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Injection of Staphylococcus aureus EDIN by the Bacillus anthracis protective antigen machinery induces vascular permeability.

ABSTRACT: Systemic injection of Bacillus anthracis lethal toxin (LT) produces vascular leakage and animal death. Recent studies suggest that LT triggers direct endothelial cell cytotoxicity that is responsible for the vascular leakage. LT is composed of heptamers of protective antigen (PA), which drives the endocytosis and translocation into host cells of the lethal factor (LF), a mitogen-activated protein kinase kinase protease. Here we investigated the consequences of injection of an endothelium-permeabilizing factor using LT as a "molecular syringe." To this end, we generated the chimeric factor LE, corresponding to the PA-binding domain of LF (LF(1-254)) fused to EDIN exoenzyme. EDIN ADP ribosylates RhoA, leading to actin cable disruption and formation of transcellular tunnels in endothelial cells. We report that systemic injection of LET (LE plus PA) triggers a PA-dependent increase in the pulmonary endothelium permeability. We also report that native LT induces a progressive loss of endothelium barrier function. We established that there is a direct correlation between the extent of endothelium permeability induced by LT and the cytotoxic activity of LT. This suggests new ways to design therapeutic drugs against anthrax directed toward vascular permeability.

SUBMITTER: Rolando M

PROVIDER: S-EPMC2738014 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

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Injection of Staphylococcus aureus EDIN by the Bacillus anthracis protective antigen machinery induces vascular permeability.

Rolando Monica M Munro Patrick P Stefani Caroline C Auberger Patrick P Flatau Gilles G Lemichez Emmanuel E

Infection and immunity 20090622 9

Systemic injection of Bacillus anthracis lethal toxin (LT) produces vascular leakage and animal death. Recent studies suggest that LT triggers direct endothelial cell cytotoxicity that is responsible for the vascular leakage. LT is composed of heptamers of protective antigen (PA), which drives the endocytosis and translocation into host cells of the lethal factor (LF), a mitogen-activated protein kinase kinase protease. Here we investigated the consequences of injection of an endothelium-permeab ...[more]

PMID: 19546197

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Project description:BackgroundAnthrax is caused by Bacillus anthracis that produce two exotoxins, lethal toxin and edema toxin. The lethal toxin is composed of the lethal factor (LF) complexed with the cell binding protective antigen (PA83, 83 kDa). Likewise, the edema factor (EF) binds to the PA83 to form the edema toxin. Once PA83 is bound to the host cell surface, a furin-like protease cleaves the full-length, inactive protein into 63 kDa and 20 kDa antigens (PA63 and PA20). PA63 forms a heptamer and is internalized via receptor mediated endocytosis forming a protease-stable pore, which allows EF and LF to enter the cell and exert their toxic effects.Both proteolytically cleaved protective antigens (PA63 and PA20 fragments) are found in the blood of infected animals. The 63 kDa protective antigen PA63 fragment has been thoroughly studied while little is known about the PA20.MethodsIn this study we examined the role of PA20 using high throughput gene expression analysis of human peripheral blood mononuclear cells (PBMC) exposed to the PA20. We constructed a PA mutant in which a Factor Xa proteolytic recognition site was genetically engineered into the protective antigen PA83 to obtain PA20 using limited digestion of this recombinant PA83 with trypsin.ResultsGlobal gene expression response studies indicated modulation of various immune functions and showed gene patterns indicative of apoptosis via the Fas pathway in a subset of the lymphoid cells. This finding was extended to include observations of increased Caspase-3 enzymatic activity and the identification of increases in the population of apoptotic, but not necrotic cells, based on differential staining methods. We identified a list of approximately 40 inflammatory mediators and heat-shock proteins that were altered similarly upon exposure of PBMC to either rPA20 or B. anthracis spores/vegetative cells.ConclusionThis study shows that the PA20 has an effect on human peripheral blood leukocytes and can induce apoptosis in the absence of other PA components.

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Injection of Staphylococcus aureus EDIN by the Bacillus anthracis protective antigen machinery induces vascular permeability.

Publications

Injection of Staphylococcus aureus EDIN by the Bacillus anthracis protective antigen machinery induces vascular permeability.

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