1
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Hong NTX, Baruah K, Nguyen Van H, Vanrompay D, Bossier P. Expression profiles of heat shock protein 70 and high-mobility groups box-1 protein in gnotobiotic brine shrimp challenged with different virulence levels of isogenic Vibrio harveyi strains. JOURNAL OF FISH DISEASES 2024; 47:e13954. [PMID: 38555529 DOI: 10.1111/jfd.13954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 03/16/2024] [Accepted: 03/19/2024] [Indexed: 04/02/2024]
Affiliation(s)
- Nguyen Thi Xuan Hong
- Laboratory of Aquaculture & Artemia Reference Center, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
- Faculty of Fisheries, University of Agriculture and Forestry, Hue University, Hue, Vietnam
| | - Kartik Baruah
- Department of Animal Nutrition and Management, Aquaculture Nutraceuticals Research Group, Faculty of Veterinary Medicine and Animal Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Hung Nguyen Van
- Research Institute for Aquaculture No. 3, Nha Trang, Vietnam
| | - Daisy Vanrompay
- Laboratory of Immunology and Animal Biotechnology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Peter Bossier
- Laboratory of Aquaculture & Artemia Reference Center, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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2
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Ledvina HE, Whiteley AT. Conservation and similarity of bacterial and eukaryotic innate immunity. Nat Rev Microbiol 2024; 22:420-434. [PMID: 38418927 DOI: 10.1038/s41579-024-01017-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/24/2024] [Indexed: 03/02/2024]
Abstract
Pathogens are ubiquitous and a constant threat to their hosts, which has led to the evolution of sophisticated immune systems in bacteria, archaea and eukaryotes. Bacterial immune systems encode an astoundingly large array of antiviral (antiphage) systems, and recent investigations have identified unexpected similarities between the immune systems of bacteria and animals. In this Review, we discuss advances in our understanding of the bacterial innate immune system and highlight the components, strategies and pathogen restriction mechanisms conserved between bacteria and eukaryotes. We summarize evidence for the hypothesis that components of the human immune system originated in bacteria, where they first evolved to defend against phages. Further, we discuss shared mechanisms that pathogens use to overcome host immune pathways and unexpected similarities between bacterial immune systems and interbacterial antagonism. Understanding the shared evolutionary path of immune components across domains of life and the successful strategies that organisms have arrived at to restrict their pathogens will enable future development of therapeutics that activate the human immune system for the precise treatment of disease.
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Affiliation(s)
- Hannah E Ledvina
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA
| | - Aaron T Whiteley
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA.
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3
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Hershkovitz D, Chen EJ, Ensminger AW, Dugan AS, Conway KT, Joyce AC, Segal G, Isberg RR. Genetic evidence for a regulated cysteine protease catalytic triad in LegA7, a Legionella pneumophila protein that impinges on a stress response pathway. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.17.585421. [PMID: 38562771 PMCID: PMC10983931 DOI: 10.1101/2024.03.17.585421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Legionella pneumophila grows within membrane-bound vacuoles in phylogenetically diverse hosts. Intracellular growth requires the function of the Icm/Dot type-IVb secretion system, which translocates more than 300 proteins into host cells. A screen was performed to identify L. pneumophila proteins that stimulate MAPK activation, using Icm/Dot translocated proteins ectopically expressed in mammalian cells. In parallel, a second screen was performed to identify L. pneumophila proteins expressed in yeast that cause growth inhibition in MAPK pathway-stimulatory high osmolarity medium. LegA7 was shared in both screens, a protein predicted to be a member of the bacterial cysteine protease family that has five carboxyl-terminal ankyrin repeats. Three conserved residues in the predicted catalytic triad of LegA7 were mutated. These mutations abolished the ability of LegA7 to inhibit yeast growth. To identify other residues important for LegA7 function, a generalizable selection strategy in yeast was devised to isolate mutants that have lost function and no longer cause growth inhibition on high osmolarity medium. Mutations were isolated in the two carboxyl-terminal ankyrin repeats, as well as an inter-domain region located between the cysteine protease domain and the ankyrin repeats. These mutations were predicted by AlphaFold modeling to localize to the face opposite from the catalytic site, arguing that they interfere with the positive regulation of the catalytic activity. Based on our data, we present a model in which LegA7 harbors a cysteine protease domain with an inter-domain and two carboxyl-terminal ankyrin repeat regions that modulate the function of the catalytic domain.
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Affiliation(s)
- Dar Hershkovitz
- The Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Emy J. Chen
- Department of Molecular Biology and Microbiology
- Program in Genetics, Molecular and Cellular Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine,150 Harrison Ave., Boston, MA 02115, USA
| | | | - Aisling S. Dugan
- Department of Molecular Biology and Microbiology
- Current Address: Dept. of Biology, Brown University, Providence, RI 02912
| | - Kaleigh T. Conway
- Department of Molecular Biology and Microbiology
- Program in Genetics, Molecular and Cellular Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine,150 Harrison Ave., Boston, MA 02115, USA
| | | | - Gil Segal
- The Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, 6997801, Israel
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4
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Ma K, Xian W, Liu H, Shu R, Ge J, Luo ZQ, Liu X, Qiu J. Bacterial ubiquitin ligases hijack the host deubiquitinase OTUB1 to inhibit MTORC1 signaling and promote autophagy. Autophagy 2024:1-16. [PMID: 38818749 DOI: 10.1080/15548627.2024.2353492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 05/05/2024] [Indexed: 06/01/2024] Open
Abstract
Many bacterial pathogens have evolved effective strategies to interfere with the ubiquitination network to evade clearance by the innate immune system. Here, we report that OTUB1, one of the most abundant deubiquitinases (DUBs) in mammalian cells, is subjected to both canonical and noncanonical ubiquitination during Legionella pneumophila infection. The effectors SidC and SdcA catalyze OTUB1 ubiquitination at multiple lysine residues, resulting in its association with a Legionella-containing vacuole. Lysine ubiquitination by SidC and SdcA promotes interactions between OTUB1 and DEPTOR, an inhibitor of the MTORC1 pathway, thus suppressing MTORC1 signaling. The inhibition of MTORC1 leads to suppression of host protein synthesis and promotion of host macroautophagy/autophagy during L. pneumophila infection. In addition, members of the SidE family effectors (SidEs) induce phosphoribosyl (PR)-linked ubiquitination of OTUB1 at Ser16 and Ser18 and block its DUB activity. The levels of the lysine and serine ubiquitination of OTUB1 are further regulated by effectors that function to antagonize the activities of SidC, SdcA and SidEs, including Lem27, DupA, DupB, SidJ and SdjA. Our study reveals an effectors-mediated complicated mechanism in regulating the activity of a host DUB.Abbreviations: BafA1: bafilomycin A1; BMDMs: bone marrow-derived macrophages; DUB: deubiquitinase; Dot/Icm: defective for organelle trafficking/intracellular multiplication; DEPTOR: DEP domain containing MTOR interacting protein; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; L. pneumophila: Legionella pneumophila; LCV: Legionella-containing vacuole; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MOI: multiplicity of infection; MTORC1: mechanistic target of rapamycin kinase complex 1; OTUB1: OTU deubiquitinase, ubiquitin aldehyde binding 1; PR-Ub: phosphoribosyl (PR)-linked ubiquitin; PTM: posttranslational modification; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SidEs: SidE family effectors; Ub: ubiquitin.
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Affiliation(s)
- Kelong Ma
- State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Key Laboratory for Zoonosis Research of the Ministry of Education, College of Veterinary Medicine, Jilin University, Center for Pathogen Biology and Infectious Diseases, The First Hospital of Jilin University, Changchun, China
| | - Wei Xian
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Hongtao Liu
- State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Key Laboratory for Zoonosis Research of the Ministry of Education, College of Veterinary Medicine, Jilin University, Center for Pathogen Biology and Infectious Diseases, The First Hospital of Jilin University, Changchun, China
| | - Rundong Shu
- State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Key Laboratory for Zoonosis Research of the Ministry of Education, College of Veterinary Medicine, Jilin University, Center for Pathogen Biology and Infectious Diseases, The First Hospital of Jilin University, Changchun, China
| | - Jinli Ge
- State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Key Laboratory for Zoonosis Research of the Ministry of Education, College of Veterinary Medicine, Jilin University, Center for Pathogen Biology and Infectious Diseases, The First Hospital of Jilin University, Changchun, China
| | - Zhao-Qing Luo
- Purdue Institute for Inflammation, Immunology and Infectious Disease and Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Xiaoyun Liu
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
- NHC Key Laboratory of Medical Immunology, Peking University, Beijing, China
| | - Jiazhang Qiu
- State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Key Laboratory for Zoonosis Research of the Ministry of Education, College of Veterinary Medicine, Jilin University, Center for Pathogen Biology and Infectious Diseases, The First Hospital of Jilin University, Changchun, China
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5
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Li C, Fu J, Shao S, Luo ZQ. Legionella pneumophila exploits the endo-lysosomal network for phagosome biogenesis by co-opting SUMOylated Rab7. PLoS Pathog 2024; 20:e1011783. [PMID: 38739652 PMCID: PMC11115209 DOI: 10.1371/journal.ppat.1011783] [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: 10/30/2023] [Revised: 05/23/2024] [Accepted: 04/30/2024] [Indexed: 05/16/2024] Open
Abstract
Legionella pneumophila strains harboring wild-type rpsL such as Lp02rpsLWT cannot replicate in mouse bone marrow-derived macrophages (BMDMs) due to induction of extensive lysosome damage and apoptosis. The bacterial factor directly responsible for inducing such cell death and the host factor involved in initiating the signaling cascade that leads to lysosome damage remain unknown. Similarly, host factors that may alleviate cell death induced by these bacterial strains have not yet been investigated. Using a genome-wide CRISPR/Cas9 screening, we identified Hmg20a and Nol9 as host factors important for restricting strain Lp02rpsLWT in BMDMs. Depletion of Hmg20a protects macrophages from infection-induced lysosomal damage and apoptosis, allowing productive bacterial replication. The restriction imposed by Hmg20a was mediated by repressing the expression of several endo-lysosomal proteins, including the small GTPase Rab7. We found that SUMOylated Rab7 is recruited to the bacterial phagosome via SulF, a Dot/Icm effector that harbors a SUMO-interacting motif (SIM). Moreover, overexpression of Rab7 rescues intracellular growth of strain Lp02rpsLWT in BMDMs. Our results establish that L. pneumophila exploits the lysosomal network for the biogenesis of its phagosome in BMDMs.
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Affiliation(s)
- Chuang Li
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Jiaqi Fu
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Shuai Shao
- College of Pharmacy, The Ohio State University, Columbus, Ohio, United States of America
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Zhao-Qing Luo
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
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6
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Syriste L, Patel DT, Stogios PJ, Skarina T, Patel D, Savchenko A. An acetyltransferase effector conserved across Legionella species targets the eukaryotic eIF3 complex to modulate protein translation. mBio 2024; 15:e0322123. [PMID: 38335095 PMCID: PMC10936415 DOI: 10.1128/mbio.03221-23] [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: 12/05/2023] [Accepted: 01/16/2024] [Indexed: 02/12/2024] Open
Abstract
The survival of Legionella spp. as intracellular pathogens relies on the combined action of protein effectors delivered inside their eukaryotic hosts by the Dot/Icm (defective in organelle trafficking/intracellular multiplication) type IVb secretion system. The specific repertoire of effector arsenals varies dramatically across over 60 known species of this genera with Legionella pneumophila responsible for most cases of Legionnaires' disease in humans encoding over 360 Dot/Icm effectors. However, a small subset of "core" effectors appears to be conserved across all Legionella species raising an intriguing question of their role in these bacteria's pathogenic strategy, which for most of these effectors remains unknown. L. pneumophila Lpg0103 effector, also known as VipF, represents one of the core effector families that features a tandem of Gcn5-related N-acetyltransferase (GNAT) domains. Here, we present the crystal structure of the Lha0223, the VipF representative from Legionella hackeliae in complex with acetyl-coenzyme A determined to 1.75 Å resolution. Our structural analysis suggested that this effector family shares a common fold with the two GNAT domains forming a deep groove occupied by residues conserved across VipF homologs. Further analysis suggested that only the C-terminal GNAT domain of VipF effectors retains the active site composition compatible with catalysis, whereas the N-terminal GNAT domain binds the ligand in a non-catalytical mode. We confirmed this by in vitro enzymatic assays which revealed VipF activity not only against generic small molecule substrates, such as chloramphenicol, but also against poly-L-lysine and histone-derived peptides. We identified the human eukaryotic translation initiation factor 3 (eIF3) complex co-precipitating with Lpg0103 and demonstrated the direct interaction between the several representatives of the VipF family, including Lpg0103 and Lha0223 with the K subunit of eIF3. According to our data, these interactions involve primarily the C-terminal tail of eIF3-K containing two lysine residues that are acetylated by VipF. VipF catalytic activity results in the suppression of eukaryotic protein translation in vitro, revealing the potential function of VipF "core" effectors in Legionella's pathogenic strategy.IMPORTANCEBy translocating effectors inside the eukaryotic host cell, bacteria can modulate host cellular processes in their favor. Legionella species, which includes the pneumonia-causing Legionella pneumophila, encode a widely diverse set of effectors with only a small subset that is conserved across this genus. Here, we demonstrate that one of these conserved effector families, represented by L. pneumophila VipF (Lpg0103), is a tandem Gcn5-related N-acetyltransferase interacting with the K subunit of human eukaryotic initiation factor 3 complex. VipF catalyzes the acetylation of lysine residues on the C-terminal tail of the K subunit, resulting in the suppression of eukaryotic translation initiation factor 3-mediated protein translation in vitro. These new data provide the first insight into the molecular function of this pathogenic factor family common across Legionellae.
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Affiliation(s)
- Lukas Syriste
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Deepak T. Patel
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Peter J. Stogios
- Department of Chemical Engineering and Applied Chemistry, Toronto University, Toronto, Ontario, Canada
| | - Tatiana Skarina
- Department of Chemical Engineering and Applied Chemistry, Toronto University, Toronto, Ontario, Canada
| | - Dhruvin Patel
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Alexei Savchenko
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
- Department of Chemical Engineering and Applied Chemistry, Toronto University, Toronto, Ontario, Canada
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7
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Graham CI, MacMartin TL, de Kievit TR, Brassinga AKC. Molecular regulation of virulence in Legionella pneumophila. Mol Microbiol 2024; 121:167-195. [PMID: 37908155 DOI: 10.1111/mmi.15172] [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: 05/31/2023] [Revised: 09/15/2023] [Accepted: 09/17/2023] [Indexed: 11/02/2023]
Abstract
Legionella pneumophila is a gram-negative bacteria found in natural and anthropogenic aquatic environments such as evaporative cooling towers, where it reproduces as an intracellular parasite of cohabiting protozoa. If L. pneumophila is aerosolized and inhaled by a susceptible person, bacteria may colonize their alveolar macrophages causing the opportunistic pneumonia Legionnaires' disease. L. pneumophila utilizes an elaborate regulatory network to control virulence processes such as the Dot/Icm Type IV secretion system and effector repertoire, responding to changing nutritional cues as their host becomes depleted. The bacteria subsequently differentiate to a transmissive state that can survive in the environment until a replacement host is encountered and colonized. In this review, we discuss the lifecycle of L. pneumophila and the molecular regulatory network that senses nutritional depletion via the stringent response, a link to stationary phase-like metabolic changes via alternative sigma factors, and two-component systems that are homologous to stress sensors in other pathogens, to regulate differentiation between the intracellular replicative phase and more transmissible states. Together, we highlight how this prototypic intracellular pathogen offers enormous potential in understanding how molecular mechanisms enable intracellular parasitism and pathogenicity.
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Affiliation(s)
- Christopher I Graham
- Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Teassa L MacMartin
- Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Teresa R de Kievit
- Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Ann Karen C Brassinga
- Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada
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8
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Allen CNS, Banks DA, Shuster M, Vogel SN, O’Connor TJ, Briken V. Legionella pneumophila inhibits type I interferon signaling to avoid cell-intrinsic host cell defense. Infect Immun 2023; 91:e0036523. [PMID: 37843413 PMCID: PMC10652965 DOI: 10.1128/iai.00365-23] [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: 09/08/2023] [Accepted: 09/15/2023] [Indexed: 10/17/2023] Open
Abstract
The host type I interferon (IFN) response protects against Legionella pneumophila infections. Other bacterial pathogens inhibit type I IFN-mediated cell signaling; however, the interaction between this signaling pathway and L. pneumophila has not been well described. Here, we demonstrate that L. pneumophila inhibits the IFN-β signaling pathway but does not inhibit IFN-γ-mediated cell signaling. The addition of IFN-β to L. pneumophila-infected macrophages limited bacterial growth independently of NOS2 and reactive nitrogen species. The type IV secretion system of L. pneumophila is required to inhibit IFN-β-mediated cell signaling. Finally, we show that the inhibition of the IFN-β signaling pathway occurs downstream of STAT1 and STAT2 phosphorylation. In conclusion, our findings describe a novel host cell signaling pathway inhibited by L. pneumophila via its type IV secretion system.
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Affiliation(s)
- Charles N. S. Allen
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Dallas A. Banks
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Michael Shuster
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Stefanie N. Vogel
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Tamara J. O’Connor
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Volker Briken
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
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9
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Subramanian A, Wang L, Moss T, Voorhies M, Sangwan S, Stevenson E, Pulido EH, Kwok S, Chalkley RJ, Li KH, Krogan NJ, Swaney DL, Burlingame AL, Floor SN, Sil A, Walter P, Mukherjee S. A Legionella toxin exhibits tRNA mimicry and glycosyl transferase activity to target the translation machinery and trigger a ribotoxic stress response. Nat Cell Biol 2023; 25:1600-1615. [PMID: 37857833 PMCID: PMC11005034 DOI: 10.1038/s41556-023-01248-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 09/01/2023] [Indexed: 10/21/2023]
Abstract
A widespread strategy employed by pathogens to establish infection is to inhibit host-cell protein synthesis. Legionella pneumophila, an intracellular bacterial pathogen and the causative organism of Legionnaires' disease, secretes a subset of protein effectors into host cells that inhibit translation elongation. Mechanistic insights into how the bacterium targets translation elongation remain poorly defined. We report here that the Legionella effector SidI functions in an unprecedented way as a transfer-RNA mimic that directly binds to and glycosylates the ribosome. The 3.1 Å cryo-electron microscopy structure of SidI reveals an N-terminal domain with an 'inverted L' shape and surface-charge distribution characteristic of tRNA mimicry, and a C-terminal domain that adopts a glycosyl transferase fold that licenses SidI to utilize GDP-mannose as a sugar precursor. This coupling of tRNA mimicry and enzymatic action endows SidI with the ability to block protein synthesis with a potency comparable to ricin, one of the most powerful toxins known. In Legionella-infected cells, the translational pausing activated by SidI elicits a stress response signature mimicking the ribotoxic stress response, which is activated by elongation inhibitors that induce ribosome collisions. SidI-mediated effects on the ribosome activate the stress kinases ZAKα and p38, which in turn drive an accumulation of the protein activating transcription factor 3 (ATF3). Intriguingly, ATF3 escapes the translation block imposed by SidI, translocates to the nucleus and orchestrates the transcription of stress-inducible genes that promote cell death, revealing a major role for ATF3 in the response to collided ribosome stress. Together, our findings elucidate a novel mechanism by which a pathogenic bacterium employs tRNA mimicry to hijack a ribosome-to-nuclear signalling pathway that regulates cell fate.
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Affiliation(s)
- Advait Subramanian
- G.W. Hooper Foundation, University of California at San Francisco, San Francisco, CA, USA
- Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
| | - Lan Wang
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
| | - Tom Moss
- G.W. Hooper Foundation, University of California at San Francisco, San Francisco, CA, USA
- Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, CA, USA
| | - Mark Voorhies
- Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, CA, USA
| | - Smriti Sangwan
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
| | - Erica Stevenson
- Gladstone Institute of Data Science and Biotechnology, J. Gladstone Institutes, San Francisco, CA, USA
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, CA, USA
- Quantitative Biosciences Institute, University of California at San Francisco, San Francisco, CA, USA
| | - Ernst H Pulido
- Gladstone Institute of Data Science and Biotechnology, J. Gladstone Institutes, San Francisco, CA, USA
| | - Samentha Kwok
- Department of Cell and Tissue Biology, University of California at San Francisco, San Francisco, CA, USA
| | - Robert J Chalkley
- Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, CA, USA
| | - Kathy H Li
- Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, CA, USA
| | - Nevan J Krogan
- Gladstone Institute of Data Science and Biotechnology, J. Gladstone Institutes, San Francisco, CA, USA
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, CA, USA
- Quantitative Biosciences Institute, University of California at San Francisco, San Francisco, CA, USA
| | - Danielle L Swaney
- Gladstone Institute of Data Science and Biotechnology, J. Gladstone Institutes, San Francisco, CA, USA
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, CA, USA
- Quantitative Biosciences Institute, University of California at San Francisco, San Francisco, CA, USA
| | - Alma L Burlingame
- Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, CA, USA
| | - Stephen N Floor
- Department of Cell and Tissue Biology, University of California at San Francisco, San Francisco, CA, USA
- Helen Diller Family Comprehensive Cancer Center, University of California at San Francisco, San Francisco, CA, USA
| | - Anita Sil
- Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Peter Walter
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA.
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, CA, USA.
- Bay Area Institute of Science, Altos Labs, Redwood City, CA, USA.
| | - Shaeri Mukherjee
- G.W. Hooper Foundation, University of California at San Francisco, San Francisco, CA, USA.
- Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, CA, USA.
- Chan Zuckerberg Biohub, San Francisco, CA, USA.
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10
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Li C, Fu J, Shao S, Luo ZQ. Legionella pneumophila exploits the endo-lysosomal network for phagosome biogenesis by co-opting SUMOylated Rab7. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.31.564884. [PMID: 37961430 PMCID: PMC10634985 DOI: 10.1101/2023.10.31.564884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
L. pneumophila strains harboring wild-type rpsL such as Lp02rpsLWT cannot replicate in mouse bone marrow-derived macrophages (BMDMs) due to induction of extensive lysosome damage and apoptosis. The mechanism of this unique infection-induced cell death remains unknown. Using a genome-wide CRISPR/Cas9 screening, we identified Hmg20a and Nol9 as host factors important for restricting strain Lp02rpsLWT in BMDMs. Depletion of Hmg20a protects macrophages from infection-induced lysosomal damage and apoptosis, allowing productive bacterial replication. The restriction imposed by Hmg20a was mediated by repressing the expression of several endo-lysosomal proteins, including the small GTPase Rab7. We found that SUMOylated Rab7 is recruited to the bacterial phagosome via SulF, a Dot/Icm effector that harbors a SUMO-interacting motif (SIM). Moreover, overexpression of Rab7 rescues intracellular growth of strain Lp02rpsLWT in BMDMs. Our results establish that L. pneumophila exploits the lysosomal network for the biogenesis of its phagosome in BMDMs.
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Affiliation(s)
- Chuang Li
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Department of Biological Sciences, Purdue University, West Lafayette, IN 47906, USA
| | - Jiaqi Fu
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Department of Biological Sciences, Purdue University, West Lafayette, IN 47906, USA
| | - Shuai Shao
- College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Zhao-Qing Luo
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Department of Biological Sciences, Purdue University, West Lafayette, IN 47906, USA
- Lead Contact
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11
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Ngwaga T, Chauhan D, Salberg AG, Shames SR. Effector-mediated subversion of proteasome activator (PA)28αβ enhances host defense against Legionella pneumophila under inflammatory and oxidative stress conditions. PLoS Pathog 2023; 19:e1011473. [PMID: 37347796 PMCID: PMC10321654 DOI: 10.1371/journal.ppat.1011473] [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: 05/03/2022] [Revised: 07/05/2023] [Accepted: 06/09/2023] [Indexed: 06/24/2023] Open
Abstract
Legionella pneumophila is a natural pathogen of amoebae that causes Legionnaires' Disease in immunocompromised individuals via replication within macrophages. L. pneumophila virulence and intracellular replication hinges on hundreds of Dot/Icm-translocated effector proteins, which are essential for biogenesis of the replication-permissive Legionella-containing vacuole (LCV). However, effector activity can also enhance mammalian host defense via effector-triggered immunity. The L. pneumophila effector LegC4 is important for virulence in amoebae but enhances host defense against L. pneumophila in the mouse lung and, uniquely, within macrophages activated with either tumor necrosis factor (TNF) or interferon (IFN)-γ. The mechanism by which LegC4 potentiates cytokine-mediated host defense in macrophages is unknown. Here, we found that LegC4 enhances cytokine-mediated phagolysosomal fusion with Legionella-containing vacuole (LCV) and binds host proteasome activator (PA)28α, which forms a heterooligomer with PA28β to facilitate ubiquitin-independent proteasomal degradation of oxidant-damaged (carbonylated) proteins. We found that oxidative stress was sustained in the presence of LegC4 and that the LegC4 restriction phenotype was relieved in PA28αβ-deficient macrophages and in the lungs of mice in vivo. Our data also show that oxidative stress is sufficient for LegC4-mediated restriction in macrophages producing PA28αβ. PA28αβ has been traditionally associated with antigen presentation; however, our data support a novel mechanism whereby effector-mediated subversion of PA28αβ enhances cell-autonomous host defense against L. pneumophila under inflammatory and oxidative stress conditions. This work provides a solid foundation to evaluate induced proteasome regulators as mediators of innate immunity.
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Affiliation(s)
- Tshegofatso Ngwaga
- Division of Biology, Kansas State University, Manhattan, Kansas, United States of America
| | - Deepika Chauhan
- Division of Biology, Kansas State University, Manhattan, Kansas, United States of America
| | - Abigail G. Salberg
- Division of Biology, Kansas State University, Manhattan, Kansas, United States of America
| | - Stephanie R. Shames
- Division of Biology, Kansas State University, Manhattan, Kansas, United States of America
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
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12
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Viana F, Boucontet L, Laghi V, Schator D, Ibranosyan M, Jarraud S, Colucci-Guyon E, Buchrieser C. Hiding in the yolk: A unique feature of Legionella pneumophila infection of zebrafish. PLoS Pathog 2023; 19:e1011375. [PMID: 37155695 DOI: 10.1371/journal.ppat.1011375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 05/18/2023] [Accepted: 04/19/2023] [Indexed: 05/10/2023] Open
Abstract
The zebrafish has become a powerful model organism to study host-pathogen interactions. Here, we developed a zebrafish model to dissect the innate immune response to Legionella pneumophila during infection. We show that L. pneumophila cause zebrafish larvae death in a dose dependent manner. Additionally, we show that macrophages are the first line of defence and cooperate with neutrophils to clear the infection. Immunocompromised humans have an increased propensity to develop pneumonia, when either macrophages or neutrophils are depleted, these "immunocompromised" larvae become lethally sensitive to L. pneumophila. Also, as observed in human infections, the adaptor signalling molecule Myd88 is not required to control disease in the larvae. Furthermore, proinflammatory cytokine genes il1β and tnf-α were upregulated during infection, recapitulating key immune responses seen in human infection. Strikingly, we uncovered a previously undescribed infection phenotype in zebrafish larvae, whereby bloodborne, wild type L. pneumophila invade and grow in the larval yolk region, a phenotype not observed with a type IV secretion system deficient mutant that cannot translocate effectors into its host cell. Thus, zebrafish larva represents an innovative L. pneumophila infection model that mimics important aspects of the human immune response to L. pneumophila infection and will allow the elucidation of mechanisms by which type IV secretion effectors allow L. pneumophila to cross host cell membranes and obtain nutrients from nutrient rich environments.
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Affiliation(s)
- Flávia Viana
- Institut Pasteur, Université Paris Cité, Biologie des Bactéries Intracellulaires and CNRS UMR 6047, Paris, France
| | - Laurent Boucontet
- Institut Pasteur, Unité Macrophages et Développement de l'Immunité and CNRS UMR 3738, Paris, France
| | - Valerio Laghi
- Institut Pasteur, Unité Macrophages et Développement de l'Immunité and CNRS UMR 3738, Paris, France
| | - Daniel Schator
- Institut Pasteur, Université Paris Cité, Biologie des Bactéries Intracellulaires and CNRS UMR 6047, Paris, France
- Sorbonne Université, Collège doctoral, Paris, France
| | - Marine Ibranosyan
- National Reference Centre of Legionella, Institute of Infectious Agents, Hospices Civils de Lyon, Lyon, France
| | - Sophie Jarraud
- National Reference Centre of Legionella, Institute of Infectious Agents, Hospices Civils de Lyon, Lyon, France
- Centre International de Recherche en Infectiologie, Université Lyon 1, UMR CNRS 5308, Inserm U1111, ENS de Lyon, Lyon, France
| | - Emma Colucci-Guyon
- Institut Pasteur, Unité Macrophages et Développement de l'Immunité and CNRS UMR 3738, Paris, France
| | - Carmen Buchrieser
- Institut Pasteur, Université Paris Cité, Biologie des Bactéries Intracellulaires and CNRS UMR 6047, Paris, France
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13
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Machtens DA, Willerding JM, Eschenburg S, Reubold TF. Crystal structure of the N-terminal domain of the effector protein SidI of Legionella pneumophila reveals a glucosyl transferase domain. Biochem Biophys Res Commun 2023; 661:50-55. [PMID: 37087798 DOI: 10.1016/j.bbrc.2023.04.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 04/13/2023] [Indexed: 04/25/2023]
Abstract
The Gram-negative bacterium Legionella pneumophila is an accidental human pathogen that can cause a life-threatening respiratory infection called Legionellosis. In the course of infection, L. pneumophila injects more than 300 effector proteins into the host cell. The effector proteins modify the intracellular environment in order to create a stable compartment for proliferation within the host cell. The effector protein SidI has been shown to potently inhibit host translation upon translocation. SidI is able to interact with the translation elongation factor eEF1A, which has been hypothesized to be a target of SidI. A postulated glycosyltransferase domain in the C-terminal half may be responsible for the toxic effect of SidI. Here, we present the crystal structure of an N-terminal fragment of SidI containing residues 37-573. The structure is divided into three subdomains, two of which display a novel fold. The third subdomain shows close structural homology to GT-B fold glycosyltransferases. Based on structural analysis we predict that the two previously identified residues R453 and E482 assume roles in the catalytic activity of SidI. Furthermore, we show that the N-terminal fragment of SidI is able to directly interact with a postulated target, the translation elongation factor eEF1A.
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Affiliation(s)
- Dominik A Machtens
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany; Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Jonas M Willerding
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Susanne Eschenburg
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany; Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Thomas F Reubold
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.
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14
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Yang JL, Li D, Zhan XY. Concept about the Virulence Factor of Legionella. Microorganisms 2022; 11:microorganisms11010074. [PMID: 36677366 PMCID: PMC9867486 DOI: 10.3390/microorganisms11010074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/23/2022] [Accepted: 12/23/2022] [Indexed: 12/29/2022] Open
Abstract
Pathogenic species of Legionella can infect human alveolar macrophages through Legionella-containing aerosols to cause a disease called Legionellosis, which has two forms: a flu-like Pontiac fever and severe pneumonia named Legionnaires' disease (LD). Legionella is an opportunistic pathogen that frequently presents in aquatic environments as a biofilm or protozoa parasite. Long-term interaction and extensive co-evolution with various genera of amoebae render Legionellae pathogenic to infect humans and also generate virulence differentiation and heterogeneity. Conventionally, the proteins involved in initiating replication processes and human macrophage infections have been regarded as virulence factors and linked to pathogenicity. However, because some of the virulence factors are associated with the infection of protozoa and macrophages, it would be more accurate to classify them as survival factors rather than virulence factors. Given that the molecular basis of virulence variations among non-pathogenic, pathogenic, and highly pathogenic Legionella has not yet been elaborated from the perspective of virulence factors, a comprehensive explanation of how Legionella infects its natural hosts, protozoans, and accidental hosts, humans is essential to show a novel concept regarding the virulence factor of Legionella. In this review, we overviewed the pathogenic development of Legionella from protozoa, the function of conventional virulence factors in the infections of protozoa and macrophages, the host's innate immune system, and factors involved in regulating the host immune response, before discussing a probably new definition for the virulence factors of Legionella.
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15
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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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16
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Fraschilla I, Evavold CL. Biting the hand that feeds: Metabolic determinants of cell fate during infection. Front Immunol 2022; 13:923024. [DOI: 10.3389/fimmu.2022.923024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 09/14/2022] [Indexed: 11/13/2022] Open
Abstract
Metabolic shifts can occur in cells of the innate immune system in response to microbial infection. Whether these metabolic shifts benefit host defense and propagation of an immune response appears to be context dependent. In an arms race, host-adapted microbes and mammalian cells vie for control of biosynthetic machinery, organelles, and metabolites. Herein, we discuss the intersection of host metabolism and cell-intrinsic immunity with implications for cell fate during infection. Sensation of microbial ligands in isolation results in host metabolic shifts that imbues normal innate immune function, such as cytokine secretion. However, living microbes have an arsenal of effectors and strategies to subvert cell-intrinsic immune responses by manipulating host metabolism. Consequently, host metabolism is monitored as an indicator of invasion or manipulation by a pathogen, primarily through the actions of guard proteins and inflammasome pathways. In this review, we frame initiation of cell-intrinsic immunity in the context of host metabolism to include a physiologic “Goldilocks zone” of allowable shifts with guard circuits monitoring wide perturbations away from this zone for the initiation of innate immune responses. Through comparison of studies with purified microbial ligands, dead microbes, and live pathogens we may begin to understand how shifts in metabolism determine the outcome of host-pathogen interactions.
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17
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Lockwood DC, Amin H, Costa TRD, Schroeder GN. The Legionella pneumophila Dot/Icm type IV secretion system and its effectors. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35639581 DOI: 10.1099/mic.0.001187] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
To prevail in the interaction with eukaryotic hosts, many bacterial pathogens use protein secretion systems to release virulence factors at the host–pathogen interface and/or deliver them directly into host cells. An outstanding example of the complexity and sophistication of secretion systems and the diversity of their protein substrates, effectors, is the Defective in organelle trafficking/Intracellular multiplication (Dot/Icm) Type IVB secretion system (T4BSS) of
Legionella pneumophila
and related species.
Legionella
species are facultative intracellular pathogens of environmental protozoa and opportunistic human respiratory pathogens. The Dot/Icm T4BSS translocates an exceptionally large number of effectors, more than 300 per
L. pneumophila
strain, and is essential for evasion of phagolysosomal degradation and exploitation of protozoa and human macrophages as replicative niches. Recent technological advancements in the imaging of large protein complexes have provided new insight into the architecture of the T4BSS and allowed us to propose models for the transport mechanism. At the same time, significant progress has been made in assigning functions to about a third of
L. pneumophila
effectors, discovering unprecedented new enzymatic activities and concepts of host subversion. In this review, we describe the current knowledge of the workings of the Dot/Icm T4BSS machinery and provide an overview of the activities and functions of the to-date characterized effectors in the interaction of
L. pneumophila
with host cells.
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Affiliation(s)
- Daniel C Lockwood
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL, Northern Ireland, UK
| | - Himani Amin
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | - Tiago R D Costa
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | - Gunnar N Schroeder
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL, Northern Ireland, UK
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18
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Glycosylating Effectors of Legionella pneumophila: Finding the Sweet Spots for Host Cell Subversion. Biomolecules 2022; 12:biom12020255. [PMID: 35204756 PMCID: PMC8961657 DOI: 10.3390/biom12020255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 01/30/2022] [Accepted: 01/31/2022] [Indexed: 02/04/2023] Open
Abstract
Work over the past two decades clearly defined a significant role of glycosyltransferase effectors in the infection strategy of the Gram-negative, respiratory pathogen Legionella pneumophila. Identification of the glucosyltransferase effectors Lgt1-3, specifically modifying elongation factor eEF1A, disclosed a novel mechanism of host protein synthesis manipulation by pathogens and illuminated its impact on the physiological state of the target cell, in particular cell cycle progression and immune and stress responses. Recent characterization of SetA as a general O-glucosyltransferase with a wide range of targets including the proteins Rab1 and Snx1, mediators of membrane transport processes, and the discovery of new types of glycosyltransferases such as LtpM and SidI indicate that the vast effector arsenal might still hold more so-far unrecognized family members with new catalytic features and substrates. In this article, we review our current knowledge regarding these fascinating biomolecules and discuss their role in introducing new or overriding endogenous post-translational regulatory mechanisms enabling the subversion of eukaryotic cells by L. pneumophila.
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19
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Wibawa RR, Li P, McCaffrey K, Hartland EL. Using Genomic Deletion Mutants to Investigate Effector-Triggered Immunity During Legionella pneumophila Infection. Methods Mol Biol 2022; 2523:23-41. [PMID: 35759189 DOI: 10.1007/978-1-0716-2449-4_3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Legionella pneumophila is an intracellular bacterial pathogen that uses a type IV secretion system (T4SS), termed Dot/Icm, to secrete more than 330 virulence effector proteins into the infected host cell. Many Dot/Icm effectors are involved in biogenesis of the Legionella-containing vacuole (LCV), which allows intracellular bacterial replication in environmental amoebae and alveolar macrophages. Through their activity, some effectors trigger the mammalian host immune response in a phenomenon termed effector-triggered immunity (ETI). Here, we describe a protocol to create and use L. pneumophila genome deletion mutants to identify effector(s) that alter pro-inflammatory cytokine production and bacterial clearance in the lungs of mice.
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Affiliation(s)
- Rachelia R Wibawa
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
- Department of Molecular and Translational Science, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC, Australia
| | - Pengfei Li
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
- Department of Molecular and Translational Science, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC, Australia
- National Clinical Research Center for Hematologic Diseases, Soochow University, Suzhou, China
| | - Kathleen McCaffrey
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
- Department of Molecular and Translational Science, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC, Australia
| | - Elizabeth L Hartland
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia.
- Department of Molecular and Translational Science, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC, Australia.
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20
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Budowa IV systemu sekrecji Legionella pneumophilai jego znaczenie w patogenezie. POSTEP HIG MED DOSW 2021. [DOI: 10.2478/ahem-2021-0023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstrakt
Bakterie Legionella pneumophila w środowisku naturalnym pasożytują wewnątrz komórek wybranych gatunków pierwotniaków, a po przedostaniu się do sztucznych systemów dystrybucji wody stają się ważnym czynnikiem etiologicznym zapalenia płuc u ludzi. Główną cechą determinującą patogenność tych bakterii jest zdolność do życia i replikacji w makrofagach płucnych, czyli w komórkach wyspecjalizowanych do fagocytozy, zabijania i trawienia mikroorganizmów. Warunkiem wstępnym rozwoju infekcji jest przełamanie mechanizmów bójczych makrofagów i utworzenie wakuoli replikacyjnej LCV (Legionella containing vacuole). Biogeneza wakuoli LCV jest możliwa dzięki sprawnemu funkcjonowaniu IV systemu sekrecji Dot/Icm, który jest wielobiałkowym, złożonym kompleksem umiejscowionym w wewnętrznej i zewnętrznej membranie osłony komórkowej bakterii. System Dot/Icm liczy 27 elementów, na które składają się m.in. kompleks rdzeniowo-transmembranowy, tworzący strukturalny szkielet całego systemu oraz kompleks białek sprzęgających. Geny kodujące komponenty systemu Dot/Icm są zorganizowane na dwóch regionach chromosomu bak-teryjnego. System sekrecji Dot/Icm umożliwia L. pneumophila wprowadzenie do cytozolu komórki gospodarza ponad 300 białek efektorowych, których skoordynowane działanie powoduje utrzymanie integralności błony wakuoli replikacyjnej oraz pozwala na manipulowanie różnymi procesami komórki. Ważnym elementem strategii wewnątrzkomórkowego namnażania się L. pneumophila jest modulowanie transportu pęcherzykowego, interakcja z retikulum endoplazmatycznym oraz zakłócenie biosyntezy białek, procesów autofagii i apoptozy komórki gospodarza. Poznanie złożonych mechanizmów regulacji i funkcji białek efektorowych systemu Dot/Icm ma decydujące znaczenie w zapobieganiu i leczeniu choroby legionistów.
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21
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Ibe NU, Subramanian A, Mukherjee S. Non-canonical activation of the ER stress sensor ATF6 by Legionella pneumophila effectors. Life Sci Alliance 2021; 4:4/12/e202101247. [PMID: 34635501 PMCID: PMC8507491 DOI: 10.26508/lsa.202101247] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 09/29/2021] [Accepted: 10/01/2021] [Indexed: 12/16/2022] Open
Abstract
Legionella pneumophila secretes toxins into the host cell that induce the non-canonical processing and activation of the ER stress sensor and transcription factor ATF6 via a mechanism that is distinct from the canonical pathway activated by unfolded protein buildup. The intracellular bacterial pathogen Legionella pneumophila (L.p.) secretes ∼330 effector proteins into the host cell to sculpt an ER-derived replicative niche. We previously reported five L.p. effectors that inhibit IRE1, a key sensor of the homeostatic unfolded protein response (UPR) pathway. In this study, we discovered a subset of L.p. toxins that selectively activate the UPR sensor ATF6, resulting in its cleavage, nuclear translocation, and target gene transcription. In a deviation from the conventional model, this L.p.–dependent activation of ATF6 does not require its transport to the Golgi or its cleavage by the S1P/S2P proteases. We believe that our findings highlight the unique regulatory control that L.p. exerts upon the three UPR sensors and expand the repertoire of bacterial proteins that selectively perturb host homeostatic pathways.
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Affiliation(s)
- Nnejiuwa U Ibe
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA.,George Williams Hooper Foundation, University of California, San Francisco, San Francisco, CA, USA
| | - Advait Subramanian
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA.,George Williams Hooper Foundation, University of California, San Francisco, San Francisco, CA, USA.,Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Shaeri Mukherjee
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA .,George Williams Hooper Foundation, University of California, San Francisco, San Francisco, CA, USA
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22
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Modulation of the mTOR pathway plays a central role in dendritic cell functions after Echinococcus granulosus antigen recognition. Sci Rep 2021; 11:17238. [PMID: 34446757 PMCID: PMC8390662 DOI: 10.1038/s41598-021-96435-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 07/09/2021] [Indexed: 12/12/2022] Open
Abstract
Immune evasion is a hallmark of persistent echinococcal infection, comprising modulation of innate immune cells and antigen-specific T cell responses. However, recognition of Echinococcus granulosus by dendritic cells (DCs) is a key determinant of the host's response to this parasite. Given that mTOR signaling pathway has been described as a regulator linking metabolism and immune function in DCs, we reported for the first time in these cells, global translation levels, antigen uptake, phenotype, cytokine transcriptional levels, and splenocyte priming activity upon recognition of the hydatid fluid (HF) and the highly glycosylated laminar layer (LL). We found that LL induced a slight up-regulation of CD86 and MHC II in DCs and also stimulated the production of IL-6 and TNF-α. By contrast, HF did not increase the expression of any co-stimulatory molecules, but also down-modulated CD40 and stimulated the expression of the anti-inflammatory cytokine IL-10. Both parasitic antigens promoted protein synthesis through mTOR activation. The use of rapamycin decreased the expression of the cytokines tested, empowered the down-modulation of CD40 and also reduced splenocyte proliferation. Finally, we showed that E. granulosus antigens increase the amounts of LC3-positive structures in DCs which play critical roles in the presentation of these antigens to T cells.
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23
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Chatterjee S, Yabaji SM, Rukhlenko OS, Bhattacharya B, Waligurski E, Vallavoju N, Ray S, Kholodenko BN, Brown LE, Beeler AB, Ivanov AR, Kobzik L, Porco JA, Kramnik I. Channeling macrophage polarization by rocaglates increases macrophage resistance to Mycobacterium tuberculosis. iScience 2021; 24:102845. [PMID: 34381970 PMCID: PMC8333345 DOI: 10.1016/j.isci.2021.102845] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 02/22/2021] [Accepted: 07/09/2021] [Indexed: 12/12/2022] Open
Abstract
Macrophages contribute to host immunity and tissue homeostasis via alternative activation programs. M1-like macrophages control intracellular bacterial pathogens and tumor progression. In contrast, M2-like macrophages shape reparative microenvironments that can be conducive for pathogen survival or tumor growth. An imbalance of these macrophages phenotypes may perpetuate sites of chronic unresolved inflammation, such as infectious granulomas and solid tumors. We have found that plant-derived and synthetic rocaglates sensitize macrophages to low concentrations of the M1-inducing cytokine IFN-gamma and inhibit their responsiveness to IL-4, a prototypical activator of the M2-like phenotype. Treatment of primary macrophages with rocaglates enhanced phagosome-lysosome fusion and control of intracellular mycobacteria. Thus, rocaglates represent a novel class of immunomodulators that can direct macrophage polarization toward the M1-like phenotype in complex microenvironments associated with hypofunction of type 1 and/or hyperactivation of type 2 immunity, e.g., chronic bacterial infections, allergies, and, possibly, certain tumors.
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Affiliation(s)
- Sujoy Chatterjee
- Pulmonary Center, Department of Medicine, Boston University School of Medicine, National Emerging Infectious Diseases Laboratories (NEIDL), Boston University, Boston, MA 02118, USA
| | - Shivraj M. Yabaji
- Pulmonary Center, Department of Medicine, Boston University School of Medicine, National Emerging Infectious Diseases Laboratories (NEIDL), Boston University, Boston, MA 02118, USA
| | - Oleksii S. Rukhlenko
- Systems Biology Ireland, School of Medicine, University College Dublin, Dublin 4, Ireland
| | - Bidisha Bhattacharya
- Pulmonary Center, Department of Medicine, Boston University School of Medicine, National Emerging Infectious Diseases Laboratories (NEIDL), Boston University, Boston, MA 02118, USA
| | - Emily Waligurski
- Pulmonary Center, Department of Medicine, Boston University School of Medicine, National Emerging Infectious Diseases Laboratories (NEIDL), Boston University, Boston, MA 02118, USA
| | - Nandini Vallavoju
- Department of Chemistry, Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA 02215, USA
| | - Somak Ray
- Barnett Institute of Chemical and Biological Analysis, Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA
| | - Boris N. Kholodenko
- Systems Biology Ireland, School of Medicine, University College Dublin, Dublin 4, Ireland
- Department of Pharmacology, Yale University School of Medicine, New Haven, USA
| | - Lauren E. Brown
- Department of Chemistry, Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA 02215, USA
| | - Aaron B. Beeler
- Department of Chemistry, Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA 02215, USA
| | - Alexander R. Ivanov
- Barnett Institute of Chemical and Biological Analysis, Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA
| | - Lester Kobzik
- Department of Environmental Health, Harvard School of Public Health, Boston, MA 02115, USA
| | - John A. Porco
- Department of Chemistry, Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA 02215, USA
| | - Igor Kramnik
- Pulmonary Center, Department of Medicine, Boston University School of Medicine, National Emerging Infectious Diseases Laboratories (NEIDL), Boston University, Boston, MA 02118, USA
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24
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Pei G, Zyla J, He L, Moura-Alves P, Steinle H, Saikali P, Lozza L, Nieuwenhuizen N, Weiner J, Mollenkopf HJ, Ellwanger K, Arnold C, Duan M, Dagil Y, Pashenkov M, Boneca IG, Kufer TA, Dorhoi A, Kaufmann SH. Cellular stress promotes NOD1/2-dependent inflammation via the endogenous metabolite sphingosine-1-phosphate. EMBO J 2021; 40:e106272. [PMID: 33942347 PMCID: PMC8246065 DOI: 10.15252/embj.2020106272] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 03/25/2021] [Accepted: 03/29/2021] [Indexed: 12/13/2022] Open
Abstract
Cellular stress has been associated with inflammation, yet precise underlying mechanisms remain elusive. In this study, various unrelated stress inducers were employed to screen for sensors linking altered cellular homeostasis and inflammation. We identified the intracellular pattern recognition receptors NOD1/2, which sense bacterial peptidoglycans, as general stress sensors detecting perturbations of cellular homeostasis. NOD1/2 activation upon such perturbations required generation of the endogenous metabolite sphingosine‐1‐phosphate (S1P). Unlike peptidoglycan sensing via the leucine‐rich repeats domain, cytosolic S1P directly bound to the nucleotide binding domains of NOD1/2, triggering NF‐κB activation and inflammatory responses. In sum, we unveiled a hitherto unknown role of NOD1/2 in surveillance of cellular homeostasis through sensing of the cytosolic metabolite S1P. We propose S1P, an endogenous metabolite, as a novel NOD1/2 activator and NOD1/2 as molecular hubs integrating bacterial and metabolic cues.
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Affiliation(s)
- Gang Pei
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Joanna Zyla
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany.,Department of Data Science and Engineering, Silesian University of Technology, Gliwice, Poland
| | - Lichun He
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Pedro Moura-Alves
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany.,Nuffield Department of Medicine, Ludwig Institute for Cancer Research, University of Oxford, Oxford, UK
| | - Heidrun Steinle
- Department of Immunology, Institute of Nutritional Medicine, University of Hohenheim, Stuttgart, Germany
| | - Philippe Saikali
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Laura Lozza
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Natalie Nieuwenhuizen
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - January Weiner
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany
| | | | - Kornelia Ellwanger
- Department of Immunology, Institute of Nutritional Medicine, University of Hohenheim, Stuttgart, Germany
| | - Christine Arnold
- Department of Immunology, Institute of Nutritional Medicine, University of Hohenheim, Stuttgart, Germany
| | - Mojie Duan
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yulia Dagil
- Institute of Immunology of the Federal Medical-Biological Agency of Russia, Moscow, Russia
| | - Mikhail Pashenkov
- Institute of Immunology of the Federal Medical-Biological Agency of Russia, Moscow, Russia
| | - Ivo Gomperts Boneca
- Institut Pasteur, Department of Microbiology, Biology and Genetics of the Bacterial Cell Wall, Paris, France.,CNRS UMR2001, Integrative and Molecular Microbiology, Paris, France.,INSERM, Équipe AVENIR, Paris, France
| | - Thomas A Kufer
- Department of Immunology, Institute of Nutritional Medicine, University of Hohenheim, Stuttgart, Germany
| | - Anca Dorhoi
- Institute of Immunology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.,Faculty of Mathematics and Natural Sciences, University of Greifswald, Greifswald, Germany
| | - Stefan He Kaufmann
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany.,Hagler Institute for Advanced Study at Texas A&M University, College Station, TX, USA
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25
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Chauhan D, Shames SR. Pathogenicity and Virulence of Legionella: Intracellular replication and host response. Virulence 2021; 12:1122-1144. [PMID: 33843434 PMCID: PMC8043192 DOI: 10.1080/21505594.2021.1903199] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Bacteria of the genus Legionella are natural pathogens of amoebae that can cause a severe pneumonia in humans called Legionnaires’ Disease. Human disease results from inhalation of Legionella-contaminated aerosols and subsequent bacterial replication within alveolar macrophages. Legionella pathogenicity in humans has resulted from extensive co-evolution with diverse genera of amoebae. To replicate intracellularly, Legionella generates a replication-permissive compartment called the Legionella-containing vacuole (LCV) through the concerted action of hundreds of Dot/Icm-translocated effector proteins. In this review, we present a collective overview of Legionella pathogenicity including infection mechanisms, secretion systems, and translocated effector function. We also discuss innate and adaptive immune responses to L. pneumophila, the implications of Legionella genome diversity and future avenues for the field.
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Affiliation(s)
- Deepika Chauhan
- Division of Biology, Kansas State University, Manhattan, Kansas, USA
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26
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Effectors Targeting the Unfolded Protein Response during Intracellular Bacterial Infection. Microorganisms 2021; 9:microorganisms9040705. [PMID: 33805575 PMCID: PMC8065698 DOI: 10.3390/microorganisms9040705] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 03/21/2021] [Accepted: 03/24/2021] [Indexed: 12/12/2022] Open
Abstract
The unfolded protein response (UPR) is a homeostatic response to endoplasmic reticulum (ER) stress within eukaryotic cells. The UPR initiates transcriptional and post-transcriptional programs to resolve ER stress; or, if ER stress is severe or prolonged, initiates apoptosis. ER stress is a common feature of bacterial infection although the role of the UPR in host defense is only beginning to be understood. While the UPR is important for host defense against pore-forming toxins produced by some bacteria, other bacterial effector proteins hijack the UPR through the activity of translocated effector proteins that facilitate intracellular survival and proliferation. UPR-mediated apoptosis can limit bacterial replication but also often contributes to tissue damage and disease. Here, we discuss the dual nature of the UPR during infection and the implications of UPR activation or inhibition for inflammation and immunity as illustrated by different bacterial pathogens.
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27
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The metaeffector MesI regulates the activity of the Legionella effector SidI through direct protein-protein interactions. Microbes Infect 2021; 23:104794. [PMID: 33571674 DOI: 10.1016/j.micinf.2021.104794] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 12/10/2020] [Accepted: 01/26/2021] [Indexed: 12/25/2022]
Abstract
To create an intracellular niche permissive for its replication, Legionella pneumophila uses hundreds of effectors to target a wide variety of host proteins and manipulate specific host processes such as immune response, and vesicle trafficking. To avoid unwanted disruption of host physiology, this pathogen also imposes precise control of its virulence by the use of effectors called metaeffectors to regulate the activity of other effectors. A number of effector/metaeffector pairs with distinct regulatory mechanisms have been characterized, including abrogation of protein modifications, direct modification of the effector and direct binding to the catalytic pocket of the cognate effector. Recently, MesI (Lpg2505) was found to be a metaeffector of SidI, an effector involved in inhibiting host protein translation. Here we demonstrate that MesI functions by inhibiting the activity of SidI via direct protein-protein interactions. We show that this interaction occurs within L. pneumophila and thus interferes with the translocation of SidI into host cells. We also solved the structure of MesI, which suggests that this protein does not have an active site similar to any known enzymes. Analysis of deletion mutants allowed the identification of regions within SidI and MesI that are important for their interactions.
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28
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Ngwaga T, Chauhan D, Shames SR. Mechanisms of Effector-Mediated Immunity Revealed by the Accidental Human Pathogen Legionella pneumophila. Front Cell Infect Microbiol 2021; 10:593823. [PMID: 33614523 PMCID: PMC7886983 DOI: 10.3389/fcimb.2020.593823] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 12/22/2020] [Indexed: 12/25/2022] Open
Abstract
Many Gram-negative bacterial pathogens employ translocated virulence factors, termed effector proteins, to facilitate their parasitism of host cells and evade host anti-microbial defenses. However, eukaryotes have evolved to detect effector-mediated virulence strategies through a phenomenon termed effector-triggered immunity (ETI). Although ETI was discovered in plants, a growing body of literature demonstrates that metazoans also utilize effector-mediated immunity to detect and clear bacterial pathogens. This mini review is focused on mechanisms of effector-mediated immune responses by the accidental human pathogen Legionella pneumophila. We highlight recent advancements in the field and discuss the future prospects of harnessing effectors for the development of novel therapeutics, a critical need due to the prevalence and rapid spread of antibiotic resistance.
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Affiliation(s)
- Tshegofatso Ngwaga
- Division of Biology, Kansas State University, Manhattan, KS, United States
| | - Deepika Chauhan
- Division of Biology, Kansas State University, Manhattan, KS, United States
| | - Stephanie R Shames
- Division of Biology, Kansas State University, Manhattan, KS, United States
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29
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Affecting the Effectors: Regulation of Legionella pneumophila Effector Function by Metaeffectors. Pathogens 2021; 10:pathogens10020108. [PMID: 33499048 PMCID: PMC7911563 DOI: 10.3390/pathogens10020108] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/19/2021] [Accepted: 01/20/2021] [Indexed: 11/24/2022] Open
Abstract
Many bacterial pathogens utilize translocated virulence factors called effectors to successfully infect their host. Within the host cell, effector proteins facilitate pathogen replication through subversion of host cell targets and processes. Legionella pneumophila is a Gram-negative intracellular bacterial pathogen that relies on hundreds of translocated effectors to replicate within host phagocytes. Within this large arsenal of translocated effectors is a unique subset of effectors called metaeffectors, which target and regulate other effectors. At least one dozen metaeffectors are encoded by L. pneumophila; however, mechanisms by which they promote virulence are largely unknown. This review details current knowledge of L pneumophila metaeffector function, challenges associated with their identification, and potential avenues to reveal the contribution of metaeffectors to bacterial pathogenesis.
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30
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Thompson D, Watt JA, Brissette CA. Host transcriptome response to Borrelia burgdorferi sensu lato. Ticks Tick Borne Dis 2020; 12:101638. [PMID: 33360384 DOI: 10.1016/j.ttbdis.2020.101638] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 11/30/2020] [Accepted: 12/02/2020] [Indexed: 10/22/2022]
Abstract
The host immune response to infection is a well-coordinated system of innate and adaptive immune cells working in concert to prevent the colonization and dissemination of a pathogen. While this typically leads to a beneficial outcome and the suppression of disease pathogenesis, the Lyme borreliosis bacterium, Borrelia burgdorferi sensu lato, can elicit an immune profile that leads to a deleterious state. As B. burgdorferi s.l. produces no known toxins, it is suggested that the immune and inflammatory response of the host are responsible for the manifestation of symptoms, including flu-like symptoms, musculoskeletal pain, and cognitive disorders. The past several years has seen a substantial increase in the use of microarray and sequencing technologies to investigate the transcriptome response induced by B. burgdorferi s.l., thus enabling researchers to identify key factors and pathways underlying the pathophysiology of Lyme borreliosis. In this review we present the major host transcriptional outcomes induced by the bacterium across several studies and discuss the overarching theme of the host inflammatory and immune response, and how it influences the pathology of Lyme borreliosis.
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Affiliation(s)
- Derick Thompson
- Department of Biomedical Sciences, University of North Dakota, Grand Forks, ND, United States.
| | - John A Watt
- Department of Biomedical Sciences, University of North Dakota, Grand Forks, ND, United States.
| | - Catherine A Brissette
- Department of Biomedical Sciences, University of North Dakota, Grand Forks, ND, United States.
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31
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Besic V, Habibolahi F, Noël B, Rupp S, Genovesio A, Lebreton A. Coordination of transcriptional and translational regulations in human epithelial cells infected by Listeria monocytogenes. RNA Biol 2020; 17:1492-1507. [PMID: 32584699 PMCID: PMC7549700 DOI: 10.1080/15476286.2020.1777380] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 05/04/2020] [Accepted: 05/28/2020] [Indexed: 12/12/2022] Open
Abstract
The invasion of mammalian cells by intracellular bacterial pathogens reshuffles their gene expression and functions; however, we lack dynamic insight into the distinct control levels that shape the host response. Here, we have addressed the respective contribution of transcriptional and translational regulations during a time-course of infection of human intestinal epithelial cells by an epidemic strain of Listeria monocytogenes, using transcriptome analysis paralleled with ribosome profiling. Upregulations were dominated by early transcriptional activation of pro-inflammatory genes, whereas translation inhibition appeared as the major driver of downregulations. Instead of a widespread but transient shutoff, translation inhibition affected specifically and durably transcripts encoding components of the translation machinery harbouring a 5'-terminal oligopyrimidine motif. Pre-silencing the most repressed target gene (PABPC1) slowed down the intracellular multiplication of Listeria monocytogenes, suggesting that the infected host cell can benefit from the repression of genes involved in protein synthesis and thereby better control infection.
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Affiliation(s)
- Vinko Besic
- Bacterial Infection & RNA Destiny Group, Institut de biologie de l’ENS (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Fatemeh Habibolahi
- Bacterial Infection & RNA Destiny Group, Institut de biologie de l’ENS (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France
- Computational Biology and Bioinformatics Group, Institut de biologie de l’ENS (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Benoît Noël
- Bacterial Infection & RNA Destiny Group, Institut de biologie de l’ENS (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France
- Computational Biology and Bioinformatics Group, Institut de biologie de l’ENS (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Sebastian Rupp
- Bacterial Infection & RNA Destiny Group, Institut de biologie de l’ENS (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Auguste Genovesio
- Computational Biology and Bioinformatics Group, Institut de biologie de l’ENS (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Alice Lebreton
- Bacterial Infection & RNA Destiny Group, Institut de biologie de l’ENS (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France
- INRAE, IBENS, Paris, France
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32
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Liu X, Boyer MA, Holmgren AM, Shin S. Legionella-Infected Macrophages Engage the Alveolar Epithelium to Metabolically Reprogram Myeloid Cells and Promote Antibacterial Inflammation. Cell Host Microbe 2020; 28:683-698.e6. [PMID: 32841604 DOI: 10.1016/j.chom.2020.07.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/18/2020] [Accepted: 07/27/2020] [Indexed: 01/05/2023]
Abstract
Alveolar macrophages are among the first immune cells that respond to inhaled pathogens. However, numerous pathogens block macrophage-intrinsic immune responses, making it unclear how robust antimicrobial responses are generated. The intracellular bacterium Legionella pneumophila inhibits host translation, thereby impairing cytokine production by infected macrophages. Nevertheless, Legionella-infected macrophages induce an interleukin-1 (IL-1)-dependent inflammatory cytokine response by recruited monocytes and other cells that controls infection. How IL-1 directs these cells to produce inflammatory cytokines is unknown. Here, we show that collaboration with the alveolar epithelium is critical for controlling infection. IL-1 induces the alveolar epithelium to produce granulocyte-macrophage colony-stimulating factor (GM-CSF). Intriguingly, GM-CSF signaling amplifies inflammatory cytokine production in recruited monocytes by enhancing Toll-like receptor (TLR)-induced glycolysis. Our findings reveal that alveolar macrophages engage alveolar epithelial signals to metabolically reprogram monocytes for antibacterial inflammation.
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Affiliation(s)
- Xin Liu
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mark A Boyer
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Alicia M Holmgren
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sunny Shin
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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33
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Tabatabaei N, Hou S, Kim KW, Tahmasebi S. Signaling pathways that control mRNA translation initiation in macrophages. Cell Signal 2020; 73:109700. [PMID: 32593651 DOI: 10.1016/j.cellsig.2020.109700] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 06/11/2020] [Accepted: 06/23/2020] [Indexed: 12/14/2022]
Abstract
Translational control in mammalian cells plays a critical role in regulating differentiation, cell growth, cell cycle and response to diverse stresses. Macrophages are one of the most versatile cell types in the body. They are professional phagocytic cells that can be found in almost all tissues and adapt tissue-specific functions. Recent studies highlight the importance of translational control in macrophages during invasion of pathogens, exposure to cytokines and in the context of tissue specific functions. In this review, we summarize the current knowledge regarding the role of mRNA translational control in regulation of macrophages.
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Affiliation(s)
- Negar Tabatabaei
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA
| | - Shikun Hou
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA
| | - Ki-Wook Kim
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA.
| | - Soroush Tahmasebi
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA.
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34
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Beck WHJ, Kim D, Das J, Yu H, Smolka MB, Mao Y. Glucosylation by the Legionella Effector SetA Promotes the Nuclear Localization of the Transcription Factor TFEB. iScience 2020; 23:101300. [PMID: 32622269 PMCID: PMC7334434 DOI: 10.1016/j.isci.2020.101300] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 05/19/2020] [Accepted: 06/16/2020] [Indexed: 02/01/2023] Open
Abstract
Legionella pneumophila is an intracellular pathogen that requires nutrients from the host for its replication. It has been shown that replicating L. pneumophila prefers amino acids as main sources of carbon and energy. The homeostasis of amino acids in eukaryotic cells is regulated by the transcription factor EB (TFEB), which translocates into the nucleus and activates genes for autophagy and lysosomal biogenesis. Here we show that the Legionella effector SetA causes a robust nuclear translocation of TFEB when exogenously expressed in mammalian cells and that the translocation is dependent on the glucosyltransferase activity of SetA. We further show that SetA directly glucosylates TFEB at multiple sites. Our findings of TFEB glucosylation by SetA may suggest an alternative strategy for exploiting host nutrients in addition to the control of host mTORC1 signaling by L. pneumophila. Our results provide further insight into the molecular mechanism of the delicate TFEB nuclear shuttling.
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Affiliation(s)
- Wendy H J Beck
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Dongsung Kim
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Jishnu Das
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA; Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Haiyuan Yu
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA; Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Marcus B Smolka
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Yuxin Mao
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
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35
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Mameri RM, Bodennec J, Bezin L, Demanèche S. Mitigation of Expression of Virulence Genes in Legionella pneumophila Internalized in the Free-Living Amoeba Willaertia magna C2c Maky. Pathogens 2020; 9:pathogens9060447. [PMID: 32517040 PMCID: PMC7350332 DOI: 10.3390/pathogens9060447] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 05/29/2020] [Accepted: 06/03/2020] [Indexed: 12/11/2022] Open
Abstract
Legionella pneumophila is a human pathogen responsible for a severe form of pneumonia named Legionnaire disease. Its natural habitat is aquatic environments, being in a free state or intracellular parasites of free-living amoebae, such as Acanthamoeba castellanii. This pathogen is able to replicate within some amoebae. Willaertia magna C2c Maky, a non-pathogenic amoeba, was previously demonstrated to resist to L. pneumophila and even to be able to eliminate the L. pneumophila strains Philadelphia, Lens, and Paris. Here, we studied the induction of seven virulence genes of three L. pneumophila strains (Paris, Philadelphia, and Lens) within W. magna C2c Maky in comparison within A. castellanii and with the gene expression level of L. pneumophila strains alone used as controls. We defined a gene expression-based virulence index to compare easily and without bias the transcript levels in different conditions and demonstrated that W. magna C2c Maky did not increase the virulence of L. pneumophila strains in contrast to A. castellanii. These results confirmed the non-permissiveness of W. magna C2c Maky toward L. pneumophila strains.
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Affiliation(s)
| | - Jacques Bodennec
- Lyon Neuroscience Research Center CRNL UMR5292 U1028, University of Lyon, Univ Lyon 1, CNRS, Inserm, 69500 Bron, France; (J.B.); (L.B.)
| | - Laurent Bezin
- Lyon Neuroscience Research Center CRNL UMR5292 U1028, University of Lyon, Univ Lyon 1, CNRS, Inserm, 69500 Bron, France; (J.B.); (L.B.)
| | - Sandrine Demanèche
- R&D Department, Amoéba, 69680 Chassieu, France;
- Correspondence: ; Tel.: +33-(04)-2669-1600
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36
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Denzer L, Schroten H, Schwerk C. From Gene to Protein-How Bacterial Virulence Factors Manipulate Host Gene Expression During Infection. Int J Mol Sci 2020; 21:ijms21103730. [PMID: 32466312 PMCID: PMC7279228 DOI: 10.3390/ijms21103730] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 02/06/2023] Open
Abstract
Bacteria evolved many strategies to survive and persist within host cells. Secretion of bacterial effectors enables bacteria not only to enter the host cell but also to manipulate host gene expression to circumvent clearance by the host immune response. Some effectors were also shown to evade the nucleus to manipulate epigenetic processes as well as transcription and mRNA procession and are therefore classified as nucleomodulins. Others were shown to interfere downstream with gene expression at the level of mRNA stability, favoring either mRNA stabilization or mRNA degradation, translation or protein stability, including mechanisms of protein activation and degradation. Finally, manipulation of innate immune signaling and nutrient supply creates a replicative niche that enables bacterial intracellular persistence and survival. In this review, we want to highlight the divergent strategies applied by intracellular bacteria to evade host immune responses through subversion of host gene expression via bacterial effectors. Since these virulence proteins mimic host cell enzymes or own novel enzymatic functions, characterizing their properties could help to understand the complex interactions between host and pathogen during infections. Additionally, these insights could propose potential targets for medical therapy.
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37
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Christensen LM, Sule P, Cirillo SLG, Strain M, Plumlee Q, Adams LG, Cirillo JD. Legionnaires' Disease Mortality in Guinea Pigs Involves the p45 Mobile Genomic Element. J Infect Dis 2020; 220:1700-1710. [PMID: 31268152 PMCID: PMC6782102 DOI: 10.1093/infdis/jiz340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 07/01/2019] [Indexed: 12/21/2022] Open
Abstract
Background Legionella can cause Legionnaires’ disease, a potentially fatal form of pneumonia that occurs as sporadic epidemics. Not all strains display the same propensity to cause disease in humans. Because Legionella pneumophila serogroup 1 is responsible for >85% of infections, the majority of studies have examined this serogroup, but there are 3 commonly used laboratory strains: L pneumophila serogroup 1 Philadelphia (Phil-1)-derived strains JR32 and Lp01 and 130b-derived strain AA100. Methods We evaluated the ability of Phil-1, JR32, Lp01, and AA100 to cause disease in guinea pigs. Results We found that, although Phil-1, JR32, and AA100 cause an acute pneumonia and death by 4 days postinfection (100%), strain Lp01 does not cause mortality (0%). We also noted that Lp01 lacks a mobile element, designated p45, whose presence correlates with virulence. Transfer of p45 into Lp01 results in recovery of the ability of this strain to cause mortality, leads to more pronounced disease, and correlates with increased interferon-γ levels in the lungs and spleens before death. Conclusions These observations suggest a mechanism of Legionnaires’ disease pathogenesis due to the presence of type IVA secretion systems that cause higher mortality due to overinduction of a proinflammatory response in the host.
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Affiliation(s)
- Lanette M Christensen
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University Health Science Center, Bryan
| | - Preeti Sule
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University Health Science Center, Bryan
| | - Suat L G Cirillo
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University Health Science Center, Bryan
| | - Madison Strain
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University Health Science Center, Bryan
| | - Quinci Plumlee
- Department of Veterinary Pathobiology, Texas A&M University, College Station
| | - L Garry Adams
- Department of Veterinary Pathobiology, Texas A&M University, College Station
| | - Jeffrey D Cirillo
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University Health Science Center, Bryan
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Machtens DA, Willerding JM, Eschenburg S, Reubold TF. Crystal structure of the metaeffector MesI (Lpg2505) from Legionella pneumophila. Biochem Biophys Res Commun 2020; 527:696-701. [PMID: 32423822 DOI: 10.1016/j.bbrc.2020.05.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 05/04/2020] [Indexed: 10/24/2022]
Abstract
Persistence and replication of the gram-negative bacterium Legionella pneumophila in the human host cell depend on so-called effector proteins that target diverse cellular functions and modulate them in favor of the pathogen. We solved the crystal structure of the L. pneumophila effector protein MesI de novo to a resolution of 2.2 Å. The 34 kDa polypeptide chain folds into two distinct α-helical domains. The larger C-terminal domain shows similarity to tetratricopeptide repeat proteins. Using size-exclusion chromatography, we confirmed that MesI binds tightly to full-length SidI and that deletion of either the N- or the C-terminus weakens the interaction. Based on the three-dimensional structure of MesI we suggest a possible binding mode for SidI and identified two homologs of MesI within the proteome of L. pneumophila that do not bind to SidI, but may act as specific inhibitors of other yet to be identified effectors.
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Affiliation(s)
- Dominik A Machtens
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany; Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Jonas M Willerding
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany; Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Susanne Eschenburg
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany; Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Thomas F Reubold
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.
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Belyi Y. Targeting Eukaryotic mRNA Translation by Legionella pneumophila. Front Mol Biosci 2020; 7:80. [PMID: 32411722 PMCID: PMC7201127 DOI: 10.3389/fmolb.2020.00080] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 04/07/2020] [Indexed: 02/01/2023] Open
Abstract
Legionella is a gram-negative microorganism and an infectious agent of pneumonia in humans. It is an intracellular pathogen and multiplies in different eukaryotic cells like amoebae, ciliated protozoa, macrophages, monocytes, and lung epithelial cells. Proliferation of L. pneumophila in eukaryotic cells depends on its type 4 secretion system, which delivers an arsenal of bacterial effector proteins to cytoplasm of its host. Once within the cytoplasm, effectors modify a broad range of host activities, including mRNA translation. Translation is inhibited by Legionella through the action of several effector proteins including Lgt1, Lgt2, Lgt3, SidI, LegK4, SidL, and RavX. Lgt1-3 and SidI target elongation factors: Lgt1-3 mono-glucosylate elongation factor eEF1A, while SidI binds eEF1A, and eEF1Bγ. Effector LegK4 inhibits protein synthesis by phosphorylating Hsp70 proteins, while SidL and RavX have no defined targets in protein synthesis machinery thus far. In addition to direct inhibition of protein synthesis, SidI also affects the stress response, whereas Lgt1-3 – unfolded protein response and cell-cycle progression of host cells. Whether manipulation of these processes is linked to canonical or non-canonical function(s) of targeted elongation factors remains unknown.
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Affiliation(s)
- Yury Belyi
- Gamaleya Research Centre for Epidemiology and Microbiology, Moscow, Russia
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40
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The Legionella pneumophila Metaeffector Lpg2505 (MesI) Regulates SidI-Mediated Translation Inhibition and Novel Glycosyl Hydrolase Activity. Infect Immun 2020; 88:IAI.00853-19. [PMID: 32122942 DOI: 10.1128/iai.00853-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 02/27/2020] [Indexed: 12/19/2022] Open
Abstract
Legionella pneumophila, the etiological agent of Legionnaires' disease, employs an arsenal of hundreds of Dot/Icm-translocated effector proteins to facilitate replication within eukaryotic phagocytes. Several effectors, called metaeffectors, function to regulate the activity of other Dot/Icm-translocated effectors during infection. The metaeffector Lpg2505 is essential for L. pneumophila intracellular replication only when its cognate effector, SidI, is present. SidI is a cytotoxic effector that interacts with the host translation factor eEF1A and potently inhibits eukaryotic protein translation by an unknown mechanism. Here, we evaluated the impact of Lpg2505 on SidI-mediated phenotypes and investigated the mechanism of SidI function. We determined that Lpg2505 binds with nanomolar affinity to SidI and suppresses SidI-mediated inhibition of protein translation. SidI binding to eEF1A and Lpg2505 is not mutually exclusive, and the proteins bind distinct regions of SidI. We also discovered that SidI possesses GDP-dependent glycosyl hydrolase activity and that this activity is regulated by Lpg2505. We have therefore renamed Lpg2505 MesI (metaeffector of SidI). This work reveals novel enzymatic activity for SidI and provides insight into how intracellular replication of L. pneumophila is regulated by a metaeffector.
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41
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Colgan TJ, Carolan JC, Sumner S, Blaxter ML, Brown MJF. Infection by the castrating parasitic nematode Sphaerularia bombi changes gene expression in Bombus terrestris bumblebee queens. INSECT MOLECULAR BIOLOGY 2020; 29:170-182. [PMID: 31566835 DOI: 10.1111/imb.12618] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 08/20/2019] [Accepted: 09/13/2019] [Indexed: 06/10/2023]
Abstract
Parasitism can result in dramatic changes in host phenotype, which are themselves underpinned by genes and their expression. Understanding how hosts respond at the molecular level to parasites can therefore reveal the molecular architecture of an altered host phenotype. The entomoparasitic nematode Sphaerularia bombi is a parasite of bumblebee (Bombus) hosts where it induces complex behavioural changes and host castration. To examine this interaction at the molecular level, we performed genome-wide transcriptional profiling using RNA-Sequencing (RNA-Seq) of S. bombi-infected Bombus terrestris queens at two critical time-points: during and just after overwintering diapause. We found that infection by S. bombi affects the transcription of genes underlying host biological processes associated with energy usage, translation, and circadian rhythm. We also found that the parasite affects the expression of immune genes, including members of the Toll signalling pathway providing evidence for a novel interaction between the parasite and the host immune response. Taken together, our results identify host biological processes and genes affected by an entomoparasitic nematode providing the first steps towards a molecular understanding of this ecologically important host-parasite interaction.
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Affiliation(s)
- T J Colgan
- Department of Zoology, School of Natural Sciences, University of Dublin, Trinity College, Dublin, Ireland
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
- School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
| | - J C Carolan
- Department of Biology, Maynooth University, Maynooth, County Kildare, Ireland
| | - S Sumner
- Centre for Biodiversity and Environment Research, University College London, London, UK
| | - M L Blaxter
- School of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK
| | - M J F Brown
- Centre of Ecology, Evolution and Behaviour, Department of Biological Sciences, Royal Holloway University of London, Egham, UK
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Paradoxical Pro-inflammatory Responses by Human Macrophages to an Amoebae Host-Adapted Legionella Effector. Cell Host Microbe 2020; 27:571-584.e7. [PMID: 32220647 DOI: 10.1016/j.chom.2020.03.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 08/08/2019] [Accepted: 02/10/2020] [Indexed: 12/14/2022]
Abstract
Legionella pneumophila has co-evolved with amoebae, their natural hosts. Upon transmission to humans, the bacteria proliferate within alveolar macrophages causing pneumonia. Here, we show L. pneumophila injects the effector LamA, an amylase, into the cytosol of human macrophage (hMDMs) and amoebae to rapidly degrade glycogen to generate cytosolic hyper-glucose. In response, hMDMs shift their metabolism to aerobic glycolysis, which directly triggers an M1-like pro-inflammatory differentiation and nutritional innate immunity through enhanced tryptophan degradation. This leads to a modest restriction of bacterial proliferation in hMDMs. In contrast, LamA-mediated glycogenolysis in amoebae deprives the natural host from the main building blocks for synthesis of the cellulose-rich cyst wall, leading to subversion of amoeba encystation. This is non-permissive for bacterial proliferation. Therefore, LamA of L. pneumophila is an amoebae host-adapted effector that subverts encystation of the amoebae natural host, and the paradoxical hMDMs' pro-inflammatory response is likely an evolutionary accident.
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43
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Divergent Evolution of Legionella RCC1 Repeat Effectors Defines the Range of Ran GTPase Cycle Targets. mBio 2020; 11:mBio.00405-20. [PMID: 32209684 PMCID: PMC7157520 DOI: 10.1128/mbio.00405-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Legionella pneumophila is a ubiquitous environmental bacterium which, upon inhalation, causes a life-threatening pneumonia termed Legionnaires’ disease. The opportunistic pathogen grows in amoebae and macrophages by employing a “type IV” secretion system, which secretes more than 300 different “effector” proteins into the host cell, where they subvert pivotal processes. The function of many of these effector proteins is unknown, and their evolution has not been studied. L. pneumophila RCC1 repeat effectors target the small GTPase Ran, a molecular switch implicated in different cellular processes such as nucleocytoplasmic transport and microtubule cytoskeleton dynamics. We provide evidence that one or more RCC1 repeat genes are distributed in two main clusters of L. pneumophila strains and have divergently evolved to target different components of the Ran GTPase activation cycle at different subcellular sites. Thus, L. pneumophila employs a sophisticated strategy to subvert host cell Ran GTPase during infection. Legionella pneumophila governs its interactions with host cells by secreting >300 different “effector” proteins. Some of these effectors contain eukaryotic domains such as the RCC1 (regulator of chromosome condensation 1) repeats promoting the activation of the small GTPase Ran. In this report, we reveal a conserved pattern of L. pneumophila RCC1 repeat genes, which are distributed in two main clusters of strains. Accordingly, strain Philadelphia-1 contains two RCC1 genes implicated in bacterial virulence, legG1 (Legionella eukaryotic gene 1), and ppgA, while strain Paris contains only one, pieG. The RCC1 repeat effectors localize to different cellular compartments and bind distinct components of the Ran GTPase cycle, including Ran modulators and the small GTPase itself, and yet they all promote the activation of Ran. The pieG gene spans the corresponding open reading frames of legG1 and a separate adjacent upstream gene, lpg1975. legG1 and lpg1975 are fused upon addition of a single nucleotide to encode a protein that adopts the binding specificity of PieG. Thus, a point mutation in pieG splits the gene, altering the effector target. These results indicate that divergent evolution of RCC1 repeat effectors defines the Ran GTPase cycle targets and that modulation of different components of the cycle might fine-tune Ran activation during Legionella infection.
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Mondino S, Schmidt S, Rolando M, Escoll P, Gomez-Valero L, Buchrieser C. Legionnaires’ Disease: State of the Art Knowledge of Pathogenesis Mechanisms of Legionella. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2020; 15:439-466. [DOI: 10.1146/annurev-pathmechdis-012419-032742] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Legionella species are environmental gram-negative bacteria able to cause a severe form of pneumonia in humans known as Legionnaires’ disease. Since the identification of Legionella pneumophila in 1977, four decades of research on Legionella biology and Legionnaires’ disease have brought important insights into the biology of the bacteria and the molecular mechanisms that these intracellular pathogens use to cause disease in humans. Nowadays, Legionella species constitute a remarkable model of bacterial adaptation, with a genus genome shaped by their close coevolution with amoebae and an ability to exploit many hosts and signaling pathways through the secretion of a myriad of effector proteins, many of which have a eukaryotic origin. This review aims to discuss current knowledge of Legionella infection mechanisms and future research directions to be taken that might answer the many remaining open questions. This research will without a doubt be a terrific scientific journey worth taking.
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Affiliation(s)
- Sonia Mondino
- Institut Pasteur, Biologie des Bactéries Intracellulaires, CNRS UMR 3525, 75015 Paris, France;, , , , ,
| | - Silke Schmidt
- Institut Pasteur, Biologie des Bactéries Intracellulaires, CNRS UMR 3525, 75015 Paris, France;, , , , ,
- Sorbonne Université, Collège doctoral, 75005 Paris, France
| | - Monica Rolando
- Institut Pasteur, Biologie des Bactéries Intracellulaires, CNRS UMR 3525, 75015 Paris, France;, , , , ,
| | - Pedro Escoll
- Institut Pasteur, Biologie des Bactéries Intracellulaires, CNRS UMR 3525, 75015 Paris, France;, , , , ,
| | - Laura Gomez-Valero
- Institut Pasteur, Biologie des Bactéries Intracellulaires, CNRS UMR 3525, 75015 Paris, France;, , , , ,
| | - Carmen Buchrieser
- Institut Pasteur, Biologie des Bactéries Intracellulaires, CNRS UMR 3525, 75015 Paris, France;, , , , ,
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45
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Margalit A, Kavanagh K, Carolan JC. Characterization of the Proteomic Response of A549 Cells Following Sequential Exposure to Aspergillus fumigatus and Pseudomonas aeruginosa. J Proteome Res 2020; 19:279-291. [PMID: 31693381 DOI: 10.1021/acs.jproteome.9b00520] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Aspergillus fumigatus and Pseudomonas aeruginosa are the most prevalent fungal and bacterial pathogens associated with cystic-fibrosis-related infections, respectively. P. aeruginosa eventually predominates as the primary pathogen, though it is unknown why this is the case. Label-free quantitative proteomics was employed to investigate the cellular response of the alveolar epithelial cell line, A549, to coexposure of A. fumigatus and P. aeruginosa. These studies revealed a significant increase in the rate of P. aeruginosa proliferation where A. fumigatus was present. Shotgun proteomics performed on A549 cells exposed to either A. fumigatus or P. aeruginosa or to A. fumigatus and P. aeruginosa sequentially revealed distinct changes to the host cell proteome in response to either or both pathogens. While key signatures of infection were retained among all pathogen-exposed groups, including changes in mitochondrial activity and energy output, the relative abundance of proteins associated with endocytosis, phagosomes, and lysosomes was decreased in sequentially exposed cells compared to cells exposed to either pathogen. Our findings indicate that A. fumigatus renders A549 cells unable to internalize bacteria, thus providing an environment in which P. aeruginosa can proliferate. This research provides novel insights into the whole-cell proteomic response of A549 cells to A. fumigatus and P. aeruginosa and highlights distinct differences in the proteome following sequential exposure to both pathogens, which may explain why P. aeruginosa can predominate.
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Affiliation(s)
- Anatte Margalit
- Department of Biology , Maynooth University , Maynooth, Co. Kildare W23F2H6 , Ireland
| | - Kevin Kavanagh
- Department of Biology , Maynooth University , Maynooth, Co. Kildare W23F2H6 , Ireland
| | - James C Carolan
- Department of Biology , Maynooth University , Maynooth, Co. Kildare W23F2H6 , Ireland
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46
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Abstract
Bacteria participate in a wide diversity of symbiotic associations with eukaryotic hosts that require precise interactions for bacterial recognition and persistence. Most commonly, host-associated bacteria interfere with host gene expression to modulate the immune response to the infection. However, many of these bacteria also interfere with host cellular differentiation pathways to create a hospitable niche, resulting in the formation of novel cell types, tissues, and organs. In both of these situations, bacterial symbionts must interact with eukaryotic regulatory pathways. Here, we detail what is known about how bacterial symbionts, from pathogens to mutualists, control host cellular differentiation across the central dogma, from epigenetic chromatin modifications, to transcription and mRNA processing, to translation and protein modifications. We identify four main trends from this survey. First, mechanisms for controlling host gene expression appear to evolve from symbionts co-opting cross-talk between host signaling pathways. Second, symbiont regulatory capacity is constrained by the processes that drive reductive genome evolution in host-associated bacteria. Third, the regulatory mechanisms symbionts exhibit correlate with the cost/benefit nature of the association. And, fourth, symbiont mechanisms for interacting with host genetic regulatory elements are not bound by native bacterial capabilities. Using this knowledge, we explore how the ubiquitous intracellular Wolbachia symbiont of arthropods and nematodes may modulate host cellular differentiation to manipulate host reproduction. Our survey of the literature on how infection alters gene expression in Wolbachia and its hosts revealed that, despite their intermediate-sized genomes, different strains appear capable of a wide diversity of regulatory manipulations. Given this and Wolbachia's diversity of phenotypes and eukaryotic-like proteins, we expect that many symbiont-induced host differentiation mechanisms will be discovered in this system.
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Affiliation(s)
- Shelbi L Russell
- Department of Molecular Cell and Developmental Biology, University of California, Santa Cruz, CA, USA.
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47
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Lopes Fischer N, Naseer N, Shin S, Brodsky IE. Effector-triggered immunity and pathogen sensing in metazoans. Nat Microbiol 2019; 5:14-26. [DOI: 10.1038/s41564-019-0623-2] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 10/29/2019] [Indexed: 01/06/2023]
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48
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Kjellin J, Pränting M, Bach F, Vaid R, Edelbroek B, Li Z, Hoeppner MP, Grabherr M, Isberg RR, Hagedorn M, Söderbom F. Investigation of the host transcriptional response to intracellular bacterial infection using Dictyostelium discoideum as a host model. BMC Genomics 2019; 20:961. [PMID: 31823727 PMCID: PMC6902447 DOI: 10.1186/s12864-019-6269-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 11/07/2019] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND During infection by intracellular pathogens, a highly complex interplay occurs between the infected cell trying to degrade the invader and the pathogen which actively manipulates the host cell to enable survival and proliferation. Many intracellular pathogens pose important threats to human health and major efforts have been undertaken to better understand the host-pathogen interactions that eventually determine the outcome of the infection. Over the last decades, the unicellular eukaryote Dictyostelium discoideum has become an established infection model, serving as a surrogate macrophage that can be infected with a wide range of intracellular pathogens. In this study, we use high-throughput RNA-sequencing to analyze the transcriptional response of D. discoideum when infected with Mycobacterium marinum and Legionella pneumophila. The results were compared to available data from human macrophages. RESULTS The majority of the transcriptional regulation triggered by the two pathogens was found to be unique for each bacterial challenge. Hallmark transcriptional signatures were identified for each infection, e.g. induction of endosomal sorting complexes required for transport (ESCRT) and autophagy genes in response to M. marinum and inhibition of genes associated with the translation machinery and energy metabolism in response to L. pneumophila. However, a common response to the pathogenic bacteria was also identified, which was not induced by non-pathogenic food bacteria. Finally, comparison with available data sets of regulation in human monocyte derived macrophages shows that the elicited response in D. discoideum is in many aspects similar to what has been observed in human immune cells in response to Mycobacterium tuberculosis and L. pneumophila. CONCLUSIONS Our study presents high-throughput characterization of D. discoideum transcriptional response to intracellular pathogens using RNA-seq. We demonstrate that the transcriptional response is in essence distinct to each pathogen and that in many cases, the corresponding regulation is recapitulated in human macrophages after infection by mycobacteria and L. pneumophila. This indicates that host-pathogen interactions are evolutionary conserved, derived from the early interactions between free-living phagocytic cells and bacteria. Taken together, our results strengthen the use of D. discoideum as a general infection model.
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Affiliation(s)
- Jonas Kjellin
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
| | - Maria Pränting
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.,Present Address: ReAct - Action on Antibiotic Resistance, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Frauke Bach
- Section Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.,Present Address: Department of Stem Cell Transplantation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Roshan Vaid
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.,Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Bart Edelbroek
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Zhiru Li
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, 02111, USA.,Present Address: New England Biolabs, Ipswich, MA, USA
| | - Marc P Hoeppner
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.,Institute of Clinical Molecular Biology, Kiel University, University Hospital Schleswig-Holstein, Kiel, Germany
| | - Manfred Grabherr
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, 02111, USA
| | - Monica Hagedorn
- Section Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.,Life Sciences and Chemistry, Jacobs University Bremen gGmbH, Group Ribogenetics, Bremen, Germany
| | - Fredrik Söderbom
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
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49
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Shah JA, Emery R, Lee B, Venkatasubramanian S, Simmons JD, Brown M, Hung CF, Prins JM, Verbon A, Hawn TR, Skerrett SJ. TOLLIP deficiency is associated with increased resistance to Legionella pneumophila pneumonia. Mucosal Immunol 2019; 12:1382-1390. [PMID: 31462698 PMCID: PMC6824992 DOI: 10.1038/s41385-019-0196-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 07/08/2019] [Accepted: 08/02/2019] [Indexed: 02/04/2023]
Abstract
Legionella pneumophila (Lp) is a flagellated, intracellular bacterium that can cause Legionnaires' disease (LD). Lp activates multiple innate immune receptors, and TOLLIP dampens MyD88-dependent signaling and may influence susceptibility to LD. We evaluated the effect of TOLLIP on innate immunity, pneumonia severity, and LD susceptibility in mouse lungs and human populations. To accomplish this, we evaluated the effect of TOLLIP on lung-specific Lp control and immune response and associated a common functional TOLLIP variant with Lp-induced innate immune responses and LD susceptibility in humans. After aerosol Lp infection, Tollip-/- mice demonstrated significantly fewer bacterial colony-forming unit and increased cytokine responses from BAL fluid. Tollip-/- macrophages also suppressed intracellular Lp replication in a flagellin-independent manner. The presence of a previously characterized, functionally active SNP associated with decreased TOLLIP mRNA transcript in monocytes was associated with increased TNF and IL-6 secretion after Lp stimulation of PBMC ex vivo. This genotype was separately associated with decreased LD susceptibility (309 controls, 88 cases, p = 0.008, OR 0.36, 95% CI 0.16-0.76) in a candidate gene association study. These results suggest that TOLLIP decreases lung-specific TLR responses to increase LD susceptibility in human populations. Better understanding of TOLLIP may lead to novel immunomodulatory therapies.
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Affiliation(s)
- Javeed A. Shah
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington.,Veterans Affairs Puget Sound Health Care System, Seattle, Washington
| | - Robyn Emery
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington
| | - Brian Lee
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington
| | | | - Jason D. Simmons
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington
| | - Melanie Brown
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington
| | - Chi F. Hung
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington
| | - Jan M. Prins
- University of Amsterdam, Amsterdam, the Netherlands
| | | | - Thomas R. Hawn
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington
| | - Shawn J. Skerrett
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington
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50
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Christenson ET, Isaac DT, Yoshida K, Lipo E, Kim JS, Ghirlando R, Isberg RR, Banerjee A. The iron-regulated vacuolar Legionella pneumophila MavN protein is a transition-metal transporter. Proc Natl Acad Sci U S A 2019; 116:17775-17785. [PMID: 31431530 PMCID: PMC6731752 DOI: 10.1073/pnas.1902806116] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Legionella pneumophila causes a potentially fatal form of pneumonia by replicating within macrophages in the Legionella-containing vacuole (LCV). Bacterial survival and proliferation within the LCV rely on hundreds of secreted effector proteins comprising high functional redundancy. The vacuolar membrane-localized MavN, hypothesized to support iron transport, is unique among effectors because loss-of-function mutations result in severe intracellular growth defects. We show here an iron starvation response by L. pneumophila after infection of macrophages that was prematurely induced in the absence of MavN, consistent with MavN granting access to limiting cellular iron stores. MavN cysteine accessibilities to a membrane-impermeant label were determined during macrophage infections, revealing a topological pattern supporting multipass membrane transporter models. Mutations to several highly conserved residues that can take part in metal recognition and transport resulted in defective intracellular growth. Purified MavN and mutant derivatives were directly tested for transporter activity after heterologous purification and liposome reconstitution. Proteoliposomes harboring MavN exhibited robust transport of Fe2+, with the severity of defect of most mutants closely mimicking the magnitude of defects during intracellular growth. Surprisingly, MavN was equivalently proficient at transporting Fe2+, Mn2+, Co2+, or Zn2+ Consequently, flooding infected cells with either Mn2+ or Zn2+ allowed collaboration with iron to enhance intracellular growth of L. pneumophila ΔmavN strains, indicating a clear role for MavN in transporting each of these ions. These findings reveal that MavN is a transition-metal-ion transporter that plays a critical role in response to iron limitation during Legionella infection.
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Affiliation(s)
- Eric T Christenson
- Unit on Structural and Chemical Biology of Membrane Proteins, Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Dervla T Isaac
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111
| | - Karin Yoshida
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111
| | - Erion Lipo
- Program in Genetics, Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111
| | - Jin-Sik Kim
- Unit on Structural and Chemical Biology of Membrane Proteins, Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111;
| | - Anirban Banerjee
- Unit on Structural and Chemical Biology of Membrane Proteins, Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892;
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