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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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2
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Sheedlo MJ, Durie CL, Chung JM, Chang L, Roberts J, Swanson M, Lacy DB, Ohi MD. Cryo-EM reveals new species-specific proteins and symmetry elements in the Legionella pneumophila Dot/Icm T4SS. eLife 2021; 10:e70427. [PMID: 34519271 PMCID: PMC8486379 DOI: 10.7554/elife.70427] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Accepted: 09/14/2021] [Indexed: 01/21/2023] Open
Abstract
Legionella pneumophila is an opportunistic pathogen that causes the potentially fatal pneumonia known as Legionnaires' disease. The pathology associated with infection depends on bacterial delivery of effector proteins into the host via the membrane spanning Dot/Icm type IV secretion system (T4SS). We have determined sub-3.0 Å resolution maps of the Dot/Icm T4SS core complex by single particle cryo-EM. The high-resolution structural analysis has allowed us to identify proteins encoded outside the Dot/Icm genetic locus that contribute to the core T4SS structure. We can also now define two distinct areas of symmetry mismatch, one that connects the C18 periplasmic ring (PR) and the C13 outer membrane cap (OMC) and one that connects the C13 OMC with a 16-fold symmetric dome. Unexpectedly, the connection between the PR and OMC is DotH, with five copies sandwiched between the OMC and PR to accommodate the symmetry mismatch. Finally, we observe multiple conformations in the reconstructions that indicate flexibility within the structure.
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Affiliation(s)
- Michael J Sheedlo
- Department of Pharmacology, University of MinnesotaMinneapolisUnited States
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical CenterNashvilleUnited States
| | - Clarissa L Durie
- Life Sciences Institute, University of MichiganAnn ArborUnited States
| | - Jeong Min Chung
- Life Sciences Institute, University of MichiganAnn ArborUnited States
- Department of Biotechnology, The Catholic University of KoreaGyeonggiRepublic of Korea
| | - Louise Chang
- Life Sciences Institute, University of MichiganAnn ArborUnited States
| | - Jacquelyn Roberts
- Life Sciences Institute, University of MichiganAnn ArborUnited States
| | - Michele Swanson
- Department of Microbiology and Immunology, University Of MichiganAnn ArborUnited States
| | - Dana Borden Lacy
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical CenterNashvilleUnited States
- The Veterans Affairs Tennessee Valley Healthcare SystemNasvhilleUnited States
| | - Melanie D Ohi
- Life Sciences Institute, University of MichiganAnn ArborUnited States
- Department of Cell and Developmental Biology, University of MichiganAnn ArborUnited States
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3
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Long CM, Beare PA, Cockrell DC, Fintzi J, Tesfamariam M, Shaia CI, Heinzen RA. Contributions of lipopolysaccharide and the type IVB secretion system to Coxiella burnetii vaccine efficacy and reactogenicity. NPJ Vaccines 2021; 6:38. [PMID: 33741986 PMCID: PMC7979919 DOI: 10.1038/s41541-021-00296-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 02/12/2021] [Indexed: 12/15/2022] Open
Abstract
Coxiella burnetii is the bacterial causative agent of the zoonosis Q fever. The current human Q fever vaccine, Q-VAX®, is a fixed, whole cell vaccine (WCV) licensed solely for use in Australia. C. burnetii WCV administration is associated with a dermal hypersensitivity reaction in people with pre-existing immunity to C. burnetii, limiting wider use. Consequently, a less reactogenic vaccine is needed. Here, we investigated contributions of the C. burnetii Dot/Icm type IVB secretion system (T4BSS) and lipopolysaccharide (LPS) in protection and reactogenicity of fixed WCVs. A 32.5 kb region containing 23 dot/icm genes was deleted in the virulent Nine Mile phase I (NMI) strain and the resulting mutant was evaluated in guinea pig models of C. burnetii infection, vaccination-challenge, and post-vaccination hypersensitivity. The NMI ∆dot/icm strain was avirulent, protective as a WCV against a robust C. burnetii challenge, and displayed potentially altered reactogenicity compared to NMI. Nine Mile phase II (NMII) strains of C. burnetii that produce rough LPS, were similarly tested. NMI was significantly more protective than NMII as a WCV; however, both vaccines exhibited similar reactogenicity. Collectively, our results indicate that, like phase I LPS, the T4BSS is required for full virulence by C. burnetii. Conversely, unlike phase I LPS, the T4BSS is not required for vaccine-induced protection. LPS length does not appear to contribute to reactogenicity while the T4BSS may contribute to this response. NMI ∆dot/icm represents an avirulent phase I strain with full vaccine efficacy, illustrating the potential of genetically modified C. burnetii as improved WCVs.
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Affiliation(s)
- Carrie M Long
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA.
| | - Paul A Beare
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA
| | - Diane C Cockrell
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA
| | - Jonathan Fintzi
- Biostatistics Research Branch, Division of Clinical Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA
| | - Mahelat Tesfamariam
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA
| | - Carl I Shaia
- Rocky Mountain Veterinary Branch, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA
| | - Robert A Heinzen
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA
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4
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A multiplex CRISPR interference tool for virulence gene interrogation in Legionella pneumophila. Commun Biol 2021; 4:157. [PMID: 33542442 PMCID: PMC7862264 DOI: 10.1038/s42003-021-01672-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 11/27/2020] [Indexed: 11/08/2022] Open
Abstract
Catalytically inactive dCas9 imposes transcriptional gene repression by sterically precluding RNA polymerase activity at a given gene to which it was directed by CRISPR (cr)RNAs. This gene silencing technology, known as CRISPR interference (CRISPRi), has been employed in various bacterial species to interrogate genes, mostly individually or in pairs. Here, we developed a multiplex CRISPRi platform in the pathogen Legionella pneumophila capable of silencing up to ten genes simultaneously. Constraints on precursor-crRNA expression were overcome by combining a strong promoter with a boxA element upstream of a CRISPR array. Using crRNAs directed against virulence protein-encoding genes, we demonstrated that CRISPRi is fully functional not only during growth in axenic media, but also during macrophage infection, and that gene depletion by CRISPRi recapitulated the growth defect of deletion strains. By altering the position of crRNA-encoding spacers within the CRISPR array, our platform achieved the gradual depletion of targets that was mirrored by the severity in phenotypes. Multiplex CRISPRi thus holds great promise for probing large sets of genes in bulk in order to decipher virulence strategies of L. pneumophila and other bacterial pathogens.
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Ghosal D, Jeong KC, Chang YW, Gyore J, Teng L, Gardner A, Vogel JP, Jensen GJ. Molecular architecture, polar targeting and biogenesis of the Legionella Dot/Icm T4SS. Nat Microbiol 2019; 4:1173-1182. [PMID: 31011165 PMCID: PMC6588468 DOI: 10.1038/s41564-019-0427-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 03/12/2019] [Indexed: 01/10/2023]
Abstract
Legionella pneumophila survives and replicates inside host cells by secreting ~300 effectors through the defective in organelle trafficking (Dot)/intracellular multiplication (Icm) type IVB secretion system (T4BSS). Here, we used complementary electron cryotomography and immunofluorescence microscopy to investigate the molecular architecture and biogenesis of the Dot/Icm secretion apparatus. Electron cryotomography mapped the location of the core and accessory components of the Legionella core transmembrane subcomplex, revealing a well-ordered central channel that opens into a large, windowed secretion chamber with an unusual 13-fold symmetry. Immunofluorescence microscopy deciphered an early-stage assembly process that begins with the targeting of Dot/Icm components to the bacterial poles. Polar targeting of this T4BSS is mediated by two Dot/Icm proteins, DotU and IcmF, that, interestingly, are homologues of the T6SS membrane complex components TssL and TssM, suggesting that the Dot/Icm T4BSS is a hybrid system. Together, these results revealed that the Dot/Icm complex assembles in an 'axial-to-peripheral' pattern.
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Affiliation(s)
- Debnath Ghosal
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Kwangcheol C Jeong
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA
- Department of Animal Sciences & Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Yi-Wei Chang
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Jacob Gyore
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA
| | - Lin Teng
- Department of Animal Sciences & Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Adam Gardner
- Molecular Graphics Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Joseph P Vogel
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA.
| | - Grant J Jensen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA.
- Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA, USA.
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Christie PJ, Gomez Valero L, Buchrieser C. Biological Diversity and Evolution of Type IV Secretion Systems. Curr Top Microbiol Immunol 2019; 413:1-30. [PMID: 29536353 PMCID: PMC5912172 DOI: 10.1007/978-3-319-75241-9_1] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The bacterial type IV secretion systems (T4SSs) are a highly functionally and structurally diverse superfamily of secretion systems found in many species of Gram-negative and -positive bacteria. Collectively, the T4SSs can translocate DNA and monomeric and multimeric protein substrates to a variety of bacterial and eukaryotic cell types. Detailed phylogenomics analyses have established that the T4SSs evolved from ancient conjugation machines whose original functions were to disseminate mobile DNA elements within and between bacterial species. How members of the T4SS superfamily evolved to recognize and translocate specific substrate repertoires to prokaryotic or eukaryotic target cells is a fascinating question from evolutionary, biological, and structural perspectives. In this chapter, we will summarize recent findings that have shaped our current view of the biological diversity of the T4SSs. We focus mainly on two subtypes, designated as the types IVA (T4ASS) and IVB (T4BSS) systems that respectively are represented by the paradigmatic Agrobacterium tumefaciens VirB/VirD4 and Legionella pneumophila Dot/Icm T4SSs. We present current information about the composition and architectures of these representative systems. We also describe how these and a few related T4ASS and T4BSS members evolved as specialized nanomachines through acquisition of novel domains or subunits, a process that ultimately generated extensive genetic and structural mosaicism among this secretion superfamily. Finally, we present new phylogenomics information establishing that the T4BSSs are much more broadly distributed than initially envisioned.
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Affiliation(s)
- Peter J Christie
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin St, Houston, TX, 77030, USA.
| | - Laura Gomez Valero
- Institut Pasteur, Biologie des Bactéries Intracellulaires, 75724, Paris, France
- CNRS, UMR 3525, 75724, Paris, France
| | - Carmen Buchrieser
- Institut Pasteur, Biologie des Bactéries Intracellulaires, 75724, Paris, France
- CNRS, UMR 3525, 75724, Paris, France
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Kubori T, Nagai H. The Type IVB secretion system: an enigmatic chimera. Curr Opin Microbiol 2016; 29:22-9. [DOI: 10.1016/j.mib.2015.10.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Revised: 10/14/2015] [Accepted: 10/15/2015] [Indexed: 10/22/2022]
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Roszczenko P, Grzeszczuk M, Kobierecka P, Wywial E, Urbanowicz P, Wincek P, Nowak E, Jagusztyn-Krynicka EK. Helicobacter pylori HP0377, a member of the Dsb family, is an untypical multifunctional CcmG that cooperates with dimeric thioldisulfide oxidase HP0231. BMC Microbiol 2015; 15:135. [PMID: 26141380 PMCID: PMC4491210 DOI: 10.1186/s12866-015-0471-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 06/23/2015] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND In the genome of H. pylori 26695, 149 proteins containing the CXXC motif characteristic of thioldisulfide oxidoreductases have been identified to date. However, only two of these proteins have a thioredoxin-like fold (i.e., HP0377 and HP0231) and are periplasm-located. We have previously shown that HP0231 is a dimeric oxidoreductase that catalyzes disulfide bond formation in the periplasm. Although HP0377 was originally described as DsbC homologue, its resolved structure and location of the hp0377 gene in the genome indicate that it is a counterpart of CcmG/DsbE. RESULTS The present work shows that HP0377 is present in H. pylori cells only in a reduced form and that absence of the main periplasmic oxidase HP0231 influences its redox state. Our biochemical analysis indicates that HP0377 is a specific reductase, as it does not reduce insulin. However, it possesses disulfide isomerase activity, as it catalyzes the refolding of scrambled RNase. Additionally, although its standard redox potential is -176 mV, it is the first described CcmG protein having an acidic pKa of the N-terminal cysteine of the CXXC motif, similar to E. coli DsbA or E. coli DsbC. The CcmG proteins that play a role in a cytochrome c-maturation, both in system I and system II, are kept in the reduced form by an integral membrane protein DsbD or its analogue, CcdA. In H. pylori HP0377 is re-reduced by CcdA (HP0265); however in E. coli it remains in the oxidized state as it does not interact with E. coli DsbD. Our in vivo work also suggests that both HP0377, which plays a role in apocytochrome reduction, and HP0378, which is involved in heme transport and its ligation into apocytochrome, provide essential functions in H. pylori. CONCLUSIONS The present data, in combination with the resolved three-dimensional structure of the HP0377, suggest that HP0377 is an unusual, multifunctional CcmG protein.
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Affiliation(s)
- Paula Roszczenko
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland. .,Present address: Department of Cell Biology, Nencki Institute of Experimental Biology, PAS, Warsaw, Poland.
| | - Magdalena Grzeszczuk
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Patrycja Kobierecka
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Ewa Wywial
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Warsaw, Poland.
| | - Paweł Urbanowicz
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Piotr Wincek
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Elzbieta Nowak
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland.
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A screen of Coxiella burnetii mutants reveals important roles for Dot/Icm effectors and host autophagy in vacuole biogenesis. PLoS Pathog 2014; 10:e1004286. [PMID: 25080348 PMCID: PMC4117601 DOI: 10.1371/journal.ppat.1004286] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 06/17/2014] [Indexed: 12/18/2022] Open
Abstract
Coxiella burnetii is an intracellular pathogen that replicates in a lysosome-derived vacuole. The molecular mechanisms used by this bacterium to create a pathogen-occupied vacuole remain largely unknown. Here, we conducted a visual screen on an arrayed library of C. burnetii NMII transposon insertion mutants to identify genes required for biogenesis of a mature Coxiella-containing vacuole (CCV). Mutants defective in Dot/Icm secretion system function or the PmrAB regulatory system were incapable of intracellular replication. Several mutants with intracellular growth defects were found to have insertions in genes encoding effector proteins translocated into host cells by the Dot/Icm system. These included mutants deficient in the effector proteins Cig57, CoxCC8 and Cbu1754. Mutants that had transposon insertions in genes important in central metabolism or encoding tRNA modification enzymes were identified based on the appearance filamentous bacteria intracellularly. Lastly, mutants that displayed a multi-vacuolar phenotype were identified. All of these mutants had a transposon insertion in the gene encoding the effector protein Cig2. Whereas vacuoles containing wild type C. burnetii displayed robust accumulation of the autophagosome protein LC3, the vacuoles formed by the cig2 mutant did not contain detectible amounts of LC3. Furthermore, interfering with host autophagy during infection by wild type C. burnetii resulted in a multi-vacuolar phenotype similar to that displayed by the cig2 mutant. Thus, a functional Cig2 protein is important for interactions between the CCV and host autophagosomes and this drives a process that enhances the fusogenic properties of this pathogen-occupied organelle. Coxiella burnetii is the causative agent of the human disease Q fever. This bacterium uses the Dot/Icm type IV secretion system to deliver effectors into the cytosol of host cells. The Dot/Icm system is required for intracellular replication of C. burnetii. To determine the contribution of individual proteins to the establishment of a vacuole that supports C. burnetii replication, we conducted a visual screen on a library of C. burnetii transposon insertion mutants and identified genes required for distinct stages of intracellular replication. This approach was validated through the identification of intracellular replication mutants that included insertions in most of the dot and icm genes, and through the identification of individual effector proteins delivered into host cell by the Dot/Icm system that participate in creating a vacuole that supports intracellular replication of C. burnetii. Complementation studies showed convincingly that the effector Cig57 was critical for intracellular replication. The effector protein Cig2 was found to play a unique role in promoting homotypic fusion of C. burnetii vacuoles. Disrupting host autophagy phenocopied the defect displayed by the cig2 mutant. Thus, our visual screen has successfully identified effectors required for intracellular replication of C. burnetii and indicates that Dot/Icm-dependent subversion of host autophagy promotes homotypic fusion of CCVs.
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Native structure of a type IV secretion system core complex essential for Legionella pathogenesis. Proc Natl Acad Sci U S A 2014; 111:11804-9. [PMID: 25062693 DOI: 10.1073/pnas.1404506111] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Bacterial type IV secretion systems are evolutionarily related to conjugation systems and play a pivotal role in infection by delivering numerous virulence factors into host cells. Using transmission electron microscopy, we report the native molecular structure of the core complex of the Dot/Icm type IV secretion system encoded by Legionella pneumophila, an intracellular human pathogen. The biochemically isolated core complex, composed of at least five proteins--DotC, DotD, DotF, DotG, and DotH--has a ring-shaped structure. Intriguingly, morphologically distinct premature complexes are formed in the absence of DotG or DotF. Our data suggest that DotG forms a central channel spanning inner and outer membranes. DotF, a component dispensable for type IV secretion, plays a role in efficient embedment of DotG into the functional core complex. These results highlight a common scheme for the biogenesis of transport machinery.
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11
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Brzuszkiewicz E, Schulz T, Rydzewski K, Daniel R, Gillmaier N, Dittmann C, Holland G, Schunder E, Lautner M, Eisenreich W, Lück C, Heuner K. Legionella oakridgensis ATCC 33761 genome sequence and phenotypic characterization reveals its replication capacity in amoebae. Int J Med Microbiol 2013; 303:514-28. [PMID: 23932911 DOI: 10.1016/j.ijmm.2013.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 06/27/2013] [Accepted: 07/10/2013] [Indexed: 11/30/2022] Open
Abstract
Legionella oakridgensis is able to cause Legionnaires' disease, but is less virulent compared to L. pneumophila strains and very rarely associated with human disease. L. oakridgensis is the only species of the family legionellae which is able to grow on media without additional cysteine. In contrast to earlier publications, we found that L. oakridgensis is able to multiply in amoebae. We sequenced the genome of L. oakridgensis type strain OR-10 (ATCC 33761). The genome is smaller than the other yet sequenced Legionella genomes and has a higher G+C-content of 40.9%. L. oakridgensis lacks a flagellum and it also lacks all genes of the flagellar regulon except of the alternative sigma-28 factor FliA and the anti-sigma-28 factor FlgM. Genes encoding structural components of type I, type II, type IV Lvh and type IV Dot/Icm, Sec- and Tat-secretion systems could be identified. Only a limited set of Dot/Icm effector proteins have been recognized within the genome sequence of L. oakridgensis. Like in L. pneumophila strains, various proteins with eukaryotic motifs and eukaryote-like proteins were detected. We could demonstrate that the Dot/Icm system is essential for intracellular replication of L. oakridgensis. Furthermore, we identified new putative virulence factors of Legionella.
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Affiliation(s)
- Elzbieta Brzuszkiewicz
- Department of Genomics and Applied Microbiology & Göttinger Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August-University of Göttingen, Grisebachstr. 8, 37077 Göttingen, Germany
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12
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Nagai H, Kubori T. Type IVB Secretion Systems of Legionella and Other Gram-Negative Bacteria. Front Microbiol 2011; 2:136. [PMID: 21743810 PMCID: PMC3127085 DOI: 10.3389/fmicb.2011.00136] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Accepted: 06/11/2011] [Indexed: 12/03/2022] Open
Abstract
Type IV secretion systems (T4SSs) play a central role in the pathogenicity of many important pathogens, including Agrobacterium tumefaciens, Helicobacter pylori, and Legionella pneumophila. The T4SSs are related to bacterial conjugation systems, and are classified into two subgroups, type IVA (T4ASS) and type IVB (T4BSS). The T4BSS, which is closely related to conjugation systems of IncI plasmids, was originally found in human pathogen L. pneumophila; pathogenesis by L. pneumophila infection requires functional Dot/Icm T4BSS. A zoonotic pathogen, Coxiella burnetii, and an arthropod pathogen, Rickettsiella grylli – both of which carry T4BSSs highly similar to the Legionella Dot/Icm system – are evolutionarily closely related and comprise a monophyletic group. A growing body of bacterial genomic information now suggests that T4BSSs are not limited to Legionella and related bacteria and IncI plasmids. Here, we review the current knowledge on T4BSS apparatus and component proteins, gained mainly from studies on L. pneumophila Dot/Icm T4BSS. Recent structural studies, along with previous findings, suggest that the Dot/Icm T4BSS contains components with primary or higher-order structures similar to those in other types of secretion systems – types II, III, IVA, and VI, thus highlighting the mosaic nature of T4BSS architecture.
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Affiliation(s)
- Hiroki Nagai
- Research Institute for Microbial Diseases, Osaka University Osaka, Japan
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13
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Shevchuk O, Jäger J, Steinert M. Virulence properties of the legionella pneumophila cell envelope. Front Microbiol 2011; 2:74. [PMID: 21747794 PMCID: PMC3129009 DOI: 10.3389/fmicb.2011.00074] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Accepted: 03/30/2011] [Indexed: 01/15/2023] Open
Abstract
The bacterial envelope plays a crucial role in the pathogenesis of infectious diseases. In this review, we summarize the current knowledge of the structure and molecular composition of the Legionella pneumophila cell envelope. We describe lipopolysaccharides biosynthesis and the biological activities of membrane and periplasmic proteins and discuss their decisive functions during the pathogen–host interaction. In addition to adherence, invasion, and intracellular survival of L. pneumophila, special emphasis is laid on iron acquisition, detoxification, key elicitors of the immune response and the diverse functions of outer membrane vesicles. The critical analysis of the literature reveals that the dynamics and phenotypic plasticity of the Legionella cell surface during the different metabolic stages require more attention in the future.
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Affiliation(s)
- Olga Shevchuk
- Institut für Mikrobiologie, Technische Universität Braunschweig Braunschweig, Germany
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Nakano N, Kubori T, Kinoshita M, Imada K, Nagai H. Crystal structure of Legionella DotD: insights into the relationship between type IVB and type II/III secretion systems. PLoS Pathog 2010; 6:e1001129. [PMID: 20949065 PMCID: PMC2951367 DOI: 10.1371/journal.ppat.1001129] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 09/02/2010] [Indexed: 11/23/2022] Open
Abstract
The Dot/Icm type IVB secretion system (T4BSS) is a pivotal determinant of Legionella pneumophila pathogenesis. L. pneumophila translocate more than 100 effector proteins into host cytoplasm using Dot/Icm T4BSS, modulating host cellular functions to establish a replicative niche within host cells. The T4BSS core complex spanning the inner and outer membranes is thought to be made up of at least five proteins: DotC, DotD, DotF, DotG and DotH. DotH is the outer membrane protein; its targeting depends on lipoproteins DotC and DotD. However, the core complex structure and assembly mechanism are still unknown. Here, we report the crystal structure of DotD at 2.0 Å resolution. The structure of DotD is distinct from that of VirB7, the outer membrane lipoprotein of the type IVA secretion system. In contrast, the C-terminal domain of DotD is remarkably similar to the N-terminal subdomain of secretins, the integral outer membrane proteins that form substrate conduits for the type II and the type III secretion systems (T2SS and T3SS). A short β-segment in the otherwise disordered N-terminal region, located on the hydrophobic cleft of the C-terminal domain, is essential for outer membrane targeting of DotH and Dot/Icm T4BSS core complex formation. These findings uncover an intriguing link between T4BSS and T2SS/T3SS. Bacterial pathogens deliver virulence factors such as exotoxins and effector proteins to host cells. To accomplish this bacteria utilize specialized secretion systems such as type III and type IV secretion systems. The type IV secretion systems (T4SS) play a central role in pathogenesis by many important pathogens including Agrobacterium tumefaciens, Helicobacter pylori and Legionella pneumophila. T4SS is ancestrally related to the bacterial conjugation system and is divided into two subgroups, type IVA (T4ASS) and type IVB (T4BSS), which are derived from distinct conjugation systems. In spite of its pivotal role in bacterial pathogenesis, the structural bases and molecular mechanisms of the type IVB secretion still remain largely unknown. Here we show the crystal structure of DotD, one of the core components of Legionella T4BSS. Surprisingly, the structure of DotD is not related to those of T4ASS core components. In contrast, the structure of DotD is remarkably similar to that of a subdomain of secretin family proteins, which form substrate conduits for other types of secretion systems. This finding provides intriguing insights into the nature and the evolution of bacterial secretion systems essential for pathogenesis.
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Affiliation(s)
- Noboru Nakano
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Tomoko Kubori
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Katsumi Imada
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
- * E-mail: (KI); (HN)
| | - Hiroki Nagai
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
- * E-mail: (KI); (HN)
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15
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Proteomic analysis of growth phase-dependent expression of Legionella pneumophila proteins which involves regulation of bacterial virulence traits. PLoS One 2010; 5:e11718. [PMID: 20661449 PMCID: PMC2908689 DOI: 10.1371/journal.pone.0011718] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Accepted: 06/17/2010] [Indexed: 01/05/2023] Open
Abstract
Legionella pneumophila, which is a causative pathogen of Legionnaires' disease, expresses its virulent traits in response to growth conditions. In particular, it is known to become virulent at a post-exponential phase in vitro culture. In this study, we performed a proteomic analysis of differences in expression between the exponential phase and post-exponential phase to identify candidates associated with L. pneumophila virulence using 2-Dimentional Fluorescence Difference Gel Electrophoresis (2D-DIGE) combined with Matrix-Assisted Laser Desorption/Ionization–Mass Spectrometry (MALDI-TOF-MS). Of 68 identified proteins that significantly differed in expression between the two growth phases, 64 were up-regulated at a post-exponential phase. The up-regulated proteins included enzymes related to glycolysis, ketone body biogenesis and poly-3-hydroxybutyrate (PHB) biogenesis, suggesting that L. pneumophila may utilize sugars and lipids as energy sources, when amino acids become scarce. Proteins related to motility (flagella components and twitching motility-associated proteins) were also up-regulated, predicting that they enhance infectivity of the bacteria in host cells under certain conditions. Furthermore, 9 up-regulated proteins of unknown function were found. Two of them were identified as novel bacterial factors associated with hemolysis of sheep red blood cells (SRBCs). Another 2 were found to be translocated into macrophages via the Icm/Dot type IV secretion apparatus as effector candidates in a reporter assay with Bordetella pertussis adenylate cyclase. The study will be helpful for virulent analysis of L. pneumophila from the viewpoint of physiological or metabolic modulation dependent on growth phase.
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16
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Naka H, López CS, Crosa JH. Role of the pJM1 plasmid-encoded transport proteins FatB, C and D in ferric anguibactin uptake in the fish pathogen Vibrio anguillarum. ENVIRONMENTAL MICROBIOLOGY REPORTS 2010; 2:104-111. [PMID: 21304833 PMCID: PMC3034151 DOI: 10.1111/j.1758-2229.2009.00110.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Vibrio anguillarum serotype O1 is part of the natural flora in the aquatic habitat, but under certain circumstances it can cause terminal haemorrhagic septicemia in marine and fresh water fish due to the action of the anguibactin iron uptake system encoded by the virulence plasmid pJM1. This plasmid harbours the genes for the biosynthesis of the siderophore anguibactin and the ferric anguibactin transport proteins FatD, C, B and A encoded in the iron transport operon. The FatA protein is the outer membrane receptor for the ferric siderophore complex and the FatB lipoprotein provides the periplasmic domain for its internalization, whereas the FatC and D proteins are located in the cytoplasmic membrane and might play a role as part of the ABC transporter for internalization of the ferric siderophore. In this work we demonstrate the essential role of these two inner membrane proteins in ferric anguibactin transport and that the lipo-protein nature of FatB is not necessary for ferric anguibactin transport.
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Affiliation(s)
| | | | - Jorge H. Crosa
- For correspondence. ; Tel. (+1) 503 494 7583; Fax (+1) 503 494 6862
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17
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A chromosomally located traHIJKCLMN operon encoding a putative type IV secretion system is involved in the virulence of Yersinia ruckeri. Appl Environ Microbiol 2008; 75:937-45. [PMID: 19088314 DOI: 10.1128/aem.01377-08] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nucleotide sequence analysis of the region surrounding the pIVET8 insertion site in Yersinia ruckeri 150RiviXII, previously selected by in vivo expression technology (IVET), revealed the presence of eight genes (traHIJKCLMN [hereafter referred to collectively as the tra operon or tra cluster]), which are similar both in sequence and organization to the tra operon cluster found in the virulence-related plasmid pADAP from Serratia entomophila. Interestingly, the tra cluster of Y. ruckeri is chromosomally encoded, and no similar tra cluster has been identified yet in the genomic analysis of human pathogenic yersiniae. A traI insertional mutant was obtained by homologous recombination. Coinfection experiments with the mutant and the parental strain, as well as 50% lethal dose determinations, indicate that this operon is involved in the virulence of this bacterium. All of these results suggest the implication of the tra cluster in a virulence-related type IV secretion/transfer system. Reverse transcriptase PCR studies showed that this cluster is transcribed as an operon from a putative promoter located upstream of traH and that the mutation of traI had a polar effect. A traI::lacZY transcriptional fusion displayed higher expression levels at 18 degrees C, the temperature of occurrence of the disease, and under nutrient-limiting conditions. PCR detection analysis indicated that the tra cluster is present in 15 Y. ruckeri strains from different origins and with different plasmid profiles. The results obtained in the present study support the conclusion, already suggested by different authors, that Y. ruckeri is a very homogeneous species that is quite different from the other members of the genus Yersinia.
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18
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Isberg RR, O'Connor TJ, Heidtman M. The Legionella pneumophila replication vacuole: making a cosy niche inside host cells. Nat Rev Microbiol 2008; 7:13-24. [PMID: 19011659 PMCID: PMC2631402 DOI: 10.1038/nrmicro1967] [Citation(s) in RCA: 514] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The pathogenesis of Legionella pneumophila is derived from its growth within lung macrophages after aerosols are inhaled from contaminated water sources. Interest in this bacterium stems from its ability to manipulate host cell vesicular-trafficking pathways and establish a membrane-bound replication vacuole, making it a model for intravacuolar pathogens. Establishment of the replication compartment requires a specialized translocation system that transports a large cadre of protein substrates across the vacuolar membrane. These substrates regulate vesicle traffic and survival pathways in the host cell. This Review focuses on the strategies that L. pneumophila uses to establish intracellular growth and evaluates why this microorganism has accumulated an unprecedented number of translocated substrates that are targeted at host cells.
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Affiliation(s)
- Ralph R Isberg
- Howard Hughes Medical Institute, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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19
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Geukens N, De Buck E, Meyen E, Maes L, Vranckx L, Van Mellaert L, Anné J, Lammertyn E. The type II signal peptidase of Legionella pneumophila. Res Microbiol 2006; 157:836-41. [PMID: 17005379 DOI: 10.1016/j.resmic.2006.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 05/15/2006] [Accepted: 06/13/2006] [Indexed: 10/24/2022]
Abstract
Legionella pneumophila is a facultative intracellular Gram-negative bacterium that has become an important cause of community-acquired and nosocomial pneumonia. Recent studies concerning the unravelling of bacterial virulence have suggested the involvement of protein secretion systems in bacterial pathogenicity. In this respect, the type II signal peptidase (LspA), which is specifically required for the maturation of lipoproteins, is of particular interest. This paper reports the cloning and functional characterization of the L. pneumophila lspA gene encoding the type II signal peptidase (SPase II). Activity of the L. pneumophila LspA was demonstrated using a globomycin sensitivity assay in Escherichia coli. In L. pneumophila, the lspA gene is flanked by the isoleucyl-tRNA synthetase (ileS) gene and the gene encoding a 2-hydroxy-3-deoxy-phosphogluconate aldolase. Although there is no apparent physiological connection, transcriptional analysis demonstrated that, as in some other Gram-negative bacteria, lspA is cotranscribed with ileS in L. pneumophila. Finally, in silico analysis revealed that several proteins known to be crucial for virulence and intracellular growth of L. pneumophila are predicted to be lipoproteins. These include, in particular, proteins involved in protein secretion and motility. Results obtained strongly suggest an important role for LspA in the pathogenicity of L. pneumophila, making it a promising new target for therapeutic intervention.
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Affiliation(s)
- Nick Geukens
- Laboratory of Bacteriology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium
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Vincent CD, Friedman JR, Jeong KC, Buford EC, Miller JL, Vogel JP. Identification of the core transmembrane complex of the Legionella Dot/Icm type IV secretion system. Mol Microbiol 2006; 62:1278-91. [PMID: 17040490 DOI: 10.1111/j.1365-2958.2006.05446.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Type IV secretion systems (T4SS) are utilized by a wide range of Gram negative bacteria to deliver protein and DNA substrates to recipient cells. The best characterized T4SS are the type IVA systems, which exhibit extensive similarity to the Agrobacterium VirB T4SS. In contrast, type IVB secretion systems share almost no sequence homology to the type IVA systems, are composed of approximately twice as many proteins, and remain largely uncharacterized. Type IVB systems include the Dot/Icm systems found in the pathogens Legionella and Coxiella and the conjugative apparatus of IncI plasmids. Here we report the first extensive characterization of a type IVB system, the Legionella Dot/Icm secretion apparatus. Based on biochemical and genetic analysis, we discerned the existence of a critical five-protein subassembly that spans both bacterial membranes and comprises the core of the secretion complex. This transmembrane connection is mediated by protein dimer pairs consisting of two inner membrane proteins, DotF and DotG, which are able to independently associate with DotH/DotC/DotD in the outer membrane. The Legionella core subcomplex appears to be functionally analogous to the Agrobacterium VirB7-10 subcomplex, suggesting a remarkable conservation of the core subassembly in these evolutionarily distant type IV secretion machines.
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Affiliation(s)
- Carr D Vincent
- Department of Molecular Microbiology, Washington University, St. Louis, MO 63110, USA
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