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Xie Q, Wei B, Zhan Z, He Q, Wu K, Chen Y, Liu S, He C, Niu X, Li C, Tang C, Tao J. Arabidopsis membrane protein AMAR1 interaction with type III effector XopAM triggers a hypersensitive response. PLANT PHYSIOLOGY 2023; 193:2768-2787. [PMID: 37648267 DOI: 10.1093/plphys/kiad478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/07/2023] [Accepted: 07/27/2023] [Indexed: 09/01/2023]
Abstract
The efficient infection of plants by the bacteria Xanthomonas campestris pv. campestris (Xcc) depends on its type III effectors (T3Es). Although the functions of AvrE family T3Es have been reported in some bacteria, the member XopAM in Xcc has not been studied. As XopAM has low sequence similarity to reported AvrE-T3Es and different reports have shown that these T3Es have different targets in hosts, we investigated the functions of XopAM in the Xcc-plant interaction. Deletion of xopAM from Xcc reduced its virulence in cruciferous crops but increased virulence in Arabidopsis (Arabidopsis thaliana) Col-0, indicating that XopAM may perform opposite functions depending on the host species. We further found that XopAM is a lipase that may target the cytomembrane and that this activity might be enhanced by its membrane-targeted protein XOPAM-ACTIVATED RESISTANCE 1 (AMAR1) in Arabidopsis Col-0. The binding of XopAM to AMAR1 induced an intense hypersensitive response that restricted Xcc proliferation. Our results showed that the roles of XopAM in Xcc infection are not the same as those of other AvrE-T3Es, indicating that the functions of this type of T3E have differentiated during long-term bacterium‒host interactions.
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Affiliation(s)
- Qingbiao Xie
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Bingzheng Wei
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Zhaohong Zhan
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Qiguang He
- Rubber Research Institute, Chinese Academy of Tropical Agricultural Science, Haikou 571101, China
| | - Kejian Wu
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Yu Chen
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Shiyao Liu
- Sanya Nanfan Research Institute, Hainan University, Sanya 572024, China
| | - Chaozu He
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
- Sanya Nanfan Research Institute, Hainan University, Sanya 572024, China
- Hainan Yazhou Bay Seed Laboratory, Sanya 572025, China
| | - Xiaolei Niu
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
- Sanya Nanfan Research Institute, Hainan University, Sanya 572024, China
| | - Chunxia Li
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
- Hainan Yazhou Bay Seed Laboratory, Sanya 572025, China
| | - Chaorong Tang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Jun Tao
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
- Hainan Yazhou Bay Seed Laboratory, Sanya 572025, China
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Wood SJ, Goldufsky JW, Seu MY, Dorafshar AH, Shafikhani SH. Pseudomonas aeruginosa Cytotoxins: Mechanisms of Cytotoxicity and Impact on Inflammatory Responses. Cells 2023; 12:cells12010195. [PMID: 36611990 PMCID: PMC9818787 DOI: 10.3390/cells12010195] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/01/2022] [Accepted: 12/01/2022] [Indexed: 01/05/2023] Open
Abstract
Pseudomonas aeruginosa is one of the most virulent opportunistic Gram-negative bacterial pathogens in humans. It causes many acute and chronic infections with morbidity and mortality rates as high as 40%. P. aeruginosa owes its pathogenic versatility to a large arsenal of cell-associated and secreted virulence factors which enable this pathogen to colonize various niches within hosts and protect it from host innate immune defenses. Induction of cytotoxicity in target host cells is a major virulence strategy for P. aeruginosa during the course of infection. P. aeruginosa has invested heavily in this strategy, as manifested by a plethora of cytotoxins that can induce various forms of cell death in target host cells. In this review, we provide an in-depth review of P. aeruginosa cytotoxins based on their mechanisms of cytotoxicity and the possible consequences of their cytotoxicity on host immune responses.
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Affiliation(s)
- Stephen J. Wood
- Department of Medicine, Division of Hematology, Oncology and Cell Therapy, Rush University Medical Center, Chicago, IL 60612, USA
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Rush University Medical Center, Chicago, IL 60612, USA
| | - Josef W. Goldufsky
- Department of Medicine, Division of Hematology, Oncology and Cell Therapy, Rush University Medical Center, Chicago, IL 60612, USA
| | - Michelle Y. Seu
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Rush University Medical Center, Chicago, IL 60612, USA
| | - Amir H. Dorafshar
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Rush University Medical Center, Chicago, IL 60612, USA
| | - Sasha H. Shafikhani
- Department of Medicine, Division of Hematology, Oncology and Cell Therapy, Rush University Medical Center, Chicago, IL 60612, USA
- Department of Microbial Pathogens and Immunity, Rush University Medical Center, Chicago, IL 60612, USA
- Cancer Center, Rush University Medical Center, Chicago, IL 60612, USA
- Correspondence:
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3
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Constantino-Teles P, Jouault A, Touqui L, Saliba AM. Role of Host and Bacterial Lipids in Pseudomonas aeruginosa Respiratory Infections. Front Immunol 2022; 13:931027. [PMID: 35860265 PMCID: PMC9289105 DOI: 10.3389/fimmu.2022.931027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 06/07/2022] [Indexed: 11/13/2022] Open
Abstract
The opportunistic pathogen Pseudomonas aeruginosa is one of the most common agents of respiratory infections and has been associated with high morbidity and mortality rates. The ability of P. aeruginosa to cause severe respiratory infections results from the coordinated action of a variety of virulence factors that promote bacterial persistence in the lungs. Several of these P. aeruginosa virulence mechanisms are mediated by bacterial lipids, mainly lipopolysaccharide, rhamnolipid, and outer membrane vesicles. Other mechanisms arise from the activity of P. aeruginosa enzymes, particularly ExoU, phospholipase C, and lipoxygenase A, which modulate host lipid signaling pathways. Moreover, host phospholipases, such as cPLA2α and sPLA2, are also activated during the infectious process and play important roles in P. aeruginosa pathogenesis. These mechanisms affect key points of the P. aeruginosa-host interaction, such as: i) biofilm formation that contributes to bacterial colonization and survival, ii) invasion of tissue barriers that allows bacterial dissemination, iii) modulation of inflammatory responses, and iv) escape from host defenses. In this mini-review, we present the lipid-based mechanism that interferes with the establishment of P. aeruginosa in the lungs and discuss how bacterial and host lipids can impact the outcome of P. aeruginosa respiratory infections.
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Affiliation(s)
- Pamella Constantino-Teles
- Department of Microbiology, Immunology and Parasitology, Faculty of Medical Sciences, Rio de Janeiro State University, Rio de Janeiro, Brazil
| | - Albane Jouault
- Sorbonne Université, Centre de Recherche Saint-Antoine, Inserm, Institut Pasteur, Mucoviscidose et Bronchopathies Chroniques, Département Santé Globale, Paris, France
| | - Lhousseine Touqui
- Sorbonne Université, Centre de Recherche Saint-Antoine, Inserm, Institut Pasteur, Mucoviscidose et Bronchopathies Chroniques, Département Santé Globale, Paris, France
| | - Alessandra Mattos Saliba
- Department of Microbiology, Immunology and Parasitology, Faculty of Medical Sciences, Rio de Janeiro State University, Rio de Janeiro, Brazil
- *Correspondence: Alessandra Mattos Saliba,
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Campoccia D, Montanaro L, Arciola CR. Tracing the origins of extracellular DNA in bacterial biofilms: story of death and predation to community benefit. BIOFOULING 2021; 37:1022-1039. [PMID: 34823431 DOI: 10.1080/08927014.2021.2002987] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/28/2021] [Indexed: 06/13/2023]
Abstract
Extracellular DNA (eDNA) is a macromolecule copiously found in various natural microenvironments, but its origin and significance still remain partly mysterious phenomena. Here, the multifaceted origins of eDNA in bacterial biofilms are explored. The release of eDNA can follow a suicidal programmed bacterial apoptosis or a fratricide-induced death, under the control of quorum sensing systems or triggered by specific stressors. eDNA can be released into the extracellular space or as a free macromolecule or enclosed within membrane vesicles or even through an explosion of bubbles. eDNA can also be derived from host tissue cells through bacterial cytolytic/proapoptotic toxins or stolen from neutrophil extracellular traps (NETs). eDNA can alternatively be produced by lysis-independent mechanisms. Sub-inhibitory doses of antibiotics, by killing a fraction of bacteria, result in stimulating the release of eDNA. Even phages appear to play a role in favoring eDNA release. Unveiling the origins of eDNA is critical to correctly address biofilm-associated infections.
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Affiliation(s)
- Davide Campoccia
- Laboratorio di Patologia delle Infezioni Associate all'Impianto, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Lucio Montanaro
- Laboratorio di Patologia delle Infezioni Associate all'Impianto, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy
| | - Carla Renata Arciola
- Laboratorio di Patologia delle Infezioni Associate all'Impianto, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
- Laboratorio di Immunoreumatologia e Rigenerazione Tissutale, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy
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5
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Bagayoko S, Leon-Icaza SA, Pinilla M, Hessel A, Santoni K, Péricat D, Bordignon PJ, Moreau F, Eren E, Boyancé A, Naser E, Lefèvre L, Berrone C, Iakobachvili N, Metais A, Rombouts Y, Lugo-Villarino G, Coste A, Attrée I, Frank DW, Clevers H, Peters PJ, Cougoule C, Planès R, Meunier E. Host phospholipid peroxidation fuels ExoU-dependent cell necrosis and supports Pseudomonas aeruginosa-driven pathology. PLoS Pathog 2021; 17:e1009927. [PMID: 34516571 PMCID: PMC8460005 DOI: 10.1371/journal.ppat.1009927] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 09/23/2021] [Accepted: 08/29/2021] [Indexed: 11/20/2022] Open
Abstract
Regulated cell necrosis supports immune and anti-infectious strategies of the body; however, dysregulation of these processes drives pathological organ damage. Pseudomonas aeruginosa expresses a phospholipase, ExoU that triggers pathological host cell necrosis through a poorly characterized pathway. Here, we investigated the molecular and cellular mechanisms of ExoU-mediated necrosis. We show that cellular peroxidised phospholipids enhance ExoU phospholipase activity, which drives necrosis of immune and non-immune cells. Conversely, both the endogenous lipid peroxidation regulator GPX4 and the pharmacological inhibition of lipid peroxidation delay ExoU-dependent cell necrosis and improve bacterial elimination in vitro and in vivo. Our findings also pertain to the ExoU-related phospholipase from the bacterial pathogen Burkholderia thailandensis, suggesting that exploitation of peroxidised phospholipids might be a conserved virulence mechanism among various microbial phospholipases. Overall, our results identify an original lipid peroxidation-based virulence mechanism as a strong contributor of microbial phospholipase-driven pathology.
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Affiliation(s)
- Salimata Bagayoko
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Stephen Adonai Leon-Icaza
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Miriam Pinilla
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Audrey Hessel
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Karin Santoni
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - David Péricat
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Pierre-Jean Bordignon
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Flavie Moreau
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
- Level 3 Biosafety Animal Core facility, Anexplo platform, Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Elif Eren
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Aurélien Boyancé
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Emmanuelle Naser
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
- Cytometry & Imaging Core facility, Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Lise Lefèvre
- RESTORE institute, University of Toulouse, CNRS, Toulouse, France
| | - Céline Berrone
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
- Level 3 Biosafety Animal Core facility, Anexplo platform, Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Nino Iakobachvili
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, The Netherlands
| | - Arnaud Metais
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Yoann Rombouts
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Geanncarlo Lugo-Villarino
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Agnès Coste
- RESTORE institute, University of Toulouse, CNRS, Toulouse, France
| | - Ina Attrée
- Univ. Grenoble Alpes, CNRS, CEA, IBS, Bacterial Pathogenesis and Cellular Responses, Grenoble, France
| | - Dara W. Frank
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Hans Clevers
- Oncode Institute, Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center, Utrecht, Netherlands
| | - Peter J. Peters
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, The Netherlands
| | - Céline Cougoule
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Rémi Planès
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
| | - Etienne Meunier
- Institute of Pharmacology and Structural Biology (IPBS), University of Toulouse, CNRS, Toulouse, France
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6
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Horna G, Ruiz J. Type 3 secretion system of Pseudomonas aeruginosa. Microbiol Res 2021; 246:126719. [PMID: 33582609 DOI: 10.1016/j.micres.2021.126719] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 01/19/2021] [Accepted: 01/26/2021] [Indexed: 12/27/2022]
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen, mainly affecting severe patients, such as those in intensive care units (ICUs). High levels of antibiotic resistance and a long battery of virulence factors characterise this pathogen. Among virulence factors, the T3SS (Type 3 Secretion Systems) are especially relevant, being one of the most important virulence factors in P. aeruginosa. T3SS are a complex "molecular syringe" able to inject different effectors in host cells, subverting cell machinery influencing immune responses, and increasing bacterial survival rates. While T3SS have been largely studied and the molecular structure and main effector functions have been established, a series of questions and further points remain to be clarified or established. The key role of T3SS in P. aeruginosa virulence has resulted in the search for T3SS-targeting molecules able to impair their functions and subsequently improve patient outcomes. This review aims to summarise the most relevant features of the P. aeruginosa T3SS.
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Affiliation(s)
- Gertrudis Horna
- Universidad Catolica Los Angeles de Chimbote, Instituto de Investigación, Chimbote, Peru.
| | - Joaquim Ruiz
- Laboratorio de Microbiología Molecular y Genómica Bacteriana, Universidad Científica del Sur, Panamericana Sur, Km 19, Lima, Peru.
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Springer TI, Reid TE, Gies SL, Feix JB. Interactions of the effector ExoU from Pseudomonas aeruginosa with short-chain phosphatidylinositides provide insights into ExoU targeting to host membranes. J Biol Chem 2019; 294:19012-19021. [PMID: 31662432 DOI: 10.1074/jbc.ra119.010278] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 10/21/2019] [Indexed: 12/25/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic multidrug-resistant pathogen and a common cause of infection in cystic fibrosis and ventilator-associated pneumonia and in burn and wound patients. P. aeruginosa uses its type III secretion system to secrete various effector proteins directly into mammalian host cells. ExoU is a potent type III secretion system effector that, after secretion, localizes to the inner cytoplasmic membrane of eukaryotic cells, where it exerts its phospholipase A2 activity upon interacting with ubiquitin and/or ubiquitinated proteins. In this study, we used site-directed spin-labeling electron paramagnetic resonance spectroscopy to examine the interaction of ExoU with soluble analogs of phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2). We found that dioctanoyl PI(4,5)P2 binds to and induces conformational changes in a C-terminal four-helix bundle (4HB) domain of ExoU implicated previously in membrane binding. Other soluble phosphoinositides also interacted with the 4HB but less effectively. Molecular modeling and ligand docking studies indicated the potential for numerous hydrogen bond interactions within and between interhelical loops of the 4HB and suggested several potential interaction sites for PI(4,5)P2 Site-directed mutagenesis experiments confirmed that the side chains of Gln-623 and Arg-661 play important roles in mediating PI(4,5)P2-induced conformational changes in ExoU. These results support a mechanism in which direct interactions with phosphatidylinositol-containing lipids play an essential role in targeting ExoU to host membrane bilayers. Molecules or peptides that block this interaction may prove useful in preventing the cytotoxic effects of ExoU to mitigate the virulence of P. aeruginosa strains that express this potent phospholipase toxin.
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Affiliation(s)
- Tzvia I Springer
- Department of Pharmaceutical Sciences, Concordia University Wisconsin, Mequon, Wisconsin 53097
| | - Terry-Elinor Reid
- Department of Pharmaceutical Sciences, Concordia University Wisconsin, Mequon, Wisconsin 53097
| | - Samantha L Gies
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Jimmy B Feix
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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Comparison of type 5d autotransporter phospholipases demonstrates a correlation between high activity and intracellular pathogenic lifestyle. Biochem J 2019; 476:2657-2676. [PMID: 31492736 DOI: 10.1042/bcj20190136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 09/05/2019] [Accepted: 09/06/2019] [Indexed: 12/20/2022]
Abstract
Autotransporters, or type 5 secretion systems, are widespread surface proteins of Gram-negative bacteria often associated with virulence functions. Autotransporters consist of an outer membrane β-barrel domain and an exported passenger. In the poorly studied type 5d subclass, the passenger is a patatin-like lipase. The prototype of this secretion pathway is PlpD of Pseudomonas aeruginosa, an opportunistic human pathogen. The PlpD passenger is a homodimer with phospholipase A1 (PLA1) activity. Based on sequencing data, PlpD-like proteins are present in many bacterial species. We characterized the enzymatic activity, specific lipid binding and oligomeric status of PlpD homologs from Aeromonas hydrophila (a fish pathogen), Burkholderia pseudomallei (a human pathogen) and Ralstonia solanacearum (a plant pathogen) and compared these with PlpD. We demonstrate that recombinant type 5d-secreted patatin domains have lipase activity and form dimers or higher-order oligomers. However, dimerization is not necessary for lipase activity; in fact, by making monomeric variants of PlpD, we show that enzymatic activity slightly increases while protein stability decreases. The lipases from the intracellular pathogens A. hydrophila and B. pseudomallei display PLA2 activity in addition to PLA1 activity. Although the type 5d-secreted lipases from the animal pathogens bound to intracellular lipid targets, phosphatidylserine and phosphatidylinositol phosphates, hydrolysis of these lipids could only be observed for FplA of Fusobacterium nucleatum Yet, we noted a correlation between high lipase activity in type 5d autotransporters and intracellular lifestyle. We hypothesize that type 5d phospholipases are intracellularly active and function in modulation of host cell signaling events.
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Kainuma A, Momiyama K, Kimura T, Akiyama K, Inoue K, Naito Y, Kinoshita M, Shimizu M, Kato H, Shime N, Fujita N, Sawa T. An outbreak of fluoroquinolone-resistant Pseudomonas aeruginosa ST357 harboring the exoU gene. J Infect Chemother 2018; 24:615-622. [PMID: 29628388 DOI: 10.1016/j.jiac.2018.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Revised: 03/11/2018] [Accepted: 03/14/2018] [Indexed: 12/15/2022]
Abstract
Antimicrobial-resistant isolates of Pseudomonas aeruginosa collected from 2005 to 2014 in a university hospital in Kyoto, Japan, were retrospectively analyzed by multilocus sequence typing (MLST), exoenzyme genotype determination, integron characterization, and clinical associations. During the study, 1573 P. aeruginosa isolates were detected, and 41 of these were resistant to more than two classes of antimicrobial agents. Twenty-five (61.0%) isolates were collected from urine. All isolates were resistant to ciprofloxacin, 8 (19.5%) isolates showed resistance to imipenem/cilastatin, and 8 (19.5%) isolates showed resistance to meropenem. None of the isolates fulfilled the clinical criteria for multidrug-resistant P. aeruginosa. All isolates were negative in the metallo-β lactamase test. Thirty-six (87.8%) isolates were of the exoS-exoU+ genotype and 5 (12.2%) isolates were of the exoS+exoU- genotype. Among 36 exoS-exoU+ isolates, 33 (80.5%) were ST357, and 3 (7.3%) were ST235. Five isolates of exoS+exoU- were ST186, ST244, ST314, ST508, and ST512. Thirty-three isolates were positive for class 1 integrons and four different class 1 integrons were detected: aminoglycoside (2') adenyltransferase and chloramphenicol transporter (AadB+CmlA6), OXA-4 β-lactamase and aminoglycoside 3'-adenyltransferase (OXA4+AadA2), AadB alone, and aminoglycoside acetyltransferase alone (AacA31). Among the 41 patients from which the isolates originated, the most common underlying disease was cancer in 16 patients (39%), and 9 patients (22.0%) died during the hospitalization period. There was no statistical correlation between MLST, exoenzyme genotype, and patient mortality. The results indicated outbreaks of fluoroquinolone-resistant P. aeruginosa in immunocompromised patients mainly due to the propagation of potentially virulent ST357 isolates possessing the exoU+ genotype.
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Affiliation(s)
| | - Kyoko Momiyama
- School of Pharmacy, Kyoto Pharmaceutical University, Kyoto, Japan.
| | - Takeshi Kimura
- Division of Infection Control & Laboratory Medicine at University Hospital, Kyoto Prefectural University of Medicine, Kyoto, Japan.
| | - Koichi Akiyama
- Department of Anesthesiology, School of Medicine, Japan.
| | - Keita Inoue
- Department of Anesthesiology, School of Medicine, Japan.
| | | | - Mao Kinoshita
- Department of Anesthesiology, School of Medicine, Japan.
| | - Masaru Shimizu
- Department of Anesthesiology, School of Medicine, Japan.
| | - Hideya Kato
- Department of Anesthesiology, School of Medicine, Japan.
| | - Nobuaki Shime
- Department of Emergency and Critical Care Medicine, Institute of Biochemical and Health Sciences, Hiroshima University, Hiroshima, Japan.
| | - Naohisa Fujita
- Division of Infection Control & Laboratory Medicine at University Hospital, Kyoto Prefectural University of Medicine, Kyoto, Japan.
| | - Teiji Sawa
- Department of Anesthesiology, School of Medicine, Japan.
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ExoY, an actin-activated nucleotidyl cyclase toxin from P. aeruginosa: A minireview. Toxicon 2017; 149:65-71. [PMID: 29258848 DOI: 10.1016/j.toxicon.2017.12.046] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 12/14/2017] [Accepted: 12/15/2017] [Indexed: 11/23/2022]
Abstract
ExoY is one of four well-characterized Pseudomonas aeruginosa type 3 secretion system (T3SS) effectors. It is a nucleotidyl cyclase toxin that is inactive inside the bacteria, but becomes potently activated once it is delivered into the eukaryotic target cells. Recently, filamentous actin was identified as the eukaryotic cofactor that stimulates specifically ExoY enzymatic activity by several orders of magnitude. In this review, we discuss recent advances in understanding the biochemistry of nucleotidyl cyclase activity of ExoY and its regulation by interaction with filamentous actin.
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11
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Pazos MA, Lanter BB, Yonker LM, Eaton AD, Pirzai W, Gronert K, Bonventre JV, Hurley BP. Pseudomonas aeruginosa ExoU augments neutrophil transepithelial migration. PLoS Pathog 2017; 13:e1006548. [PMID: 28771621 PMCID: PMC5557605 DOI: 10.1371/journal.ppat.1006548] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 08/15/2017] [Accepted: 07/22/2017] [Indexed: 12/21/2022] Open
Abstract
Excessive neutrophil infiltration of the lungs is a common contributor to immune-related pathology in many pulmonary disease states. In response to pathogenic infection, airway epithelial cells produce hepoxilin A3 (HXA3), initiating neutrophil transepithelial migration. Migrated neutrophils amplify this recruitment by producing a secondary gradient of leukotriene B4 (LTB4). We sought to determine whether this two-step eicosanoid chemoattractant mechanism could be exploited by the pathogen Pseudomonas aeruginosa. ExoU, a P. aeruginosa cytotoxin, exhibits phospholipase A2 (PLA2) activity in eukaryotic hosts, an enzyme critical for generation of certain eicosanoids. Using in vitro and in vivo models of neutrophil transepithelial migration, we evaluated the impact of ExoU expression on eicosanoid generation and function. We conclude that ExoU, by virtue of its PLA2 activity, augments and compensates for endogenous host neutrophil cPLA2α function, leading to enhanced transepithelial migration. This suggests that ExoU expression in P. aeruginosa can circumvent immune regulation at key signaling checkpoints in the neutrophil, resulting in exacerbated neutrophil recruitment. Pseudomonas aeruginosa is an opportunistic pathogen that causes acute pneumonia in immune compromised patients, and infects 70–80% of patients suffering from cystic fibrosis. Infections can result in excessive airway inflammation, which lead to immune-mediated lung damage, in particular through the action of recruited white blood cells known as neutrophils. Certain strains of P. aeruginosa produce the exotoxin ExoU, which has been associated with increased virulence. ExoU causes host cell lysis by hydrolyzing host membrane lipids through its phospholipase activity. However, host phospholipases play a key role in immune signaling by mediating the production of lipids known as eicosanoids. We investigated whether separate from its cytolytic activity, ExoU could modulate host immune responses through its phospholipase activity by hijacking eicosanoid production. Using in vitro and in vivo models of neutrophil recruitment, we find that ExoU producing strains of P. aeruginosa elicit higher levels of the eicosanoid chemoattractant leukotriene B4 from migrated neutrophils. This results in increased neutrophil transepithelial migration. This work reveals a new mechanism for how bacterial pathogens alter our immune function, and highlights a new potential therapeutic strategy for moderating Pseudomonas pathogenesis in patients with cystic fibrosis and acute pneumonia.
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Affiliation(s)
- Michael A. Pazos
- Mucosal Immunology & Biology Research Center, Massachusetts General Hospital for Children, Boston, Massachusetts, United States of America
- Pediatrics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Bernard B. Lanter
- Mucosal Immunology & Biology Research Center, Massachusetts General Hospital for Children, Boston, Massachusetts, United States of America
- Pediatrics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Lael M. Yonker
- Mucosal Immunology & Biology Research Center, Massachusetts General Hospital for Children, Boston, Massachusetts, United States of America
- Pediatrics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Alex D. Eaton
- Mucosal Immunology & Biology Research Center, Massachusetts General Hospital for Children, Boston, Massachusetts, United States of America
| | - Waheed Pirzai
- Mucosal Immunology & Biology Research Center, Massachusetts General Hospital for Children, Boston, Massachusetts, United States of America
| | - Karsten Gronert
- Vision Science Program, School of Optometry, University of California at Berkeley, Berkeley, California, United States of America
| | - Joseph V. Bonventre
- Renal Division and Biomedical Engineering Division, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Bryan P. Hurley
- Mucosal Immunology & Biology Research Center, Massachusetts General Hospital for Children, Boston, Massachusetts, United States of America
- Pediatrics, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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12
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Phospholipase A activity of adenylate cyclase toxin mediates translocation of its adenylate cyclase domain. Proc Natl Acad Sci U S A 2017; 114:E6784-E6793. [PMID: 28760979 DOI: 10.1073/pnas.1701783114] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Adenylate cyclase toxin (ACT or CyaA) plays a crucial role in respiratory tract colonization and virulence of the whooping cough causative bacterium Bordetella pertussis Secreted as soluble protein, it targets myeloid cells expressing the CD11b/CD18 integrin and on delivery of its N-terminal adenylate cyclase catalytic domain (AC domain) into the cytosol, generates uncontrolled toxic levels of cAMP that ablates bactericidal capacities of phagocytes. Our study deciphers the fundamentals of the heretofore poorly understood molecular mechanism by which the ACT enzyme domain directly crosses the host cell membrane. By combining molecular biology, biochemistry, and biophysics techniques, we discover that ACT has intrinsic phospholipase A (PLA) activity, and that such activity determines AC translocation. Moreover, we show that elimination of the ACT-PLA activity abrogates ACT toxicity in macrophages, particularly at toxin concentrations close to biological reality of bacterial infection. Our data support a molecular mechanism in which in situ generation of nonlamellar lysophospholipids by ACT-PLA activity into the cell membrane would form, likely in combination with membrane-interacting ACT segments, a proteolipidic toroidal pore through which AC domain transfer could directly take place. Regulation of ACT-PLA activity thus emerges as novel target for therapeutic control of the disease.
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13
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Tessmer MH, Anderson DM, Buchaklian A, Frank DW, Feix JB. Cooperative Substrate-Cofactor Interactions and Membrane Localization of the Bacterial Phospholipase A 2 (PLA 2) Enzyme, ExoU. J Biol Chem 2017; 292:3411-3419. [PMID: 28069812 DOI: 10.1074/jbc.m116.760074] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 01/05/2017] [Indexed: 11/06/2022] Open
Abstract
The ExoU type III secretion enzyme is a potent phospholipase A2 secreted by the Gram-negative opportunistic pathogen, Pseudomonas aeruginosa Activation of phospholipase activity is induced by protein-protein interactions with ubiquitin in the cytosol of a targeted eukaryotic cell, leading to destruction of host cell membranes. Previous work in our laboratory suggested that conformational changes within a C-terminal domain of the toxin might be involved in the activation mechanism. In this study, we use site-directed spin-labeling electron paramagnetic resonance spectroscopy to investigate conformational changes in a C-terminal four-helical bundle region of ExoU as it interacts with lipid substrates and ubiquitin, and to examine the localization of this domain with respect to the lipid bilayer. In the absence of ubiquitin or substrate liposomes, the overall structure of the C-terminal domain is in good agreement with crystallographic models derived from ExoU in complex with its chaperone, SpcU. Significant conformational changes are observed throughout the domain in the presence of ubiquitin and liposomes combined that are not observed with either liposomes or ubiquitin alone. In the presence of ubiquitin, two interhelical loops of the C-terminal four-helix bundle appear to penetrate the membrane bilayer, stabilizing ExoU-membrane association. Thus, ubiquitin and the substrate lipid bilayer act synergistically to induce a conformational rearrangement in the C-terminal domain of ExoU.
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Affiliation(s)
- Maxx H Tessmer
- Department of Microbiology and Molecular Genetics; Center for Infectious Disease Research
| | - David M Anderson
- Department of Microbiology and Molecular Genetics; Center for Infectious Disease Research
| | | | - Dara W Frank
- Department of Microbiology and Molecular Genetics; Center for Infectious Disease Research
| | - Jimmy B Feix
- Center for Infectious Disease Research; Department of Biophysics; National Biomedical EPR Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226.
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Sawa T, Hamaoka S, Kinoshita M, Kainuma A, Naito Y, Akiyama K, Kato H. Pseudomonas aeruginosa Type III Secretory Toxin ExoU and Its Predicted Homologs. Toxins (Basel) 2016; 8:toxins8110307. [PMID: 27792159 PMCID: PMC5127104 DOI: 10.3390/toxins8110307] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 10/20/2016] [Accepted: 10/21/2016] [Indexed: 11/16/2022] Open
Abstract
Pseudomonas aeruginosa ExoU, a type III secretory toxin and major virulence factor with patatin-like phospholipase activity, is responsible for acute lung injury and sepsis in immunocompromised patients. Through use of a recently updated bacterial genome database, protein sequences predicted to be homologous to Ps. aeruginosa ExoU were identified in 17 other Pseudomonas species (Ps. fluorescens, Ps. lundensis, Ps. weihenstephanensis, Ps. marginalis, Ps. rhodesiae, Ps. synxantha, Ps. libanensis, Ps. extremaustralis, Ps. veronii, Ps. simiae, Ps. trivialis, Ps. tolaasii, Ps. orientalis, Ps. taetrolens, Ps. syringae, Ps. viridiflava, and Ps. cannabina) and 8 Gram-negative bacteria from three other genera (Photorhabdus, Aeromonas, and Paludibacterium). In the alignment of the predicted primary amino acid sequences used for the phylogenetic analyses, both highly conserved and nonconserved parts of the toxin were discovered among the various species. Further comparative studies of the predicted ExoU homologs should provide us with more detailed information about the unique characteristics of the Ps. aeruginosa ExoU toxin.
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Affiliation(s)
- Teiji Sawa
- Department of Anesthesiology, School of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
| | - Saeko Hamaoka
- Department of Anesthesiology, School of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
| | - Mao Kinoshita
- Department of Anesthesiology, School of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
| | - Atsushi Kainuma
- Department of Anesthesiology, School of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
| | - Yoshifumi Naito
- Department of Anesthesiology, School of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
| | - Koichi Akiyama
- Department of Anesthesiology, School of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
| | - Hideya Kato
- Department of Anesthesiology, School of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
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15
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Wang C, Liu X, Wang J, Zhou J, Cui Z, Zhang LH. Design and characterization of a polyamine derivative inhibiting the expression of type III secretion system in Pseudomonas aeruginosa. Sci Rep 2016; 6:30949. [PMID: 27484745 PMCID: PMC4971474 DOI: 10.1038/srep30949] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 07/12/2016] [Indexed: 12/24/2022] Open
Abstract
The type III secretion system (TTSS) of Pseudomonas aeruginosa is a key virulence determinant for infection of eukaryotic hosts. Based on the findings that spermidine-mediated host-pathogen signalling is important for activation of type III secretion systems (TTSS), in this study, we designed, synthesized and evaluated a series of polyamine derivatives for their potentials in inhibiting the expression TTSS in P. aeruginosa. In vitro assay of 15 compounds synthesized in this study unveiled stringent structural requirements for TTSS-inhibitory activity. Among them, R101SPM, a conjugate between rhodamine 101 and spermine, showed a potent activity in inhibition of the TTSS gene expression and in attenuation of the TTSS-mediated cytotoxicity on human cells. In vivo analysis demonstrated that R101SPM could rescue mice from the lethal infection by P. aeruginosa. Moreover, genetic analysis showed that the full TTSS-inhibitory activity of R101SPM required a functional spermidine transporter. Taken together, our results present a new class of lead molecules for developing anti-virulence drugs and demonstrate that the spermidine transporter SpuDEGHF of P. aeruginosa is a promising drug target.
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Affiliation(s)
- Chao Wang
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore.,National Cancer Centre Singapore, 11 Hospital Drive, 169610, Singapore
| | - Xiaoling Liu
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore.,Chongqing Academy of Chinese Materia Medica, 400065, China
| | - Jing Wang
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore
| | - Jianuan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, 510642, China
| | - Zining Cui
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, 510642, China
| | - Lian-Hui Zhang
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore.,Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, 510642, China
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16
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IV Immunoglobulin for Acute Lung Injury and Bacteremia in Pseudomonas aeruginosa Pneumonia. Crit Care Med 2016; 44:e12-24. [PMID: 26317571 DOI: 10.1097/ccm.0000000000001271] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVES Virulent and multidrug-resistant Pseudomonas aeruginosa causes a lethal pneumonia, especially in patients who are artificially ventilated. It has been reported that the virulence mechanism used by P. aeruginosa, which is linked to acute lung injury, is strongly associated with the type III secretion system, and specific antibodies targeting this system have shown a protective effect in both experimental and clinical settings. We investigated the effect of administering IV immunoglobulins on P. aeruginosa pneumonia, including its associated bacteremia and mortality, although focusing especially on type III secretion system-associated P. aeruginosa virulence. DESIGN Prospective randomized and controlled animal study. SETTING University laboratory. SUBJECTS Male ICR mice. INTERVENTIONS Mice were infected intratracheally with a lethal dose of the virulent P. aeruginosa PA103 strain. IV immunoglobulin administration was examined in three different settings: 1) premixed; 2) pre-IV, prophylactic administration before bacterial infection; and 3) post-IV, therapeutic administration after bacterial infection. The effect of specific antigen titer depletion of IV immunoglobulins was also examined. MEASUREMENTS AND MAIN RESULTS Survival and body temperature were monitored for 24 hours. Bacteremia, cytokine concentration, myeloperoxidase activity, WBC counts in the blood, and lung bacterial load were evaluated. Survival improved significantly in mice that received IV immunoglobulins (p < 0.05). Lung edema, lung bacteriologic load, and bacteremia decreased significantly in the IV immunoglobulin-treated mice (p < 0.05). The mechanism of protection was associated with the presence of antibodies against both PcrV and some bacterial surface antigens in the IV immunoglobulins. CONCLUSIONS IV immunoglobulin administration had a significantly protective effect against lethal infection from virulent P. aeruginosa. Prophylactic IV immunoglobulin administration at the highest dose was comparable with that achieved by administrating a specific anti-PcrV polyclonal IgG into the mice. The mechanism of protection is likely to involve the synergic action of anti-PcrV titers and antibodies against some surface antigen(s) that block the type III secretion system-associated virulence of P. aeruginosa.
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Sawa T, Shimizu M, Moriyama K, Wiener-Kronish JP. Association between Pseudomonas aeruginosa type III secretion, antibiotic resistance, and clinical outcome: a review. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2014; 18:668. [PMID: 25672496 PMCID: PMC4331484 DOI: 10.1186/s13054-014-0668-9] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Pseudomonas aeruginosa uses a complex type III secretion system to inject the toxins ExoS, ExoT, ExoU, and ExoY into the cytosol of target eukaryotic cells. This system is regulated by the exoenzyme S regulon and includes the transcriptional activator ExsA. Of the four toxins, ExoU is characterized as the major virulence factor responsible for alveolar epithelial injury in patients with P. aeruginosa pneumonia. Virulent strains of P. aeruginosa possess the exoU gene, whereas non-virulent strains lack this particular gene. The mechanism of virulence for the exoU+ genotype relies on the presence of a pathogenic gene cluster (PAPI-2) encoding exoU and its chaperone, spcU. The ExoU toxin has a patatin-like phospholipase domain in its N-terminal, exhibits phospholipase A2 activity, and requires a eukaryotic cell factor for activation. The C-terminal of ExoU has a ubiquitinylation mechanism of activation. This probably induces a structural change in enzymatic active sites required for phospholipase A2 activity. In P. aeruginosa clinical isolates, the exoU+ genotype correlates with a fluoroquinolone resistance phenotype. Additionally, poor clinical outcomes have been observed in patients with pneumonia caused by exoU+-fluoroquinolone-resistant isolates. Therefore, the potential exists to improve clinical outcomes in patients with P. aeruginosa pneumonia by identifying virulent and antimicrobial drug-resistant strains through exoU genotyping or ExoU protein phenotyping or both.
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18
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Sato H, Frank DW. Intoxication of host cells by the T3SS phospholipase ExoU: PI(4,5)P2-associated, cytoskeletal collapse and late phase membrane blebbing. PLoS One 2014; 9:e103127. [PMID: 25061861 PMCID: PMC4111512 DOI: 10.1371/journal.pone.0103127] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 06/27/2014] [Indexed: 01/09/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that is associated with hospital-acquired infections, ventilator-associated pneumonia, and morbidity of immunocompromised individuals. A subpopulation of P. aeruginosa encodes a protein, ExoU, which exhibits acute cytotoxicity. Toxicity is directly related to the phospholipase A2 activity of the protein after injection into the host cytoplasm via a type III secretion system. ExoU enzymatic activity requires eukaryotic cofactors, ubiquitin or ubiquitin-modified proteins. When administered extracellularly, ExoU is unable to intoxicate epithelial cells in culture, even in the presence of the cofactor. Injection or transfection of ExoU is necessary to observe the acute cytotoxic response. Biochemical approaches indicate that ExoU possesses high affinity to a multifunctional phosphoinositide, phosphatidylinositol 4,5-bisphosphate or PI(4,5)P2 and that it is capable of utilizing this phospholipid as a substrate. In eukaryotic cells, PI(4,5)P2 is mainly located in the cytoplasmic side of the plasma membrane and anchors adaptor proteins that are involved in cytoskeletal structures, focal adhesions, and plasma membranes. Time-lapse fluorescent microscopy analyses of infected live cells demonstrate that ExoU intoxication correlates with intracellular damage in the early phases of infection, such as disruption of focal adhesions, cytoskeletal collapse, actin depolymerization, and cell rounding. At later time points, a membrane blebbing phenotype was prominent prior to the loss of the plasma membrane integrity and barrier function. Membrane blebbing appears to accelerate membrane rupture and the release of intracellular markers. Our data suggest that in eukaryotic host cells, intracellular ExoU targets and hydrolyzes PI(4,5)P2 on the plasma membrane, causing a subsequent disruption of cellular structures and membrane integrity.
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Affiliation(s)
- Hiromi Sato
- Center for Infectious Disease Research, Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- * E-mail:
| | - Dara W. Frank
- Center for Infectious Disease Research, Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
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19
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The molecular mechanism of acute lung injury caused by Pseudomonas aeruginosa: from bacterial pathogenesis to host response. J Intensive Care 2014; 2:10. [PMID: 25520826 PMCID: PMC4267601 DOI: 10.1186/2052-0492-2-10] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2013] [Accepted: 01/28/2014] [Indexed: 12/25/2022] Open
Abstract
Pseudomonas aeruginosa is the most common gram-negative pathogen causing pneumonia in immunocompromised patients. Acute lung injury induced by bacterial exoproducts is associated with a poor outcome in P. aeruginosa pneumonia. The major pathogenic toxins among the exoproducts of P. aeruginosa and the mechanism by which they cause acute lung injury have been investigated: exoenzyme S and co-regulated toxins were found to contribute to acute lung injury. P. aeruginosa secretes these toxins through the recently defined type III secretion system (TTSS), by which gram-negative bacteria directly translocate toxins into the cytosol of target eukaryotic cells. TTSS comprises the secretion apparatus (termed the injectisome), translocators, secreted toxins, and regulatory components. In the P. aeruginosa genome, a pathogenic gene cluster, the exoenzyme S regulon, encodes genes underlying the regulation, secretion, and translocation of TTSS. Four type III secretory toxins, namely ExoS, ExoT, ExoU, and ExoY, have been identified in P. aeruginosa. ExoS is a 49-kDa form of exoenzyme S, a bifunctional toxin that exerts ADP-ribosyltransferase and GTPase-activating protein (GAP) activity to disrupt endocytosis, the actin cytoskeleton, and cell proliferation. ExoT, a 53-kDa form of exoenzyme S with 75% sequence homology to ExoS, also exerts GAP activity to interfere with cell morphology and motility. ExoY is a nucleotidal cyclase that increases the intracellular levels of cyclic adenosine and guanosine monophosphates, resulting in edema formation. ExoU, which exhibits phospholipase A2 activity activated by host cell ubiquitination after translocation, is a major pathogenic cytotoxin that causes alveolar epithelial injury and macrophage necrosis. Approximately 20% of clinical isolates also secrete ExoU, a gene encoded within an insertional pathogenic gene cluster named P. aeruginosa pathogenicity island-2. The ExoU secretory phenotype is associated with a poor clinical outcome in P. aeruginosa pneumonia. Blockade of translocation by TTSS or inhibition of the enzymatic activity of translocated toxins has the potential to decrease acute lung injury and improve clinical outcome.
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20
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Rolsma SL, Frank DW. In vitro assays to monitor the activity of Pseudomonas aeruginosa Type III secreted proteins. Methods Mol Biol 2014; 1149:171-84. [PMID: 24818904 PMCID: PMC5860653 DOI: 10.1007/978-1-4939-0473-0_14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Pseudomonas aeruginosa secretes numerous toxins and destructive enzymes that play distinct roles in pathogenesis. The Type III secretion system (T3SS) of Pseudomonas is a system that delivers a subset of toxins directly into the cytoplasm of eukaryotic cells. The secreted effectors include ExoS, ExoT, ExoU, and ExoY. In this chapter, we describe methods to induce T3S expression and measure the enzymatic activities of each effector in in vitro assays. ExoU is a phospholipase and its activity can be measured in a fluorescence-based assay monitoring the cleavage of the fluorogenic substrate, PED6. ExoS and ExoT both possess ADP-ribosyltransferase (ADPRT) and GTPase-activating protein (GAP) activity. ADPRT activity can be assessed by using radiolabeled nicotinamide adenine dinucleotide (NAD(+)) and measuring the covalent incorporation of ADP-ribose into a target protein. GAP activity is measured by the release of radiolabeled phosphate from [γ-(32)P]GTP-bound target proteins. In accordance with recent trends towards reducing the use of radioactivity in the laboratory, alternative assays using fluorescent or biotin-labeled reagents are described. ExoY is a nucleotidyl cyclase; cAMP production stimulated by ExoY can be monitored using reverse-phase HPLC or with commercially available immunological assays.
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Affiliation(s)
- Stephanie L Rolsma
- Department of Microbiology and Molecular Genetics, Center of Infectious Disease Research, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI, 53226, USA
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21
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Kuhle K, Flieger A. Legionella phospholipases implicated in virulence. Curr Top Microbiol Immunol 2013; 376:175-209. [PMID: 23925490 DOI: 10.1007/82_2013_348] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Phospholipases are diverse enzymes produced in eukaryotic hosts and their bacterial pathogens. Several pathogen phospholipases have been identified as major virulence factors acting mainly in two different modes: on the one hand, they have the capability to destroy host membranes and on the other hand they are able to manipulate host signaling pathways. Reaction products of bacterial phospholipases may act as secondary messengers within the host and therefore influence inflammatory cascades and cellular processes, such as proliferation, migration, cytoskeletal changes as well as membrane traffic. The lung pathogen and intracellularly replicating bacterium Legionella pneumophila expresses a variety of phospholipases potentially involved in disease-promoting processes. So far, genes encoding 15 phospholipases A, three phospholipases C, and one phospholipase D have been identified. These cell-associated or secreted phospholipases may contribute to intracellular establishment, to egress of the pathogen from the host cell, and to the observed lung pathology. Due to the importance of phospholipase activities for host cell processes, it is conceivable that the pathogen enzymes may mimic or substitute host cell phospholipases to drive processes for the pathogen's benefit. The following chapter summarizes the current knowledge on the L. pneumophila phospholipases, especially their substrate specificity, localization, mode of secretion, and impact on host cells.
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Affiliation(s)
- Katja Kuhle
- FG 11 - Division of Enteropathogenic Bacteria and Legionella, Robert Koch-Institut, Burgstr. 37, 38855, Wernigerode, Germany
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Structure of the type III secretion effector protein ExoU in complex with its chaperone SpcU. PLoS One 2012; 7:e49388. [PMID: 23166655 PMCID: PMC3498133 DOI: 10.1371/journal.pone.0049388] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 10/10/2012] [Indexed: 11/21/2022] Open
Abstract
Disease causing bacteria often manipulate host cells in a way that facilitates the infectious process. Many pathogenic gram-negative bacteria accomplish this by using type III secretion systems. In these complex secretion pathways, bacterial chaperones direct effector proteins to a needle-like secretion apparatus, which then delivers the effector protein into the host cell cytosol. The effector protein ExoU and its chaperone SpcU are components of the Pseudomonas aeruginosa type III secretion system. Secretion of ExoU has been associated with more severe infections in both humans and animal models. Here we describe the 1.92 Å X-ray structure of the ExoU–SpcU complex, a full-length type III effector in complex with its full-length cognate chaperone. Our crystallographic data allow a better understanding of the mechanism by which ExoU kills host cells and provides a foundation for future studies aimed at designing inhibitors of this potent toxin.
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The Rickettsia prowazekii ExoU homologue possesses phospholipase A1 (PLA1), PLA2, and lyso-PLA2 activities and can function in the absence of any eukaryotic cofactors in vitro. J Bacteriol 2011; 193:4634-42. [PMID: 21764940 DOI: 10.1128/jb.00141-11] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Here we have characterized the Rickettsia prowazekii RP534 protein, a homologue of the Pseudomonas aeruginosa ExoU phospholipase A (PLA) secreted cytotoxin. Our studies showed that purified recombinant RP534 PLA possessed the predicted PLA(2) and lyso-PLA(2) activities based on what has been published for P. aeruginosa ExoU. RP534 also displayed PLA(1) activity under the conditions tested, whereas ExoU did not. In addition, recombinant RP534 displayed a basal PLA activity that could hydrolyze phosphatidylcholine in the absence of any eukaryotic cofactors. Interestingly, the addition of bovine liver superoxide dismutase 1 (SOD1), a known activator of P. aeruginosa ExoU, resulted in an increased rate of RP534-catalyzed phospholipid hydrolysis, indicating that mechanisms of activation of the ExoU family of PLAs may be evolutionarily conserved. The mechanism of SOD1-dependent stimulation of RP534 was further examined using active site mutants and a fluorogenic phospholipid substrate whose hydrolysis by RP534 over a short time course is measureable only in the presence of SOD1. These studies suggest a mechanism by which SOD1 stimulates RP534 activity once it has bound to the substrate. We also show that antibody raised against RP534 was useful for immunoprecipitating active RP534 from R. prowazekii lysed cell extracts, thus verifying that this protein is expressed and active in rickettsiae isolated from embryonated hen egg yolk sacs.
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24
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Distribution of the type III effector proteins-encoding genes among nosocomial Pseudomonas aeruginosa isolates from Bulgaria. ANN MICROBIOL 2010. [DOI: 10.1007/s13213-010-0079-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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25
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Schunder E, Adam P, Higa F, Remer KA, Lorenz U, Bender J, Schulz T, Flieger A, Steinert M, Heuner K. Phospholipase PlaB is a new virulence factor of Legionella pneumophila. Int J Med Microbiol 2010; 300:313-23. [DOI: 10.1016/j.ijmm.2010.01.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 01/08/2010] [Accepted: 01/20/2010] [Indexed: 12/01/2022] Open
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Abstract
The Gram-negative bacterium Pseudomonas aeruginosa uses a complex type III secretion apparatus to inject effector proteins into host cells. The configuration of this secretion machinery, the activities of the proteins that are injected by it and the consequences of this process for infection are now being elucidated. This Review summarizes our current knowledge of P. aeruginosa type III secretion, including the secretion and translocation machinery, the regulation of this machinery, and the associated chaperones and effector proteins. The features of this interesting secretion system have important implications for the pathogenesis of P. aeruginosa infections and for other type III secretion systems.
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Affiliation(s)
- Alan R Hauser
- Departments of MicrobiologyImmunology and Medicine, Northwestern University, Chicago, Illinois 60611, USA.
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Reina-Pinto JJ, Voisin D, Kurdyukov S, Faust A, Haslam RP, Michaelson LV, Efremova N, Franke B, Schreiber L, Napier JA, Yephremov A. Misexpression of FATTY ACID ELONGATION1 in the Arabidopsis epidermis induces cell death and suggests a critical role for phospholipase A2 in this process. THE PLANT CELL 2009; 4:625-8. [PMID: 19376931 PMCID: PMC2685613 DOI: 10.1105/tpc.109.065565] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 03/09/2009] [Accepted: 03/31/2009] [Indexed: 05/20/2023]
Abstract
Very-long-chain fatty acids (VLCFAs) are important functional components of various lipid classes, including cuticular lipids in the higher plant epidermis and lipid-derived second messengers. Here, we report the characterization of transgenic Arabidopsis thaliana plants that epidermally express FATTY ACID ELONGATION1 (FAE1), the seed-specific beta-ketoacyl-CoA synthase (KCS) catalyzing the first rate-limiting step in VLCFA biosynthesis. Misexpression of FAE1 changes the VLCFAs in different classes of lipids but surprisingly does not complement the KCS fiddlehead mutant. FAE1 misexpression plants are similar to the wild type but display an essentially glabrous phenotype, owing to the selective death of trichome cells. This cell death is accompanied by membrane damage, generation of reactive oxygen species, and callose deposition. We found that nuclei of arrested trichome cells in FAE1 misexpression plants cell-autonomously accumulate high levels of DNA damage, including double-strand breaks characteristic of lipoapoptosis. A chemical genetic screen revealed that inhibitors of KCS and phospholipase A2 (PLA2), but not inhibitors of de novo ceramide biosynthesis, rescue trichome cells from death. These results support the functional role of acyl chain length of fatty acids and PLA2 as determinants for programmed cell death, likely involving the exchange of VLCFAs between phospholipids and the acyl-CoA pool.
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Phase behavior of ternary mannosylerythritol lipid/water/oil systems. Colloids Surf B Biointerfaces 2009; 68:207-12. [DOI: 10.1016/j.colsurfb.2008.10.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 09/30/2008] [Accepted: 10/05/2008] [Indexed: 11/19/2022]
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29
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Ganter MT, Roux J, Su G, Lynch SV, Deutschman CS, Weiss YG, Christiaans SC, Myazawa B, Kipnis E, Wiener-Kronish JP, Howard M, Pittet JF. Role of small GTPases and alphavbeta5 integrin in Pseudomonas aeruginosa-induced increase in lung endothelial permeability. Am J Respir Cell Mol Biol 2008; 40:108-18. [PMID: 18703797 DOI: 10.1165/rcmb.2007-0454oc] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that can cause severe pneumonia associated with airspace flooding with protein-rich edema in critically ill patients. The type III secretion system is a major virulence factor and contributes to dissemination of P. aeruginosa. However, it is still unknown which particular bacterial toxin and which cellular pathways are responsible for the increase in lung endothelial permeability induced by P. aeruginosa. Thus, the first objective of this study was to determine the mechanisms by which this species causes an increase in lung endothelial permeability. The results showed that ExoS and ExoT, two of the four known P. aeruginosa type III cytotoxins, were primarily responsible for bacterium-induced increases in protein permeability across the lung endothelium via an inhibition of Rac1 and an activation of the RhoA signaling pathway. In addition, inhibition of the alphavbeta5 integrin, a central regulator of lung vascular permeability, prevented these P. aeruginosa-mediated increases in albumin flux due to endothelial permeability. Finally, prior activation of the stress protein response or adenoviral gene transfer of the inducible heat shock protein Hsp72 also inhibited the damaging effects of P. aeruginosa on the barrier function of lung endothelium. Taken together, these results demonstrate the critical role of the RhoA/alphavbeta5 integrin pathway in mediating P. aeruginosa-induced lung vascular permeability. In addition, activation of the stress protein response with pharmacologic inhibitors of Hsp90 may protect lungs against P. aeruginosa-induced permeability changes.
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Affiliation(s)
- Michael T Ganter
- Department of Anesthesia and Surgery, University of California San Francisco, San Francisco, California 94110, USA
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30
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Multiple roles of phospholipase A2 during lung infection and inflammation. Infect Immun 2008; 76:2259-72. [PMID: 18411286 DOI: 10.1128/iai.00059-08] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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31
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Sitkiewicz I, Stockbauer KE, Musser JM. Secreted bacterial phospholipase A2 enzymes: better living through phospholipolysis. Trends Microbiol 2006; 15:63-9. [PMID: 17194592 DOI: 10.1016/j.tim.2006.12.003] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Revised: 11/23/2006] [Accepted: 12/13/2006] [Indexed: 11/23/2022]
Abstract
Phospholipases are ubiquitous and diverse enzymes that induce changes in membrane composition, activate the inflammatory cascade and alter cell signaling pathways. Recent evidence suggests that certain bacterial pathogens have acquired genes encoding secreted phospholipase A2 enzymes through lateral gene transfer events. The two best-studied members of this class of enzyme are ExoU and SlaA, which are produced by Pseudomonas aeruginosa and group A Streptococcus, respectively. These enzymes modulate the host inflammatory response, increase the severity of disease and otherwise alter host-pathogen interactions. We propose that a key function of ExoU and SlaA is to increase the fitness of the subclones expressing these enzymes, thereby increasing the population size of the PLA2-positive strains and enhancing the likelihood of encountering an at-risk host.
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Affiliation(s)
- Izabela Sitkiewicz
- Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, Houston, TX 77030, USA
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Stirling FR, Cuzick A, Kelly SM, Oxley D, Evans TJ. Eukaryotic localization, activation and ubiquitinylation of a bacterial type III secreted toxin. Cell Microbiol 2006; 8:1294-309. [PMID: 16882033 DOI: 10.1111/j.1462-5822.2006.00710.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Type III secretion is a widespread method whereby Gram-negative bacteria introduce toxins into eukaryotic cells. These toxins mimic or subvert a normal cellular process by interacting with a specific target, although how toxins reach their site of action is unclear. We set out to investigate the intracellular localization of a type III toxin of Pseudomonas aeruginosa called ExoU, which has phospholipase activity and requires a eukaryotic factor for activity. We found that ExoU is localized to the plasma membrane and undergoes modification within the cell by addition of two ubiquitin molecules at lysine-178. A region of five amino acids at position 679-683 near the C-terminus of the ExoU protein controls both membrane localization and ubiquitinylation. Site-directed mutagenesis identified a tryptophan at position 681 as crucial for these effects. We found that the same region at position 679-683 was also required for cell toxicity produced by ExoU as well as in vitro phospholipase activity. Localization of the phospholipase ExoU to the plasma membrane is thus required for activation and allows efficient utilization of adjacent substrate phospholipids.
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Affiliation(s)
- Fiona R Stirling
- Division of Immunology, Infection and Inflammation, University of Glasgow, Glasgow, UK
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Shaver CM, Hauser AR. Interactions between effector proteins of the Pseudomonas aeruginosa type III secretion system do not significantly affect several measures of disease severity in mammals. MICROBIOLOGY-SGM 2006; 152:143-152. [PMID: 16385124 DOI: 10.1099/mic.0.28368-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
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.
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Affiliation(s)
- Ciara M Shaver
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Searle 6-495, Chicago, IL 60611, USA
| | - Alan R Hauser
- Department of Medicine, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Searle 6-495, Chicago, IL 60611, USA
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Searle 6-495, Chicago, IL 60611, USA
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Kipnis E, Sawa T, Wiener-Kronish J. Targeting mechanisms of Pseudomonas aeruginosa pathogenesis. Med Mal Infect 2006; 36:78-91. [PMID: 16427231 DOI: 10.1016/j.medmal.2005.10.007] [Citation(s) in RCA: 198] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Accepted: 10/18/2005] [Indexed: 01/08/2023]
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen responsible for ventilator-acquired pneumonia, acute lower respiratory tract infections in immunocompromised patients and chronic respiratory infections in cystic fibrosis patients. High incidence, infection severity and increasing resistance characterize P. aeruginosa infections, highlighting the need for new therapeutic options. One such option is to target the many pathogenic mechanisms conferred to P. aeruginosa by its large genome encoding many different virulence factors. This article reviews the pathogenic mechanisms and potential therapies targeting these mechanisms in P. aeruginosa respiratory infections.
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Affiliation(s)
- E Kipnis
- Department of Anesthesia and Perioperative Care, University of California San Francisco, 513 Parnassus Avenue, Room s-261, Medical Science Building, Box 0542, San Francisco, CA 94143, USA.
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35
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Saliba AM, Nascimento DO, Silva MCA, Assis MC, Gayer CRM, Raymond B, Coelho MGP, Marques EA, Touqui L, Albano RM, Lopes UG, Paiva DD, Bozza PT, Plotkowski MC. Eicosanoid-mediated proinflammatory activity of Pseudomonas aeruginosa ExoU. Cell Microbiol 2006; 7:1811-22. [PMID: 16309466 DOI: 10.1111/j.1462-5822.2005.00635.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
As Pseudomonas aeruginosa ExoU possesses two functional blocks of homology to calcium-independent (iPLA(2)) and cytosolic phospholipase A(2) (cPLA(2)), we addressed the question whether it would exhibit a proinflammatory activity by enhancing the synthesis of eicosanoids by host organisms. Endothelial cells from the HMEC-1 line infected with the ExoU-producing PA103 strain exhibited a potent release of arachidonic acid (AA) that could be significantly inhibited by methyl arachidonyl fluorophosphonate (MAFP), a specific PLA(2) inhibitor, as well as significant amounts of the cyclooxygenase (COX)-derived prostaglandins PGE(2) and PGI(2). Cells infected with an isogenic mutant defective in ExoU synthesis did not differ from non-infected cells in the AA release and produced prostanoids in significantly lower concentrations. Infection by PA103 induced a marked inflammatory response in two different in vivo experimental models. Inoculation of the parental bacteria into mice footpads led to an early increase in the infected limb volume that could be significantly reduced by inhibitors of both COX and lipoxygenase (ibuprofen and NDGA respectively). In an experimental respiratory infection model, bronchoalveolar lavage (BAL) from mice instilled with 10(4) cfu of PA103 exhibited a marked influx of inflammatory cells and PGE(2) release that could be significantly reduced by indomethacin, a non-selective COX inhibitor. Our results suggest that ExoU may contribute to P. aeruginosa pathogenesis by inducing an eicosanoid-mediated inflammatory response of host organisms.
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Affiliation(s)
- A M Saliba
- Departamento de Patologia e Laboratórios, Universidade do Estado do Rio de Janeiro, Brazil
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Li L, Ledizet M, Kar K, Koski RA, Kazmierczak BI. An indirect enzyme-linked immunosorbent assay for rapid and quantitative assessment of Type III virulence phenotypes of Pseudomonas aeruginosa isolates. Ann Clin Microbiol Antimicrob 2005; 4:22. [PMID: 16375761 PMCID: PMC1360672 DOI: 10.1186/1476-0711-4-22] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2005] [Accepted: 12/23/2005] [Indexed: 11/21/2022] Open
Abstract
Background The presence of a Type III secretion system in clinical isolates of Pseudomonas aeruginosa is associated with severe disease and poor outcomes in infections caused by this pathogen. We describe an indirect enzyme-linked immunosorbent assay that rapidly and quantitatively detects two exotoxins, ExoU and ExoT, and two structural components, PopD and PcrV, of the P. aeruginosa Type III secretion system after in-vitro growth in a calcium-free minimal medium. Methods We used this assay to characterize the Type III secretion phenotype of 74 clinical isolates of P. aeruginosa. Findings were compared with results of standard immunoblotting and correlated with Type III secretion-dependent virulence of isolates toward cultured epithelial cells. Results Results of the ELISA assay were concordant with immunoblot detection of the secreted antigens for 73 of 74 isolates. The Type III secretion phenotype assessed by this immunoassay predicted bacterial virulence toward epithelial cells in vitro for all but five of the clinical isolates. Conclusion The availability of an ELISA assay for rapid detection of Type III secreted virulence factors will facilitate large clinical studies to examine whether the Type III secretion phenotype of a P. aeruginosa isolate predicts the course of clinical disease in a patient and should be taken into account in determining optimal treatment strategies for infected patients.
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Affiliation(s)
- Li Li
- Department of Internal Medicine (Infectious Diseases), Yale University School of Medicine, New Haven CT, USA
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven CT, USA
| | | | | | | | - Barbara I Kazmierczak
- Department of Internal Medicine (Infectious Diseases), Yale University School of Medicine, New Haven CT, USA
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven CT, USA
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Saliba AM, de Assis MC, Nishi R, Raymond B, Marques EDA, Lopes UG, Touqui L, Plotkowski MC. Implications of oxidative stress in the cytotoxicity of Pseudomonas aeruginosa ExoU. Microbes Infect 2005; 8:450-9. [PMID: 16293434 DOI: 10.1016/j.micinf.2005.07.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 07/15/2005] [Accepted: 07/19/2005] [Indexed: 11/23/2022]
Abstract
ExoU PLA2-like activity has been shown to account for membrane lysis and acute death of infected cells. Translocation of effector proteins by the type III secretion systems depends on close contact between microbial and host cells. Our finding that both the ExoU-producing PA103 Pseudomonas aeruginosa and its mutant obtained by deletion of exoU adhered poorly to endothelial cells (EC) led to the hypothesis that, in some cells, the amount of injected toxin may not be enough to induce cell lysis but cells would suffer from a long-term effect of ExoU intoxication. To address this question, cells were exposed to both bacteria for 1 h and then treated with gentamicin-containing medium, to eliminate infecting microorganisms. After 24 h, the percentage of viable EC in PA103-infected cultures was significantly lower than in cultures exposed to the mutant, as determined by the MTT assay. Cell death was not likely to depend on the ExoU lytic activity since cell labeling with propidium iodide was similar in cultures infected with both bacterial strains. Bacterial cytotoxicity was significantly reduced by MAFP, a specific inhibitor of cPLA2 and iPLA2. Since the PLA2 activity on membrane phospholipids generates free fatty acid, including arachidonic acid (AA), we next compared the bacterial ability to release AA from infected EC. PA103 was shown to induce a potent AA release that was inhibited by MAFP. AA oxidation by oxygenases generates eicosanoids, known to induce both cell death and proliferation. However neither inhibitors of cyclooxygenases (ibuprofen) nor lipoxygenases (NDGA) reduced the ExoU toxicity. Since non-enzymatic oxidation of AA generates reactive radicals, we next investigated the PA103 ability to induce oxidative stress in infected cells. FACS analysis of cell labeling with the C-11 fluor probe and with anti-4-hydroxynonel antibody revealed a significant peroxidation of cell membrane lipids. These results, together with our finding that PA103-infected EC death was significantly attenuated by alpha-tocopherol, led to the conclusion that AA-induced oxidative stress may be another mechanism of cell damage in the course of infection by ExoU-producing P. aeruginosa.
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Affiliation(s)
- Alessandra M Saliba
- Department of Microbiology and Immunology, State University of Rio de Janeiro, FCM/UERJ, 551-030 Rio de Janeiro, Brazil
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Zolfaghar I, Angus AA, Kang PJ, To A, Evans DJ, Fleiszig SMJ. Mutation of retS, encoding a putative hybrid two-component regulatory protein in Pseudomonas aeruginosa, attenuates multiple virulence mechanisms. Microbes Infect 2005; 7:1305-16. [PMID: 16027020 DOI: 10.1016/j.micinf.2005.04.017] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2004] [Revised: 04/21/2005] [Accepted: 04/25/2005] [Indexed: 10/25/2022]
Abstract
Two-component regulatory systems play an important role in bacterial virulence. We report that mutation of a Pseudomonas aeruginosa gene designated retS (previously designated fimK; accession number PA4856) encoding a putative hybrid two-component regulator, attenuates multiple virulence mechanisms. The retS mutant was selected from a Tn5 transposon library of the cytotoxic P. aeruginosa strain PA103 based upon expression of a small-colony phenotype suggestive of reduced surface-associated "twitching" motility, a property dependent upon type IV pili. Subsequent analysis revealed that the mutant expressed pilin, albeit at lower levels than wild-type PA103. In a murine model of corneal infection, retS mutation was associated with delayed disease development and altered pathology. In vitro, retS mutants demonstrated loss of acute cytotoxic activity towards corneal epithelia as determined by trypan blue exclusion and by LDH release assays (P<0.0001). This coincided with loss of ExsA-regulated type III secretion. Mutation of retS also impaired ExsA-independent pathogenic mechanisms. When compared to the exsA mutant of PA103, retS mutants exhibited reduced epithelial adherence and invasion and reduced intracellular survival within the cells after invasion. Time-lapse video microscopy revealed that retS mutants, compared to exsA mutants, had a reduced capacity to access, and move along, the basal cell surfaces of corneal epithelial cell monolayers. Taken together, these data suggest that the protein encoded by retS regulates various properties of P. aeruginosa including both ExsA-dependent and ExsA-independent virulence mechanisms.
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Affiliation(s)
- Irandokht Zolfaghar
- School of Optometry, 688 Minor Hall, University of California, Berkeley, CA 94720-2020, USA
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Banerji S, Bewersdorff M, Hermes B, Cianciotto NP, Flieger A. Characterization of the major secreted zinc metalloprotease- dependent glycerophospholipid:cholesterol acyltransferase, PlaC, of Legionella pneumophila. Infect Immun 2005; 73:2899-909. [PMID: 15845496 PMCID: PMC1087370 DOI: 10.1128/iai.73.5.2899-2909.2005] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Legionella pneumophila, an intracellular pathogen causing a severe pneumonia, possesses distinct lipolytic activities which have not been completely assigned to specific enzymes so far. We cloned and characterized a gene, plaC, encoding a protein with high homology to PlaA, the major secreted lysophospholipase A of L. pneumophila and to other hydrolytic enzymes belonging to the GDSL family. Here we show that L. pneumophila plaC mutants possessed reduced phospholipase A and lysophospholipase A activities and lacked glycerophospholipid:cholesterol acyltransferase activity in their culture supernatants. The mutants' reduced phospholipase A and acyltransferase activities were complemented by reintroduction of an intact copy of plaC. Additionally, plaC conferred increased lysophospholipase A and glycerophospholipid:cholesterol acytransferase activities to recombinant Escherichia coli. Furthermore, PlaC was shown to be another candidate exported by the L. pneumophila type II secretion system and was activated by a factor present in the bacterial culture supernatant dependent on the zinc metalloprotease. Finally, the role of plaC in intracellular infection of Acanthamoeba castellanii and U937 macrophages with L. pneumophila was assessed, and plaC was found to be dispensable. Thus, L. pneumophila possesses another secreted lipolytic enzyme, a protein with acyltransferase, phospholipase A, and lysophospholipase A activities. This enzyme is distinguished from the previously characterized phospholipases A and lysophospholipases A by its capacity not only to cleave fatty acids from lipids but to transfer them to cholesterol. Cholesterol is an important compound of eukaryotic membranes, and an acyltransferase might be a tool for host cell modification to fit the needs of the bacterium.
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Affiliation(s)
- Sangeeta Banerji
- Robert Koch-Institut, Research Group NG5 Pathogenesis of Legionella Infections, Nordufer 20, D-13353 Berlin, Germany
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Sato H, Feix JB, Hillard CJ, Frank DW. Characterization of phospholipase activity of the Pseudomonas aeruginosa type III cytotoxin, ExoU. J Bacteriol 2005; 187:1192-5. [PMID: 15659695 PMCID: PMC545705 DOI: 10.1128/jb.187.3.1192-1195.2005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recombinant ExoU (rExoU) and yeast extract were used to optimize an in vitro phospholipase assay as a basis for identifying the mechanism for enzyme activation and substrate specificity. Our results support a model in which a eukaryotic protein cofactor or complex facilitates the interaction of rExoU with phospholipid substrates.
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Affiliation(s)
- Hiromi Sato
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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Pankhaniya RR, Tamura M, Allmond LR, Moriyama K, Ajayi T, Wiener-Kronish JP, Sawa T. Pseudomonas aeruginosa causes acute lung injury via the catalytic activity of the patatin-like phospholipase domain of ExoU. Crit Care Med 2005; 32:2293-9. [PMID: 15640644 DOI: 10.1097/01.ccm.0000145588.79063.07] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Acute lung injury in Pseudomonas aeruginosa pneumonia depends primarily on ExoU toxin being delivered directly into the eukaryotic cell cytosol through the type III secretion system. The amino-acid sequence of ExoU has a potato patatin-like phospholipase domain, similar to the sequence of mammalian Ca-independent phospholipase A2. We examined whether the acute lung injury caused by cytotoxic P. aeruginosa was dependent on the patatin-like phospholipase domain of ExoU. DESIGN Laboratory investigation using an established mouse model for P. aeruginosa pneumonia with quantitative measurements of acute lung injury and mortality. SETTING University experimental research laboratory. SUBJECTS Balb/c mice. INTERVENTIONS First, a site-directional mutation was introduced in the predicted catalytically active site of the patatin-like phospholipase domain of recombinant ExoU protein. The effect of the mutation on the catalytic activity of ExoU was tested by the in vitro lysophospholipase A assay. Second, the same site-directional mutation was introduced into the exoU gene of P. aeruginosa PA103. Mice were intratracheally infected with either a wild-type P. aeruginosa strain PA103 or an isogenic mutant containing the mutation in exoU. Acute epithelial lung injury, lung edema, bacteremia, and mortality were evaluated quantitatively. MEASUREMENTS AND MAIN RESULTS Recombinant ExoU had lysophospholipase A activity. Site-directional mutations in the predicted catalytic site of ExoU caused a loss of the lysophospholipase A activity. Whereas the airspace instillation of PA103 caused acute lung injury and death of the infected mice, the airspace instillation of isogenic mutants secreting catalytically inactive ExoU were noncytotoxic and did not cause acute lung injury or death of the infected mice. CONCLUSION Virulent P. aeruginosa causes acute lung injury and death by the cytotoxic activity derived from the patatin-like phospholipase domain of ExoU.
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Affiliation(s)
- Ravi R Pankhaniya
- Department of Anesthesia and Perioperative Care, School of Medicine, University of California San Francisco, San Francisco, CA 94143-0542, USA
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Maresso AW, Baldwin MR, Barbieri JT. Ezrin/radixin/moesin proteins are high affinity targets for ADP-ribosylation by Pseudomonas aeruginosa ExoS. J Biol Chem 2004; 279:38402-8. [PMID: 15252013 DOI: 10.1074/jbc.m405707200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Pseudomonas aeruginosa ExoS is a bifunctional type III-secreted cytotoxin. The N terminus (amino acids 96-233) encodes a GTPase-activating protein activity, whereas the C terminus (amino acids 234-453) encodes a factor-activating ExoS-dependent ADP-ribosyltransferase activity. The GTPase-activating protein activity inactivates the Rho GTPases Rho, Rac, and Cdc42 in cultured cells and in vitro, whereas the ADP-ribosylation by ExoS is poly-substrate-specific and includes Ras as an early target for ADP-ribosylation. Infection of HeLa cells with P. aeruginosa producing a GTPase-activating protein-deficient form of ExoS rounded cells, indicating the ADP-ribosyltransferase domain alone is sufficient to elicit cytoskeletal changes. Examination of substrates modified by type III-delivered ExoS identified a 70-kDa protein as an early and predominant target for ADP-ribosylation. Matrix-assisted laser desorption ionization mass spectroscopy identified this protein as moesin, a member of the ezrin/radixin/moesin (ERM) family of proteins. ExoS ADP-ribosylated recombinant moesin at a linear velocity that was 5-fold faster and with a K(m) that was 2 orders of magnitude lower than Ras. Moesin homologs ezrin and radixin were also ADP-ribosylated, indicating the ERMs collectively represent high affinity targets of ExoS. Type III delivered ExoS ADP-ribosylated moesin and ezrin (and/or radixin) in cultured HeLa cells. The ERM proteins contribute to cytoskeleton dynamics, and the ability of ExoS to ADP-ribosylate the ERM proteins links ADP-ribosylation with the cytoskeletal changes associated with ExoS intoxication.
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Affiliation(s)
- Anthony W Maresso
- Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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