Pseudomonas aeruginosa causes acute lung injury via the catalytic activity of the patatin-like phospholipase domain of ExoU*

Pankhaniya, Ravi R.; Tamura, Miki; Allmond, Leonard R.; Moriyama, Kiyoshi; Ajayi, Temitayo; Wiener-Kronish, Jeanine P.; Sawa, Teiji

doi:10.1097/01.ccm.0000145588.79063.07

Cited by 71 publications

(58 citation statements)

References 40 publications

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“…Mutations of the catalytic serine (S142) or aspartate (D344) residues abolishes both the phospholipase activity and cytotoxicity towards mammalian and yeast cells (Phillips et al, 2003;Sato et al, 2003;Rabin and Hauser 2005). Mutation of the N-terminal region of ExoU also reduces P. aeruginosa virulence of in a murine model of acute pneumonia (Pankhaniya et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Mutation of the phospholipase catalytic domain of the Pseudomonas aeruginosa cytotoxin ExoU abolishes colonization promoting activity and reduces corneal disease severity

Tam

Lewis

et al. 2007

Experimental Eye Research

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We have previously shown that ExoU, a type III secreted cytotoxin of Pseudomonas aeruginosa, causes acute cytotoxicity towards corneal epithelial cells in vitro, and contributes to corneal disease pathology and ocular colonization in vivo. Subsequently, we reported that ExoU represses phagocyte infiltration of infected corneas in vivo. ExoU has patatin-like phospholipase activity that is required for cytotoxic activity in vitro (mammalian cell injury and death) and for disease in a murine model of pneumonia. We hypothesized that the phospholipase activity was required for ExoU-mediated corneal disease and ocular colonization. Using the murine scarification model, corneal disease pathology was examined after inoculation with ~10 6 cfu of a P. aeruginosa effector mutant (PA103ΔexoUexoT::Tc) complemented with either exoU (pUCPexoU), phospholipase-inactive exoU (pUCPexoUD344A) or a plasmid control (pUCP18). Eyes were photographed and disease severity scored at 24 and 48 h post-infection. Viable bacteria colonizing infected eyes were quantified at 6 and 48 h. Complementation with exoU caused significantly more pathology (increased disease severity scores) and enabled bacteria to better colonize (bỹ 1000-fold) at 48 h as compared to phospholipase-inactive exoU which did not differ from plasmid control. Surprisingly, exoU did not contribute to early (6 h) colonization. In-vitro assays confirmed that the phospholipase domain of exoU was required for cytotoxicity towards human corneal epithelial cells. Taken together these data show that the phospholipase activity of the P. aeruginosa cytotoxin, ExoU, plays a role in the pathogenesis of corneal infection via mechanism(s) occurring after initial colonization of a susceptible cornea.

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Section: Introductionmentioning

confidence: 99%

Mutation of the phospholipase catalytic domain of the Pseudomonas aeruginosa cytotoxin ExoU abolishes colonization promoting activity and reduces corneal disease severity

Tam

Lewis

et al. 2007

Experimental Eye Research

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“…To test Ga's efficacy in a severe acute infection, we administered a lethal dose of the highly virulent P. aeruginosa strain PA103 to mice by inhalation. PA103 expresses cytotoxins by a type III secretion mechanism, and work in a number of models shows that this strain produces rapid bacterial dissemination and death (35,36).…”

Section: Figurementioning

confidence: 99%

The transition metal gallium disrupts Pseudomonas aeruginosa iron metabolism and has antimicrobial and antibiofilm activity

et al. 2007

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A novel antiinfective approach is to exploit stresses already imposed on invading organisms by the in vivo environment. Fe metabolism is a key vulnerability of infecting bacteria because organisms require Fe for growth, and it is critical in the pathogenesis of infections. Furthermore, humans have evolved potent Fewithholding mechanisms that can block acute infection, prevent biofilm formation leading to chronic infection, and starve bacteria that succeed in infecting the host. Here we investigate a "Trojan horse" strategy that uses the transition metal gallium to disrupt bacterial Fe metabolism and exploit the Fe stress of in vivo environments. Due to its chemical similarity to Fe, Ga can substitute for Fe in many biologic systems and inhibit Fe-dependent processes. We found that Ga inhibits Pseudomonas aeruginosa growth and biofilm formation and kills planktonic and biofilm bacteria in vitro. Ga works in part by decreasing bacterial Fe uptake and by interfering with Fe signaling by the transcriptional regulator pvdS. We also show that Ga is effective in 2 murine lung infection models. These data, along with the fact that Ga is FDA approved (for i.v. administration) and there is the dearth of new antibiotics in development, make Ga a potentially promising new therapeutic for P. aeruginosa infections.

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“…ExoY is an adenylate cyclase that increases intracellular levels of cAMP (Yahr et al, 1998). Several studies have clearly demonstrated that the enzymic activities of ExoS, ExoT and ExoU contribute to pathogenesis by affecting bacterial persistence in infected tissues, bacterial dissemination and host survival (FinckBarbançon et al, 1997;Garrity-Ryan et al, 2000;Hauser et al, 1998a;Pankhaniya et al, 2004;Shaver & Hauser, 2004). ExoY, in contrast, has not been shown to play an appreciable role in disease progression in animal models (Holder et al, 2001;Lee et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Interactions between effector proteins of the Pseudomonas aeruginosa type III secretion system do not significantly affect several measures of disease severity in mammals

Shaver

Hauser

2006

Microbiology

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The effector proteins of the type III secretion systems of many bacterial pathogens act in a coordinated manner to subvert host cells and facilitate the development and progression of disease. It is unclear whether interactions between the type-III-secreted proteins of Pseudomonas aeruginosa result in similar effects on the disease process. We have previously characterized the contributions to pathogenesis of the type-III-secreted proteins ExoS, ExoT and ExoU when secreted individually. In this study, we extend our prior work to determine whether these proteins have greater than expected effects on virulence when secreted in combination. In vitro cytotoxicity and anti-internalization activities were not enhanced when effector proteins were secreted in combinations rather than alone. Likewise in a mouse model of pneumonia, bacterial burden in the lungs, dissemination and mortality attributable to ExoS, ExoT and ExoU were not synergistically increased when combinations of these effector proteins were secreted. Because of the absence of an appreciable synergistic increase in virulence when multiple effector proteins were secreted in combination, we conclude that any cooperation between ExoS, ExoT and ExoU does not translate into a synergistically significant enhancement of disease severity as measured by these assays. INTRODUCTIONAn emerging theme in bacterial type III secretion is that the multiple effector proteins transported by these systems cooperate to subvert specific host-cell processes, resulting in enhanced virulence. Each factor alone has a minor effect on the overall virulence process, but together they cooperate to dramatically enhance virulence. Often, individual effector proteins target different points within a single host-cell pathway to facilitate an essential step in pathogenesis. For example YopE, YopH, YopT and YopO, four type III effector proteins of Yersinia, impede neutrophil and macrophage phagocytosis by targeting the actin cytoskeleton of these cells in a coordinated manner (Cornelis, 2002). The net result is that Yersinia bacteria are able to persist in the presence of a robust host immune response. Similar cooperation occurs between Salmonella type III effector proteins to orchestrate bacterial entry into intestinal epithelial cells, an essential step in the development of enteritis. A large number of type III effector proteins working in concert are required to achieve maximal levels of Salmonella bacterial uptake (Raffatellu et al., 2005). These proteins cause a complex series of actin cytoskeletal changes, which result in the transient formation of localized host-cell surface membrane ruffles that engulf the invading bacteria. SopB, SopE and SopE2 activate the Rho family GTPases Cdc42 and Rac1, thereby facilitating actin recruitment and polymerization at the site of bacterial entry (Hardt et al., 1998;Zhou et al., 2001). Two other effector proteins, SipA and SipC, further enhance actin nucleation, polymerization and cross-linking by directly binding to actin (Zhou et al., 1999a,b). O...

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Pseudomonas aeruginosa causes acute lung injury via the catalytic activity of the patatin-like phospholipase domain of ExoU*

Cited by 71 publications

References 40 publications

Mutation of the phospholipase catalytic domain of the Pseudomonas aeruginosa cytotoxin ExoU abolishes colonization promoting activity and reduces corneal disease severity

Mutation of the phospholipase catalytic domain of the Pseudomonas aeruginosa cytotoxin ExoU abolishes colonization promoting activity and reduces corneal disease severity

The transition metal gallium disrupts Pseudomonas aeruginosa iron metabolism and has antimicrobial and antibiofilm activity

Interactions between effector proteins of the Pseudomonas aeruginosa type III secretion system do not significantly affect several measures of disease severity in mammals

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