through disulfide bond, this bond prevents pentamer formation of StxB. However, due to the lack of disulfide bond between AAF/I and StxB, no protein complex is formed, thus StxB maintains its pentamer structure.
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21
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Feverati G, Achoch M, Zrimi J, Vuillon L, Lesieur C. Beta-strand interfaces of non-dimeric protein oligomers are characterized by scattered charged residue patterns. PLoS One 2012; 7:e32558. [PMID: 22496732 PMCID: PMC3322119 DOI: 10.1371/journal.pone.0032558] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 01/29/2012] [Indexed: 11/19/2022] Open
Abstract
Protein oligomers are formed either permanently, transiently or even by default. The protein chains are associated through intermolecular interactions constituting the protein interface. The protein interfaces of 40 soluble protein oligomers of stœchiometries above two are investigated using a quantitative and qualitative methodology, which analyzes the x-ray structures of the protein oligomers and considers their interfaces as interaction networks. The protein oligomers of the dataset share the same geometry of interface, made by the association of two individual β-strands (β-interfaces), but are otherwise unrelated. The results show that the β-interfaces are made of two interdigitated interaction networks. One of them involves interactions between main chain atoms (backbone network) while the other involves interactions between side chain and backbone atoms or between only side chain atoms (side chain network). Each one has its own characteristics which can be associated to a distinct role. The secondary structure of the β-interfaces is implemented through the backbone networks which are enriched with the hydrophobic amino acids favored in intramolecular β-sheets (MCWIV). The intermolecular specificity is provided by the side chain networks via positioning different types of charged residues at the extremities (arginine) and in the middle (glutamic acid and histidine) of the interface. Such charge distribution helps discriminating between sequences of intermolecular β-strands, of intramolecular β-strands and of β-strands forming β-amyloid fibers. This might open new venues for drug designs and predictive tool developments. Moreover, the β-strands of the cholera toxin B subunit interface, when produced individually as synthetic peptides, are capable of inhibiting the assembly of the toxin into pentamers. Thus, their sequences contain the features necessary for a β-interface formation. Such β-strands could be considered as ‘assemblons’, independent associating units, by homology to the foldons (independent folding unit). Such property would be extremely valuable in term of assembly inhibitory drug development.
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Affiliation(s)
| | - Mounia Achoch
- Université de Savoie, Annecy le Vieux Cedex, France
- Laboratoire de Chimie Bioorganique et Macromoléculaire (LCBM), Faculté des Sciences et Techniques-Guéliz, Université Cadi Ayyad, Marrakech, Maroc
| | - Jihad Zrimi
- Université de Savoie, Annecy le Vieux Cedex, France
- Laboratoire de Chimie Bioorganique et Macromoléculaire (LCBM), Faculté des Sciences et Techniques-Guéliz, Université Cadi Ayyad, Marrakech, Maroc
| | | | - Claire Lesieur
- Université de Savoie, Annecy le Vieux Cedex, France
- AGIM, Université Joseph Fourier, Archamps, France
- * E-mail:
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Gallegos KM, Conrady DG, Karve SS, Gunasekera TS, Herr AB, Weiss AA. Shiga toxin binding to glycolipids and glycans. PLoS One 2012; 7:e30368. [PMID: 22348006 PMCID: PMC3278406 DOI: 10.1371/journal.pone.0030368] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Accepted: 12/19/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Immunologically distinct forms of Shiga toxin (Stx1 and Stx2) display different potencies and disease outcomes, likely due to differences in host cell binding. The glycolipid globotriaosylceramide (Gb3) has been reported to be the receptor for both toxins. While there is considerable data to suggest that Gb3 can bind Stx1, binding of Stx2 to Gb3 is variable. METHODOLOGY We used isothermal titration calorimetry (ITC) and enzyme-linked immunosorbent assay (ELISA) to examine binding of Stx1 and Stx2 to various glycans, glycosphingolipids, and glycosphingolipid mixtures in the presence or absence of membrane components, phosphatidylcholine, and cholesterol. We have also assessed the ability of glycolipids mixtures to neutralize Stx-mediated inhibition of protein synthesis in Vero kidney cells. RESULTS By ITC, Stx1 bound both Pk (the trisaccharide on Gb3) and P (the tetrasaccharide on globotetraosylceramide, Gb4), while Stx2 did not bind to either glycan. Binding to neutral glycolipids individually and in combination was assessed by ELISA. Stx1 bound to glycolipids Gb3 and Gb4, and Gb3 mixed with other neural glycolipids, while Stx2 only bound to Gb3 mixtures. In the presence of phosphatidylcholine and cholesterol, both Stx1 and Stx2 bound well to Gb3 or Gb4 alone or mixed with other neutral glycolipids. Pre-incubation with Gb3 in the presence of phosphatidylcholine and cholesterol neutralized Stx1, but not Stx2 toxicity to Vero cells. CONCLUSIONS Stx1 binds primarily to the glycan, but Stx2 binding is influenced by residues in the ceramide portion of Gb3 and the lipid environment. Nanomolar affinities were obtained for both toxins to immobilized glycolipids mixtures, while the effective dose for 50% inhibition (ED(50)) of protein synthesis was about 10(-11) M. The failure of preincubation with Gb3 to protect cells from Stx2 suggests that in addition to glycolipid expression, other cellular components contribute to toxin potency.
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Affiliation(s)
- Karen M. Gallegos
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Deborah G. Conrady
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Sayali S. Karve
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Thusitha S. Gunasekera
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Andrew B. Herr
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Alison A. Weiss
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio, United States of America
- * E-mail:
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Abstract
Ricin and Shiga toxins designated as ribosome inactivating proteins (RIPs) are RNA N-glycosidases that depurinate a specific adenine (A₄₃₂₄ in rat 28S rRNA) in the conserved α-sarcin/ricin loop of the large rRNA, inhibiting protein synthesis. Evidence obtained from a number of studies suggests that interaction with ribosomal proteins plays an important role in the catalytic activity and ribosome specificity of RIPs. This review summarizes the recent developments in identification of the ribosomal proteins that interact with ricin and Shiga toxins and the principles governing these interactions.
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Affiliation(s)
- Nilgun E Tumer
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901-8520, USA.
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24
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Chiou JC, Li XP, Remacha M, Ballesta JPG, Tumer NE. Shiga toxin 1 is more dependent on the P proteins of the ribosomal stalk for depurination activity than Shiga toxin 2. Int J Biochem Cell Biol 2011; 43:1792-801. [PMID: 21907821 DOI: 10.1016/j.biocel.2011.08.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 07/27/2011] [Accepted: 08/26/2011] [Indexed: 01/01/2023]
Abstract
Shiga toxins produced by Escherichia coli O157:H7 are responsible for food poisoning and hemolytic uremic syndrome (HUS). The A subunits of Shiga toxins (Stx1A and Stx2A) inhibit translation by depurinating a specific adenine in the large rRNA. To determine if Stx1A and Stx2A require the ribosomal stalk for depurination, their activity and cytotoxicity were examined in the yeast P protein deletion mutants. Stx1A and Stx2A were less toxic and depurinated ribosomes less in a strain lacking P1/P2 on the ribosome and in the cytosol (ΔP2) than in a strain lacking P1/P2 on the ribosome, but containing free P2 in the cytosol (ΔP1). To determine if cytoplasmic P proteins facilitated depurination, Stx1A and Stx2A were expressed in the P0ΔAB mutant, in which the binding sites for P1/P2 were deleted on the ribosome, and P1/P2 accumulated in the cytosol. Stx1A was less toxic and depurinated ribosomes less in P0ΔAB, suggesting that intact binding sites for P1/P2 were critical. In contrast, Stx2A was toxic and depurinated ribosomes in P0ΔAB as in wild type, suggesting that it did not require the P1/P2 binding sites. Depurination of ΔP1, but not P0ΔAB ribosomes increased upon addition of purified P1α/P2βin vitro, and the increase was greater for Stx1 than for Stx2. We conclude that cytoplasmic P proteins stimulate depurination by Stx1 by facilitating the access of the toxin to the ribosome. Although ribosomal stalk is important for Stx1 and Stx2 to depurinate the ribosome, Stx2 is less dependent on the stalk proteins for activity than Stx1 and can depurinate ribosomes with an incomplete stalk better than Stx1.
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Affiliation(s)
- Jia-Chi Chiou
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901-8520, USA
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25
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Abstract
Purified Shiga toxin (Stx) alone is capable of producing systemic complications, including hemolytic-uremic syndrome (HUS), in animal models of disease. Stx includes two major antigenic forms (Stx1 and Stx2), with minor variants of Stx2 (Stx2a to -h). Stx2a is more potent than Stx1. Epidemiologic studies suggest that Stx2 subtypes also differ in potency, but these differences have not been well documented for purified toxin. The relative potencies of five purified Stx2 subtypes, Stx2a, Stx2b, Stx2c, Stx2d, and activated (elastase-cleaved) Stx2d, were studied in vitro by examining protein synthesis inhibition using Vero monkey kidney cells and inhibition of metabolic activity (reduction of resazurin to fluorescent resorufin) using primary human renal proximal tubule epithelial cells (RPTECs). In both RPTECs and Vero cells, Stx2a, Stx2d, and elastase-cleaved Stx2d were at least 25 times more potent than Stx2b and Stx2c. In vivo potency in mice was also assessed. Stx2b and Stx2c had potencies similar to that of Stx1, while Stx2a, Stx2d, and elastase-cleaved Stx2d were 40 to 400 times more potent than Stx1.
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