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Tissue factor–dependent procoagulant activity of subtilase cytotoxin, a potent AB5 toxin produced by shiga toxigenic Escherichia coli.

ABSTRACT: Subtilase cytotoxin (SubAB), produced by certain virulent Shiga toxigenic Escherichia coli strains, causes hemolytic uremic syndrome-like pathology in mice, including extensive microvascular thrombosis. SubAB acts by specifically cleaving the essential endoplasmic reticulum chaperone binding immunoglobulin protein (BiP). BiP has been reported to inhibit the activation of tissue factor (TF), the major initiator of extrinsic coagulation. We hypothesized that the apparent prothrombotic effect of SubAB in vivo may involve the stimulation of TF‐dependent procoagulant activity. TF‐dependent procoagulant activity, TF messenger RNA (mRNA) levels, and BiP cleavage were therefore examined in human macrophage cells and primary human umbilical vein endothelial cells exposed to SubAB. In both types of cells, SubAB significantly increased TF‐dependent procoagulant activity, induced TF mRNA expression, and mediated BiP cleavage. No effects were seen when cells were treated with a nonproteolytic mutant toxin, SubAA272B. Our results suggest that the procoagulant effect of SubAB may be dependent on both the up‐regulation of TF expression and the activation of TF by means of BiP cleavage.

SUBMITTER: Wang H

PROVIDER: S-EPMC2949535 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Tissue factor–dependent procoagulant activity of subtilase cytotoxin, a potent AB5 toxin produced by shiga toxigenic Escherichia coli.

Wang Hui H Paton James C JC Thorpe Cheleste M CM Bonder Claudine S CS Sun Wai Yan WY Paton Adrienne W AW

The Journal of infectious diseases 20101101 9

Subtilase cytotoxin (SubAB), produced by certain virulent Shiga toxigenic Escherichia coli strains, causes hemolytic uremic syndrome-like pathology in mice, including extensive microvascular thrombosis. SubAB acts by specifically cleaving the essential endoplasmic reticulum chaperone binding immunoglobulin protein (BiP). BiP has been reported to inhibit the activation of tissue factor (TF), the major initiator of extrinsic coagulation. We hypothesized that the apparent prothrombotic effect of Su ...[more]

PMID: 20874089

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Project description:Certain foodborne Shiga toxin-producing Escherichia coli (STEC) strains carry genes encoding the subtilase cytotoxin (SubAB). Although the mode of action of SubAB is under intensive investigation, information about the regulation of subAB gene expression is currently not available. In this study, we investigated the regulation of the chromosomal subAB1 gene in laboratory E. coli strain DH5α and STEC O113:H21 strain TS18/08 using a luciferase reporter gene assay. Special emphasis was given to the role of the global regulatory protein genes hfq and hns in subAB1 promoter activity. Subsequently, quantitative real-time PCR was performed to analyze the expression of Shiga toxin 2a (Stx2a), SubAB1, and cytolethal distending toxin V (Cdt-V) genes in STEC strain TS18/08 and its isogenic hfq and hns deletion mutants. The deletion of hfq led to a significant increase of up to 2-fold in subAB1 expression, especially in the late growth phase, in both strains. However, deletion of hns showed different effects on the promoter activity during the early and late exponential growth phases in both strains. Furthermore, upregulation of stx2a and cdt-V was demonstrated in hfq and hns deletion mutants in TS18/08. These data showed that the expression of subAB1, stx2a, and cdt-V is integrated in the regulatory network of global regulators Hfq and H-NS in Escherichia coliIMPORTANCE Shiga toxin-producing Escherichia coli (STEC) strains are responsible for outbreaks of foodborne diseases, such as hemorrhagic colitis and the hemolytic uremic syndrome. The pathogenicity of those strains can be attributed to, among other factors, the production of toxins. Recently, the subtilase cytotoxin was detected in locus of enterocyte effacement (LEE)-negative STEC, and it was confirmed that it contributes to the cytotoxicity of those STEC strains. Although the mode of action of SubAB1 is under intensive investigation, the regulation of gene expression is currently not known. The global regulatory proteins H-NS and Hfq have impact on many cellular processes and have been described to regulate virulence factors as well. Here, we investigate the role of hns and hfq in expression of subAB1 as well as stx2a and cdt-V in an E. coli laboratory strain as well as in wild-type STEC strain TS18/08.

Project description:UnlabelledShiga 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.ImportanceComplications 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.

Dataset Information

Tissue factor–dependent procoagulant activity of subtilase cytotoxin, a potent AB5 toxin produced by shiga toxigenic Escherichia coli.

Publications

Tissue factor–dependent procoagulant activity of subtilase cytotoxin, a potent AB5 toxin produced by shiga toxigenic Escherichia coli.

Similar Datasets

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