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ExoS and ExoT ADP ribosyltransferase activities mediate Pseudomonas aeruginosa keratitis by promoting neutrophil apoptosis and bacterial survival.

ABSTRACT: Pseudomonas aeruginosa is a leading cause of blinding corneal ulcers worldwide. To determine the role of type III secretion in the pathogenesis of P. aeruginosa keratitis, corneas of C57BL/6 mice were infected with P. aeruginosa strain PAO1 or PAK, which expresses ExoS, ExoT, and ExoY, but not ExoU. PAO1- and PAK-infected corneas developed severe disease with pronounced opacification and rapid bacterial growth. In contrast, corneas infected with ?pscD or ?pscJ mutants that cannot assemble a type III secretion system, or with mutants lacking the translocator proteins, do not develop clinical disease, and bacteria are rapidly killed by infiltrating neutrophils. Furthermore, survival of PAO1 and PAK strains in the cornea and development of corneal disease was impaired in ?exoS, ?exoT, and ?exoST mutants of both strains, but not in a ?exoY mutant. ?exoST mutants were also rapidly killed in neutrophils in vitro and were impaired in their ability to promote neutrophil apoptosis in vivo compared with PAO1. Point mutations in the ADP ribosyltransferase (ADPR) regions of ExoS or ExoT also impaired proapoptotic activity in infected neutrophils, and exoST(ADPR-) mutants replicated the ?exoST phenotype in vitro and in vivo, whereas mutations in rho-GTPase-activating protein showed the same phenotype as PAO1. Together, these findings demonstrate that the pathogenesis of P. aeruginosa keratitis in ExoS- and ExoT-producing strains is almost entirely due to their ADPR activities, which subvert the host response by targeting the antibacterial activity of infiltrating neutrophils.

SUBMITTER: Sun Y

PROVIDER: S-EPMC3273577 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature

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ExoS and ExoT ADP ribosyltransferase activities mediate Pseudomonas aeruginosa keratitis by promoting neutrophil apoptosis and bacterial survival.

Sun Yan Y Karmakar Mausita M Taylor Patricia R PR Rietsch Arne A Pearlman Eric E

Journal of immunology (Baltimore, Md. : 1950) 20120116 4

Pseudomonas aeruginosa is a leading cause of blinding corneal ulcers worldwide. To determine the role of type III secretion in the pathogenesis of P. aeruginosa keratitis, corneas of C57BL/6 mice were infected with P. aeruginosa strain PAO1 or PAK, which expresses ExoS, ExoT, and ExoY, but not ExoU. PAO1- and PAK-infected corneas developed severe disease with pronounced opacification and rapid bacterial growth. In contrast, corneas infected with ΔpscD or ΔpscJ mutants that cannot assemble a type ...[more]

PMID: 22250085

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Project description:UnlabelledPseudomonas aeruginosa is a Gram-negative pathogen commonly associated with nosocomial infections such as hospital-acquired pneumonia. It uses a type III secretion system to deliver effector proteins directly into the cytosol of host cells. Type III secretion in P. aeruginosa has been linked to severe disease and worse clinical outcomes in animal and human studies. The majority of P. aeruginosa strains secrete ExoS, a bifunctional toxin with GTPase-activating protein and ADP-ribosyltransferase activities. Numerous in vitro studies have investigated the targets and cellular effects of ExoS, linking both its enzymatic activities with inhibition of bacterial internalization. However, little is known about how this toxin facilitates the progression of infection in vivo. In this study, we used a mouse model to investigate the role of ExoS in inhibiting phagocytosis during pneumonia. We first confirmed previous findings that the ADP-ribosyltransferase activity of ExoS, but not the GTPase-activating protein activity, was responsible for bacterial persistence and decreased host survival in this model. We then used two distinct assays to demonstrate that ExoS inhibited phagocytosis during pneumonia. In contrast to the findings of several in vitro studies, this in vivo inhibition was also dependent on the ADP-ribosyltransferase activity, but not the GTPase-activating protein activity, of ExoS. These results demonstrate for the first time the antiphagocytic function of ExoS in the context of an actual infection and indicate that blocking the ADP-ribosyltransferase activity of ExoS may have potential therapeutic benefit.ImportancePseudomonas aeruginosa is a major cause of hospital-acquired infections. To cause severe disease, this bacterium uses a type III secretion system that delivers four effector proteins, ExoS, ExoT, ExoU, and ExoY, into host cells. The majority of P. aeruginosa strains secrete ExoS, a bifunctional toxin with GTPase-activating protein and ADP-ribosyltransferase activities. In cell culture models, both enzymatic activities have been associated with decreased bacterial internalization. However, our study is the first to examine a role for ExoS in blocking phagocytosis in an animal model. We report that ExoS does inhibit phagocytosis during pneumonia. The ADP-ribosyltransferase activity, but not the GTPase-activating protein activity, of ExoS is necessary for this effect. Our findings highlight the ability of P. aeruginosa to manipulate the inflammatory response during pneumonia to facilitate bacterial survival.

Dataset Information

ExoS and ExoT ADP ribosyltransferase activities mediate Pseudomonas aeruginosa keratitis by promoting neutrophil apoptosis and bacterial survival.

Publications

ExoS and ExoT ADP ribosyltransferase activities mediate Pseudomonas aeruginosa keratitis by promoting neutrophil apoptosis and bacterial survival.

Similar Datasets

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