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Reis LR, Souza Junior DR, Tomasin R, Bruni-Cardoso A, Di Mascio P, Ronsein GE. Citrullination of actin-ligand and nuclear structural proteins, cytoskeleton reorganization and protein redistribution across cellular fractions are early events in ionomycin-induced NETosis. Redox Biol 2023; 64:102784. [PMID: 37356135 DOI: 10.1016/j.redox.2023.102784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 06/07/2023] [Accepted: 06/12/2023] [Indexed: 06/27/2023] Open
Abstract
Neutrophil extracellular traps (NETs) are web-like structures of DNA coated with cytotoxic proteins and histones released by activated neutrophils through a process called NETosis. NETs release occurs through a sequence of highly organized events leading to chromatin expansion and rupture of nuclear and cellular membranes. In calcium ionophore-induced NETosis, the enzyme peptidylargine deiminase 4 (PAD4) mediates chromatin decondensation through histone citrullination, but the biochemical pathways involved in this process are not fully understood. Here we use live-imaging microscopy and proteomic studies of the neutrophil cellular fractions to investigate the early events in ionomycin-triggered NETosis. We found that before ionomycin-stimulated neutrophils release NETs, profound biochemical changes occur in and around their nucleus, such as, cytoskeleton reorganization, nuclear redistribution of actin-remodeling related proteins, and citrullination of actin-ligand and nuclear structural proteins. Ionomycin-stimulated neutrophils rapidly lose their characteristic polymorphic nucleus, and these changes are promptly communicated to the extracellular environment through the secretion of proteins related to immune response. Therefore, our findings revealed key biochemical mediators in the early process that subsequently culminates with nuclear and cell membranes rupture, and extracellular DNA release.
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Affiliation(s)
- Lorenna Rocha Reis
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | | | - Rebeka Tomasin
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Alexandre Bruni-Cardoso
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Paolo Di Mascio
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Graziella Eliza Ronsein
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil.
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Marchi J, Zborowsky S, Debarbieux L, Weitz JS. The dynamic interplay of bacteriophage, bacteria and the mammalian host during phage therapy. iScience 2023; 26:106004. [PMID: 36818291 PMCID: PMC9932479 DOI: 10.1016/j.isci.2023.106004] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
For decades, biomedically centered studies of bacteria have focused on mechanistic drivers of disease in their mammalian hosts. Likewise, molecular studies of bacteriophage have centered on understanding mechanisms by which bacteriophage exploit the intracellular environment of their bacterial hosts. These binary interactions - bacteriophage infect bacteria and bacteria infect eukaryotic hosts - have remained largely separate lines of inquiry. However, recent evidence demonstrates how tripartite interactions between bacteriophage, bacteria and the eukaryotic host shape the dynamics and fate of each component. In this perspective, we provide an overview of different ways in which bacteriophage ecology modulates bacterial infections along a spectrum of positive to negative impacts on a mammalian host. We also examine how coevolutionary processes over longer timescales may change the valence of these interactions. We argue that anticipating both ecological and evolutionary dynamics is key to understand and control tripartite interactions and ultimately to the success or failure of phage therapy.
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Affiliation(s)
- Jacopo Marchi
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Sophia Zborowsky
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Bacteriophage Bacterium Host, 75015 Paris, France
| | - Laurent Debarbieux
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Bacteriophage Bacterium Host, 75015 Paris, France
- Corresponding author
| | - Joshua S. Weitz
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
- School of Biological Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Institut de Biologie, École Normale Supérieure, 75005 Paris, France
- Corresponding author
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3
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Lee CH, Lee YY, Chang YC, Pon WL, Lee SP, Wali N, Nakazawa T, Honda Y, Shie JJ, Hsueh YP. A carnivorous mushroom paralyzes and kills nematodes via a volatile ketone. SCIENCE ADVANCES 2023; 9:eade4809. [PMID: 36652525 PMCID: PMC9848476 DOI: 10.1126/sciadv.ade4809] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 12/16/2022] [Indexed: 05/27/2023]
Abstract
The carnivorous mushroom Pleurotus ostreatus uses an unknown toxin to rapidly paralyze and kill nematode prey upon contact. We report that small lollipop-shaped structures (toxocysts) on fungal hyphae are nematicidal and that a volatile ketone, 3-octanone, is detected in these fragile toxocysts. Treatment of Caenorhabditis elegans with 3-octanone recapitulates the rapid paralysis, calcium influx, and neuronal cell death arising from fungal contact. Moreover, 3-octanone disrupts cell membrane integrity, resulting in extracellular calcium influx into cytosol and mitochondria, propagating cell death throughout the entire organism. Last, we demonstrate that structurally related compounds are also biotoxic to C. elegans, with the length of the ketone carbon chain being crucial. Our work reveals that the oyster mushroom has evolved a specialized structure containing a volatile ketone to disrupt the cell membrane integrity of its prey, leading to rapid cell and organismal death in nematodes.
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Affiliation(s)
- Ching-Han Lee
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Yi-Yun Lee
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
- Molecular Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan
| | - Yu-Chu Chang
- Department of Biochemistry and Molecular Cell Biology, School of Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Wen-Li Pon
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Sue-Ping Lee
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Niaz Wali
- Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan
- Institute of Biochemical Sciences, National Taiwan University, Taipei 10617, Taiwan
- Chemical Biology and Molecular Biophysics, Taiwan International Graduate Program, Academia Sinica, Taipei 10617, Taiwan
| | - Takehito Nakazawa
- Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yoichi Honda
- Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Jiun-Jie Shie
- Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan
- Institute of Biochemical Sciences, National Taiwan University, Taipei 10617, Taiwan
- Chemical Biology and Molecular Biophysics, Taiwan International Graduate Program, Academia Sinica, Taipei 10617, Taiwan
| | - Yen-Ping Hsueh
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
- Molecular Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan
- Department of Biochemical Science and Technology, National Taiwan University, Taipei 10617, Taiwan
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan
- Department of Biochemical Science and Technology, National Chiayi University, Chiayi City 60004, Taiwan
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4
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Exploring the Role of Staphylococcus aureus in Inflammatory Diseases. Toxins (Basel) 2022; 14:toxins14070464. [PMID: 35878202 PMCID: PMC9318596 DOI: 10.3390/toxins14070464] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 06/23/2022] [Accepted: 07/01/2022] [Indexed: 02/04/2023] Open
Abstract
Staphylococcus aureus is a very common Gram-positive bacterium, and S. aureus infections play an extremely important role in a variety of diseases. This paper describes the types of virulence factors involved, the inflammatory cells activated, the process of host cell death, and the associated diseases caused by S. aureus. S. aureus can secrete a variety of enterotoxins and other toxins to trigger inflammatory responses and activate inflammatory cells, such as keratinocytes, helper T cells, innate lymphoid cells, macrophages, dendritic cells, mast cells, neutrophils, eosinophils, and basophils. Activated inflammatory cells can express various cytokines and induce an inflammatory response. S. aureus can also induce host cell death through pyroptosis, apoptosis, necroptosis, autophagy, etc. This article discusses S. aureus and MRSA (methicillin-resistant S. aureus) in atopic dermatitis, psoriasis, pulmonary cystic fibrosis, allergic asthma, food poisoning, sarcoidosis, multiple sclerosis, and osteomyelitis. Summarizing the pathogenic mechanism of Staphylococcus aureus provides a basis for the targeted treatment of Staphylococcus aureus infection.
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Staali L, Colin DA. Bi-component HlgC/HlgB and HlgA/HlgB γ-hemolysins from S. aureus: Modulation of Ca 2+ channels activity through a differential mechanism. Toxicon 2021; 201:74-85. [PMID: 34411591 DOI: 10.1016/j.toxicon.2021.08.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 07/21/2021] [Accepted: 08/10/2021] [Indexed: 10/20/2022]
Abstract
Staphylococcal bi-component leukotoxins known as *pore-forming toxins* induce upon a specific binding to membrane receptors, two independent cellular events in human neutrophils. First, they provoke the opening of pre-existing specific ionic channels including Ca2+ channels. Then, they form membrane pores specific to monovalent cations leading to immune cells death. Among these leukotoxins, HlgC/HlgB and HlgA/HlgB γ-hemolysins do act in synergy to induce the opening of different types of Ca2+ channels in the absence as in the presence of extracellular Ca2+. Here, we investigate the mechanism underlying the modulation of Ca2+-independent Ca2+ channels in response to both active leukotoxins in human neutrophils. In the absence of extracellular Ca2+, the Mn2+ has been used as a Ca2+ surrogate to determine the activity of Ca2+-independent Ca2+ channels. Our findings provide new insights about different mechanisms involved in the staphylococcal γ-hemolysins activity to regulate three different types of Ca2+-independent Ca2+ channels. We conclude that (i) HlgC/HlgB stimulates the opening of La3+-sensitive Ca2+ channels, through a cholera toxin-sensitive G protein, (ii) HlgA/HlgB stimulates the opening of Ca2+ channels not sensitive to La3+, through a G protein-independent process, and (iii) unlike HlgA/HlgB, HlgC/HlgB toxins prevent the opening of a new type of Ca2+ channels by phosphorylation/de-phosphorylation-dependent mechanisms.
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Affiliation(s)
- Leila Staali
- Bacteriology Institute of Medical Faculty, Louis Pasteur University, 3 rue Koeberlé, F-67000, Strasbourg, France.
| | - Didier A Colin
- Bacteriology Institute of Medical Faculty, Louis Pasteur University, 3 rue Koeberlé, F-67000, Strasbourg, France
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6
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Mazzoleni V, Zimmermann K, Smirnova A, Tarassov I, Prévost G. Staphylococcus aureus Panton-Valentine Leukocidin triggers an alternative NETosis process targeting mitochondria. FASEB J 2020; 35:e21167. [PMID: 33241563 DOI: 10.1096/fj.201902981r] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 09/18/2020] [Accepted: 10/23/2020] [Indexed: 01/18/2023]
Abstract
Panton-Valentine Leukocidin (PVL) is a bicomponent leukotoxin produced by 3%-10% of clinical Staphylococcus aureus (SA) strains involved in the severity of hospital and community-acquired infections. Although PVL was long known as a pore-forming toxin, recent studies have challenged the formation of a pore at the plasma membrane, while its endocytosis and the exact mode of action remain to be defined. In vitro immunolabeling of human neutrophils shows that Neutrophil Extracellular Traps (NETosis) is triggered by the action of purified PVL, but not by Gamma hemolysin CB (HlgCB), a structurally similar SA leukotoxin. PVL causes the ejection of chromatin fibers (NETs) decorated with antibacterial peptides independently of the NADPH oxidase oxidative burst. Leukotoxin partially colocalizes with mitochondria and enhances the production of reactive oxygen species from these organelles, while showing an increased autophagy, which results unnecessary for NETs ejection. PVL NETosis is elicited through Ca2+ -activated SK channels and Myeloperoxidase activity but is abolished by Allopurinol pretreatment of neutrophils. Moreover, massive citrullination of the histone H3 is performed by peptidyl arginine deiminases. Inhibition of this latter enzymes fails to abolish NET extrusion. Unexpectedly, PVL NETosis does not seem to involve Src kinases, which is the main kinase family activated downstream the binding of PVL F subunit to CD45 receptor, while the specific kinase pathway differs from the NADPH oxidase-dependent NETosis. PVL alone causes a different and specific form of NETosis that may rather represent a bacterial strategy conceived to disarm and disrupt the immune response, eventually allowing SA to spread.
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Affiliation(s)
- Viola Mazzoleni
- University of Strasbourg, CHRU Strasbourg, ITI InnoVec, Fédération de Médecine Translationnelle de Strasbourg, UR7290, Institut de Bactériologie, Strasbourg, France
| | - Kiran Zimmermann
- University of Strasbourg, CHRU Strasbourg, ITI InnoVec, Fédération de Médecine Translationnelle de Strasbourg, UR7290, Institut de Bactériologie, Strasbourg, France
| | - Anna Smirnova
- UMR 7156 GMGM Strasbourg University/CNRS, Strasbourg, France
| | - Ivan Tarassov
- UMR 7156 GMGM Strasbourg University/CNRS, Strasbourg, France
| | - Gilles Prévost
- University of Strasbourg, CHRU Strasbourg, ITI InnoVec, Fédération de Médecine Translationnelle de Strasbourg, UR7290, Institut de Bactériologie, Strasbourg, France
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7
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Lucas R, Hadizamani Y, Gonzales J, Gorshkov B, Bodmer T, Berthiaume Y, Moehrlen U, Lode H, Huwer H, Hudel M, Mraheil MA, Toque HAF, Chakraborty T, Hamacher J. Impact of Bacterial Toxins in the Lungs. Toxins (Basel) 2020; 12:toxins12040223. [PMID: 32252376 PMCID: PMC7232160 DOI: 10.3390/toxins12040223] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 03/30/2020] [Accepted: 03/31/2020] [Indexed: 12/13/2022] Open
Abstract
Bacterial toxins play a key role in the pathogenesis of lung disease. Based on their structural and functional properties, they employ various strategies to modulate lung barrier function and to impair host defense in order to promote infection. Although in general, these toxins target common cellular signaling pathways and host compartments, toxin- and cell-specific effects have also been reported. Toxins can affect resident pulmonary cells involved in alveolar fluid clearance (AFC) and barrier function through impairing vectorial Na+ transport and through cytoskeletal collapse, as such, destroying cell-cell adhesions. The resulting loss of alveolar-capillary barrier integrity and fluid clearance capacity will induce capillary leak and foster edema formation, which will in turn impair gas exchange and endanger the survival of the host. Toxins modulate or neutralize protective host cell mechanisms of both the innate and adaptive immunity response during chronic infection. In particular, toxins can either recruit or kill central players of the lung's innate immune responses to pathogenic attacks, i.e., alveolar macrophages (AMs) and neutrophils. Pulmonary disorders resulting from these toxin actions include, e.g., acute lung injury (ALI), the acute respiratory syndrome (ARDS), and severe pneumonia. When acute infection converts to persistence, i.e., colonization and chronic infection, lung diseases, such as bronchitis, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) can arise. The aim of this review is to discuss the impact of bacterial toxins in the lungs and the resulting outcomes for pathogenesis, their roles in promoting bacterial dissemination, and bacterial survival in disease progression.
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Affiliation(s)
- Rudolf Lucas
- Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
- Department of Medicine and Division of Pulmonary Critical Care Medicine, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
- Correspondence: (R.L.); (J.H.); Tel.: +41-31-300-35-00 (J.H.)
| | - Yalda Hadizamani
- Lungen-und Atmungsstiftung, Bern, 3012 Bern, Switzerland;
- Pneumology, Clinic for General Internal Medicine, Lindenhofspital Bern, 3012 Bern, Switzerland
| | - Joyce Gonzales
- Department of Medicine and Division of Pulmonary Critical Care Medicine, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
| | - Boris Gorshkov
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
| | - Thomas Bodmer
- Labormedizinisches Zentrum Dr. Risch, Waldeggstr. 37 CH-3097 Liebefeld, Switzerland;
| | - Yves Berthiaume
- Department of Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC H3T 1J4, Canada;
| | - Ueli Moehrlen
- Pediatric Surgery, University Children’s Hospital, Zürich, Steinwiesstrasse 75, CH-8032 Zürch, Switzerland;
| | - Hartmut Lode
- Insitut für klinische Pharmakologie, Charité, Universitätsklinikum Berlin, Reichsstrasse 2, D-14052 Berlin, Germany;
| | - Hanno Huwer
- Department of Cardiothoracic Surgery, Voelklingen Heart Center, 66333 Voelklingen/Saar, Germany;
| | - Martina Hudel
- Justus-Liebig-University, Biomedical Research Centre Seltersberg, Schubertstr. 81, 35392 Giessen, Germany; (M.H.); (M.A.M.); (T.C.)
| | - Mobarak Abu Mraheil
- Justus-Liebig-University, Biomedical Research Centre Seltersberg, Schubertstr. 81, 35392 Giessen, Germany; (M.H.); (M.A.M.); (T.C.)
| | - Haroldo Alfredo Flores Toque
- Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
| | - Trinad Chakraborty
- Justus-Liebig-University, Biomedical Research Centre Seltersberg, Schubertstr. 81, 35392 Giessen, Germany; (M.H.); (M.A.M.); (T.C.)
| | - Jürg Hamacher
- Lungen-und Atmungsstiftung, Bern, 3012 Bern, Switzerland;
- Pneumology, Clinic for General Internal Medicine, Lindenhofspital Bern, 3012 Bern, Switzerland
- Medical Clinic V-Pneumology, Allergology, Intensive Care Medicine and Environmental Medicine, Faculty of Medicine, Saarland University, University Medical Centre of the Saarland, D-66421 Homburg, Germany
- Institute for Clinical & Experimental Surgery, Faculty of Medicine, Saarland University, D-66421 Homburg, Germany
- Correspondence: (R.L.); (J.H.); Tel.: +41-31-300-35-00 (J.H.)
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Staphylococcus aureus Toxins and Their Molecular Activity in Infectious Diseases. Toxins (Basel) 2018; 10:toxins10060252. [PMID: 29921792 PMCID: PMC6024779 DOI: 10.3390/toxins10060252] [Citation(s) in RCA: 234] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/14/2018] [Accepted: 06/15/2018] [Indexed: 12/04/2022] Open
Abstract
Staphylococcus aureus is a microorganism resident in the skin and nasal membranes with a dreadful pathogenic potential to cause a variety of community and hospital-acquired infections. The frequency of these infections is increasing and their treatment is becoming more difficult. The ability of S. aureus to form biofilms and the emergence of multidrug-resistant strains are the main reasons determining the challenge in dealing with these infections. S. aureus' infectious capacity and its success as a pathogen is related to the expression of virulence factors, among which the production of a wide variety of toxins is highlighted. For this reason, a better understanding of S. aureus toxins is needed to enable the development of new strategies to reduce their production and consequently improve therapeutic approaches. This review focuses on understanding the toxin-based pathogenesis of S. aureus and their role on infectious diseases.
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Staphylococcus aureus produces pain through pore-forming toxins and neuronal TRPV1 that is silenced by QX-314. Nat Commun 2018; 9:37. [PMID: 29295977 PMCID: PMC5750211 DOI: 10.1038/s41467-017-02448-6] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 11/30/2017] [Indexed: 12/22/2022] Open
Abstract
The hallmark of many bacterial infections is pain. The underlying mechanisms of pain during live pathogen invasion are not well understood. Here, we elucidate key molecular mechanisms of pain produced during live methicillin-resistant Staphylococcus aureus (MRSA) infection. We show that spontaneous pain is dependent on the virulence determinant agr and bacterial pore-forming toxins (PFTs). The cation channel, TRPV1, mediated heat hyperalgesia as a distinct pain modality. Three classes of PFTs-alpha-hemolysin (Hla), phenol-soluble modulins (PSMs), and the leukocidin HlgAB-directly induced neuronal firing and produced spontaneous pain. From these mechanisms, we hypothesized that pores formed in neurons would allow entry of the membrane-impermeable sodium channel blocker QX-314 into nociceptors to silence pain during infection. QX-314 induced immediate and long-lasting blockade of pain caused by MRSA infection, significantly more than lidocaine or ibuprofen, two widely used clinical analgesic treatments.
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Seilie ES, Bubeck Wardenburg J. Staphylococcus aureus pore-forming toxins: The interface of pathogen and host complexity. Semin Cell Dev Biol 2017; 72:101-116. [PMID: 28445785 DOI: 10.1016/j.semcdb.2017.04.003] [Citation(s) in RCA: 139] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 03/22/2017] [Accepted: 04/18/2017] [Indexed: 12/20/2022]
Abstract
Staphylococcus aureus is a prominent human pathogen capable of infecting a variety of host species and tissue sites. This versatility stems from the pathogen's ability to secrete diverse host-damaging virulence factors. Among these factors, the S. aureus pore-forming toxins (PFTs) α-toxin and the bicomponent leukocidins, have garnered much attention for their ability to lyse cells at low concentrations and modulate disease severity. Although many of these toxins were discovered nearly a century ago, their host cell specificities have only been elucidated over the past five to six years, starting with the discovery of the eukaryotic receptor for α-toxin and rapidly followed by identification of the leukocidin receptors. The identification of these receptors has revealed the species- and cell type-specificity of toxin binding, and provided insight into non-lytic effects of PFT intoxication that contribute to disease pathogenesis.
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Affiliation(s)
- E Sachiko Seilie
- Department of Pediatrics, The University of Chicago, Chicago, IL 60637, United States; Department of Microbiology, The University of Chicago, Chicago, IL 60637, United States
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11
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Zimmermann-Meisse G, Prévost G, Jover E. Above and beyond C5a Receptor Targeting by Staphylococcal Leucotoxins: Retrograde Transport of Panton-Valentine Leucocidin and γ-Hemolysin. Toxins (Basel) 2017; 9:toxins9010041. [PMID: 28117704 PMCID: PMC5308273 DOI: 10.3390/toxins9010041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 01/10/2017] [Accepted: 01/16/2017] [Indexed: 12/03/2022] Open
Abstract
Various membrane receptors associated with the innate immune response have recently been identified as mediators of the cellular action of Staphylococcus aureus leucotoxins. Two of these, the Panton–Valentine leucotoxin LukS-PV/LukF-PV and the γ-hemolysin HlgC/HlgB, bind the C5a complement-derived peptide receptor. These leucotoxins utilize the receptor to induce intracellular Ca2+ release from internal stores, other than those activated by C5a. The two leucotoxins are internalized with the phosphorylated receptor, but it is unknown whether they divert retrograde transport of the receptor or follow another pathway. Immunolabeling and confocal microscopic techniques were used to analyze the presence of leucotoxins in endosomes, lysosomes, endoplasmic reticulum, and Golgi. The two leucotoxins apparently followed retrograde transport similar to that of the C5a peptide-activated receptor. However, HlgC/HlgB reached the Golgi network very early, whereas LukS-PV/LukF-PV followed slower kinetics. The HlgC/HlgB leucotoxin remained in neutrophils 6 h after a 10-min incubation of the cells in the presence of the toxin with no signs of apoptosis, whereas apoptosis was observed 3 h after neutrophils were incubated with LukS-PV/LukF-PV. Such retrograde transport of leucotoxins provides a novel understanding of the cellular effects initiated by sublytic concentrations of these toxins.
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Affiliation(s)
- Gaëlle Zimmermann-Meisse
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), VBP EA7290, Institut de Bactériologie, Université de Strasbourg, 3 rue Koeberlé, F-67000 Strasbourg, France.
| | - Gilles Prévost
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), VBP EA7290, Institut de Bactériologie, Université de Strasbourg, 3 rue Koeberlé, F-67000 Strasbourg, France.
| | - Emmanuel Jover
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), VBP EA7290, Institut de Bactériologie, Université de Strasbourg, 3 rue Koeberlé, F-67000 Strasbourg, France.
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12
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Konig MF, Andrade F. A Critical Reappraisal of Neutrophil Extracellular Traps and NETosis Mimics Based on Differential Requirements for Protein Citrullination. Front Immunol 2016; 7:461. [PMID: 27867381 PMCID: PMC5095114 DOI: 10.3389/fimmu.2016.00461] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 10/14/2016] [Indexed: 12/18/2022] Open
Abstract
NETosis, an antimicrobial form of neutrophil cell death, is considered a primary source of citrullinated autoantigens in rheumatoid arthritis (RA) and immunogenic DNA in systemic lupus erythematosus (SLE). Activation of the citrullinating enzyme peptidylarginine deiminase type 4 (PAD4) is believed to be essential for neutrophil extracellular trap (NET) formation and NETosis. PAD4 is therefore viewed as a promising therapeutic target to inhibit the formation of NETs in both diseases. In this review, we examine the evidence for PAD4 activation during NETosis and provide experimental data to suggest that protein citrullination is not a universal feature of NETs. We delineate two distinct biological processes, leukotoxic hypercitrullination (LTH) and defective mitophagy, which have been erroneously classified as “NETosis.” While these NETosis mimics share morphological similarities with NETosis (i.e., extracellular DNA release), they are biologically distinct. As such, these processes can be readily classified by their stimuli, activation of distinct biochemical pathways, the presence of hypercitrullination, and antimicrobial effector function. NETosis is an antimicrobial form of cell death that is NADPH oxidase-dependent and not associated with hypercitrullination. In contrast, LTH is NADPH oxidase-independent and not bactericidal. Rather, LTH represents a bacterial strategy to achieve immune evasion. It is triggered by pore-forming pathways and equivalent signals that cumulate in calcium-dependent hyperactivation of PADs, protein hypercitrullination, and neutrophil death. The generation of citrullinated autoantigens in RA is likely driven by LTH, but not NETosis. Mitochondrial DNA (mtDNA) expulsion, the result of a constitutive defect in mitophagy, represents a second NETosis mimic. In the presence of interferon-α and immune complexes, this process can generate highly interferogenic oxidized mtDNA, which has previously been mistaken for NETosis in SLE. Distinguishing NETosis from LTH and defective mitophagy is paramount to understanding the role of neutrophil damage in immunity and the pathogenesis of human diseases. This provides a framework to design specific inhibitors of these distinct biological processes in human disease.
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Affiliation(s)
- Maximilian F Konig
- Division of Rheumatology, Johns Hopkins University School of Medicine , Baltimore, MD , USA
| | - Felipe Andrade
- Division of Rheumatology, Johns Hopkins University School of Medicine , Baltimore, MD , USA
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13
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Parker D, Ahn D, Cohen T, Prince A. Innate Immune Signaling Activated by MDR Bacteria in the Airway. Physiol Rev 2016; 96:19-53. [PMID: 26582515 DOI: 10.1152/physrev.00009.2015] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Health care-associated bacterial pneumonias due to multiple-drug resistant (MDR) pathogens are an important public health problem and are major causes of morbidity and mortality worldwide. In addition to antimicrobial resistance, these organisms have adapted to the milieu of the human airway and have acquired resistance to the innate immune clearance mechanisms that normally prevent pneumonia. Given the limited efficacy of antibiotics, bacterial clearance from the airway requires an effective immune response. Understanding how specific airway pathogens initiate and regulate innate immune signaling, and whether this response is excessive, leading to host-induced pathology may guide future immunomodulatory therapy. We will focus on three of the most important causes of health care-associated pneumonia, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, and review the mechanisms through which an inappropriate or damaging innate immune response is stimulated, as well as describe how airway pathogens cause persistent infection by evading immune activation.
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Affiliation(s)
- Dane Parker
- Departments of Pediatrics and Pharmacology, Columbia University, New York, New York
| | - Danielle Ahn
- Departments of Pediatrics and Pharmacology, Columbia University, New York, New York
| | - Taylor Cohen
- Departments of Pediatrics and Pharmacology, Columbia University, New York, New York
| | - Alice Prince
- Departments of Pediatrics and Pharmacology, Columbia University, New York, New York
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14
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Adhikari RP, Kort T, Shulenin S, Kanipakala T, Ganjbaksh N, Roghmann MC, Holtsberg FW, Aman MJ. Antibodies to S. aureus LukS-PV Attenuated Subunit Vaccine Neutralize a Broad Spectrum of Canonical and Non-Canonical Bicomponent Leukotoxin Pairs. PLoS One 2015; 10:e0137874. [PMID: 26367030 PMCID: PMC4569305 DOI: 10.1371/journal.pone.0137874] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 08/22/2015] [Indexed: 11/18/2022] Open
Abstract
S. aureus vaccine development has proven particularly difficult. The conventional approach to achieve sterile immunity through opsonophagocytic killing has been largely unsuccessful. S. aureus is highly toxigenic and a great body of evidence suggests that a successful future vaccine for this organism should target extracellular toxins which are responsible for host tissue destruction and immunosuppression. Major staphylococcal toxins are alpha toxin (a single subunit hemolysin) along with a group of bicomponent pore-forming toxins (BCPFT), namely Panton-Valentine leukocidin (PVL), gamma hemolysins (HlgCB and AB), LukAB and LukED. In our previous report, an attenuated mutant of LukS-PV (PVL- S subunit) named as “LukS-mut9” elicited high immunogenic response as well as provided a significant protection in a mouse sepsis model. Recent discovery of PVL receptors shows that mice lack receptors for this toxin, thus the reported protection of mice with the PVL vaccine may relate to cross protective responses against other homologous toxins. This manuscript addresses this issue by demonstrating that polyclonal antibody generated by LukS-mut9 can neutralize other canonical and non-canonical leukotoxin pairs. In this report, we also demonstrated that several potent toxins can be created by non-canonical pairing of subunits. Out of 5 pairs of canonical and 8 pairs of non-canonical toxins tested, anti-LukS-mut9 polyclonal antibodies neutralized all except for LukAB. We also studied the potential hemolytic activities of canonical and noncanonical pairs among biocomponent toxins and discovered that a novel non-canonical pair consisting of HlgA and LukD is a highly toxic combination. This pair can lyse RBC from different species including human blood far better than alpha hemolysin. Moreover, to follow-up our last report, we explored the correlation between the levels of pre-existing antibodies to new sets of leukotoxins subunits and clinical outcomes in adult patients with S. aureus bacteremia. We found that there is an inversed correlation between the antibody titer to sepsis for leukotoxins LukS-mut9, LukF-PV, HlgC, LukE and LukAB, suggesting the risk of sepsis was significantly lower in the patients with higher antibody titer against those toxins.
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Affiliation(s)
- Rajan P. Adhikari
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
- * E-mail:
| | - Thomas Kort
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Sergey Shulenin
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | | | - Nader Ganjbaksh
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Mary-Claire Roghmann
- Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- VA Maryland Health Care System, Baltimore, Maryland, United States of America
| | | | - M. Javad Aman
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
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15
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The bicomponent pore-forming leucocidins of Staphylococcus aureus. Microbiol Mol Biol Rev 2015; 78:199-230. [PMID: 24847020 DOI: 10.1128/mmbr.00055-13] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The ability to produce water-soluble proteins with the capacity to oligomerize and form pores within cellular lipid bilayers is a trait conserved among nearly all forms of life, including humans, single-celled eukaryotes, and numerous bacterial species. In bacteria, some of the most notable pore-forming molecules are protein toxins that interact with mammalian cell membranes to promote lysis, deliver effectors, and modulate cellular homeostasis. Of the bacterial species capable of producing pore-forming toxic molecules, the Gram-positive pathogen Staphylococcus aureus is one of the most notorious. S. aureus can produce seven different pore-forming protein toxins, all of which are believed to play a unique role in promoting the ability of the organism to cause disease in humans and other mammals. The most diverse of these pore-forming toxins, in terms of both functional activity and global representation within S. aureus clinical isolates, are the bicomponent leucocidins. From the first description of their activity on host immune cells over 100 years ago to the detailed investigations of their biochemical function today, the leucocidins remain at the forefront of S. aureus pathogenesis research initiatives. Study of their mode of action is of immediate interest in the realm of therapeutic agent design as well as for studies of bacterial pathogenesis. This review provides an updated perspective on our understanding of the S. aureus leucocidins and their function, specificity, and potential as therapeutic targets.
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16
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Tawk MY, Zimmermann K, Bossu J, Potrich C, Bourcier T, Dalla Serra M, Poulain B, Prévost G, Jover E. Internalization of staphylococcal leukotoxins that bind and divert the
C
5a receptor is required for intracellular
Ca
2+
mobilization by human neutrophils. Cell Microbiol 2015; 17:1241-57. [DOI: 10.1111/cmi.12434] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 01/26/2015] [Accepted: 03/01/2015] [Indexed: 01/12/2023]
Affiliation(s)
- Mira Y. Tawk
- Fédération de Médecine Translationnelle de Strasbourg EA7290 Virulence Bactérienne Précoce Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg Université de Strasbourg Strasbourg France
| | - Kiran Zimmermann
- Fédération de Médecine Translationnelle de Strasbourg EA7290 Virulence Bactérienne Précoce Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg Université de Strasbourg Strasbourg France
| | - Jean‐Louis Bossu
- INCI – UPR‐CNRS 3212 Physiologie des réseaux de neurones Strasbourg France
| | - Cristina Potrich
- National Research Council of Italy Institute of Biophysics and Bruno Kessler Foundation Trento Italy
| | - Tristan Bourcier
- Fédération de Médecine Translationnelle de Strasbourg EA7290 Virulence Bactérienne Précoce Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg Université de Strasbourg Strasbourg France
| | - Mauro Dalla Serra
- National Research Council of Italy Institute of Biophysics and Bruno Kessler Foundation Trento Italy
| | - Bernard Poulain
- INCI – UPR‐CNRS 3212 Physiologie des réseaux de neurones Strasbourg France
| | - Gilles Prévost
- Fédération de Médecine Translationnelle de Strasbourg EA7290 Virulence Bactérienne Précoce Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg Université de Strasbourg Strasbourg France
| | - Emmanuel Jover
- Fédération de Médecine Translationnelle de Strasbourg EA7290 Virulence Bactérienne Précoce Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg Université de Strasbourg Strasbourg France
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17
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Serra R, Grande R, Butrico L, Rossi A, Settimio UF, Caroleo B, Amato B, Gallelli L, de Franciscis S. Chronic wound infections: the role of Pseudomonas aeruginosa and Staphylococcus aureus. Expert Rev Anti Infect Ther 2015; 13:605-13. [PMID: 25746414 DOI: 10.1586/14787210.2015.1023291] [Citation(s) in RCA: 380] [Impact Index Per Article: 42.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Chronic leg ulcers affect 1-2% of the general population and are related to increased morbidity and health costs. Staphylococcus aureus and Pseudomonas aeruginosa are the most common bacteria isolated from chronic wounds. They can express virulence factors and surface proteins affecting wound healing. The co-infection of S. aureus and P. aeruginosa is more virulent than single infection. In particular, S. aureus and P. aeruginosa have both intrinsic and acquired antibiotic resistance, making clinical management of infection a real challenge, particularly in patients with comorbidity. Therefore, a correct and prompt diagnosis of chronic wound infection requires a detailed knowledge of skin bacterial flora. This is a necessary prerequisite for tailored pharmacological treatment, improving symptoms, and reducing side effects and antibiotic resistance.
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Affiliation(s)
- Raffaele Serra
- Interuniversity Center of Phlebolymphology (CIFL), International Research and Educational Program in Clinical and Experimental Biotechnology, Headquarters: University Magna Græcia of Catanzaro, Viale Europa 88100 Catanzaro, Italy
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18
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Residues essential for Panton-Valentine leukocidin S component binding to its cell receptor suggest both plasticity and adaptability in its interaction surface. PLoS One 2014; 9:e92094. [PMID: 24643034 PMCID: PMC3958440 DOI: 10.1371/journal.pone.0092094] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 02/18/2014] [Indexed: 01/01/2023] Open
Abstract
Panton-Valentine leukocidin (PVL), a bicomponent staphylococcal leukotoxin, is involved in the poor prognosis of necrotizing pneumonia. The present study aimed to elucidate the binding mechanism of PVL and in particular its cell-binding domain. The class S component of PVL, LukS-PV, is known to ensure cell targeting and exhibits the highest affinity for the neutrophil membrane (Kd∼10−10 M) compared to the class F component of PVL, LukF-PV (Kd∼10−9 M). Alanine scanning mutagenesis was used to identify the residues involved in LukS-PV binding to the neutrophil surface. Nineteen single alanine mutations were performed in the rim domain previously described as implicated in cell membrane interactions. Positions were chosen in order to replace polar or exposed charged residues and according to conservation between leukotoxin class S components. Characterization studies enabled to identify a cluster of residues essential for LukS-PV binding, localized on two loops of the rim domain. The mutations R73A, Y184A, T244A, H245A and Y250A led to dramatically reduced binding affinities for both human leukocytes and undifferentiated U937 cells expressing the C5a receptor. The three-dimensional structure of five of the mutants was determined using X-ray crystallography. Structure analysis identified residues Y184 and Y250 as crucial in providing structural flexibility in the receptor-binding domain of LukS-PV.
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19
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Yanai M, Rocha MA, Matolek AZ, Chintalacharuvu A, Taira Y, Chintalacharuvu K, Beenhouwer DO. Separately or combined, LukG/LukH is functionally unique compared to other staphylococcal bicomponent leukotoxins. PLoS One 2014; 9:e89308. [PMID: 24586678 PMCID: PMC3930693 DOI: 10.1371/journal.pone.0089308] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 01/20/2014] [Indexed: 11/19/2022] Open
Abstract
Staphylococcus aureus is a major human pathogen that elaborates several exotoxins. Among these are the bicomponent leukotoxins (BCLs), which include γ-hemolysin, Panton-Valentine leukocidin (PVL), and LukDE. The toxin components are classified as either F or S proteins, which are secreted individually and assemble on cell surfaces to form hetero-oligomeric pores resulting in lysis of PMNs and/or erythrocytes. F and S proteins of γ-hemolysin, PVL and LukDE have ∼ 70% sequence homology within the same class and several heterologous combinations of F and S members from these three bicomponent toxin groups are functional. Recently, an additional BCL pair, LukGH (also called LukAB) that has only 30% homology to γ-hemolysin, PVL and LukDE, has been characterized from S. aureus. Our results showed that LukGH was more cytotoxic to human PMNs than PVL. However, LukGH-induced calcium ion influx in PMNs was markedly attenuated and slower than that induced by PVL and other staphylococcal BCLs. In contrast to other heterologous BCL combinations, LukG in combination with heterologous S components, and LukH in combination with heterologous F components did not induce calcium ion entry or cell lysis in human PMNs or rabbit erythrocytes. Like PVL, LukGH induced IL-8 production by PMNs. While individual components LukG and LukH had no cytolytic or calcium influx activity, they each induced high levels of IL-8 transcription and secretion. IL-8 production induced by LukG or LukH was dependent on NF-κB. Therefore, our results indicate LukGH differs functionally from other staphylococcal BCLs.
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Affiliation(s)
- Machi Yanai
- Division of Infectious Diseases, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
- Emergency and Critical Care, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan
| | - Miguel A. Rocha
- Division of Infectious Diseases, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Anthony Z. Matolek
- Division of Infectious Diseases, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Archana Chintalacharuvu
- Division of Infectious Diseases, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Yasuhiko Taira
- Emergency and Critical Care, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan
| | - Koteswara Chintalacharuvu
- Division of Infectious Diseases, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - David O. Beenhouwer
- Division of Infectious Diseases, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- * E-mail:
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20
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The δ subunit of RNA polymerase guides promoter selectivity and virulence in Staphylococcus aureus. Infect Immun 2014; 82:1424-35. [PMID: 24491578 DOI: 10.1128/iai.01508-14] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In Gram-positive bacteria, and particularly the Firmicutes, the DNA-dependent RNA polymerase (RNAP) complex contains an additional subunit, termed the δ factor, or RpoE. This enigmatic protein has been studied for more than 30 years for various organisms, but its function is still not well understood. In this study, we investigated its role in the major human pathogen Staphylococcus aureus. We showed conservation of important structural regions of RpoE in S. aureus and other species and demonstrated binding to core RNAP that is mediated by the β and/or β' subunits. To identify the impact of the δ subunit on transcription, we performed transcriptome sequencing (RNA-seq) analysis and observed 191 differentially expressed genes in the rpoE mutant. Ontological analysis revealed, quite strikingly, that many of the downregulated genes were known virulence factors, while several mobile genetic elements (SaPI5 and prophage SA3usa) were strongly upregulated. Phenotypically, the rpoE mutant had decreased accumulation and/or activity of a number of key virulence factors, including alpha toxin, secreted proteases, and Panton-Valentine leukocidin (PVL). We further observed significantly decreased survival of the mutant in whole human blood, increased phagocytosis by human leukocytes, and impaired virulence in a murine model of infection. Collectively, our results demonstrate that the δ subunit of RNAP is a critical component of the S. aureus transcription machinery and plays an important role during infection.
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21
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Aslam R, Laventie BJ, Marban C, Prévost G, Keller D, Strub JM, Dorsselaer AV, Haikel Y, Taddei C, Metz-Boutigue MH. Activation of Neutrophils by the Two-Component Leukotoxin LukE/D from Staphylococcus aureus: Proteomic Analysis of the Secretions. J Proteome Res 2013; 12:3667-78. [DOI: 10.1021/pr400199x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Rizwan Aslam
- Inserm UMR 1121, Université de Strasbourg, Strasbourg, F-67000,
France
| | - Benoît-Joseph Laventie
- EA 7290 Virulence bactérienne
précoce, Fédération de Médecine Translationnelle
de Strasbourg, Université de Strasbourg - CHRU Strasbourg, Institut de Bactériologie, F-67000
Strasbourg, France
| | - Céline Marban
- Inserm UMR 1121, Université de Strasbourg, Strasbourg, F-67000,
France
| | - Gilles Prévost
- EA 7290 Virulence bactérienne
précoce, Fédération de Médecine Translationnelle
de Strasbourg, Université de Strasbourg - CHRU Strasbourg, Institut de Bactériologie, F-67000
Strasbourg, France
| | - Daniel Keller
- EA 7290 Virulence bactérienne
précoce, Fédération de Médecine Translationnelle
de Strasbourg, Université de Strasbourg - CHRU Strasbourg, Institut de Bactériologie, F-67000
Strasbourg, France
| | - Jean-Marc Strub
- CNRS UMR 7178, Université de Strasbourg, Strasbourg, F-67000, France
| | | | - Youssef Haikel
- Inserm UMR 1121, Université de Strasbourg, Strasbourg, F-67000,
France
- Faculté d’Odontologie, Université de Strasbourg, Strasbourg, F-67000,
France
| | - Corinne Taddei
- Faculté d’Odontologie, Université de Strasbourg, Strasbourg, F-67000,
France
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22
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Karauzum H, Adhikari RP, Sarwar J, Devi VS, Abaandou L, Haudenschild C, Mahmoudieh M, Boroun AR, Vu H, Nguyen T, Warfield KL, Shulenin S, Aman MJ. Structurally designed attenuated subunit vaccines for S. aureus LukS-PV and LukF-PV confer protection in a mouse bacteremia model. PLoS One 2013; 8:e65384. [PMID: 23762356 PMCID: PMC3676412 DOI: 10.1371/journal.pone.0065384] [Citation(s) in RCA: 37] [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: 03/11/2013] [Accepted: 04/24/2013] [Indexed: 01/29/2023] Open
Abstract
Previous efforts towards S. aureus vaccine development have largely focused on cell surface antigens to induce opsonophagocytic killing aimed at providing sterile immunity, a concept successfully applied to other Gram-positive pathogens such as Streptococcus pneumoniae. However, these approaches have largely failed, possibly in part due to the remarkable diversity of the staphylococcal virulence factors such as secreted immunosuppressive and tissue destructive toxins. S. aureus produces several pore-forming toxins including the single subunit alpha hemolysin as well as bicomponent leukotoxins such as Panton-Valentine leukocidin (PVL), gamma hemolysins (Hlg), and LukED. Here we report the generation of highly attenuated mutants of PVL subunits LukS-PV and LukF-PV that were rationally designed, based on an octameric structural model of the toxin, to be deficient in oligomerization. The attenuated subunit vaccines were highly immunogenic and showed significant protection in a mouse model of S. aureus USA300 sepsis. Protection against sepsis was also demonstrated by passive transfer of rabbit immunoglobulin raised against LukS-PV. Antibodies to LukS-PV inhibited the homologous oligomerization of LukS-PV with LukF-PV as well heterologous oligomerization with HlgB. Importantly, immune sera from mice vaccinated with the LukS mutant not only inhibited the PMN lytic activity produced by the PVL-positive USA300 but also blocked PMN lysis induced by supernatants of PVL-negative strains suggesting a broad protective activity towards other bicomponent toxins. These findings strongly support the novel concept of an anti-virulence, toxin-based vaccine intended for prevention of clinical S. aureus invasive disease, rather than achieving sterile immunity. Such a multivalent vaccine may include attenuated leukotoxins, alpha hemolysin, and superantigens.
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Affiliation(s)
- Hatice Karauzum
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Rajan P. Adhikari
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Jawad Sarwar
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - V. Sathya Devi
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Laura Abaandou
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | | | - Mahta Mahmoudieh
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Atefeh R. Boroun
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Hong Vu
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Tam Nguyen
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Kelly L. Warfield
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - Sergey Shulenin
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
| | - M. Javad Aman
- Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America
- * E-mail:
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23
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Los FCO, Randis TM, Aroian RV, Ratner AJ. Role of pore-forming toxins in bacterial infectious diseases. Microbiol Mol Biol Rev 2013; 77:173-207. [PMID: 23699254 PMCID: PMC3668673 DOI: 10.1128/mmbr.00052-12] [Citation(s) in RCA: 299] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pore-forming toxins (PFTs) are the most common bacterial cytotoxic proteins and are required for virulence in a large number of important pathogens, including Streptococcus pneumoniae, group A and B streptococci, Staphylococcus aureus, Escherichia coli, and Mycobacterium tuberculosis. PFTs generally disrupt host cell membranes, but they can have additional effects independent of pore formation. Substantial effort has been devoted to understanding the molecular mechanisms underlying the functions of certain model PFTs. Likewise, specific host pathways mediating survival and immune responses in the face of toxin-mediated cellular damage have been delineated. However, less is known about the overall functions of PFTs during infection in vivo. This review focuses on common themes in the area of PFT biology, with an emphasis on studies addressing the roles of PFTs in in vivo and ex vivo models of colonization or infection. Common functions of PFTs include disruption of epithelial barrier function and evasion of host immune responses, which contribute to bacterial growth and spreading. The widespread nature of PFTs make this group of toxins an attractive target for the development of new virulence-targeted therapies that may have broad activity against human pathogens.
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Affiliation(s)
| | - Tara M. Randis
- Department of Pediatrics, Columbia University, New York, New York, USA
| | - Raffi V. Aroian
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California, USA
| | - Adam J. Ratner
- Department of Pediatrics, Columbia University, New York, New York, USA
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24
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Characterization of a Novel Panton-Valentine leukocidin (PVL)-encoding staphylococcal phage and its naturally PVL-lacking variant. Appl Environ Microbiol 2013; 79:2828-32. [PMID: 23396328 DOI: 10.1128/aem.03852-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A new siphophage (LH1) was isolated from raw milk using a Staphylococcus aureus ST352 host. Its genome (46,048 bp, 57 open reading frames) includes the two genes encoding Panton-Valentine leukocidin (PVL), a virulence factor usually harbored by S. aureus prophages. Nine structural proteins were identified, including a tail protein generated through a +1 frameshift. A phage lytic mutant was isolated, and its analysis revealed the deletion of genes coding for the PVL and an integrase. The deletion likely occurred through recombination between direct repeats.
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25
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26
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Graves SF, Kobayashi SD, Braughton KR, Whitney AR, Sturdevant DE, Rasmussen DL, Kirpotina LN, Quinn MT, DeLeo FR. Sublytic concentrations of Staphylococcus aureus Panton-Valentine leukocidin alter human PMN gene expression and enhance bactericidal capacity. J Leukoc Biol 2012; 92:361-74. [PMID: 22581932 DOI: 10.1189/jlb.1111575] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
CA-MRSA infections are often caused by strains encoding PVL, which can cause lysis of PMNs and other myeloid cells in vitro, a function considered widely as the primary means by which PVL might contribute to disease. However, at sublytic concentrations, PVL can function as a PMN agonist. To better understand this phenomenon, we investigated the ability of PVL to alter human PMN function. PMNs exposed to PVL had enhanced capacity to produce O(2)(-) in response to fMLF, but unlike priming by LPS, this response did not require TLR signal transduction. On the other hand, there was subcellular redistribution of NADPH oxidase components in PMNs following exposure of these cells to PVL--a finding consistent with priming. Importantly, PMNs primed with PVL had an enhanced ability to bind/ingest and kill Staphylococcus aureus. Priming of PMNs with other agonists, such as IL-8 or GM-CSF, altered the ability of PVL to cause formation of pores in the plasma membranes of these cells. Microarray analysis revealed significant changes in the human PMN transcriptome following exposure to PVL, including up-regulation of molecules that regulate the inflammatory response. Consistent with the microarray data, mediators of the inflammatory response were released from PMNs after stimulation with PVL. We conclude that exposure of human PMNs to sublytic concentrations of PVL elicits a proinflammatory response that is regulated in part at the level of gene expression. We propose that PVL-mediated priming of PMNs enhances the host innate immune response.
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Affiliation(s)
- Shawna F Graves
- Laboratory of Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
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27
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Alonzo F, Benson MA, Chen J, Novick RP, Shopsin B, Torres VJ. Staphylococcus aureus leucocidin ED contributes to systemic infection by targeting neutrophils and promoting bacterial growth in vivo. Mol Microbiol 2011; 83:423-35. [PMID: 22142035 DOI: 10.1111/j.1365-2958.2011.07942.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Bloodstream infection with Staphylococcus aureus is common and can be fatal. However, virulence factors that contribute to lethality in S. aureus bloodstream infection are poorly defined. We discovered that LukED, a commonly overlooked leucotoxin, is critical for S. aureus bloodstream infection in mice. We also determined that LukED promotes S. aureus replication in vivo by directly killing phagocytes recruited to sites of haematogenously seeded tissue. Furthermore, we established that murine neutrophils are the primary target of LukED, as the greater virulence of wild-type S. aureus compared with a lukED mutant was abrogated by depleting neutrophils. The in vivo toxicity of LukED towards murine phagocytes is unique among S. aureus leucotoxins, implying its crucial role in pathogenesis. Moreover, the tropism of LukED for murine phagocytes highlights the utility of murine models to study LukED pathobiology, including development and testing of strategies to inhibit toxin activity and control bacterial infection.
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Affiliation(s)
- Francis Alonzo
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
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Parker D, Prince A. Immunopathogenesis of Staphylococcus aureus pulmonary infection. Semin Immunopathol 2011; 34:281-97. [PMID: 22037948 DOI: 10.1007/s00281-011-0291-7] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 10/14/2011] [Indexed: 01/23/2023]
Abstract
Staphylococcus aureus is a common human pathogen highly evolved as both a component of the commensal flora and as a major cause of invasive infection. Severe respiratory infection due to staphylococci has been increasing due to the prevalence of more virulent USA300 CA-MRSA strains in the general population. The ability of S. aureus to adapt to the milieu of the respiratory tract has facilitated its emergence as a respiratory pathogen. Its metabolic versatility, the ability to scavenge iron, coordinate gene expression, and the horizontal acquisition of useful genetic elements have all contributed to its success as a component of the respiratory flora, in hospitalized patients, as a complication of influenza and in normal hosts. The expression of surface adhesins facilitates its persistence in the airways. In addition, the highly sophisticated interactions of the multiple S. aureus virulence factors, particularly the α-hemolysin and protein A, with diverse immune effectors in the lung such as ADAM10, TNFR1, EGFR, immunoglobulin, and complement all contribute to the pathogenesis of staphylococcal pneumonia.
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Affiliation(s)
- Dane Parker
- Department of Pediatrics, Columbia University, New York, NY, USA
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Molecular characteristics of community-associated methicillin-resistant Staphylococcus aureus strains for clinical medicine. Arch Microbiol 2010; 192:603-17. [PMID: 20544179 DOI: 10.1007/s00203-010-0594-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Revised: 03/29/2010] [Accepted: 05/28/2010] [Indexed: 10/19/2022]
Abstract
Infections caused by methicillin-resistant S. aureus strains are mainly associated with a hospital setting. However, nowadays, the MRSA infections of non-hospitalized patients are observed more frequently. In order to distinguish them from hospital-associated methicillin-resistant S. aureus (HA-MRSA) strains, given them the name of community-associated methicillin-resistant S. aureus (CA-MRSA). CA-MRSA strains most commonly cause skin infections, but may lead to more severe diseases, and consequently the patient's death. The molecular markers of CA-MRSA strains are the presence of accessory gene regulator (agr) of group I or III, staphylococcal cassette chromosome mec (SCCmec) type IV, V or VII and genes encoding for Panton-Valentine leukocidin (PVL). In addition, CA-MRSA strains show resistance to beta-lactam antibiotics. Studies on the genetic elements of CA-MRSA strains have a key role in the unambiguous identification of strains, monitoring of infections, improving the treatment, work on new antimicrobial agents and understanding the evolution of these pathogens.
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Graves SF, Kobayashi SD, Braughton KR, Diep BA, Chambers HF, Otto M, Deleo FR. Relative contribution of Panton-Valentine leukocidin to PMN plasma membrane permeability and lysis caused by USA300 and USA400 culture supernatants. Microbes Infect 2010; 12:446-56. [PMID: 20172045 DOI: 10.1016/j.micinf.2010.02.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 02/10/2010] [Accepted: 02/15/2010] [Indexed: 01/15/2023]
Abstract
Panton-Valentine leukocidin (PVL) is a cytolytic toxin associated with severe community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections. However, the relative contribution of PVL to host cell lysis during CA-MRSA infection remains unknown. Here we investigated the relative contribution of PVL to human polymorphonuclear leukocyte (PMN) plasma membrane permeability and lysis in vitro by using culture supernatants from wild-type and isogenic lukS/F-PV negative (Deltapvl) USA300 and USA400 strains. Using S. aureus culture conditions that favor selective high production of PVL (CCY medium), there was on average more PMN plasma membrane permeability and cell lysis caused by supernatants derived from wild-type strains compared with those from Deltapvl strains. Unexpectedly, plasma membrane permeability did not necessarily correlate with ultimate cell lysis. Moreover, the level of pore formation caused by culture supernatants varied dramatically (e.g., range was 0.32-99.09% for wild-type USA300 supernatants at 30 min) and was not attributable to differences in PMN susceptibility to PVL among human blood donors. We conclude that PMN pore formation assays utilizing S. aureus culture supernatants have limited ability to estimate the relative contribution of PVL to pathogenesis (or cytolysis in vitro or in vivo), especially when assayed using culture media that promote selective high production of PVL.
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Affiliation(s)
- Shawna F Graves
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th Street, Hamilton, MT 59840, USA
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Endogenous morphine levels are increased in sepsis: a partial implication of neutrophils. PLoS One 2010; 5:e8791. [PMID: 20098709 PMCID: PMC2808358 DOI: 10.1371/journal.pone.0008791] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 12/26/2009] [Indexed: 11/19/2022] Open
Abstract
Background Mammalian cells synthesize morphine and the respective biosynthetic pathway has been elucidated. Human neutrophils release this alkaloid into the media after exposure to morphine precursors. However, the exact role of endogenous morphine in inflammatory processes remains unclear. We postulate that morphine is released during infection and can be determined in the serum of patients with severe infection such as sepsis. Methodology The presence and subcellular immunolocalization of endogenous morphine was investigated by ELISA, mass spectrometry analysis and laser confocal microscopy. Neutrophils were activated with Interleukin-8 (IL-8) or lipopolysaccharide (LPS). Morphine secretion was determined by a morphine-specific ELISA. μ opioid receptor expression was assessed with flow cytometry. Serum morphine concentrations of septic patients were determined with a morphine-specific ELISA and morphine identity was confirmed in human neutrophils and serum of septic patients by mass spectrometry analysis. The effects of the concentration of morphine found in serum of septic patients on LPS-induced release of IL-8 by human neutrophils were tested. Principal Findings We confirmed the presence of morphine in human neutrophil extracts and showed its colocalisation with lactoferrin within the secondary granules of neutrophils. Morphine secretion was quantified in the supernatant of activated human polymorphonuclear neutrophils in the presence and absence of Ca2+. LPS and IL-8 were able to induce a significant release of morphine only in presence of Ca2+. LPS treatment increased μ opioid receptor expression on neutrophils. Low concentration of morphine (8 nM) significantly inhibited the release of IL-8 from neutrophils when coincubated with LPS. This effect was reversed by naloxone. Patients with sepsis, severe sepsis and septic shock had significant higher circulating morphine levels compared to patients with systemic inflammatory response syndrome and healthy controls. Mass spectrometry analysis showed that endogenous morphine from serum of patient with sepsis was identical to poppy-derived morphine. Conclusions Our results indicate that morphine concentrations are increased significantly in the serum of patients with systemic infection and that morphine is, at least in part, secreted from neutrophils during sepsis. Morphine concentrations equivalent to those found in the serum of septic patients significantly inhibited LPS-induced IL-8 secretion in neutrophils.
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Antibody-mediated enhancement of community-acquired methicillin-resistant Staphylococcus aureus infection. Proc Natl Acad Sci U S A 2010; 107:2241-6. [PMID: 20133867 DOI: 10.1073/pnas.0910344107] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Community-acquired infections caused by methicillin-resistant Staphylococcus aureus (MRSA) expressing the Panton-Valentine leukocidin (PVL) are rampant, but the contribution of PVL to bacterial virulence remains controversial. While PVL is usually viewed as a cytotoxin, at sublytic amounts it activates protective innate immune responses. A leukotoxic effect might predominate in high inoculum studies, whereas protective proinflammatory properties might predominate in settings with lower bacterial inocula that more closely mimic what initially occurs in humans. However, these protective effects might possibly be neutralized by antibodies to PVL, which are found in normal human sera and at increased levels following PVL(+) S. aureus infections. In a low-inoculum murine skin abscess model including a foreign body at the infection site, strains deleted for the pvl genes replicated more efficiently within abscesses than isogenic PVL(+) strains. Coinfection of mice at separate sites with isogenic PVL(+) and PVL(-) MRSA abrogated the differences in bacterial burdens, indicating a systemic effect on host innate immunity from production of PVL. Mice given antibody to PVL and then infected with seven different PVL(+) strains also had significantly higher bacterial counts in abscesses compared with mice given nonimmune serum. Antibody to PVL had no effect on MRSA strains that did not produce PVL. In vitro, antibody to PVL incapacitated PVL-mediated activation of PMNs, indicating that virulence of PVL(+) MRSA is enhanced by the interference of PVL-activated innate immune responses. Given the high rates of primary and recurring MRSA infections in humans, it appears that antibodies to PVL might contribute to host susceptibility to infection.
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Hidron AI, Low CE, Honig EG, Blumberg HM. Emergence of community-acquired meticillin-resistant Staphylococcus aureus strain USA300 as a cause of necrotising community-onset pneumonia. THE LANCET. INFECTIOUS DISEASES 2009; 9:384-92. [DOI: 10.1016/s1473-3099(09)70133-1] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Prevalence of community-associated methicillin-resistant Staphylococcus aureus in patients with cystic fibrosis. J Clin Microbiol 2009; 47:1231-3. [PMID: 19225098 DOI: 10.1128/jcm.00255-09] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We prospectively determined the prevalence of community-associated Staphylococcus aureus in a large cystic fibrosis (CF) center between October 2005 and October 2007. We found that 2.7% (19/707) of the CF patients who had cultures during the study period were infected with this organism, representing 14% of the total methicillin-resistant Staphylococcus aureus strains (n = 140) recovered from the patient population during the study period.
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Analysis of the specificity of Panton-Valentine leucocidin and gamma-hemolysin F component binding. Infect Immun 2008; 77:266-73. [PMID: 18838523 DOI: 10.1128/iai.00402-08] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this study, the binding of F components of the staphylococcal bicomponent leukotoxins Panton-Valentine leucocidin (LukF-PV) and gamma-hemolysin (HlgB) on polymorphonuclear neutrophils (PMNs), monocytes, and lymphocytes was determined using labeled mutants and flow cytometry. Leukotoxin activity was evaluated by measuring Ca(2+) entry or pore formation using spectrofluorometry or flow cytometry. Although HlgB had no affinity for cells in the absence of an S component, LukF-PV had high affinity for PMNs (dissociation constant [K(d)], 6.2 +/- 1.9 nM; n = 8), monocytes (K(d), 2.8 +/- 0.8 nM; n = 7), and lymphocytes (K(d), 1.2 +/- 0.2 nM; n = 7). Specific binding of HlgB was observed only after addition of LukS-PV on PMNs (K(d), 1.1 +/- 0.2 nM; n = 4) and monocytes (K(d), 0.84 +/- 0.31 nM; n = 4) or after addition of HlgC on PMNs, monocytes, and lymphocytes. Addition of LukS-PV or HlgC induced a second specific binding of LukF-PV on PMNs. HlgB and LukD competed only with LukF-PV molecules bound after addition of LukS-PV. LukF-PV and LukD competed with HlgB in the presence of LukS-PV on PMNs and monocytes. Use of antibodies and comparisons between binding and activity time courses showed that the LukF-PV molecules that bound to target cells before addition of LukS-PV were the only LukF-PV molecules responsible for Ca(2+) entry and pore formation. In contrast, the active HlgB molecules were the HlgB molecules bound after addition of LukS-PV. In conclusion, LukF-PV must be linked to LukS-PV and to a binding site of the membrane to have toxin activity.
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Two different Panton-Valentine leukocidin phage lineages predominate in Japan. J Clin Microbiol 2008; 46:3246-58. [PMID: 18685010 DOI: 10.1128/jcm.00136-08] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We determined the entire nucleotide sequence of phiSa2958-carrying Panton-Valentine leukocidin (PVL) gene, which was lysogenized in a sequence type 5 staphylococcal cassette chromosome mec (SCCmec) type II strain of methicillin-resistant Staphylococcus aureus (MRSA). Based on the nucleotide sequences of PVL phages, we developed PCRs to discriminate among five PVL phages, with a preliminary classification into two morphological groups (elongated-head type and icosahedral-head type) with four PCRs, including two PCRs for identifying the gene lineage between lukS-PV and the tail gene. The phages were then classified into five types by four PCRs identifying each phage-specific structure. With these PCRs, we examined the PVL phage types of 67 MRSA strains isolated in Japan from 1979 through 1985 and since 2000 and found that two morphologically distinct phages were predominant in Japan. The icosahedral-head-type phage, represented by the phi108PVL type, was identified for 39 of 53 strains isolated from 1979 through 1985. Of 26 other Japanese isolates, 25 belonged either definitively or presumably to elongated-head types as follows: 3 belonged to the phiSa2958 type; 8 were determined to belong to an elongated-head type, but a determination of greater specificity was not made; and 14 belonged to a phiSa2958-like phage of unknown type. We induced prophages by treatment with mitomycin C from six strains of the phiSa2958 type or of phiSa2958-like unknown-type phages; five of six strains carried intact PVL-carrying phages, which can infect other S. aureus strains and might generate novel PVL-positive strains of S. aureus. That various SCCmec elements were carried by different strains of the same phage type suggests that S. aureus strains might independently acquire PVL phages before they acquire various SCCmec elements.
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Zhang K, McClure JA, Elsayed S, Tan J, Conly JM. Coexistence of Panton-Valentine leukocidin-positive and -negative community-associated methicillin-resistant Staphylococcus aureus USA400 sibling strains in a large Canadian health-care region. J Infect Dis 2008; 197:195-204. [PMID: 18173361 DOI: 10.1086/523763] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains often carry the Panton-Valentine leukocidin (PVL) genes. However, the specific role that PVL plays in the epidemiological features and pathogenesis of CA-MRSA infections has remained undefined and controversial. Conducting a retrospective study on a natural population of MRSA clinical isolates recovered from community and hospital patients in a large Canadian health-care region during a 6-year period, we identified the coexistence of 2 USA400 (a major clonal group of CA-MRSA) sibling strains with and without PVL genes. Polymerase chain reaction and sequence analysis indicated that the PVL-carrying prophage phiSa2mw was present in PVL(+) but absent in PVL(-) USA400 isolates. These strains shared identical genotypic and phenotypic properties and similar clinical characteristics. This study provides direct evidence that PVL genes are not necessarily the key determinants associated with the increasing dissemination of CA-MRSA strains, suggesting that the genomic milieu may play a greater role in this regard.
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Affiliation(s)
- Kunyan Zhang
- Centre for Antimicrobial Resistance, Calgary Health Region/Calgary Laboratory Services/University of Calgary, Calgary, Alberta, Canada.
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Tristan A, Ferry T, Durand G, Dauwalder O, Bes M, Lina G, Vandenesch F, Etienne J. Virulence determinants in community and hospital meticillin-resistant Staphylococcus aureus. J Hosp Infect 2007; 65 Suppl 2:105-9. [PMID: 17540252 DOI: 10.1016/s0195-6701(07)60025-5] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Staphylococcus aureus produces many virulence factors, most of which act in a synergistic and coordinated fashion. Some appear to be specifically associated with certain severe infections and are produced by meticillin-resistant Staphylococcus aureus (MRSA) clones distributed worldwide. Superantigenic exotoxins appear to be major virulence factors in hospital MRSA clones (HA-MRSA), and staphylococcal enterotoxin A (SEA) may be involved in the physiopathology of septic shock. Panton Valentine Leucocidin (PVL) has emerged as a major virulence factor in community-acquired Staphylococcus aureus (CA-MRSA) infections. In particular, the leukotoxic action of PVL is responsible for the high mortality rate associated with necrotizing pneumonia. CA-MRSA can also harbour the toxic shock toxin 1 (TSST-1) and rarely the exfoliative toxin.
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John CC, Schreiber JR. Therapies and vaccines for emerging bacterial infections: learning from methicillin-resistant Staphylococcus aureus. Pediatr Clin North Am 2006; 53:699-713. [PMID: 16873000 DOI: 10.1016/j.pcl.2006.05.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging bacterial infection worldwide, and community-acquired MRSA (CA-MRSA) infection, which has increased dramatically in frequency in many areas, is of particular clinical and public health concern. CA-MRSA outbreaks and severe infections have been reported more frequently in children, often manifesting in one of two distinct clinical syndromes, furunculosis or necrotizing pneumonia. This article outlines the molecular biology of MRSA, how molecular biology has contributed to the understanding of MRSA infections, current therapy and prevention of MRSA, and the prospects for a vaccine against S aureus.
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Affiliation(s)
- Chandy C John
- Department of Pediatrics, University of Minnesota Medical School, 420 Delaware Street SE, Minneapolis, MN 55455, USA.
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McClure JA, Conly JM, Lau V, Elsayed S, Louie T, Hutchins W, Zhang K. Novel multiplex PCR assay for detection of the staphylococcal virulence marker Panton-Valentine leukocidin genes and simultaneous discrimination of methicillin-susceptible from -resistant staphylococci. J Clin Microbiol 2006; 44:1141-4. [PMID: 16517915 PMCID: PMC1393128 DOI: 10.1128/jcm.44.3.1141-1144.2006] [Citation(s) in RCA: 230] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We developed a new multiplex PCR assay for detection of Panton-Valentine leukocidin virulence genes and simultaneous discrimination of methicillin-susceptible from -resistant staphylococci. This assay is simple, rapid, and accurate and offers the potential for prompt detection of newly emerging community-associated methicillin-resistant Staphylococcus aureus.
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Affiliation(s)
- Jo-Ann McClure
- Centre for Antimicrobial Resistance, Calgary Health Region/Calgary Laboratory Services/University of Calgary, Calgary, Alberta, Canada
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Genestier AL, Michallet MC, Prévost G, Bellot G, Chalabreysse L, Peyrol S, Thivolet F, Etienne J, Lina G, Vallette FM, Vandenesch F, Genestier L. Staphylococcus aureus Panton-Valentine leukocidin directly targets mitochondria and induces Bax-independent apoptosis of human neutrophils. J Clin Invest 2006; 115:3117-27. [PMID: 16276417 PMCID: PMC1265849 DOI: 10.1172/jci22684] [Citation(s) in RCA: 281] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Accepted: 08/23/2005] [Indexed: 11/17/2022] Open
Abstract
Panton-Valentine leukocidin (PVL) is a pore-forming toxin secreted by Staphylococcus aureus that has recently been associated with necrotizing pneumonia. In the present study, we report that in vitro, PVL induces polymorphonuclear cell death by necrosis or by apoptosis, depending on the PVL concentration. PVL-induced apoptosis was associated with a rapid disruption of mitochondrial homeostasis and activation of caspase-9 and caspase-3, suggesting that PVL-induced apoptosis is preferentially mediated by the mitochondrial pathway. Polymorphonuclear cell exposure to PVL leads to mitochondrial localization of the toxin, whereas Bax, 1 of the 2 essential proapoptotic members of the Bcl-2 family, was still localized in the cytosol. Addition of PVL to isolated mitochondria induced the release of the apoptogenic proteins cytochrome c and Smac/DIABLO. Therefore, we suggest that PVL, which belongs to the pore-forming toxin family, could act at the mitochondrion level by creating pores in the mitochondrial outer membrane. Furthermore, LukS-PV, 1 of the 2 components of PVL, was detected in lung sections of patients with necrotizing pneumonia together with DNA fragmentation, suggesting that PVL induces apoptosis in vivo and thereby is directly involved in the pathophysiology of necrotizing pneumonia.
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Ferry T, Perpoint T, Vandenesch F, Etienne J. Virulence determinants in Staphylococcus aureus and their involvement in clinical syndromes. Curr Infect Dis Rep 2006; 7:420-8. [PMID: 16225779 DOI: 10.1007/s11908-005-0043-8] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Staphylococcus aureus is a major human pathogen responsible for a variety of toxin-mediated and suppurative diseases. About 50 staphylococcal virulence factors have been described to date. In this review, we examine the clinical implications of key staphylococcal virulence factors in toxin-mediated diseases, septic shock, and severe focal infections such as arthritis, infective endocarditis, pneumonia acquired during mechanical ventilation, and necrotizing pneumonia. Staphylococcal pathogenicity is sometimes due principally to a single virulence factor, as in toxic shock syndrome and necrotizing pneumonia. In contrast, several virulence factors are involved in other staphylococcal disease, such as septic shock. A better knowledge of the mechanism of action of each virulence factor involved in the different staphylococcal diseases could open the way to the use of specific inhibitors in the clinical setting.
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Affiliation(s)
- Tristan Ferry
- Centre National de Référence des Staphylocoques, INSERM E0230, Faculté de Médecine Laennec, 7 rue Guillaume Paradin, 69008 Lyon, France.
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Brüssow H, Canchaya C, Hardt WD. Phages and the evolution of bacterial pathogens: from genomic rearrangements to lysogenic conversion. Microbiol Mol Biol Rev 2004; 68:560-602, table of contents. [PMID: 15353570 PMCID: PMC515249 DOI: 10.1128/mmbr.68.3.560-602.2004] [Citation(s) in RCA: 1088] [Impact Index Per Article: 54.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Comparative genomics demonstrated that the chromosomes from bacteria and their viruses (bacteriophages) are coevolving. This process is most evident for bacterial pathogens where the majority contain prophages or phage remnants integrated into the bacterial DNA. Many prophages from bacterial pathogens encode virulence factors. Two situations can be distinguished: Vibrio cholerae, Shiga toxin-producing Escherichia coli, Corynebacterium diphtheriae, and Clostridium botulinum depend on a specific prophage-encoded toxin for causing a specific disease, whereas Staphylococcus aureus, Streptococcus pyogenes, and Salmonella enterica serovar Typhimurium harbor a multitude of prophages and each phage-encoded virulence or fitness factor makes an incremental contribution to the fitness of the lysogen. These prophages behave like "swarms" of related prophages. Prophage diversification seems to be fueled by the frequent transfer of phage material by recombination with superinfecting phages, resident prophages, or occasional acquisition of other mobile DNA elements or bacterial chromosomal genes. Prophages also contribute to the diversification of the bacterial genome architecture. In many cases, they actually represent a large fraction of the strain-specific DNA sequences. In addition, they can serve as anchoring points for genome inversions. The current review presents the available genomics and biological data on prophages from bacterial pathogens in an evolutionary framework.
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Affiliation(s)
- Harald Brüssow
- Nestlé, Research Center, Vers-chez-les-Blanc, CH-1000 Lausanne, Switzerland.
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Menestrina G, Dalla Serra M, Comai M, Coraiola M, Viero G, Werner S, Colin DA, Monteil H, Prévost G. Ion channels and bacterial infection: the case of beta-barrel pore-forming protein toxins of Staphylococcus aureus. FEBS Lett 2003; 552:54-60. [PMID: 12972152 DOI: 10.1016/s0014-5793(03)00850-0] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Staphylococcus aureus strains causing human pathologies produce several toxins, including a pore-forming protein family formed by the single-component alpha-hemolysin and the bicomponent leukocidins and gamma-hemolysins. The last comprise two protein elements, S and F, that co-operatively form the active toxin. alpha-Hemolysin is always expressed by S. aureus strains, whereas bicomponent leukotoxins are more specifically involved in a few diseases. X-ray crystallography of the alpha-hemolysin pore has shown it is a mushroom-shaped, hollow heptamer, almost entirely consisting of beta-structure. Monomeric F subunits have a very similar core structure, except for the transmembrane stem domain which has to refold during pore formation. Large deletions in this domain abolished activity, whereas shorter deletions sometimes improved it, possibly by removing some of the interactions stabilizing the folded structure. Even before stem extension is completed, the formation of an oligomeric pre-pore can trigger Ca(2+)-mediated activation of some white cells, initiating an inflammatory response. Within the bicomponent toxins, gamma-hemolysins define three proteins (HlgA, HlgB, HlgC) that can generate two toxins: HlgA+HlgB and HlgC+HlgB. Like alpha-hemolysin they form pores in planar bilayers with similar conductance, but opposite selectivity (cation instead of anion) for the presence of negative charges in the ion pathway. gamma-Hemolysin pores seem to be organized as alpha-hemolysin, but should contain an even number of each component, alternating in a 1:1 stoichiometry.
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Affiliation(s)
- G Menestrina
- CNR-ITC Istituto di Biofisica, Sezione di Trento, Via Sommarive 18, I-38050 Povo, Italy.
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Colin DA, Monteil H. Control of the oxidative burst of human neutrophils by staphylococcal leukotoxins. Infect Immun 2003; 71:3724-9. [PMID: 12819053 PMCID: PMC161991 DOI: 10.1128/iai.71.7.3724-3729.2003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ability of staphylococcal two-component leukotoxins to induce an oxidative burst and/or to prime human polymorphonuclear cells (PMNs) was studied by using spectrofluorometry or flow cytometry. At sublytic concentrations, the HlgA-HlgB, HlgA-LukF-PV, LukS-PV-LukF-PV, and HlgC-LukF-PV combinations of leukotoxins, but not the LukS-PV-HlgB and HlgC-HlgB combinations, were able to induce H(2)O(2) production similar to the H(2)O(2) production induced by 1 micro M N-formyl-Met-Leu-Phe (fMLP). In addition, when added at sublytic concentrations, all of the leukotoxin combinations primed PMNs for H(2)O(2) production induced by fMLP. Leukotoxin activation was dependent on the presence of Ca(2+) and was inhibited by wortmannin, an inhibitor of phosphatidylinositol 3-kinase, but not by N-methyl-L-arginine, an inhibitor of NO generation, which eliminates the possibility that NO plays a role in the action of leukotoxins. At higher concentrations, all leukotoxins inhibited H(2)O(2) production by PMNs activated by fMLP, phorbol 12-myristate 13-acetate (PMA), or the leukotoxins themselves. This inhibition was not related to the pore formation induced by leukotoxins. Intracellular release of H(2)O(2) induced by fMLP and PMA was not primed by leukotoxins but was inhibited. It seems that leukotoxin inhibition of H(2)O(2) release is independent of pore formation but secondary to an intracellular event, as yet unknown, triggered by leukotoxins.
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Affiliation(s)
- Didier A Colin
- Laboratoire de Physiopathologie et d'Antibiologie des Infections Bactériennes Emergentes et Nosocomiales, UPRES-EA 3432, Institut de Bactériologie, Université Louis Pasteur-Hôpitaux Universitaires de Strasbourg, France.
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Comai M, Dalla Serra M, Coraiola M, Werner S, Colin DA, Monteil H, Prévost G, Menestrina G. Protein engineering modulates the transport properties and ion selectivity of the pores formed by staphylococcal gamma-haemolysins in lipid membranes. Mol Microbiol 2002; 44:1251-67. [PMID: 12068809 DOI: 10.1046/j.1365-2958.2002.02943.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Staphylococcal gamma-haemolysins are bicomponent toxins in a family including other leucocidins and alpha-toxin. Two active toxins are formed combining HlgA or HlgC with HlgB. Both open pores in lipid membranes with conductance, current voltage characteristics and stability similar to alpha-toxin, but different selectivity (cation instead of anion). Structural analogies between gamma-haemolysins and alpha-toxin indicate the presence, at the pore entry, of a conserved region containing four positive charges in alpha-toxin, but either positive or negative in gamma-haemolysins. Four mutants were produced (HlgA D44K, HlgB D47K, HlgB D49K and HlgB D47K/D49K) converting those negative charges to positive in HlgA and HlgB. When all charges were positive, the pores had the same selectivity and conductance as alpha-toxin, suggesting that the cluster may form an entrance electrostatic filter. As mutated HlgC-HlgB pores were less affected, additional charges in the lumen of the pore were changed (HlgB E107Q, HlgB D121N, HlgB T136D and HlgA K108T). Removing a negative charge from the lumen made the selectivity of both HlgA-HlgB D121N and HlgC-HlgB D121N more anionic. Residue D121 of HlgB is compensated by a positive residue (HlgA K108) in the HlgA-HlgB pore, but isolated in the more cation-selective HlgC-HlgB pore. Interestingly, the pore formed by HlgA K108T-HlgB, in which the positive charge of HlgA was removed, was as cation selective as HlgC-HlgB. Meanwhile, the pore formed by HlgA K108T-HlgB D121N, in which the two charge changes compensated, retrieved the properties of wild-type HlgA-HlgB. We conclude that the conductance and selectivity of the gamma-haemolysin pores depend substantially on the presence and location of charged residues in the channel.
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Affiliation(s)
- Massimiliano Comai
- CNR-ITC Centro di Fisica degli Stati Aggregati, Istituto di Biofisica del CNR, Via Sommarive 18, I-38050 Povo (Trento), Italy
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Menestrina G, Serra MD, Prévost G. Mode of action of beta-barrel pore-forming toxins of the staphylococcal alpha-hemolysin family. Toxicon 2001; 39:1661-72. [PMID: 11595629 DOI: 10.1016/s0041-0101(01)00153-2] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Staphylococcal alpha-hemolysin is the prototype of a family of bacterial exotoxins with membrane-damaging function, which share sequence and structure homology. These toxins are secreted in a soluble form which finally converts into a transmembrane pore by assembling an oligomeric beta-barrel, with hydrophobic residues facing the lipids and hydrophilic residues facing the lumen of the channel. Besides alpha-hemolysin the family includes other single chain toxins forming homo-oligomers, e.g. beta-toxin of Clostridium perfringens, hemolysin II and cytotoxin K of Bacillus cereus, but also the staphylococcal bi-component toxins, like gamma-hemolysins and leucocidins, which are only active as the combination of two similar proteins which form hetero-oligomers. The molecular basis of membrane insertion has become clearer after the determination of the crystal structure of both the oligomeric pore and the soluble monomer. Studies on this family of beta-barrel pore-forming toxins are important for many aspects: (i) they are involved in serious pathologies of humans and farmed animals, (ii) they are a good model system to investigate protein-membrane interaction and (iii) they are the basic elements for the construction of nanopores with biotechnological applications in various fields.
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Affiliation(s)
- G Menestrina
- CNR-ITC Centro Fisica Stati Aggregati, Via Sommarive 18, I-38050 Povo, Trento, Italy.
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Affiliation(s)
- G Prévost
- Institut de Bactériologie de la Faculté de Médecine, Université Louis Pasteur-Hôpitaux Universitaires de Strasbourg, 3, rue Koeberlé, 67000 Strasbourg, France
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Gauduchon V, Werner S, Prévost G, Monteil H, Colin DA. Flow cytometric determination of Panton-Valentine leucocidin S component binding. Infect Immun 2001; 69:2390-5. [PMID: 11254598 PMCID: PMC98170 DOI: 10.1128/iai.69.4.2390-2395.2001] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The binding of the S component (LukS-PV) from the bicomponent staphylococcal Panton-Valentine leucocidin to human polymorphonuclear neutrophils (PMNs) and monocytes was determined using flow cytometry and a single-cysteine substitution mutant of LukS-PV. The mutant was engineered by replacing a glycine at position 10 with a cysteine and was labeled with a fluorescein moiety. The biological activity of the mutant was identical to that of the native protein. It has been shown that LukS-PV has a high affinity for PMNs (Kd = 0.07 +/- 0.02 nM, n = 5) and monocytes (Kd = 0.020 +/- 0.003 nM, n = 3) with maximal binding capacities of 197,000 and 80,000 LukS-PV molecules per cell, respectively. The nonspecifically bound molecules of LukS-PV do not form pores in the presence of the F component (LukF-PV) of leucocidin. LukS-PV and HlgC share the same receptor on PMNs, but the S components of other staphylococcal leukotoxins, HlgA, LukE, and LukM, do not compete with LukS-PV for its receptor. Extracellular Ca2+ at physiological concentrations (1 to 2 nM) has only a slight influence on the LukS-PV binding, in contrast to its complete inhibition by Zn2+. The down-regulation by phorbol 12-myristate 13-acetate (PMA) of the binding of LukS-PV was blocked by staurosporine, suggesting that the regulatory effect of PMA depends on protein kinase C activation. The labeled mutant form of LukS-PV has proved very useful for detailed binding studies of circulating white cells by flow cytometry. LukS-PV possesses a high specific affinity for a unique receptor on PMNs and monocytes.
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Affiliation(s)
- V Gauduchon
- Laboratoire de Toxinologie et d'Antibiologie Bactériennes (UPRES-EA 1318), Institut de Bactériologie de la Faculté de Médecine, Université Louis Pasteur-Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
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