1
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Stegmann F, Diersing C, Lepenies B. Legionella pneumophila modulates macrophage functions through epigenetic reprogramming via the C-type lectin receptor Mincle. iScience 2024; 27:110700. [PMID: 39252966 PMCID: PMC11382120 DOI: 10.1016/j.isci.2024.110700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 12/12/2023] [Accepted: 08/06/2024] [Indexed: 09/11/2024] Open
Abstract
Legionella pneumophila is a pathogen which can lead to a severe form of pneumonia in humans known as Legionnaires disease after replication in alveolar macrophages. Viable L. pneumophila actively secrete effector molecules to modulate the host's immune response. Here, we report that L. pneumophila-derived factors reprogram macrophages into a tolerogenic state, a process to which the C-type lectin receptor Mincle (CLEC4E) markedly contributes. The underlying epigenetic state is characterized by increases of the closing mark H3K9me3 and decreases of the opening mark H3K4me3, subsequently leading to the reduced secretion of the cytokines TNF, IL-6, IL-12, the production of reactive oxygen species, and cell-surface expression of MHC-II and CD80 upon re-stimulation. In summary, these findings provide important implications for our understanding of Legionellosis and the contribution of Mincle to reprogramming of macrophages by L. pneumophila.
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Affiliation(s)
- Felix Stegmann
- Institute for Immunology, University of Veterinary Medicine Hannover, 30559 Hanover, Lower Saxony, Germany
- Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine Hannover, 30559 Hanover, Lower Saxony, Germany
| | - Christina Diersing
- Institute for Immunology, University of Veterinary Medicine Hannover, 30559 Hanover, Lower Saxony, Germany
- Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine Hannover, 30559 Hanover, Lower Saxony, Germany
| | - Bernd Lepenies
- Institute for Immunology, University of Veterinary Medicine Hannover, 30559 Hanover, Lower Saxony, Germany
- Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine Hannover, 30559 Hanover, Lower Saxony, Germany
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2
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Pollock TY, Vázquez Marrero VR, Brodsky IE, Shin S. TNF licenses macrophages to undergo rapid caspase-1, -11, and -8-mediated cell death that restricts Legionella pneumophila infection. PLoS Pathog 2023; 19:e1010767. [PMID: 37279255 DOI: 10.1371/journal.ppat.1010767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 05/25/2023] [Indexed: 06/08/2023] Open
Abstract
The inflammatory cytokine tumor necrosis factor (TNF) is necessary for host defense against many intracellular pathogens, including Legionella pneumophila. Legionella causes the severe pneumonia Legionnaires' disease and predominantly affects individuals with a suppressed immune system, including those receiving therapeutic TNF blockade to treat autoinflammatory disorders. TNF induces pro-inflammatory gene expression, cellular proliferation, and survival signals in certain contexts, but can also trigger programmed cell death in others. It remains unclear, however, which of the pleiotropic functions of TNF mediate control of intracellular bacterial pathogens like Legionella. In this study, we demonstrate that TNF signaling licenses macrophages to die rapidly in response to Legionella infection. We find that TNF-licensed cells undergo rapid gasdermin-dependent, pyroptotic death downstream of inflammasome activation. We also find that TNF signaling upregulates components of the inflammasome response, and that the caspase-11-mediated non-canonical inflammasome is the first inflammasome to be activated, with caspase-1 and caspase-8 mediating delayed pyroptotic death. We find that all three caspases are collectively required for optimal TNF-mediated restriction of bacterial replication in macrophages. Furthermore, caspase-8 is required for control of pulmonary Legionella infection. These findings reveal a TNF-dependent mechanism in macrophages for activating rapid cell death that is collectively mediated by caspases-1, -8, and -11 and subsequent restriction of Legionella infection.
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Affiliation(s)
- Tzvi Y Pollock
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Víctor R Vázquez Marrero
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Igor E Brodsky
- Department of Pathobiology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, United States of America
| | - Sunny Shin
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States of America
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3
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Morrison HM, Craft J, Rivera-Lugo R, Johnson JR, Golovkine GR, Bell SL, Dodd CE, Van Dis E, Beatty WL, Margolis SR, Repasy T, Shaker I, Lee AY, Vance RE, Stanley SA, Watson RO, Krogan NJ, Portnoy DA, Penn BH, Cox JS. Deficiency in Galectin-3, -8, and -9 impairs immunity to chronic Mycobacterium tuberculosis infection but not acute infection with multiple intracellular pathogens. PLoS Pathog 2023; 19:e1011088. [PMID: 37352334 PMCID: PMC10325092 DOI: 10.1371/journal.ppat.1011088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 07/06/2023] [Accepted: 05/01/2023] [Indexed: 06/25/2023] Open
Abstract
Macrophages employ an array of pattern recognition receptors to detect and eliminate intracellular pathogens that access the cytosol. The cytosolic carbohydrate sensors Galectin-3, -8, and -9 (Gal-3, Gal-8, and Gal-9) recognize damaged pathogen-containing phagosomes, and Gal-3 and Gal-8 are reported to restrict bacterial growth via autophagy in cultured cells. However, the contribution of these galectins to host resistance during bacterial infection in vivo remains unclear. We found that Gal-9 binds directly to Mycobacterium tuberculosis (Mtb) and Salmonella enterica serovar Typhimurium (Stm) and localizes to Mtb in macrophages. To determine the combined contribution of membrane damage-sensing galectins to immunity, we generated Gal-3, -8, and -9 triple knockout (TKO) mice. Mtb infection of primary macrophages from TKO mice resulted in defective autophagic flux but normal bacterial replication. Surprisingly, these mice had no discernable defect in resistance to acute infection with Mtb, Stm or Listeria monocytogenes, and had only modest impairments in bacterial growth restriction and CD4 T cell activation during chronic Mtb infection. Collectively, these findings indicate that while Gal-3, -8, and -9 respond to an array of intracellular pathogens, together these membrane damage-sensing galectins play a limited role in host resistance to bacterial infection.
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Affiliation(s)
- Huntly M. Morrison
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
| | - Julia Craft
- Department of Internal Medicine, Division of Infectious Diseases, University of California, Davis, Davis, California, United States of America
| | - Rafael Rivera-Lugo
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
| | - Jeffery R. Johnson
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco; Quantitative Biosciences Institute (QBI), University of California, San Francisco; Gladstone Institutes, San Francisco, California, United States of America
| | - Guillaume R. Golovkine
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
| | - Samantha L. Bell
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, School of Medicine, Bryan, Texas, United States of America
| | - Claire E. Dodd
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
| | - Erik Van Dis
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
| | - Wandy L. Beatty
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Shally R. Margolis
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
| | - Teresa Repasy
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
| | - Isaac Shaker
- Department of Internal Medicine, Division of Infectious Diseases, University of California, Davis, Davis, California, United States of America
| | - Angus Y. Lee
- Cancer Research Laboratory, University of California, Berkeley, Berkeley, California, United States of America
| | - Russell E. Vance
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, California, United States of America
| | - Sarah A. Stanley
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
- School of Public Health, Division of Infectious Diseases and Vaccinology, University of California, Berkeley, Berkeley, California, United States of America
| | - Robert O. Watson
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, School of Medicine, Bryan, Texas, United States of America
| | - Nevan J. Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco; Quantitative Biosciences Institute (QBI), University of California, San Francisco; Gladstone Institutes, San Francisco, California, United States of America
| | - Daniel A. Portnoy
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
| | - Bennett H. Penn
- Department of Internal Medicine, Division of Infectious Diseases, University of California, Davis, Davis, California, United States of America
| | - Jeffery S. Cox
- Department of Molecular and Cell Biology, Division of Immunology and Molecular Medicine, University of California, Berkeley, Berkeley, California, United States of America
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4
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Aurass P, Kim S, Pinedo V, Cava F, Isberg RR. Identification of Genes Required for Long-Term Survival of Legionella pneumophila in Water. mSphere 2023; 8:e0045422. [PMID: 36988466 PMCID: PMC10117105 DOI: 10.1128/msphere.00454-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 02/24/2023] [Indexed: 03/30/2023] Open
Abstract
Long-term survival of Legionella pneumophila in aquatic environments is thought to be important for facilitating epidemic outbreaks. Eliminating bacterial colonization in plumbing systems is the primary strategy that depletes this reservoir and prevents disease. To uncover L. pneumophila determinants facilitating survival in water, a Tn-seq strategy was used to identify survival-defective mutants during 50-day starvation in tap water at 42°C. The mutants with the most drastic survival defects carried insertions in electron transport chain genes, indicating that membrane energy charge and/or ATP synthesis requires the generation of a proton gradient by the respiratory chain to maintain survival in the presence of water stress. In addition, periplasmically localized proteins that are known (EnhC) or hypothesized (lpg1697) to stabilize the cell wall against turnover were essential for water survival. To test that the identified mutations disrupted water survival, candidate genes were knocked down by CRISPRi. The vast majority of knockdown strains with verified transcript depletion showed remarkably low viability after 50-day incubations. To demonstrate that maintenance of cell wall integrity was an important survival determinant, a deletion mutation in lpg1697, in a gene encoding a predicted l,d-transpeptidase domain, was analyzed. The loss of this gene resulted in increased osmolar sensitivity and carbenicillin hypersensitivity relative to the wild type, as predicted for loss of an l,d-transpeptidase. These results indicate that the L. pneumophila envelope has been evolutionarily selected to allow survival under conditions in which the bacteria are subjected to long-term exposure to starvation and low osmolar conditions. IMPORTANCE Water is the primary vector for transmission of L. pneumophila to humans, and the pathogen is adapted to persist in this environment for extended periods of time. Preventing survival of L. pneumophila in water is therefore critical for prevention of Legionnaires' disease. We analyzed dense transposon mutation pools for strains with severe survival defects during a 50-day water incubation at 42°C. By tracking the associated transposon insertion sites in the genome, we defined a distinct essential gene set for water survival and demonstrate that a predicted peptidoglycan cross-linking enzyme, lpg1697, and components of the electron transport chain are required to ensure survival of the pathogen. Our results indicate that select characteristics of the cell wall and components of the respiratory chain of L. pneumophila are primary evolutionary targets being shaped to promote its survival in water.
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Affiliation(s)
- Philipp Aurass
- Department of Enteropathogenic Bacteria and Legionella, Robert Koch Institute, Wernigerode, Germany
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Seongok Kim
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Victor Pinedo
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Felipe Cava
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Ralph R. Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
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5
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Gopallawa I, Dehinwal R, Bhatia V, Gujar V, Chirmule N. A four-part guide to lung immunology: Invasion, inflammation, immunity, and intervention. Front Immunol 2023; 14:1119564. [PMID: 37063828 PMCID: PMC10102582 DOI: 10.3389/fimmu.2023.1119564] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 03/09/2023] [Indexed: 04/03/2023] Open
Abstract
Lungs are important respiratory organs primarily involved in gas exchange. Lungs interact directly with the environment and their primary function is affected by several inflammatory responses caused by allergens, inflammatory mediators, and pathogens, eventually leading to disease. The immune architecture of the lung consists of an extensive network of innate immune cells, which induce adaptive immune responses based on the nature of the pathogen(s). The balance of immune responses is critical for maintaining immune homeostasis in the lung. Infection by pathogens and physical or genetic dysregulation of immune homeostasis result in inflammatory diseases. These responses culminate in the production of a plethora of cytokines such as TSLP, IL-9, IL-25, and IL-33, which have been implicated in the pathogenesis of several inflammatory and autoimmune diseases. Shifting the balance of Th1, Th2, Th9, and Th17 responses have been the targets of therapeutic interventions in the treatment of these diseases. Here, we have briefly reviewed the innate and adaptive i3mmune responses in the lung. Genetic and environmental factors, and infection are the major causes of dysregulation of various functions of the lung. We have elaborated on the impact of inflammatory and infectious diseases, advances in therapies, and drug delivery devices on this critical organ. Finally, we have provided a comprehensive compilation of different inflammatory and infectious diseases of the lungs and commented on the pros and cons of different inhalation devices for the management of lung diseases. The review is intended to provide a summary of the immunology of the lung, with an emphasis on drug and device development.
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Affiliation(s)
- Indiwari Gopallawa
- Clinical Pharmacology & Safety Sciences, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, MD, United States
| | - Ruchika Dehinwal
- Department of Microbiology, Division of Infectious Disease, Brigham Women’s Hospital, Harvard Medical School, Howard Hughes Medical Institute, Boston, MA, United States
| | | | - Vikramsingh Gujar
- Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Tulsa, OK, United States
| | - Narendra Chirmule
- R&D Department, SymphonyTech Biologics, Philadelphia, PA, United States
- *Correspondence: Narendra Chirmule,
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6
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Kim S, Isberg RR. The Sde Phosphoribosyl-Linked Ubiquitin Transferases protect the Legionella pneumophila vacuole from degradation by the host. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.19.533379. [PMID: 36993347 PMCID: PMC10055210 DOI: 10.1101/2023.03.19.533379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Legionella pneumophila grows intracellularly within a host membrane-bound vacuole that is formed in response to a bacterial type IV secretion system (T4SS). T4SS translocated Sde proteins promote phosphoribosyl-linked ubiquitination of endoplasmic reticulum protein Rtn4, but the role played by this modification is obscure due to lack of clear growth defects of mutants. To identify the steps in vacuole biogenesis promoted by these proteins, mutations were identified that unmasked growth defects in Δ sde strains. Mutations in the sdhA , ridL and legA3 genes aggravated the Δ sde fitness defect, resulting in disruption of the Legionella -containing vacuole (LCV) membrane within 2 hrs of bacterial contact with host cells. Depletion of Rab5B and sorting nexin 1 partially bypassed loss of Sde proteins, consistent with Sde blocking early endosome and retrograde trafficking, similar to roles previously demonstrated for SdhA and RidL proteins. Sde protein protection of LCV lysis was only observed shortly after infection, presumably because Sde proteins are inactivated by the metaeffector SidJ during the course of infection. Deletion of SidJ extended the time that Sde proteins could prevent vacuole disruption, indicating that Sde proteins are negatively regulated at the posttranslational level and are limited to protecting membrane integrity at the earliest stages of replication. Transcriptional analysis was consistent with this timing model for an early point of execution of Sde protein. Therefore, Sde proteins act as temporally-regulated vacuole guards during establishment of the replication niche, possibly by constructing a physical barrier that blocks access of disruptive host compartments early during biogenesis of the LCV. Significance statement Maintaining replication compartment integrity is critical for growth of intravacuolar pathogens within host cells. By identifying genetically redundant pathways, Legionella pneumophila Sde proteins that promote phosphoribosyl-linked ubiquitination of target eukaryotic proteins are shown to be temporally-regulated vacuole guards, preventing replication vacuole dissolution during early stages of infection. As targeting of reticulon 4 by these proteins leads to tubular endoplasmic reticulum aggregation, Sde proteins are likely to construct a barrier that blocks access of disruptive early endosomal compartments to the replication vacuole. Our study provides a new framework for how vacuole guards function to support biogenesis of the L. pneumophila replicative niche.
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Affiliation(s)
- Seongok Kim
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Avenue, Boston, MA 02111, USA
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Avenue, Boston, MA 02111, USA
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7
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Kang YS, Kirby JE. A Versatile Nanoluciferase Reporter Reveals Structural Properties Associated with a Highly Efficient, N-Terminal Legionella pneumophila Type IV Secretion Translocation Signal. Microbiol Spectr 2023; 11:e0233822. [PMID: 36815834 PMCID: PMC10100965 DOI: 10.1128/spectrum.02338-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Accepted: 01/31/2023] [Indexed: 02/24/2023] Open
Abstract
Many Gram-negative pathogens rely on type IV secretion systems (T4SS) for infection. One limitation has been the lack of ideal reporters to identify T4SS translocated effectors and study T4SS function. Most reporter systems make use of fusions to reporter proteins, in particular, β-lactamase (TEM) and calmodulin-dependent adenylate cyclase (CYA), that allow detection of translocated enzymatic activity inside host cells. However, both systems require costly reagents and use complex, multistep procedures for loading host cells with substrate (TEM) or for analysis (CYA). Therefore, we have developed and characterized a novel reporter system using nanoluciferase (NLuc) fusions to address these limitations. Serendipitously, we discovered that Nluc itself is efficiently translocated by Legionella pneumophila T4SS in an IcmSW chaperone-dependent manner via an N-terminal translocation signal. Extensive mutagenesis in the NLuc N terminus suggested the importance of an α-helical domain spanning D5 to V9, as mutations predicted to disrupt this structure, with one exception, were translocation defective. Notably, NLuc was capable of translocating several proteins examined when fused to the N or C terminus, while maintaining robust luciferase activity. In particular, it delivered the split GFP11 fragment into J774 macrophages transfected with GFPopt, thereby resulting in in vivo assembly of superfolder green fluorescent protein (GFP). This provided a bifunctional assay in which translocation could be assayed by fluorescence microplate, confocal microscopy, and/or luciferase assays. We further identified an optimal NLuc substrate which allowed a robust, inexpensive, one-step, high-throughput screening assay to identify T4SS translocation substrates and inhibitors. Taken together, these results indicate that NLuc provides both new insight into and also tools for studying T4SS biology. IMPORTANCE Type IV secretion systems (T4SS) are used by Gram-negative pathogens to coopt host cell function. However, the translocation signals recognized by T4SS are not fully explained by primary amino acid sequence, suggesting yet-to-be-defined contributions of secondary and tertiary structure. Here, we unexpectedly identified nanoluciferase (NLuc) as an efficient IcmSW-dependent translocated T4SS substrate, and we provide extensive mutagenesis data suggesting that the first N-terminal, alpha-helix domain is a critical translocation recognition motif. Notably, most existing reporter systems for studying translocated proteins make use of fusions to reporters to permit detection of translocated enzymatic activity inside the host cell. However, existing systems require extremely costly substrates, complex technical procedures to isolate eukaryotic cytoplasm for analysis, and/or are insensitive. Importantly, we found that NLuc provides a powerful, cost-effective new tool to address these limitations and facilitate high-throughput exploration of secretion system biology.
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Affiliation(s)
- Yoon-Suk Kang
- Department of Pathology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | - James E. Kirby
- Department of Pathology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
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8
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Warren GD, Kitao T, Franklin TG, Nguyen JV, Geurink PP, Kubori T, Nagai H, Pruneda JN. Mechanism of Lys6 poly-ubiquitin specificity by the L. pneumophila deubiquitinase LotA. Mol Cell 2023; 83:105-120.e5. [PMID: 36538933 PMCID: PMC9825671 DOI: 10.1016/j.molcel.2022.11.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 10/13/2022] [Accepted: 11/29/2022] [Indexed: 12/23/2022]
Abstract
The versatility of ubiquitination to control vast domains of eukaryotic biology is due, in part, to diversification through differently linked poly-ubiquitin chains. Deciphering signaling roles for some chain types, including those linked via K6, has been stymied by a lack of specificity among the implicated regulatory proteins. Forged through strong evolutionary pressures, pathogenic bacteria have evolved intricate mechanisms to regulate host ubiquitin during infection. Herein, we identify and characterize a deubiquitinase domain of the secreted effector LotA from Legionella pneumophila that specifically regulates K6-linked poly-ubiquitin. We demonstrate the utility of LotA for studying K6 poly-ubiquitin signals. We identify the structural basis of LotA activation and poly-ubiquitin specificity and describe an essential "adaptive" ubiquitin-binding domain. Without LotA activity during infection, the Legionella-containing vacuole becomes decorated with K6 poly-ubiquitin as well as the AAA ATPase VCP/p97/Cdc48. We propose that LotA's deubiquitinase activity guards Legionella-containing vacuole components from ubiquitin-dependent extraction.
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Affiliation(s)
- Gus D Warren
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University, Portland, OR 97239, USA
| | - Tomoe Kitao
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Gifu 501-1194, Japan
| | - Tyler G Franklin
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University, Portland, OR 97239, USA
| | - Justine V Nguyen
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University, Portland, OR 97239, USA
| | - Paul P Geurink
- Oncode Institute, Department of Cell and Chemical Biology, Leiden University Medical Centre, Leiden, the Netherlands
| | - Tomoko Kubori
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Gifu 501-1194, Japan; G-CHAIN, Gifu University, Gifu, Gifu 501-1194, Japan
| | - Hiroki Nagai
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Gifu 501-1194, Japan; G-CHAIN, Gifu University, Gifu, Gifu 501-1194, Japan
| | - Jonathan N Pruneda
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University, Portland, OR 97239, USA.
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9
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5′ Untranslated mRNA Regions Allow Bypass of Host Cell Translation Inhibition by Legionella pneumophila. Infect Immun 2022; 90:e0017922. [DOI: 10.1128/iai.00179-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Legionella pneumophila
grows within membrane-bound vacuoles in alveolar macrophages during human disease. Pathogen manipulation of the host cell is driven by bacterial proteins translocated through a type IV secretion system (T4SS).
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10
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Maciag K, Raychowdhury R, Smith K, Schneider AM, Coers J, Mumbach MR, Schwartz S, Hacohen N. IRF3 inhibits IFN-γ-mediated restriction of intracellular pathogens in macrophages independently of IFNAR. J Leukoc Biol 2022; 112:257-271. [PMID: 34826345 PMCID: PMC9550582 DOI: 10.1002/jlb.3a0218-069rr] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 10/25/2021] [Accepted: 10/30/2021] [Indexed: 01/14/2023] Open
Abstract
Macrophages use an array of innate immune sensors to detect intracellular pathogens and to tailor effective antimicrobial responses. In addition, extrinsic activation with the cytokine IFN-γ is often required as well to tip the scales of the host-pathogen balance toward pathogen restriction. However, little is known about how host-pathogen sensing impacts the antimicrobial IFN-γ-activated state. It was observed that in the absence of IRF3, a key downstream component of pathogen sensing pathways, IFN-γ-primed macrophages more efficiently restricted the intracellular bacterium Legionella pneumophila and the intracellular protozoan parasite Trypanosoma cruzi. This effect did not require IFNAR, the receptor for Type I IFNs known to be induced by IRF3, nor the sensing adaptors MyD88/TRIF, MAVS, or STING. This effect also did not involve differential activation of STAT1, the major signaling protein downstream of both Type 1 and Type 2 IFN receptors. IRF3-deficient macrophages displayed a significantly altered IFN-γ-induced gene expression program, with up-regulation of microbial restriction factors such as Nos2. Finally, we found that IFN-γ-primed but not unprimed macrophages largely excluded the activated form of IRF3 from the nucleus following bacterial infection. These data are consistent with a relationship of mutual inhibition between IRF3 and IFN-γ-activated programs, possibly as a component of a partially reversible mechanism for modulating the activity of potent innate immune effectors (such as Nos2) in the context of intracellular infection.
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Affiliation(s)
- Karolina Maciag
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA,Program in Immunology, Harvard Medical School, Boston, MA 02115, USA,Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | | | - Karen Smith
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Alexis M. Schneider
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jörn Coers
- Departments of Molecular Genetics and Microbiology and Immunology, Duke University Medical Center, Durham, NC 27710, USA
| | | | | | - Nir Hacohen
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA,Program in Immunology, Harvard Medical School, Boston, MA 02115, USA,Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Charlestown, MA 02129, USA
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11
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Reversible modification of mitochondrial ADP/ATP translocases by paired Legionella effector proteins. Proc Natl Acad Sci U S A 2022; 119:e2122872119. [PMID: 35653564 DOI: 10.1073/pnas.2122872119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
SignificanceMitochondria are organelles of the central metabolism that produce ATP and play fundamental roles in eukaryotic cell function and thereby become targets for pathogenic bacteria to manipulate. We found that the intracellular bacterial pathogen, Legionella pneumophila, targets mitochondrial ADP/ATP translocases (ANTs), the function of which is linked to the mitochondrial ATP synthesis. This is achieved by a pair of effector proteins, Lpg0080 and Lpg0081, which have opposing enzymatic activities as an ADP ribosyltransferase (ART) and an ADP ribosylhydrolase (ARH), respectively, coordinately regulating the chemical modification of ANTs upon infection. Our structural analyses indicate that Lpg0081 is an ARH with a noncanonical macrodomain, whose folding topology is distinct from that of the canonical macrodomain of known eukaryotic, archaeal, and bacterial proteins.
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12
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Guillemot J, Ginevra C, Allam C, Kay E, Gilbert C, Doublet P, Jarraud S, Chapalain A. TNF-α response in macrophages depends on clinical Legionella pneumophila isolates genotypes. Virulence 2022; 13:160-173. [PMID: 35030980 PMCID: PMC8765069 DOI: 10.1080/21505594.2021.2022861] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Legionnaires' Disease (LD) is a severe pneumonia mainly caused in Europe by Legionella pneumophila serogroup 1 (Lp1). Sequence-based typing methods reveal that some sequence types (ST) are overrepresented in clinical samples such as ST1 and ST47, suggesting that some strains are more fit for infection than others. In the present study, a collection of 108 Lp1 clinical isolates were used to evaluate the strain-dependent immune responses from human macrophages. Clinical Lp1 isolates induced differential TNFα secretion from macrophages. ST1 isolates induced a significantly higher TNF-α secretion than non-ST1, whereas ST47 isolates induced a significantly lower TNF-α secretion than non-ST47 isolates. ST1 isolates induced a significantly higher cell death than ST47 isolates evaluated by lactate dehydrogenase activity (cytotoxicity) and caspase-3 activity (apoptosis). Treatment of macrophages with anti-TNF-α antibodies significantly reduced the cell death in macrophages infected with ST1 or ST47 strains. The TNF-α secretion was neither explained by a differential bacterial replication nor by the number or type (bystander or infected) of TNF-α producing cells following infection but by a differential response from macrophages. The Paris ST1 reference strain elicited a significantly higher TNF-α gene transcription and a higher induction of NF-κB signaling pathway than the Lorraine ST47 reference strain.Clinical Lp1 isolates induce a diverse immune response and cell death, which could be related to the genotype. The two predominant sequence-types ST1 and ST47 trigger opposite inflammatory response that could be related to the host susceptibility.
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Affiliation(s)
- Johann Guillemot
- Ciri, Centre International de Recherche En Infectiologie, Équipe Pathogenèse Des Légionelles, Université Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, Lyon, France
| | - Christophe Ginevra
- Ciri, Centre International de Recherche En Infectiologie, Équipe Pathogenèse Des Légionelles, Université Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, Lyon, France.,Hospices Civils de Lyon, Institut Des Agents Infectieux, Centre National de Référence Des Légionelles, Lyon, France
| | - Camille Allam
- Ciri, Centre International de Recherche En Infectiologie, Équipe Pathogenèse Des Légionelles, Université Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, Lyon, France.,Hospices Civils de Lyon, Institut Des Agents Infectieux, Centre National de Référence Des Légionelles, Lyon, France
| | - Elisabeth Kay
- Ciri, Centre International de Recherche En Infectiologie, Équipe Pathogenèse Des Légionelles, Université Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, Lyon, France
| | - Christophe Gilbert
- Ciri, Centre International de Recherche En Infectiologie, Équipe Pathogenèse Des Légionelles, Université Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, Lyon, France
| | - Patricia Doublet
- Ciri, Centre International de Recherche En Infectiologie, Équipe Pathogenèse Des Légionelles, Université Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, Lyon, France
| | - Sophie Jarraud
- Ciri, Centre International de Recherche En Infectiologie, Équipe Pathogenèse Des Légionelles, Université Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, Lyon, France.,Hospices Civils de Lyon, Institut Des Agents Infectieux, Centre National de Référence Des Légionelles, Lyon, France
| | - Annelise Chapalain
- Ciri, Centre International de Recherche En Infectiologie, Équipe Pathogenèse Des Légionelles, Université Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, Lyon, France
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13
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Mraz AL, Weir MH. Knowledge to Predict Pathogens: Legionella pneumophila Lifecycle Systematic Review Part II Growth within and Egress from a Host Cell. Microorganisms 2022; 10:141. [PMID: 35056590 PMCID: PMC8780890 DOI: 10.3390/microorganisms10010141] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 12/30/2021] [Accepted: 01/04/2022] [Indexed: 11/17/2022] Open
Abstract
Legionella pneumophila (L. pneumophila) is a pathogenic bacterium of increasing concern, due to its ability to cause a severe pneumonia, Legionnaires' Disease (LD), and the challenges in controlling the bacteria within premise plumbing systems. L. pneumophila can thrive within the biofilm of premise plumbing systems, utilizing protozoan hosts for protection from environmental stressors and to increase its growth rate, which increases the bacteria's infectivity to human host cells. Typical disinfectant techniques have proven to be inadequate in controlling L. pneumophila in the premise plumbing system, exposing users to LD risks. As the bacteria have limited infectivity to human macrophages without replicating within a host protozoan cell, the replication within, and egress from, a protozoan host cell is an integral part of the bacteria's lifecycle. While there is a great deal of information regarding how L. pneumophila interacts with protozoa, the ability to use this data in a model to attempt to predict a concentration of L. pneumophila in a water system is not known. This systematic review summarizes the information in the literature regarding L. pneumophila's growth within and egress from the host cell, summarizes the genes which affect these processes, and calculates how oxidative stress can downregulate those genes.
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Affiliation(s)
- Alexis L. Mraz
- School of Nursing, Health, Exercise Science, The College of New Jersey, P.O. Box 7718, 2000 Pennington Rd., Ewing, NJ 08628, USA
| | - Mark H. Weir
- Division of Environmental Health Sciences, College of Public Health, The Ohio State University, Columbus, OH 43210, USA;
- Sustainability Institute, The Ohio State University, Columbus, OH 43210, USA
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14
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Anand IS, Choi W, Isberg RR. Components of the endocytic and recycling trafficking pathways interfere with the integrity of the Legionella-containing vacuole. Cell Microbiol 2021; 22:e13151. [PMID: 32096265 PMCID: PMC7154685 DOI: 10.1111/cmi.13151] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 11/10/2019] [Accepted: 12/03/2019] [Indexed: 12/27/2022]
Abstract
Legionella pneumophila requires the Dot/Icm translocation system to replicate in a vacuolar compartment within host cells. Strains lacking the translocated substrate SdhA form a permeable vacuole during residence in the host cell, exposing bacteria to the host cytoplasm. In primary macrophages, mutants are defective for intracellular growth, with a pyroptotic cell death response mounted due to bacterial exposure to the cytosol. To understand how SdhA maintains vacuole integrity during intracellular growth, we performed high-throughput RNAi screens against host membrane trafficking genes to identify factors that antagonise vacuole integrity in the absence of SdhA. Depletion of host proteins involved in endocytic uptake and recycling resulted in enhanced intracellular growth and lower levels of permeable vacuoles surrounding the ΔsdhA mutant. Of interest were three different Rab GTPases involved in these processes: Rab11b, Rab8b and Rab5 isoforms, that when depleted resulted in enhanced vacuole integrity surrounding the sdhA mutant. Proteins regulated by these Rabs are responsible for interfering with proper vacuole membrane maintenance, as depletion of the downstream effectors EEA1, Rab11FIP1, or VAMP3 rescued vacuole integrity and intracellular growth of the sdhA mutant. To test the model that specific vesicular components associated with these effectors could act to destabilise the replication vacuole, EEA1 and Rab11FIP1 showed increased density about the sdhA mutant vacuole compared with the wild type (WT) vacuole. Depletion of Rab5 isoforms or Rab11b reduced this aberrant redistribution. These findings are consistent with SdhA interfering with both endocytic and recycling membrane trafficking events that act to destabilise vacuole integrity during infection.
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Affiliation(s)
- Ila S Anand
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
| | - Wonyoung Choi
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
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15
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Gilchrist AK, Smolensky D, Ngwaga T, Chauhan D, Cox S, Perumal R, Noronha LE, Shames SR. High-polyphenol extracts from Sorghum bicolor attenuate replication of Legionella pneumophila within RAW 264.7 macrophages. FEMS Microbiol Lett 2020; 367:fnaa053. [PMID: 32188994 PMCID: PMC8023677 DOI: 10.1093/femsle/fnaa053] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/17/2020] [Indexed: 12/12/2022] Open
Abstract
Polyphenols derived from a variety of plants have demonstrated antimicrobial activity against diverse microbial pathogens. Legionella pneumophila is an intracellular bacterial pathogen that opportunistically causes a severe inflammatory pneumonia in humans, called Legionnaires' Disease, via replication within macrophages. Previous studies demonstrated that tea polyphenols attenuate L. pneumophila intracellular replication within mouse macrophages via increased tumor necrosis factor (TNF) production. Sorghum bicolor is a sustainable cereal crop that thrives in arid environments and is well-suited to continued production in warming climates. Sorghum polyphenols have anticancer and antioxidant properties, but their antimicrobial activity has not been evaluated. Here, we investigated the impact of sorghum polyphenols on L. pneumophila intracellular replication within RAW 264.7 mouse macrophages. Sorghum high-polyphenol extract (HPE) attenuated L. pneumophila intracellular replication in a dose-dependent manner but did not impair either bacterial replication in rich media or macrophage viability. Moreover, HPE treatment enhanced both TNF and IL-6 secretion from L. pneumophila infected macrophages. Thus, polyphenols derived from sorghum enhance macrophage restriction of L. pneumophila, likely via increased pro-inflammatory cytokine production. This work reveals commonalities between plant polyphenol-mediated antimicrobial activity and provides a foundation for future evaluation of sorghum as an antimicrobial agent.
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Affiliation(s)
- Aubrey K Gilchrist
- Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, Kansas, 66506 USA
| | - Dmitriy Smolensky
- Grain Quality and Structure Research Unit, Agricultural Research Service, U.S. Department of Agriculture, 1515 College Avenue, Manhattan, Kansas, 66506 USA
| | - Tshegofatso Ngwaga
- Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, Kansas, 66506 USA
| | - Deepika Chauhan
- Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, Kansas, 66506 USA
| | - Sarah Cox
- Grain Quality and Structure Research Unit, Agricultural Research Service, U.S. Department of Agriculture, 1515 College Avenue, Manhattan, Kansas, 66506 USA
| | - Ramasamy Perumal
- Kansas State University Agricultural Research Center, 1232 240th Avenue, Hays, Kansas, 67601 USA
| | - Leela E Noronha
- Arthropod-borne Animal Disease Research Unit, Agricultural Research Service, U. S. Department of Agriculture, 1515 College Avenue, Manhattan, Kansas, 66506 USA
| | - Stephanie R Shames
- Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, Kansas, 66506 USA
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IRG1 and Inducible Nitric Oxide Synthase Act Redundantly with Other Interferon-Gamma-Induced Factors To Restrict Intracellular Replication of Legionella pneumophila. mBio 2019; 10:mBio.02629-19. [PMID: 31719183 PMCID: PMC6851286 DOI: 10.1128/mbio.02629-19] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Legionella pneumophila is one example among many species of pathogenic bacteria that replicate within mammalian macrophages during infection. The immune signaling factor interferon gamma (IFN-γ) blocks L. pneumophila replication in macrophages and is an essential component of the immune response to L. pneumophila and other intracellular pathogens. However, to date, no study has identified the exact molecular factors induced by IFN-γ that are required for its activity. We generated macrophages lacking different combinations of IFN-γ-induced genes in an attempt to find a genetic background in which there is a complete loss of IFN-γ-mediated restriction of L. pneumophila. We identified six genes that comprise the totality of the IFN-γ-dependent restriction of L. pneumophila replication in macrophages. Our results clarify the molecular basis underlying the potent effects of IFN-γ and highlight how redundancy downstream of IFN-γ is key to prevent exploitation of macrophages by pathogens. Interferon gamma (IFN-γ) restricts the intracellular replication of many pathogens, but the mechanism by which IFN-γ confers cell-intrinsic pathogen resistance remains unclear. For example, intracellular replication of the bacterial pathogen Legionella pneumophila in macrophages is potently curtailed by IFN-γ. However, consistent with prior studies, no individual genetic deficiency that we tested completely abolished IFN-γ-mediated control. Intriguingly, we observed that the glycolysis inhibitor 2-deoxyglucose (2DG) partially rescued L. pneumophila replication in IFN-γ-treated macrophages. 2DG inhibits glycolysis and triggers the unfolded protein response, but unexpectedly, it appears these effects are not responsible for perturbing the antimicrobial activity of IFN-γ. Instead, we found that 2DG rescues bacterial replication by inhibiting the expression of two key antimicrobial factors, inducible nitric oxide synthase (iNOS) and immune-responsive gene 1 (IRG1). Using immortalized and primary macrophages deficient in iNOS and IRG1, we confirmed that loss of both iNOS and IRG1, but not individual deficiency in either gene, partially reduced IFN-γ-mediated restriction of L. pneumophila. Further, using a combinatorial CRISPR/Cas9 mutagenesis approach, we found that mutation of iNOS and IRG1 in combination with four other genes (CASP11, IRGM1, IRGM3, and NOX2) resulted in a total loss of L. pneumophila restriction by IFN-γ in primary bone marrow macrophages. Our study defines a complete set of cell-intrinsic factors required for IFN-γ-mediated restriction of an intracellular bacterial pathogen and highlights the combinatorial strategy used by hosts to block bacterial replication in macrophages.
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Viewing Legionella pneumophila Pathogenesis through an Immunological Lens. J Mol Biol 2019; 431:4321-4344. [PMID: 31351897 DOI: 10.1016/j.jmb.2019.07.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 06/25/2019] [Accepted: 07/13/2019] [Indexed: 12/14/2022]
Abstract
Legionella pneumophila is the causative agent of the severe pneumonia Legionnaires' disease. L. pneumophila is ubiquitously found in freshwater environments, where it replicates within free-living protozoa. Aerosolization of contaminated water supplies allows the bacteria to be inhaled into the human lung, where L. pneumophila can be phagocytosed by alveolar macrophages and replicate intracellularly. The Dot/Icm type IV secretion system (T4SS) is one of the key virulence factors required for intracellular bacterial replication and subsequent disease. The Dot/Icm apparatus translocates more than 300 effector proteins into the host cell cytosol. These effectors interfere with a variety of cellular processes, thus enabling the bacterium to evade phagosome-lysosome fusion and establish an endoplasmic reticulum-derived Legionella-containing vacuole, which facilitates bacterial replication. In turn, the immune system has evolved numerous strategies to recognize intracellular bacteria such as L. pneumophila, leading to potent inflammatory responses that aid in eliminating infection. This review aims to provide an overview of L. pneumophila pathogenesis in the context of the host immune response.
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18
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A Chemical Genetics Screen Reveals Influence of p38 Mitogen-Activated Protein Kinase and Autophagy on Phagosome Development and Intracellular Replication of Brucella neotomae in Macrophages. Infect Immun 2019; 87:IAI.00044-19. [PMID: 31160361 DOI: 10.1128/iai.00044-19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 05/24/2019] [Indexed: 11/20/2022] Open
Abstract
Brucella is an intracellular bacterial pathogen that causes chronic systemic infection in domesticated livestock and poses a zoonotic infectious risk to humans. The virulence of Brucella is critically dependent on its ability to replicate and survive within host macrophages. Brucella modulates host physiological pathways and cell biology in order to establish a productive intracellular replicative niche. Conversely, the host cell presumably activates pathways that limit infection. To identify host pathways contributing to this yin and yang during host cell infection, we performed a high-throughput chemical genetics screen of known inhibitors and agonists of host cell targets to identify host factors that contribute to intracellular growth of the model pathogen Brucella neotomae Using this approach, we identified the p38 mitogen-activated protein (MAP) kinase pathway and autophagy machinery as both a linchpin and an Achilles' heel in B. neotomae's ability to coopt host cell machinery and replicate within macrophages. Specifically, B. neotomae induced p38 MAP kinase phosphorylation and autophagy in a type IV secretion system-dependent fashion. Both p38 MAP kinase stimulation and an intact autophagy machinery in turn were required for phagosome maturation and intracellular replication. These findings contrasted with those for Legionella pneumophila, where chemical inhibition of the p38 MAP kinase pathway and autophagy factor depletion failed to block intracellular replication. Therefore, results from a chemical genetics screen suggest that intersections of the MAP kinase pathways and autophagy machinery are critical components of Brucella's intracellular life cycle.
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19
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Gonçalves AV, Margolis SR, Quirino GFS, Mascarenhas DPA, Rauch I, Nichols RD, Ansaldo E, Fontana MF, Vance RE, Zamboni DS. Gasdermin-D and Caspase-7 are the key Caspase-1/8 substrates downstream of the NAIP5/NLRC4 inflammasome required for restriction of Legionella pneumophila. PLoS Pathog 2019; 15:e1007886. [PMID: 31251782 PMCID: PMC6622555 DOI: 10.1371/journal.ppat.1007886] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 07/11/2019] [Accepted: 06/03/2019] [Indexed: 11/24/2022] Open
Abstract
Inflammasomes are cytosolic multi-protein complexes that detect infection or cellular damage and activate the Caspase-1 (CASP1) protease. The NAIP5/NLRC4 inflammasome detects bacterial flagellin and is essential for resistance to the flagellated intracellular bacterium Legionella pneumophila. The effectors required downstream of NAIP5/NLRC4 to restrict bacterial replication remain unclear. Upon NAIP5/NLRC4 activation, CASP1 cleaves and activates the pore-forming protein Gasdermin-D (GSDMD) and the effector caspase-7 (CASP7). However, Casp1–/– (and Casp1/11–/–) mice are only partially susceptible to L. pneumophila and do not phenocopy Nlrc4–/–mice, because NAIP5/NLRC4 also activates CASP8 for restriction of L. pneumophila infection. Here we show that CASP8 promotes the activation of CASP7 and that Casp7/1/11–/– and Casp8/1/11–/– mice recapitulate the full susceptibility of Nlrc4–/– mice. Gsdmd–/– mice exhibit only mild susceptibility to L. pneumophila, but Gsdmd–/–Casp7–/– mice are as susceptible as the Nlrc4–/– mice. These results demonstrate that GSDMD and CASP7 are the key substrates downstream of NAIP5/NLRC4/CASP1/8 required for resistance to L. pneumophila. Inflammasomes are multi-protein complexes that detect infection and other stimuli and activate the Caspase-1 (CASP1) protease. The effectors required downstream of NAIP5/NLRC4 to restrict bacterial replication remain unclear. Active CASP1 cleaves and activates the pore-forming protein gasdermin D (GSDMD) to induce inflammation and cell death. We have previously shown that CASP8 is activated by the NAIP5/NLRC4 inflammasome independently of CASP1 and functions to restrict replication of the intracellular bacterium Legionella pneumophila. Here, we show that CASP7 is activated downstream of CASP8 and is required for CASP8-dependent restriction of L. pneumophila replication in macrophages and in vivo. In addition, CASP7 is also activated by CASP1. Taken together, these results imply that CASP7 and GSDMD are the two key caspase substrates downstream of NAIP5/NLRC4. In support of this hypothesis, we found that mice double deficient in CASP7 and GSDMD are more susceptible than the single knockouts and are as susceptible as the Nlrc4 deficient mice for restriction of L. pneumophila replication in vivo. Collectively, our data indicate that GSDMD and CASP7 are activated by CASP1 and induce cell death and restriction of bacterial infection. Therefore, GSDMD and multiple caspases (CASP1, CASP7 and CASP8) operate downstream of the NAIP5/NLRC4 inflammasome for restriction of infection by pathogenic bacteria.
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Affiliation(s)
- Augusto V. Gonçalves
- Department of Cell Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Shally R. Margolis
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, and Cancer Research Laboratory, University of California, Berkeley, California, United States of America
| | - Gustavo F. S. Quirino
- Department of Cell Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Danielle P. A. Mascarenhas
- Department of Cell Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Isabella Rauch
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, and Cancer Research Laboratory, University of California, Berkeley, California, United States of America
| | - Randilea D. Nichols
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, and Cancer Research Laboratory, University of California, Berkeley, California, United States of America
| | - Eduard Ansaldo
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, and Cancer Research Laboratory, University of California, Berkeley, California, United States of America
| | - Mary F. Fontana
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, and Cancer Research Laboratory, University of California, Berkeley, California, United States of America
| | - Russell E. Vance
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, and Cancer Research Laboratory, University of California, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, California, United States of America
- * E-mail: (REV); (DSZ)
| | - Dario S. Zamboni
- Department of Cell Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
- * E-mail: (REV); (DSZ)
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Potentiation of Cytokine-Mediated Restriction of Legionella Intracellular Replication by a Dot/Icm-Translocated Effector. J Bacteriol 2019; 201:JB.00755-18. [PMID: 31036725 DOI: 10.1128/jb.00755-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 04/22/2019] [Indexed: 01/23/2023] Open
Abstract
Legionella pneumophila is ubiquitous in freshwater environments, where it replicates within unicellular protozoa. However, L. pneumophila is also an accidental human pathogen that can cause Legionnaires' disease in immunocompromised individuals by uncontrolled replication within alveolar macrophages. To replicate within eukaryotic phagocytes, L. pneumophila utilizes a Dot/Icm type IV secretion system to translocate a large arsenal of over 300 effector proteins directly into host cells. In mammals, translocated effectors contribute to innate immune restriction of L. pneumophila We found previously that the effector LegC4 is important for L. pneumophila replication within a natural host protist but is deleterious to replication in a mouse model of Legionnaires' disease. In the present study, we used cultured mouse primary macrophages to investigate how LegC4 attenuates L. pneumophila replication. We found that LegC4 enhanced restriction of L. pneumophila replication within macrophages activated with tumor necrosis factor (TNF) or interferon gamma (IFN-γ). In addition, expression of legC4 was sufficient to restrict Legionella longbeachae replication within TNF- or IFN-γ-activated macrophages. Thus, this study demonstrates that LegC4 contributes to L. pneumophila clearance from healthy hosts by potentiating cytokine-mediated host defense mechanisms.IMPORTANCE Legionella spp. are natural pathogens of protozoa and accidental pathogens of humans. Innate immunity in healthy individuals effectively controls Legionella infection due in part to rapid and robust production of proinflammatory cytokines resulting from detection of Dot/Icm-translocated substrates, including effectors. Here, we demonstrate that the effector LegC4 enhances proinflammatory host restriction of Legionella by macrophages. These data suggest that LegC4 may augment proinflammatory signaling or antimicrobial activity of macrophages, a function that has not previously been observed for another bacterial effector. Further insight into LegC4 function will likely reveal novel mechanisms to enhance immunity against pathogens.
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Best AM, Abu Kwaik Y. Evasion of phagotrophic predation by protist hosts and innate immunity of metazoan hosts by Legionella pneumophila. Cell Microbiol 2018; 21:e12971. [PMID: 30370624 DOI: 10.1111/cmi.12971] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 10/08/2018] [Accepted: 10/24/2018] [Indexed: 12/18/2022]
Abstract
Legionella pneumophila is a ubiquitous environmental bacterium that has evolved to infect and proliferate within amoebae and other protists. It is thought that accidental inhalation of contaminated water particles by humans is what has enabled this pathogen to proliferate within alveolar macrophages and cause pneumonia. However, the highly evolved macrophages are equipped with more sophisticated innate defence mechanisms than are protists, such as the evolution of phagotrophic feeding into phagocytosis with more evolved innate defence processes. Not surprisingly, the majority of proteins involved in phagosome biogenesis (~80%) have origins in the phagotrophy stage of evolution. There are a plethora of highly evolved cellular and innate metazoan processes, not represented in protist biology, that are modulated by L. pneumophila, including TLR2 signalling, NF-κB, apoptotic and inflammatory processes, histone modification, caspases, and the NLRC-Naip5 inflammasomes. Importantly, L. pneumophila infects haemocytes of the invertebrate Galleria mellonella, kill G. mellonella larvae, and proliferate in and kill Drosophila adult flies and Caenorhabditis elegans. Although coevolution with protist hosts has provided a substantial blueprint for L. pneumophila to infect macrophages, we discuss the further evolutionary aspects of coevolution of L. pneumophila and its adaptation to modulate various highly evolved innate metazoan processes prior to becoming a human pathogen.
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Affiliation(s)
- Ashley M Best
- Department of Microbiology and Immunology, College of Medicine, University of Louisville, Louisville, Kentucky
| | - Yousef Abu Kwaik
- Department of Microbiology and Immunology, College of Medicine, University of Louisville, Louisville, Kentucky.,Center for Predictive Medicine, College of Medicine, University of Louisville, Louisville, Kentucky
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Legionella pneumophila Is Directly Sensitive to 2-Deoxyglucose-Phosphate via Its UhpC Transporter but Is Indifferent to Shifts in Host Cell Glycolytic Metabolism. J Bacteriol 2018; 200:JB.00176-18. [PMID: 29784886 DOI: 10.1128/jb.00176-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 05/15/2018] [Indexed: 12/14/2022] Open
Abstract
Toll-like receptor (TLR) stimulation induces a pronounced shift to increased glycolytic metabolism in mammalian macrophages. We observed that bone marrow-derived macrophages (BMMs) increase glycolysis in response to infection with Legionella pneumophila, but the role of host macrophage glycolysis in terms of intracellular L. pneumophila replication is not currently understood. Treatment with 2-deoxyglucose (2DG) blocks L. pneumophila replication in mammalian macrophages but has no effect on bacteria grown in broth. In addition, we found that 2DG had no effect on bacteria grown in amoebae. We used a serial enrichment strategy to reveal that the effect of 2DG on L. pneumophila in macrophages requires the L. pneumophila hexose-phosphate transporter UhpC. Experiments with UhpC-deficient L. pneumophila revealed that mutant bacteria are also resistant to growth inhibition following treatment with phosphorylated 2DG in broth, suggesting that the inhibitory effect of 2DG on L. pneumophila in mammalian cells requires 2DG phosphorylation. UhpC-deficient L. pneumophila replicates without a growth defect in BMMs and protozoan host cells and also replicates without a growth defect in BMMs treated with 2DG. Our data indicate that neither TLR signaling-dependent increased macrophage glycolysis nor inhibition of macrophage glycolysis has a substantial effect on intracellular L. pneumophila replication. These results are consistent with the view that L. pneumophila can employ diverse metabolic strategies to exploit its host cells.IMPORTANCE We explored the relationship between macrophage glycolysis and replication of an intracellular bacterial pathogen, Legionella pneumophila Previous studies demonstrated that a glycolysis inhibitor, 2-deoxyglucose (2DG), blocks replication of L. pneumophila during infection of macrophages, leading to speculation that L. pneumophila may exploit macrophage glycolysis. We isolated L. pneumophila mutants resistant to the inhibitory effect of 2DG in macrophages, identifying a L. pneumophila hexose-phosphate transporter, UhpC, that is required for bacterial sensitivity to 2DG during infection. Our results reveal how a bacterial transporter mediates the direct antimicrobial effect of a toxic metabolite. Moreover, our results indicate that neither induction nor impairment of host glycolysis inhibits intracellular replication of L. pneumophila, which is consistent with a view of L. pneumophila as a metabolic generalist.
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Liu BC, Sarhan J, Poltorak A. Host-Intrinsic Interferon Status in Infection and Immunity. Trends Mol Med 2018; 24:658-668. [PMID: 30060835 DOI: 10.1016/j.molmed.2018.06.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Revised: 05/31/2018] [Accepted: 06/07/2018] [Indexed: 01/09/2023]
Abstract
Most genetic ablations of interferon (IFN) signaling abolish both the experimentally induced IFN response and constitutive IFN, whose effects are well established in autoimmunity but understudied during infection. In host-pathogen interactions, most IFN-mediated responses are attributed to infection-driven IFN. However, IFNs confer their activity by regulating networks of interferon-stimulated genes (ISGs), a process that requires de novo transcription and translation of both IFN and downstream ISGs through feedback of IFN receptor signaling. Due to the temporal requirement for IFN activity, many rapid antimicrobial responses may instead result from pre-established IFN signature stemming from host-intrinsic processes. Addressing the permeating effects of constitutive IFN is therefore needed to accurately describe immunity as host intrinsic or pathogen induced.
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Affiliation(s)
- Beiyun C Liu
- Graduate Program in Immunology, Sackler School of Biomedical Sciences, Tufts University Boston, MA 02111, USA
| | - Joseph Sarhan
- Graduate Program in Immunology, Sackler School of Biomedical Sciences, Tufts University Boston, MA 02111, USA; Medical Scientist Training Program, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Alexander Poltorak
- Graduate Program in Immunology, Sackler School of Biomedical Sciences, Tufts University Boston, MA 02111, USA; Medical Scientist Training Program, Tufts University School of Medicine, Boston, MA 02111, USA; Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA.
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Liu BC, Sarhan J, Panda A, Muendlein HI, Ilyukha V, Coers J, Yamamoto M, Isberg RR, Poltorak A. Constitutive Interferon Maintains GBP Expression Required for Release of Bacterial Components Upstream of Pyroptosis and Anti-DNA Responses. Cell Rep 2018; 24:155-168.e5. [PMID: 29972777 PMCID: PMC6063733 DOI: 10.1016/j.celrep.2018.06.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 03/19/2018] [Accepted: 06/01/2018] [Indexed: 12/12/2022] Open
Abstract
Legionella pneumophila elicits caspase-11-driven macrophage pyroptosis through guanylate-binding proteins (GBPs) encoded on chromosome 3. It has been proposed that microbe-driven IFN upregulates GBPs to facilitate pathogen vacuole rupture and bacteriolysis preceding caspase-11 activation. We show here that macrophage death occurred independently of microbial-induced IFN signaling and that GBPs are dispensable for pathogen vacuole rupture. Instead, the host-intrinsic IFN status sustained sufficient GBP expression levels to drive caspase-1 and caspase-11 activation in response to cytosol-exposed bacteria. In addition, endogenous GBP levels were sufficient for the release of DNA from cytosol-exposed bacteria, preceding the cyclic GMP-AMP synthase/stimulator of interferon genes (cGAS/STING) pathway for Ifnb induction. Mice deficient for chromosome 3 GBPs were unable to mount a rapid IL-1/chemokine (C-X-C motif) ligand 1 (CXCL1) response during Legionella-induced pneumonia, with defective bacterial clearance. Our results show that rapid GBP activity is controlled by host-intrinsic cytokine signaling and that GBP activities precede immune amplification responses, including IFN induction, inflammasome activation, and cell death.
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Affiliation(s)
- Beiyun C Liu
- Graduate Program in Immunology, Tufts University Sackler School of Biomedical Sciences, Boston, MA 02111, USA
| | - Joseph Sarhan
- Graduate Program in Immunology, Tufts University Sackler School of Biomedical Sciences, Boston, MA 02111, USA; MSTP, Tufts University School of Medicine, Boston, MA 02111, USA
| | | | - Hayley I Muendlein
- Graduate Program in Genetics, Tufts University Sackler School of Biomedical Sciences, Boston, MA 02111, USA
| | - Vladimir Ilyukha
- Petrozavodsk State University, Republic of Karelia, Russian Federation
| | - Jörn Coers
- Department of Molecular Genetics and Microbiology, and Immunology, Duke University Medical Center, Durham, NC 27710, USA
| | - Masahiro Yamamoto
- Department of Immunoparasitology, Research Institute for Microbial Diseases, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
| | - Ralph R Isberg
- Howard Hughes Medical Institute, Boston MA, USA; Department of Molecular Biology & Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA.
| | - Alexander Poltorak
- Petrozavodsk State University, Republic of Karelia, Russian Federation; Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA.
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Kubori T, Kitao T, Ando H, Nagai H. LotA, a Legionella deubiquitinase, has dual catalytic activity and contributes to intracellular growth. Cell Microbiol 2018. [PMID: 29543380 DOI: 10.1111/cmi.12840] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The intracellular bacterial pathogen, Legionella pneumophila, establishes the replicative niche as a result of the actions of a large array of effector proteins delivered via the Legionella Type 4 secretion system. Many effector proteins are expected to be involved in biogenesis and regulation of the Legionella-containing vacuole (LCV) that is highly decorated with ubiquitin. Here, we identified a Legionella deubiquitinase, designated LotA, by carrying out a genome analysis to find proteins resembling the eukaryotic ovarian tumour superfamily of cysteine proteases. LotA exhibits a dual ability to cleave ubiquitin chains that is dependent on 2 distinctive catalytic cysteine residues in the eukaryotic ovarian tumour domains. One cysteine dominantly contributes to the removal of ubiquitin from the LCVs by its polyubiquitin cleavage activity. The other specifically cleaves conjugated Lys6-linked ubiquitin. After delivered by the Type 4 secretion system, LotA localises on the LCVs via its PI(3)P-binding domain. The lipid-binding ability of LotA is crucial for ubiquitin removal from the vacuoles. We further analysed the functional interaction of the protein with the recently reported noncanonical ubiquitin ligases of L. pneumophila, revealing that the effector proteins are involved in coordinated regulation that contributes to bacterial growth in the host cells.
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Affiliation(s)
- Tomoko Kubori
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Japan.,Department of Infectious Disease Control, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
| | - Tomoe Kitao
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Japan
| | - Hiroki Ando
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Japan
| | - Hiroki Nagai
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Japan.,Department of Infectious Disease Control, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
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Schroeder GN. The Toolbox for Uncovering the Functions of Legionella Dot/Icm Type IVb Secretion System Effectors: Current State and Future Directions. Front Cell Infect Microbiol 2018; 7:528. [PMID: 29354599 PMCID: PMC5760550 DOI: 10.3389/fcimb.2017.00528] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 12/13/2017] [Indexed: 12/13/2022] Open
Abstract
The defective in organelle trafficking/intracellular multiplication (Dot/Icm) Type IVb secretion system (T4SS) is the essential virulence factor for the intracellular life style and pathogenicity of Legionella species. Screens demonstrated that an individual L. pneumophila strain can use the Dot/Icm T4SS to translocate an unprecedented number of more than 300 proteins into host cells, where these, so called Icm/Dot-translocated substrates (IDTS) or effectors, manipulate host cell functions to the benefit of the bacteria. Bioinformatic analysis of the pan-genus genome predicts at least 608 orthologous groups of putative effectors. Deciphering the function of these effectors is key to understanding Legionella pathogenesis; however, the analysis is challenging. Substantial functional redundancy renders classical, phenotypic screening of single gene deletion mutants mostly ineffective. Here, I review experimental approaches that were successfully used to identify, validate and functionally characterize T4SS effectors and highlight new methods, which promise to facilitate unlocking the secrets of Legionella's extraordinary weapons arsenal.
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Affiliation(s)
- Gunnar N Schroeder
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, United Kingdom
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Ghosh S, O'Connor TJ. Beyond Paralogs: The Multiple Layers of Redundancy in Bacterial Pathogenesis. Front Cell Infect Microbiol 2017; 7:467. [PMID: 29188194 PMCID: PMC5694747 DOI: 10.3389/fcimb.2017.00467] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 10/20/2017] [Indexed: 01/06/2023] Open
Abstract
Redundancy has been referred to as a state of no longer being needed or useful. Microbiologists often theorize that the only case of true redundancy in a haploid organism would be a recent gene duplication event, prior to divergence through selective pressure. However, a growing number of examples exist where an organism encodes two genes that appear to perform the same function. For example, many pathogens translocate multiple effector proteins into hosts. While disruption of individual effector genes does not result in a discernable phenotype, deleting genes in combination impairs pathogenesis: this has been described as redundancy. In many cases, this apparent redundancy could be due to limitations of laboratory models of pathogenesis that do not fully recapitulate the disease process. Alternatively, it is possible that the selective advantage achieved by this perceived redundancy is too subtle to be measured in the laboratory. Moreover, there are numerous possibilities for different types of redundancy. The most common and recognized form of redundancy is functional redundancy whereby two proteins have similar biochemical activities and substrate specificities allowing each one to compensate in the absence of the other. However, redundancy can also exist between seemingly unrelated proteins that manipulate the same or complementary host cell pathways. In this article, we outline 5 types of redundancy in pathogenesis: molecular, target, pathway, cellular process, and system redundancy that incorporate the biochemical activities, the host target specificities and the impact of effector function on the pathways and cellular process they modulate. For each type of redundancy, we provide examples from Legionella pathogenesis as this organism employs over 300 secreted virulence proteins and loss of individual proteins rarely impacts intracellular growth. We also discuss selective pressures that drive the maintenance of redundant mechanisms, the current methods used to resolve redundancy and features that distinguish between redundant and non-redundant virulence mechanisms.
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Affiliation(s)
- Soma Ghosh
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Tamara J O'Connor
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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Naujoks J, Lippmann J, Suttorp N, Opitz B. Innate sensing and cell-autonomous resistance pathways in Legionella pneumophila infection. Int J Med Microbiol 2017; 308:161-167. [PMID: 29097162 DOI: 10.1016/j.ijmm.2017.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 10/20/2017] [Accepted: 10/23/2017] [Indexed: 12/20/2022] Open
Abstract
Legionella pneumophila is a facultative intracellular bacterium which can cause a severe pneumonia called Legionnaires' disease after inhalation of contaminated water droplets and replication in alveolar macrophages. The innate immune system is generally able to sense and -in most cases- control L. pneumophila infection. Comorbidities and genetic risk factors, however, can compromise the immune system and high infection doses might overwhelm its capacity, thereby enabling L. pneumophila to grow and disseminate inside the lung. The innate immune system mediates sensing of L. pneumophila by employing e.g. NOD-like receptors (NLRs), Toll-like receptors (TLRs), as well as the cGAS/STING pathway to stimulate death of infected macrophages as well as production of proinflammatory cytokines and interferons (IFNs). Control of pulmonary L. pneumophila infection is largely mediated by inflammasome-, TNFα- and IFN-dependent macrophage-intrinsic resistance mechanisms. This article summarizes the current knowledge of innate immune responses to L. pneumophila infection in general, and of macrophage-intrinsic defense mechanisms in particular.
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Affiliation(s)
- Jan Naujoks
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Juliane Lippmann
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Norbert Suttorp
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Bastian Opitz
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Augustenburger Platz 1, 13353 Berlin, Germany; German Center for Lung Research (DZL), Germany.
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Feng J, Lin P, Wang Y, Guo S, Zhang Z, Yu L. Identification of a type I interferon (IFN) gene from Japanese eel and its expression analysis in vivo and in vitro. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/j.aggene.2017.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Host Cell S Phase Restricts Legionella pneumophila Intracellular Replication by Destabilizing the Membrane-Bound Replication Compartment. mBio 2017; 8:mBio.02345-16. [PMID: 28830950 PMCID: PMC5565972 DOI: 10.1128/mbio.02345-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Legionella pneumophila grows within cells ranging from environmental amoebae to human macrophages. In spite of this conserved strategy of pathogenesis, identification of host factors that restrict L. pneumophila intracellular replication has not been extended outside components of the mammalian innate immune response. We performed a double-stranded RNA (dsRNA) screen against more than 50% of the Drosophila melanogaster annotated open reading frames (ORFs) to identify host cell factors that restrict L. pneumophila. The majority of analyzed dsRNAs that stimulated L. pneumophila intracellular replication were directed against host proteins involved in protein synthesis or cell cycle control. Consistent with disruption of the cell cycle stimulating intracellular replication, proteins involved in translation initiation also resulted in G1 arrest. Stimulation of replication was dependent on the stage of cell cycle arrest, as dsRNAs causing arrest during S phase had an inhibitory effect on intracellular replication. The inhibitory effects of S phase arrest could be recapitulated in a human cell line, indicating that cell cycle control of L. pneumophila replication is evolutionarily conserved. Synchronized HeLa cell populations in S phase and challenged with L. pneumophila failed to progress through the cell cycle and were depressed for supporting intracellular replication. Poor bacterial replication in S phase was associated with loss of the vacuole membrane barrier, resulting in exposure of bacteria to the cytosol and their eventual degradation. These results are consistent with the model that S phase is inhibitory for L. pneumophila intracellular survival as a consequence of failure to maintain the integrity of the membrane surrounding intracellular bacteria. Legionella pneumophila has the ability to replicate within human macrophages and amoebal hosts. Here, we report that the host cell cycle influences L. pneumophila intracellular replication. Our data demonstrate that the G1 and G2/M phases of the host cell cycle are permissive for bacterial replication, while S phase is toxic for the bacterium. L. pneumophila replicates poorly within host cells present in S phase. The inability of L. pneumophila to replicate relies on its failure to control the integrity of its vacuole, leading to cytosolic exposure of the bacteria and eventual degradation. The data presented here argue that growth-arrested host cells that are encountered by L. pneumophila in either the environment or within human hosts are ideal targets for intracellular replication because their transit through S phase is blocked.
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Mascarenhas DPA, Cerqueira DM, Pereira MSF, Castanheira FVS, Fernandes TD, Manin GZ, Cunha LD, Zamboni DS. Inhibition of caspase-1 or gasdermin-D enable caspase-8 activation in the Naip5/NLRC4/ASC inflammasome. PLoS Pathog 2017; 13:e1006502. [PMID: 28771586 PMCID: PMC5542441 DOI: 10.1371/journal.ppat.1006502] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 06/30/2017] [Indexed: 11/19/2022] Open
Abstract
Legionella pneumophila is a Gram-negative, flagellated bacterium that survives in phagocytes and causes Legionnaires’ disease. Upon infection of mammalian macrophages, cytosolic flagellin triggers the activation of Naip/NLRC4 inflammasome, which culminates in pyroptosis and restriction of bacterial replication. Although NLRC4 and caspase-1 participate in the same inflammasome, Nlrc4-/- mice and their macrophages are more permissive to L. pneumophila replication compared with Casp1/11-/-. This feature supports the existence of a pathway that is NLRC4-dependent and caspase-1/11-independent. Here, we demonstrate that caspase-8 is recruited to the Naip5/NLRC4/ASC inflammasome in response to flagellin-positive bacteria. Accordingly, caspase-8 is activated in Casp1/11-/- macrophages in a process dependent on flagellin, Naip5, NLRC4 and ASC. Silencing caspase-8 in Casp1/11-/- cells culminated in macrophages that were as susceptible as Nlrc4-/- for the restriction of L. pneumophila replication. Accordingly, macrophages and mice deficient in Asc/Casp1/11-/- were more susceptible than Casp1/11-/- and as susceptible as Nlrc4-/- for the restriction of infection. Mechanistically, we found that caspase-8 activation triggers gasdermin-D-independent pore formation and cell death. Interestingly, caspase-8 is recruited to the Naip5/NLRC4/ASC inflammasome in wild-type macrophages, but it is only activated when caspase-1 or gasdermin-D is inhibited. Our data suggest that caspase-8 activation in the Naip5/NLRC4/ASC inflammasome enable induction of cell death when caspase-1 or gasdermin-D is suppressed. Legionella pneumophila is the causative agent of Legionnaires’ disease, an atypical pneumophila that affects people worldwide. Besides the clinical importance, L. pneumophila is a very useful model of pathogenic bacteria for investigation of the interactions of innate immune cells with bacterial pathogens. Studies using L. pneumophila demonstrated that Naip5 and NLRC4 activate caspase-1 and this inflammasome is activated by bacterial flagellin. However, macrophages and mice deficient in NLRC4 are more susceptible for L. pneumophila replication than those deficient in caspase-1, indicating that the flagellin/Naip5/NLRC4 inflammasome triggers responses that are independent on caspase-1. Here, we used L. pneumophila to investigate this novel pathway and found that caspase-8 interacts with NLRC4 in a process that is dependent on ASC and independent of caspase-1 and caspase-11. Although caspase-8 is recruited to the Naip5/NLRC4/ASC inflammasome, it is only activated when caspase-1 or gasdermin-D is inhibited. Our data suggest that caspase-8 activation in the Naip5/NLRC4/ASC inflammasome may favor host responses during infections against pathogens that inhibit components of the pyroptotic cell death including caspase-1 and gasdermin-D.
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Affiliation(s)
- Danielle P. A. Mascarenhas
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo. Ribeirão Preto, Brazil
| | - Daiane M. Cerqueira
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo. Ribeirão Preto, Brazil
| | - Marcelo S. F. Pereira
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo. Ribeirão Preto, Brazil
| | - Fernanda V. S. Castanheira
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo. Ribeirão Preto, Brazil
| | - Talita D. Fernandes
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo. Ribeirão Preto, Brazil
| | - Graziele Z. Manin
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo. Ribeirão Preto, Brazil
| | - Larissa D. Cunha
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo. Ribeirão Preto, Brazil
| | - Dario S. Zamboni
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo. Ribeirão Preto, Brazil
- * E-mail:
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Geoepidemiology and Immunologic Features of Autoinflammatory Diseases: a Comprehensive Review. Clin Rev Allergy Immunol 2017; 54:454-479. [DOI: 10.1007/s12016-017-8613-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Awuh JA, Flo TH. Molecular basis of mycobacterial survival in macrophages. Cell Mol Life Sci 2017; 74:1625-1648. [PMID: 27866220 PMCID: PMC11107535 DOI: 10.1007/s00018-016-2422-8] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 11/06/2016] [Accepted: 11/14/2016] [Indexed: 12/31/2022]
Abstract
Macrophages play an essential role in the immune system by ingesting and degrading invading pathogens, initiating an inflammatory response and instructing adaptive immune cells, and resolving inflammation to restore homeostasis. More interesting is the fact that some bacteria have evolved to use macrophages as a natural habitat and tools of spread in the host, e.g., Mycobacterium tuberculosis (Mtb) and some non-tuberculous mycobacteria (NTM). Mtb is considered one of humanity's most successful pathogens and is the causal agent of tuberculosis, while NTMs cause opportunistic infections all of which are of significant public health concern. Here, we describe mechanisms by which intracellular pathogens, with an emphasis on mycobacteria, manipulate macrophage functions to circumvent killing and live inside these cells even under considerable immunological pressure. Such macrophage functions include the selective evasion or engagement of pattern recognition receptors, production of cytokines, reactive oxygen and nitrogen species, phagosome maturation, as well as other killing mechanisms like autophagy and cell death. A clear understanding of host responses elicited by a specific pathogen and strategies employed by the microbe to evade or exploit these is of significant importance for the development of effective vaccines and targeted immunotherapy against persistent intracellular infections like tuberculosis.
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Affiliation(s)
- Jane Atesoh Awuh
- Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, PB 8905, 7491, Trondheim, Norway
| | - Trude Helen Flo
- Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, PB 8905, 7491, Trondheim, Norway.
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Promotion and Rescue of Intracellular Brucella neotomae Replication during Coinfection with Legionella pneumophila. Infect Immun 2017; 85:IAI.00991-16. [PMID: 28264909 DOI: 10.1128/iai.00991-16] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 02/28/2017] [Indexed: 12/17/2022] Open
Abstract
We established a new Brucella neotomaein vitro model system for study of type IV secretion system-dependent (T4SS) pathogenesis in the Brucella genus. Importantly, B. neotomae is a rodent pathogen, and unlike B. abortus, B. melitensis, and B. suis, B. neotomae has not been observed to infect humans. It therefore can be handled more facilely using biosafety level 2 practices. More particularly, using a series of novel fluorescent protein and lux operon reporter systems to differentially label pathogens and track intracellular replication, we confirmed T4SS-dependent intracellular growth of B. neotomae in macrophage cell lines. Furthermore, B. neotomae exhibited early endosomal (LAMP-1) and late endoplasmic reticulum (calreticulin)-associated phagosome maturation. These findings recapitulate prior observations for human-pathogenic Brucella spp. In addition, during coinfection experiments with Legionella pneumophila, we found that defective intracellular replication of a B. neotomae T4SS virB4 mutant was rescued and baseline levels of intracellular replication of wild-type B. neotomae were significantly stimulated by coinfection with wild-type but not T4SS mutant L. pneumophila Using confocal microscopy, it was determined that intracellular colocalization of B. neotomae and L. pneumophila was required for rescue and that colocalization came at a cost to L. pneumophila fitness. These findings were not completely expected based on known temporal and qualitative differences in the intracellular life cycles of these two pathogens. Taken together, we have developed a new system for studying in vitroBrucella pathogenesis and found a remarkable T4SS-dependent interplay between Brucella and Legionella during macrophage coinfection.
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Galectin-3 directs antimicrobial guanylate binding proteins to vacuoles furnished with bacterial secretion systems. Proc Natl Acad Sci U S A 2017; 114:E1698-E1706. [PMID: 28193861 DOI: 10.1073/pnas.1615771114] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Many invasive bacteria establish pathogen-containing vacuoles (PVs) as intracellular niches for microbial growth. Immunity to these infections is dependent on the ability of host cells to recognize PVs as targets for host defense. The delivery of several host defense proteins to PVs is controlled by IFN-inducible guanylate binding proteins (GBPs), which themselves dock to PVs through poorly characterized mechanisms. Here, we demonstrate that GBPs detect the presence of bacterial protein secretion systems as "patterns of pathogenesis" associated with PVs. We report that the delivery of GBP2 to Legionella-containing vacuoles is dependent on the bacterial Dot/Icm secretion system, whereas the delivery of GBP2 to Yersinia-containing vacuoles (YCVs) requires hypersecretion of Yersinia translocon proteins. We show that the presence of bacterial secretion systems directs cytosolic carbohydrate-binding protein Galectin-3 to PVs and that the delivery of GBP1 and GBP2 to Legionella-containing vacuoles or YCVs is substantially diminished in Galectin-3-deficient cells. Our results illustrate that insertion of bacterial secretion systems into PV membranes stimulates Galectin-3-dependent recruitment of antimicrobial GBPs to PVs as part of a coordinated host defense program.
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White RC, Cianciotto NP. Type II Secretion Is Necessary for Optimal Association of the Legionella-Containing Vacuole with Macrophage Rab1B but Enhances Intracellular Replication Mainly by Rab1B-Independent Mechanisms. Infect Immun 2016; 84:3313-3327. [PMID: 27600508 PMCID: PMC5116710 DOI: 10.1128/iai.00750-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 08/31/2016] [Indexed: 12/12/2022] Open
Abstract
Previously, we documented that type II secretion (T2S) promotes intracellular infection of macrophages by Legionella pneumophila In the present study, we identified infection events that are modulated by T2S by comparing the behaviors of wild-type and T2S mutant bacteria in murine bone marrow-derived macrophages and human U937 cells. Although the two strains behaved similarly for entry into the host cells and evasion of lysosomal fusion, the mutant was impaired in the ability to initiate replication between 4 and 8 h postentry and to grow to large numbers in the Legionella-containing vacuole (LCV), as evident at 12 h. At 4 h postinoculation, mutant LCVs had a significantly reduced association with Rab1B, a host GTPase that facilitates the tethering of endoplasmic reticulum (ER)-derived vesicles to LCVs. The mutant did not lose expression or translocation of six type IV secretion effectors (e.g., SidM) that are well known for mediating Rab1B association with the LCV, indicating that T2S promotes the interaction between the LCV and Rab1B via a novel mechanism. Interestingly, the mutant's growth defect was exacerbated in macrophages that had been depleted of Rab1B by short hairpin RNA (shRNA) treatment, indicating that T2S also potentiates events beyond Rab1B association. In support of this, a sidM lspF double mutant had an intracellular growth defect that was more dramatic than that of the lspF mutant (and a sidM mutant) and showed a growth difference of as much as a 400-fold compared to the wild type. Together, these data reveal a new role for T2S in intracellular infection that involves both Rab1B-dependent and Rab1B-independent processes.
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Affiliation(s)
- Richard C White
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois, USA
| | - Nicholas P Cianciotto
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois, USA
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Chiaraviglio L, Kang YS, Kirby JE. High Throughput, Real-time, Dual-readout Testing of Intracellular Antimicrobial Activity and Eukaryotic Cell Cytotoxicity. J Vis Exp 2016:54841. [PMID: 27911388 PMCID: PMC5226247 DOI: 10.3791/54841] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Traditional measures of intracellular antimicrobial activity and eukaryotic cell cytotoxicity rely on endpoint assays. Such endpoint assays require several additional experimental steps prior to readout, such as cell lysis, colony forming unit determination, or reagent addition. When performing thousands of assays, for example, during high-throughput screening, the downstream effort required for these types of assays is considerable. Therefore, to facilitate high-throughput antimicrobial discovery, we developed a real-time assay to simultaneously identify inhibitors of intracellular bacterial growth and assess eukaryotic cell cytotoxicity. Specifically, real-time intracellular bacterial growth detection was enabled by marking bacterial screening strains with either a bacterial lux operon (1st generation assay) or fluorescent protein reporters (2nd generation, orthogonal assay). A non-toxic, cell membrane-impermeant, nucleic acid-binding dye was also added during initial infection of macrophages. These dyes are excluded from viable cells. However, non-viable host cells lose membrane integrity permitting entry and fluorescent labeling of nuclear DNA (deoxyribonucleic acid). Notably, DNA binding is associated with a large increase in fluorescent quantum yield that provides a solution-based readout of host cell death. We have used this combined assay to perform a high-throughput screen in microplate format, and to assess intracellular growth and cytotoxicity by microscopy. Notably, antimicrobials may demonstrate synergy in which the combined effect of two or more antimicrobials when applied together is greater than when applied separately. Testing for in vitro synergy against intracellular pathogens is normally a prodigious task as combinatorial permutations of antibiotics at different concentrations must be assessed. However, we found that our real-time assay combined with automated, digital dispensing technology permitted facile synergy testing. Using these approaches, we were able to systematically survey action of a large number of antimicrobials alone and in combination against the intracellular pathogen, Legionella pneumophila.
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Affiliation(s)
| | - Yoon-Suk Kang
- Department of Pathology, Beth Israel Deaconess Medical Center
| | - James E Kirby
- Department of Pathology, Beth Israel Deaconess Medical Center;
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Type I Interferon Counters or Promotes Coxiella burnetii Replication Dependent on Tissue. Infect Immun 2016; 84:1815-1825. [PMID: 27068091 DOI: 10.1128/iai.01540-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 04/01/2016] [Indexed: 01/09/2023] Open
Abstract
Coxiella burnetii is an intracellular pathogen and the cause of Q fever. Gamma interferon (IFN-γ) is critical for host protection from infection, but a role for type I IFN in C. burnetii infection has not been determined. Type I IFN supports host protection from a related pathogen, Legionella pneumophila, and we hypothesized that it would be similarly protective in C. burnetii infection. In contrast to our prediction, IFN-α receptor-deficient (IFNAR(-/-)) mice were protected from C. burnetii-induced infection. Therefore, the role of type I IFN in C. burnetii infection was distinct from that in L. pneumophila Mice treated with a double-stranded-RNA mimetic were protected from C. burnetii-induced weight loss through an IFNAR-independent pathway. We next treated mice with recombinant IFN-α (rIFN-α). When rIFN-α was injected by the intraperitoneal route during infection, disease-induced weight loss was exacerbated. Mice that received rIFN-α by this route had dampened interleukin 1β (IL-1β) expression in bronchoalveolar lavage fluids. However, when rIFN-α was delivered to the lung, bacterial replication was decreased in all tissues. Thus, the presence of type I IFN in the lung protected from infection, but when delivered to the periphery, type I IFN enhanced disease, potentially by dampening inflammatory cytokines. To better characterize the capacity for type I IFN induction by C. burnetii, we assessed expression of IFN-β transcripts by human macrophages following stimulation with lipopolysaccharide (LPS) from C. burnetii Understanding innate responses in C. burnetii infection will support the discovery of novel therapies that may be alternative or complementary to the current antibiotic treatment.
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Microbially cleaved immunoglobulins are sensed by the innate immune receptor LILRA2. Nat Microbiol 2016; 1:16054. [DOI: 10.1038/nmicrobiol.2016.54] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 03/22/2016] [Indexed: 12/15/2022]
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Neutrophil and Alveolar Macrophage-Mediated Innate Immune Control of Legionella pneumophila Lung Infection via TNF and ROS. PLoS Pathog 2016; 12:e1005591. [PMID: 27105352 PMCID: PMC4841525 DOI: 10.1371/journal.ppat.1005591] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 04/01/2016] [Indexed: 12/31/2022] Open
Abstract
Legionella pneumophila is a facultative intracellular bacterium that lives in aquatic environments where it parasitizes amoeba. However, upon inhalation of contaminated aerosols it can infect and replicate in human alveolar macrophages, which can result in Legionnaires' disease, a severe form of pneumonia. Upon experimental airway infection of mice, L. pneumophila is rapidly controlled by innate immune mechanisms. Here we identified, on a cell-type specific level, the key innate effector functions responsible for rapid control of infection. In addition to the well-characterized NLRC4-NAIP5 flagellin recognition pathway, tumor necrosis factor (TNF) and reactive oxygen species (ROS) are also essential for effective innate immune control of L. pneumophila. While ROS are essential for the bactericidal activity of neutrophils, alveolar macrophages (AM) rely on neutrophil and monocyte-derived TNF signaling via TNFR1 to restrict bacterial replication. This TNF-mediated antibacterial mechanism depends on the acidification of lysosomes and their fusion with L. pneumophila containing vacuoles (LCVs), as well as caspases with a minor contribution from cysteine-type cathepsins or calpains, and is independent of NLRC4, caspase-1, caspase-11 and NOX2. This study highlights the differential utilization of innate effector pathways to curtail intracellular bacterial replication in specific host cells upon L. pneumophila airway infection.
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Shin S. Innate Immunity to Intracellular Pathogens: Lessons Learned from Legionella pneumophila. ADVANCES IN APPLIED MICROBIOLOGY 2016; 79:43-71. [PMID: 22569517 DOI: 10.1016/b978-0-12-394318-7.00003-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Intracellular bacterial pathogens have the remarkable ability to manipulate host cell processes in order to establish a replicative niche within the host cell. In response, the host can initiate immune defenses that lead to the eventual restriction and clearance of intracellular infection. The bacterial pathogen Legionella pneumophila has evolved elaborate virulence mechanisms that allow for its survival inside protozoa within a specialized membrane-bound organelle. These strategies also enable L. pneumophila to survive and replicate within alveolar macrophages, and can result in the severe pneumonia Legionnaires' disease. Essential to L. pneumophila's intracellular lifestyle is a specialized type IV secretion system, termed Dot/Icm, that translocates bacterial effector proteins into host cells. The ease with which L. pneumophila can be genetically manipulated has facilitated the comparison of host responses to virulent and isogenic avirulent mutants lacking a functional Dot/Icm system. This has made L. pneumophila an excellent model for understanding how the host discriminates between pathogenic and nonpathogenic bacteria and for systematically dissecting host defense mechanisms against intracellular pathogens. In this chapter, I discuss a few examples demonstrating how the study of immune responses triggered specifically by the L. pneumophila type IV secretion system has provided unique insight into our understanding of host immunity against intracellular bacterial pathogens.
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Affiliation(s)
- Sunny Shin
- Department of Microbiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania, USA.
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Primary Role for Toll-Like Receptor-Driven Tumor Necrosis Factor Rather than Cytosolic Immune Detection in Restricting Coxiella burnetii Phase II Replication within Mouse Macrophages. Infect Immun 2016; 84:998-1015. [PMID: 26787725 DOI: 10.1128/iai.01536-15] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 01/14/2016] [Indexed: 12/13/2022] Open
Abstract
Coxiella burnetii replicates within permissive host cells by employing a Dot/Icm type IV secretion system (T4SS) to translocate effector proteins that direct the formation of a parasitophorous vacuole. C57BL/6 mouse macrophages restrict the intracellular replication of the C. burnetii. Nine Mile phase II (NMII) strain. However, eliminating Toll-like receptor 2 (TLR2) permits bacterial replication, indicating that the restriction of bacterial replication is immune mediated. Here, we examined whether additional innate immune pathways are employed by C57BL/6 macrophages to sense and restrict NMII replication. In addition to the known role of TLR2 in detecting and restricting NMII infection, we found that TLR4 also contributes to cytokine responses but is not required to restrict bacterial replication. Furthermore, the TLR signaling adaptors MyD88 and Trif are required for cytokine responses and restricting bacterial replication. The C. burnetii NMII T4SS translocates bacterial products into C57BL/6 macrophages. However, there was little evidence of cytosolic immune sensing of NMII, as there was a lack of inflammasome activation, T4SS-dependent cytokine responses, and robust type I interferon (IFN) production, and these pathways were not required to restrict bacterial replication. Instead, endogenous tumor necrosis factor (TNF) produced upon TLR sensing of C. burnetii NMII was required to control bacterial replication. Therefore, our findings indicate a primary role for TNF produced upon immune detection of C. burnetii NMII by TLRs, rather than cytosolic PRRs, in enabling C57BL/6 macrophages to restrict bacterial replication.
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Majoros A, Platanitis E, Szappanos D, Cheon H, Vogl C, Shukla P, Stark GR, Sexl V, Schreiber R, Schindler C, Müller M, Decker T. Response to interferons and antibacterial innate immunity in the absence of tyrosine-phosphorylated STAT1. EMBO Rep 2016; 17:367-82. [PMID: 26882544 PMCID: PMC4772975 DOI: 10.15252/embr.201540726] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 01/13/2016] [Indexed: 01/12/2023] Open
Abstract
Signal transducer and activator of transcription 1 (STAT1) plays a pivotal role in the innate immune system by directing the transcriptional response to interferons (IFNs). STAT1 is activated by Janus kinase (JAK)‐mediated phosphorylation of Y701. To determine whether STAT1 contributes to cellular responses without this phosphorylation event, we generated mice with Y701 mutated to a phenylalanine (Stat1Y701F). We show that heterozygous mice do not exhibit a dominant‐negative phenotype. Homozygous Stat1Y701F mice show a profound reduction in Stat1 expression, highlighting an important role for basal IFN‐dependent signaling. The rapid transcriptional response to type I IFN (IFN‐I) and type II IFN (IFNγ) was absent in Stat1Y701F cells. Intriguingly, STAT1Y701F suppresses the delayed expression of IFN‐I‐stimulated genes (ISG) observed in Stat1−/− cells, mediated by the STAT2/IRF9 complex. Thus, Stat1Y701F macrophages are more susceptible to Legionella pneumophila infection than Stat1−/− macrophages. Listeria monocytogenes grew less robustly in Stat1Y701F macrophages and mice compared to Stat1−/− counterparts, but STAT1Y701F is not sufficient to rescue the animals. Our studies are consistent with a potential contribution of Y701‐unphosphorylated STAT1 to innate antibacterial immunity.
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Affiliation(s)
- Andrea Majoros
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
| | | | - Daniel Szappanos
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
| | - HyeonJoo Cheon
- Department of Molecular Genetics and Proteomics Core, Lerner Research Institute Cleveland Clinic, Cleveland, OH, USA
| | - Claus Vogl
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Priyank Shukla
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Vienna, Austria
| | - George R Stark
- Department of Molecular Genetics and Proteomics Core, Lerner Research Institute Cleveland Clinic, Cleveland, OH, USA
| | - Veronika Sexl
- Department for Biomedical Sciences, Institute of Pharmacology and Toxicology University of Veterinary Medicine Vienna, Vienna, Austria
| | - Robert Schreiber
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, USA
| | - Christian Schindler
- Departments of Microbiology & Immunology and Medicine, Columbia University, New York, NY, USA
| | - Mathias Müller
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Thomas Decker
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
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Naujoks J, Tabeling C, Dill BD, Hoffmann C, Brown AS, Kunze M, Kempa S, Peter A, Mollenkopf HJ, Dorhoi A, Kershaw O, Gruber AD, Sander LE, Witzenrath M, Herold S, Nerlich A, Hocke AC, van Driel I, Suttorp N, Bedoui S, Hilbi H, Trost M, Opitz B. IFNs Modify the Proteome of Legionella-Containing Vacuoles and Restrict Infection Via IRG1-Derived Itaconic Acid. PLoS Pathog 2016; 12:e1005408. [PMID: 26829557 PMCID: PMC4734697 DOI: 10.1371/journal.ppat.1005408] [Citation(s) in RCA: 183] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 12/30/2015] [Indexed: 11/21/2022] Open
Abstract
Macrophages can be niches for bacterial pathogens or antibacterial effector cells depending on the pathogen and signals from the immune system. Here we show that type I and II IFNs are master regulators of gene expression during Legionella pneumophila infection, and activators of an alveolar macrophage-intrinsic immune response that restricts bacterial growth during pneumonia. Quantitative mass spectrometry revealed that both IFNs substantially modify Legionella-containing vacuoles, and comparative analyses reveal distinct subsets of transcriptionally and spatially IFN-regulated proteins. Immune-responsive gene (IRG)1 is induced by IFNs in mitochondria that closely associate with Legionella-containing vacuoles, and mediates production of itaconic acid. This metabolite is bactericidal against intravacuolar L. pneumophila as well as extracellular multidrug-resistant Gram-positive and -negative bacteria. Our study explores the overall role IFNs play in inducing substantial remodeling of bacterial vacuoles and in stimulating production of IRG1-derived itaconic acid which targets intravacuolar pathogens. IRG1 or its product itaconic acid might be therapeutically targetable to fight intracellular and drug-resistant bacteria. Numerous intracellular bacterial pathogens replicate in specialized vacuoles within macrophages. We systematically study the molecular mechanism and the impact of macrophage-intrinsic antibacterial defense. Using L. pneumophila, an important cause of pneumonia and model organism for intracellular bacteria, we found that type I and II interferons critically modify the proteome of bacterial vacuoles to restrict infection. We identify IRG1 and demonstrate a bactericidal activity of its metabolite itaconic acid on bacteria in their vacuole. Moreover, our study provides evidence for the impact of this cell-autonomous defense pathway in alveolar macrophages to restrict lung infection. We speculate that vacuolar IRG1 or its product itaconic acid could serve as future therapeutic targets to fight intracellular and drug-resistant bacteria.
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Affiliation(s)
- Jan Naujoks
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Christoph Tabeling
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Brian D. Dill
- MRC Protein Phosphorylation Unit, University of Dundee, Dundee, United Kingdom
| | - Christine Hoffmann
- Max-von-Pettenkofer Institute, Ludwig Maximilian University, Munich, Germany
| | - Andrew S. Brown
- The Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Australia
| | - Mareike Kunze
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Stefan Kempa
- Integrative Metabolomics and Proteomics, Institute of Medical Systems Biology/Max-Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Andrea Peter
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | | | - Anca Dorhoi
- Max Planck Institute for Infection Biology, Berlin, Germany
| | - Olivia Kershaw
- Department of Veterinary Pathology, Free University Berlin, Berlin, Germany
| | - Achim D. Gruber
- Department of Veterinary Pathology, Free University Berlin, Berlin, Germany
| | - Leif E. Sander
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Martin Witzenrath
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Susanne Herold
- Medizinische Klinik II, University Giessen and Marburg Lung Center, Justus-Liebig-University Giessen, Giessen, Germany
| | - Andreas Nerlich
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Andreas C. Hocke
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Ian van Driel
- The Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Australia
| | - Norbert Suttorp
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Sammy Bedoui
- The Department of Microbiology and Immunology, The University of Melbourne, Melbourne, Australia
| | - Hubert Hilbi
- Max-von-Pettenkofer Institute, Ludwig Maximilian University, Munich, Germany
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Matthias Trost
- MRC Protein Phosphorylation Unit, University of Dundee, Dundee, United Kingdom
| | - Bastian Opitz
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
- * E-mail:
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Schell U, Simon S, Hilbi H. Inflammasome Recognition and Regulation of the Legionella Flagellum. Curr Top Microbiol Immunol 2016; 397:161-81. [PMID: 27460809 DOI: 10.1007/978-3-319-41171-2_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The Gram-negative bacterium Legionella pneumophila colonizes extracellular environmental niches and infects free-living protozoa. Upon inhalation into the human lung, the opportunistic pathogen grows in macrophages and causes a fulminant pneumonia termed Legionnaires' disease. L. pneumophila employs a biphasic life cycle, comprising a replicative, non-virulent, and a stationary, virulent form. In the latter phase, the pathogen produces a plethora of so-called effector proteins, which are injected into host cells, where they subvert pivotal processes and promote the formation of a distinct membrane-bound compartment, the Legionella-containing vacuole. In the stationary phase, the bacteria also produce a single monopolar flagellum and become motile. L. pneumophila flagellin is recognized by and triggers the host's NAIP5 (Birc1e)/NLRC4 (Ipaf) inflammasome, which leads to caspase-1 activation, pore formation, and pyroptosis. The production of L. pneumophila flagellin and pathogen-host interactions are controlled by a complex stationary phase regulatory network, detecting nutrient availability as well as the Legionella quorum sensing (Lqs) signaling compound LAI-1 (3-hydroxypentadecane-4-one). Thus, the small molecule LAI-1 coordinates L. pneumophila flagellin production and motility, inflammasome activation, and virulence.
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Affiliation(s)
- Ursula Schell
- Max von Pettenkofer Institute, Ludwig-Maximilians University, Pettenkoferstraße 9a, 80336, Munich, Germany
| | - Sylvia Simon
- Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30/32, 8006, Zürich, Switzerland
| | - Hubert Hilbi
- Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30/32, 8006, Zürich, Switzerland.
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High-Throughput Intracellular Antimicrobial Susceptibility Testing of Legionella pneumophila. Antimicrob Agents Chemother 2015; 59:7517-29. [PMID: 26392509 DOI: 10.1128/aac.01248-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 09/16/2015] [Indexed: 02/07/2023] Open
Abstract
Legionella pneumophila is a Gram-negative opportunistic human pathogen that causes a severe pneumonia known as Legionnaires' disease. Notably, in the human host, the organism is believed to replicate solely within an intracellular compartment, predominantly within pulmonary macrophages. Consequently, successful therapy is predicated on antimicrobials penetrating into this intracellular growth niche. However, standard antimicrobial susceptibility testing methods test solely for extracellular growth inhibition. Here, we make use of a high-throughput assay to characterize intracellular growth inhibition activity of known antimicrobials. For select antimicrobials, high-resolution dose-response analysis was then performed to characterize and compare activity levels in both macrophage infection and axenic growth assays. Results support the superiority of several classes of nonpolar antimicrobials in abrogating intracellular growth. Importantly, our assay results show excellent correlations with prior clinical observations of antimicrobial efficacy. Furthermore, we also show the applicability of high-throughput automation to two- and three-dimensional synergy testing. High-resolution isocontour isobolograms provide in vitro support for specific combination antimicrobial therapy. Taken together, findings suggest that high-throughput screening technology may be successfully applied to identify and characterize antimicrobials that target bacterial pathogens that make use of an intracellular growth niche.
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Simon S, Hilbi H. Subversion of Cell-Autonomous Immunity and Cell Migration by Legionella pneumophila Effectors. Front Immunol 2015; 6:447. [PMID: 26441958 PMCID: PMC4568765 DOI: 10.3389/fimmu.2015.00447] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/17/2015] [Indexed: 12/14/2022] Open
Abstract
Bacteria trigger host defense and inflammatory processes, such as cytokine production, pyroptosis, and the chemotactic migration of immune cells toward the source of infection. However, a number of pathogens interfere with these immune functions by producing specific so-called “effector” proteins, which are delivered to host cells via dedicated secretion systems. Air-borne Legionella pneumophila bacteria trigger an acute and potential fatal inflammation in the lung termed Legionnaires’ disease. The opportunistic pathogen L. pneumophila is a natural parasite of free-living amoebae, but also replicates in alveolar macrophages and accidentally infects humans. The bacteria employ the intracellular multiplication/defective for organelle trafficking (Icm/Dot) type IV secretion system and as many as 300 different effector proteins to govern host–cell interactions and establish in phagocytes an intracellular replication niche, the Legionella-containing vacuole. Some Icm/Dot-translocated effector proteins target cell-autonomous immunity or cell migration, i.e., they interfere with (i) endocytic, secretory, or retrograde vesicle trafficking pathways, (ii) organelle or cell motility, (iii) the inflammasome and programed cell death, or (iv) the transcription factor NF-κB. Here, we review recent mechanistic insights into the subversion of cellular immune functions by L. pneumophila.
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Affiliation(s)
- Sylvia Simon
- Institute of Medical Microbiology, University of Zürich , Zürich , Switzerland
| | - Hubert Hilbi
- Institute of Medical Microbiology, University of Zürich , Zürich , Switzerland ; Max von Pettenkofer Institute, Ludwig-Maximilians University , Munich , Germany
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Abdul-Sater AA, Majoros A, Plumlee CR, Perry S, Gu AD, Lee C, Shresta S, Decker T, Schindler C. Different STAT Transcription Complexes Drive Early and Delayed Responses to Type I IFNs. THE JOURNAL OF IMMUNOLOGY 2015; 195:210-216. [PMID: 26019270 DOI: 10.4049/jimmunol.1401139] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 04/24/2015] [Indexed: 01/12/2023]
Abstract
IFNs, which transduce pivotal signals through Stat1 and Stat2, effectively suppress the replication of Legionella pneumophila in primary murine macrophages. Although the ability of IFN-γ to impede L. pneumophila growth is fully dependent on Stat1, IFN-αβ unexpectedly suppresses L. pneumophila growth in both Stat1- and Stat2-deficient macrophages. New studies demonstrating that the robust response to IFN-αβ is lost in Stat1-Stat2 double-knockout macrophages suggest that Stat1 and Stat2 are functionally redundant in their ability to direct an innate response toward L. pneumophila. Because the ability of IFN-αβ to signal through Stat1-dependent complexes (i.e., Stat1-Stat1 and Stat1-Stat2 dimers) has been well characterized, the current studies focus on how Stat2 is able to direct a potent response to IFN-αβ in the absence of Stat1. These studies reveal that IFN-αβ is able to drive the formation of a Stat2 and IFN regulatory factor 9 complex that drives the expression of a subset of IFN-stimulated genes, but with substantially delayed kinetics. These observations raise the possibility that this pathway evolved in response to microbes that have devised strategies to subvert Stat1-dependent responses.
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Affiliation(s)
- Ali A Abdul-Sater
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA
| | - Andrea Majoros
- Department of Microbiology, Immunology & Genetics, University of Vienna, Vienna A-1030 Austria
| | - Courtney R Plumlee
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA
| | - Stuart Perry
- Division of Vaccine Discovery, La Jolla Inst. for Allergy and Immunology, La Jolla, CA 92037 USA
| | - Ai Di Gu
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA
| | - Carolyn Lee
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA
| | - Sujan Shresta
- Division of Vaccine Discovery, La Jolla Inst. for Allergy and Immunology, La Jolla, CA 92037 USA
| | - Thomas Decker
- Department of Microbiology, Immunology & Genetics, University of Vienna, Vienna A-1030 Austria
| | - Christian Schindler
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA.,Department of Medicine, Columbia University, New York, NY 10032 USA
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Motta V, Soares F, Sun T, Philpott DJ. NOD-like receptors: versatile cytosolic sentinels. Physiol Rev 2015; 95:149-78. [PMID: 25540141 DOI: 10.1152/physrev.00009.2014] [Citation(s) in RCA: 211] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Nucleotide binding oligomerization domain (NOD)-like receptors are cytoplasmic pattern-recognition receptors that together with RIG-I-like receptor (retinoic acid-inducible gene 1), Toll-like receptor (TLR), and C-type lectin families make up the innate pathogen pattern recognition system. There are 22 members of NLRs in humans, 34 in mice, and even a larger number in some invertebrates like sea urchins, which contain more than 200 receptors. Although initially described to respond to intracellular pathogens, NLRs have been shown to play important roles in distinct biological processes ranging from regulation of antigen presentation, sensing metabolic changes in the cell, modulation of inflammation, embryo development, cell death, and differentiation of the adaptive immune response. The diversity among NLR receptors is derived from ligand specificity conferred by the leucine-rich repeats and an NH2-terminal effector domain that triggers the activation of different biological pathways. Here, we describe NLR genes associated with different biological processes and the molecular mechanisms underlying their function. Furthermore, we discuss mutations in NLR genes that have been associated with human diseases.
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Affiliation(s)
- Vinicius Motta
- Departments of Immunology and of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
| | - Fraser Soares
- Departments of Immunology and of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
| | - Tian Sun
- Departments of Immunology and of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
| | - Dana J Philpott
- Departments of Immunology and of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
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50
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Chiaraviglio L, Kirby JE. Evaluation of impermeant, DNA-binding dye fluorescence as a real-time readout of eukaryotic cell toxicity in a high throughput screening format. Assay Drug Dev Technol 2015; 12:219-28. [PMID: 24831788 DOI: 10.1089/adt.2014.577] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Interpretation of high throughput screening (HTS) data in cell-based assays may be confounded by cytotoxic properties of screening compounds. Therefore, assessing cell toxicity in real time during the HTS process itself would be highly advantageous. Here, we investigate the potential of putatively impermeant, fluorescent, DNA-binding dyes to give cell toxicity readout during HTS. Amongst 19 DNA-binding dyes examined, three classes were identified that were (1) permeant, (2) cytotoxic, or (3) neither permeant nor cytotoxic during 3-day incubation with a macrophage cell line. In the last class, four dyes (SYTOX Green, CellTox Green, GelGreen, and EvaGreen) gave highly robust cytotoxicity data in 384-well screening plates. As proof of principle, successful combination with a luminescence-based assay in HTS format was demonstrated. Here, both intracellular growth of Legionella pneumophila (luminescence) and host cell viability (SYTOX Green exclusion) were assayed in the same screening well. Incorporation of membrane-impermeant, DNA-binding, fluorescent dyes in HTS assays should prove useful by allowing evaluation of cytotoxicity in real time, eliminating reagent addition steps and effort associated with endpoint cell viability analysis, and reducing the need for follow-up cytotoxicity screening.
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Affiliation(s)
- Lucius Chiaraviglio
- Department of Pathology, Beth Israel Deaconess Medical Center , Boston, Massachusetts
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