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Ong SY, Schuelein R, Wibawa RR, Thomas DW, Handoko Y, Freytag S, Bahlo M, Simpson KJ, Hartland EL. Genome-wide genetic screen identifies host ubiquitination as important for Legionella pneumophila Dot/Icm effector translocation. Cell Microbiol 2021; 23:e13368. [PMID: 34041837 DOI: 10.1111/cmi.13368] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/20/2021] [Accepted: 05/24/2021] [Indexed: 11/30/2022]
Abstract
The Dot/Icm system of Legionella pneumophila is essential for virulence and delivers a large repertoire of effectors into infected host cells to create the Legionella containing vacuole. Since the secretion of effectors via the Dot/Icm system does not occur in the absence of host cells, we hypothesised that host factors actively participate in Dot/Icm effector translocation. Here we employed a high-throughput, genome-wide siRNA screen to systematically test the effect of silencing 18,120 human genes on translocation of the Dot/Icm effector, RalF, into HeLa cells. For the primary screen, we found that silencing of 119 genes led to increased translocation of RalF, while silencing of 321 genes resulted in decreased translocation. Following secondary screening, 70 genes were successfully validated as 'high confidence' targets. Gene set enrichment analysis of siRNAs leading to decreased RalF translocation, showed that ubiquitination was the most highly overrepresented category in the pathway analysis. We further showed that two host factors, the E2 ubiquitin-conjugating enzyme, UBE2E1, and the E3 ubiquitin ligase, CUL7, were important for supporting Dot/Icm translocation and L. pneumophila intracellular replication. In summary, we identified host ubiquitin pathways as important for the efficiency of Dot/Icm effector translocation by L. pneumophila, suggesting that host-derived ubiquitin-conjugating enzymes and ubiquitin ligases participate in the translocation of Legionella effector proteins and influence intracellular persistence and survival.
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Affiliation(s)
- Sze Ying Ong
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Victoria, Australia
| | - Ralf Schuelein
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Rachelia R Wibawa
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Victoria, Australia
| | - Daniel W Thomas
- Victorian Centre for Functional Genomics, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Yanny Handoko
- Victorian Centre for Functional Genomics, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Saskia Freytag
- Division of Population Health and Immunity, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Melanie Bahlo
- Division of Population Health and Immunity, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Kaylene J Simpson
- Victorian Centre for Functional Genomics, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Elizabeth L Hartland
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.,Department of Molecular and Translational Science, Monash University, Clayton, Victoria, Australia
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2
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Schuelein R, Spencer H, Dagley LF, Li PF, Luo L, Stow JL, Abraham G, Naderer T, Gomez-Valero L, Buchrieser C, Sugimoto C, Yamagishi J, Webb AI, Pasricha S, Hartland EL. Targeting of RNA Polymerase II by a nuclear Legionella pneumophila Dot/Icm effector SnpL. Cell Microbiol 2018; 20:e12852. [PMID: 29691989 DOI: 10.1111/cmi.12852] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 03/24/2018] [Accepted: 04/11/2018] [Indexed: 12/28/2022]
Abstract
The intracellular pathogen Legionella pneumophila influences numerous eukaryotic cellular processes through the Dot/Icm-dependent translocation of more than 300 effector proteins into the host cell. Although many translocated effectors localise to the Legionella replicative vacuole, other effectors can affect remote intracellular sites. Following infection, a subset of effector proteins localises to the nucleus where they subvert host cell transcriptional responses to infection. Here, we identified Lpw27461 (Lpp2587), Lpg2519 as a new nuclear-localised effector that we have termed SnpL. Upon ectopic expression or during L. pneumophila infection, SnpL showed strong nuclear localisation by immunofluorescence microscopy but was excluded from nucleoli. Using immunoprecipitation and mass spectrometry, we determined the host-binding partner of SnpL as the eukaryotic transcription elongation factor, Suppressor of Ty5 (SUPT5H)/Spt5. SUPT5H is an evolutionarily conserved component of the DRB sensitivity-inducing factor complex that regulates RNA Polymerase II dependent mRNA processing and transcription elongation. Protein interaction studies showed that SnpL bound to the central Kyprides, Ouzounis, Woese motif region of SUPT5H. Ectopic expression of SnpL led to massive upregulation of host gene expression and macrophage cell death. The activity of SnpL further highlights the ability of L. pneumophila to control fundamental eukaryotic processes such as transcription that, in the case of SnpL, leads to global upregulation of host gene expression.
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Affiliation(s)
- Ralf Schuelein
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Hugh Spencer
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Laura F Dagley
- The Walter and Eliza Hall Institute of Medical Research and Department of Medical Biology, University of Melbourne, Parkville, Australia
| | - Peng Fei Li
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia.,Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Australia
| | - Lin Luo
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Jennifer L Stow
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Gilu Abraham
- Biomedicine Discovery Institute and Department of Biochemistry & Molecular Biology, Monash University, Clayton, Australia
| | - Thomas Naderer
- Biomedicine Discovery Institute and Department of Biochemistry & Molecular Biology, Monash University, Clayton, Australia
| | - Laura Gomez-Valero
- Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France.,CNRS UMR 3525, Paris, France
| | - Carmen Buchrieser
- Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France.,CNRS UMR 3525, Paris, France
| | - Chihiro Sugimoto
- Global Station for Zoonosis Control, GI-CoRE, Hokkaido University, Sapporo, Hokkaido, Japan.,Research Center for Zoonosis Control, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Junya Yamagishi
- Global Station for Zoonosis Control, GI-CoRE, Hokkaido University, Sapporo, Hokkaido, Japan.,Research Center for Zoonosis Control, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Andrew I Webb
- The Walter and Eliza Hall Institute of Medical Research and Department of Medical Biology, University of Melbourne, Parkville, Australia
| | - Shivani Pasricha
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia.,Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Australia
| | - Elizabeth L Hartland
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia.,Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Australia.,Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France.,Department of Molecular and Translational Science, Monash University, Clayton, Australia
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3
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King NP, Newton P, Schuelein R, Brown DL, Petru M, Zarsky V, Dolezal P, Luo L, Bugarcic A, Stanley AC, Murray RZ, Collins BM, Teasdale RD, Hartland EL, Stow JL. Soluble NSF attachment protein receptor molecular mimicry by a Legionella pneumophila Dot/Icm effector. Cell Microbiol 2015; 17:767-84. [PMID: 25488819 DOI: 10.1111/cmi.12405] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 11/10/2014] [Accepted: 12/02/2014] [Indexed: 01/17/2023]
Abstract
Upon infection, Legionella pneumophila uses the Dot/Icm type IV secretion system to translocate effector proteins from the Legionella-containing vacuole (LCV) into the host cell cytoplasm. The effectors target a wide array of host cellular processes that aid LCV biogenesis, including the manipulation of membrane trafficking. In this study, we used a hidden Markov model screen to identify two novel, non-eukaryotic soluble NSF attachment protein receptor (SNARE) homologs: the bacterial Legionella SNARE effector A (LseA) and viral SNARE homolog A proteins. We characterized LseA as a Dot/Icm effector of L. pneumophila, which has close homology to the Qc-SNARE subfamily. The lseA gene was present in multiple sequenced L. pneumophila strains including Corby and was well distributed among L. pneumophila clinical and environmental isolates. Employing a variety of biochemical, cell biological and microbiological techniques, we found that farnesylated LseA localized to membranes associated with the Golgi complex in mammalian cells and LseA interacted with a subset of Qa-, Qb- and R-SNAREs in host cells. Our results suggested that LseA acts as a SNARE protein and has the potential to regulate or mediate membrane fusion events in Golgi-associated pathways.
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Affiliation(s)
- Nathan P King
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld., Australia
| | - Patrice Newton
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Vic., Australia
| | - Ralf Schuelein
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Vic., Australia
| | - Darren L Brown
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld., Australia
| | - Marketa Petru
- Department of Parasitology, Charles University in Prague, Czech Republic
| | - Vojtech Zarsky
- Department of Parasitology, Charles University in Prague, Czech Republic
| | - Pavel Dolezal
- Department of Parasitology, Charles University in Prague, Czech Republic
| | - Lin Luo
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld., Australia
| | - Andrea Bugarcic
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld., Australia
| | - Amanda C Stanley
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld., Australia
| | - Rachael Z Murray
- Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Qld., Australia
| | - Brett M Collins
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld., Australia
| | - Rohan D Teasdale
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld., Australia
| | - Elizabeth L Hartland
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Vic., Australia
| | - Jennifer L Stow
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld., Australia
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Grzesik P, Kreuchwig A, Rutz C, Furkert J, Wiesner B, Schuelein R, Kleinau G, Gromoll J, Krause G. Differences in Signal Activation by LH and hCG are Mediated by the LH/CG Receptor's Extracellular Hinge Region. Front Endocrinol (Lausanne) 2015; 6:140. [PMID: 26441830 PMCID: PMC4585211 DOI: 10.3389/fendo.2015.00140] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 08/24/2015] [Indexed: 01/03/2023] Open
Abstract
The human lutropin (hLH)/choriogonadotropin (hCG) receptor (LHCGR) can be activated by binding two slightly different gonadotropic glycoprotein hormones, choriogonadotropin (CG) - secreted by the placenta, and lutropin (LH) - produced by the pituitary. They induce different signaling profiles at the LHCGR. This cannot be explained by binding to the receptor's leucine-rich-repeat domain (LRRD), as this binding is similar for the two hormones. We therefore speculate that there are previously unknown differences in the hormone/receptor interaction at the extracellular hinge region, which might help to understand functional differences between the two hormones. We have therefore performed a detailed study of the binding and action of LH and CG at the LHCGR hinge region. We focused on a primate-specific additional exon in the hinge region, which is located between LRRD and the serpentine domain. The segment of the hinge region encoded by exon10 was previously reported to be only relevant to hLH signaling, as the exon10-deletion receptor exhibits decreased hLH signaling, but unchanged hCG signaling. We designed an advanced homology model of the hormone/LHCGR complex, followed by experimental characterization of relevant fragments in the hinge region. In addition, we examined predictions of a helical exon10-encoded conformation by block-wise polyalanine (helix supporting) mutations. These helix preserving modifications showed no effect on hormone-induced signaling. However, introduction of a structure-disturbing double-proline mutant LHCGR-Q303P/E305P within the exon10-helix has, in contrast to exon10-deletion, no impact on hLH, but only on hCG signaling. This opposite effect on signaling by hLH and hCG can be explained by distinct sites of hormone interaction in the hinge region. In conclusion, our analysis provides details of the differences between hLH- and hCG-induced signaling that are mainly determined in the L2-beta loop of the hormones and in the hinge region of the receptor.
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Affiliation(s)
- Paul Grzesik
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Annika Kreuchwig
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Claudia Rutz
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Jens Furkert
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Burkhard Wiesner
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Ralf Schuelein
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Gunnar Kleinau
- Institute of Experimental Paediatric Endocrinology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Joerg Gromoll
- Centre of Reproductive Medicine and Andrology, University Hospital Münster, Munich, Germany
| | - Gerd Krause
- Leibniz Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
- *Correspondence: Gerd Krause, Leibniz Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, Berlin 13125, Germany,
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5
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Wong Fok Lung T, Pearson JS, Schuelein R, Hartland EL. The cell death response to enteropathogenic Escherichia coli infection. Cell Microbiol 2014; 16:1736-45. [PMID: 25266336 DOI: 10.1111/cmi.12371] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/24/2014] [Accepted: 09/26/2014] [Indexed: 12/13/2022]
Abstract
Given the critical roles of inflammation and programmed cell death in fighting infection, it is not surprising that many bacterial pathogens have evolved strategies to inactivate these defences. The causative agent of infant diarrhoea, enteropathogenic Escherichia coli (EPEC), is an extracellular, intestinal pathogen that blocks both inflammation and programmed cell death. EPEC attaches to enterocytes, remains in the gut lumen and utilizes a type III secretion system (T3SS) to inject multiple virulence effector proteins directly into the infected cell, many of which subvert host antimicrobial processes through the disruption of signalling pathways. Recently, T3SS effector proteins from EPEC have been identified that inhibit death receptor-induced apoptosis. Here we review the mechanisms used by EPEC T3SS effectors to manipulate apoptosis and promote host cell survival and discuss the role of these activities during infection.
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Affiliation(s)
- Tania Wong Fok Lung
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, 3000, Australia
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6
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Dolezal P, Aili M, Tong J, Jiang JH, Marobbio CM, Lee SF, Schuelein R, Belluzzo S, Binova E, Mousnier A, Frankel G, Giannuzzi G, Palmieri F, Gabriel K, Naderer T, Hartland EL, Lithgow T. Legionella pneumophila secretes a mitochondrial carrier protein during infection. PLoS Pathog 2012; 8:e1002459. [PMID: 22241989 PMCID: PMC3252375 DOI: 10.1371/journal.ppat.1002459] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 11/09/2011] [Indexed: 12/25/2022] Open
Abstract
The Mitochondrial Carrier Family (MCF) is a signature group of integral membrane proteins that transport metabolites across the mitochondrial inner membrane in eukaryotes. MCF proteins are characterized by six transmembrane segments that assemble to form a highly-selective channel for metabolite transport. We discovered a novel MCF member, termed Legionellanucleotide carrier Protein (LncP), encoded in the genome of Legionella pneumophila, the causative agent of Legionnaire's disease. LncP was secreted via the bacterial Dot/Icm type IV secretion system into macrophages and assembled in the mitochondrial inner membrane. In a yeast cellular system, LncP induced a dominant-negative phenotype that was rescued by deleting an endogenous ATP carrier. Substrate transport studies on purified LncP reconstituted in liposomes revealed that it catalyzes unidirectional transport and exchange of ATP transport across membranes, thereby supporting a role for LncP as an ATP transporter. A hidden Markov model revealed further MCF proteins in the intracellular pathogens, Legionella longbeachae and Neorickettsia sennetsu, thereby challenging the notion that MCF proteins exist exclusively in eukaryotic organisms. Mitochondrial carrier proteins evolved during endosymbiosis to transport substrates across the mitochondrial inner membrane. As such the proteins are associated exclusively with eukaryotic organisms. Despite this, we identified putative mitochondrial carrier proteins in the genomes of different intracellular bacterial pathogens, including Legionella pneumophila, the causative agent of Legionnaire's disease. We named the mitochondrial carrier protein from L. pneumophila LncP and determined that the protein is translocated into host cells during infection by the bacterial Dot/Icm type IV secretion system. From there, LncP accesses the classical mitochondrial import pathway and is incorporated into the mitochondrial inner membrane as an integral membrane protein. Remarkably, LncP crosses five biological membranes to reach its final location. Biochemically, LncP is a unidirectional nucleotide transporter similar to Aac1 in yeast. Although not essential for intracellular replication, the high carriage rate of lncP among isolates of L. pneumophila suggests that the ability of the pathogen to manipulate mitochondrial ATP transport assists survival of the bacteria in an intracellular environment.
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Affiliation(s)
- Pavel Dolezal
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia
- Department of Parasitology, Charles University, Prague, Czech Republic
| | - Margareta Aili
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia
| | - Janette Tong
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia
| | - Jhih-Hang Jiang
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia
| | - Carlo M. Marobbio
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, Bari, Italy
| | - Sau fung Lee
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia
| | - Ralf Schuelein
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia
| | - Simon Belluzzo
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia
| | - Eva Binova
- Department of Tropical Medicine, 1st Faculty of Medicine, Charles University in Prague and Faculty Hospital Bulovka, Prague, Czech Republic
| | - Aurelie Mousnier
- Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Gad Frankel
- Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Giulia Giannuzzi
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, Bari, Italy
| | - Ferdinando Palmieri
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, Bari, Italy
| | - Kipros Gabriel
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia
| | - Thomas Naderer
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia
| | - Elizabeth L. Hartland
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia
- * E-mail: (ELH); (TL)
| | - Trevor Lithgow
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia
- * E-mail: (ELH); (TL)
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Thilo F, Liu Y, Loddenkemper C, Schuelein R, Schmidt A, Yan Z, Zhu Z, Zakrzewicz A, Gollasch M, Tepel M. VEGF regulates TRPC6 channels in podocytes. Nephrol Dial Transplant 2011; 27:921-9. [DOI: 10.1093/ndt/gfr457] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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8
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Schuelein R, Ang DKY, van Driel IR, Hartland EL. Immune Control of Legionella Infection: An in vivo Perspective. Front Microbiol 2011; 2:126. [PMID: 21687433 PMCID: PMC3109619 DOI: 10.3389/fmicb.2011.00126] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 05/23/2011] [Indexed: 11/13/2022] Open
Abstract
Legionella pneumophila is an intracellular pathogen that replicates within alveolar macrophages. Through its ability to activate multiple host innate immune components, L. pneumophila has emerged as a useful tool to dissect inflammatory signaling pathways in macrophages. However the resolution of L. pneumophila infection in the lung requires multiple cell types and abundant cross talk between immune cells. Few studies have examined the coordination of events that lead to effective immune control of the pathogen. Here we discuss L. pneumophila interactions with macrophages and dendritic cell subsets and highlight the paucity of knowledge around how these interactions recruit and activate other immune effector cells in the lung.
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Affiliation(s)
- Ralf Schuelein
- Department of Microbiology and Immunology, University of Melbourne Parkville, Victoria, Australia
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Schuelein R, Everingham P, Kwok T. Integrin-mediated type IV secretion by Helicobacter: what makes it tick? Trends Microbiol 2011; 19:211-6. [PMID: 21371889 DOI: 10.1016/j.tim.2011.01.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Revised: 01/18/2011] [Accepted: 01/27/2011] [Indexed: 12/13/2022]
Abstract
Helicobacter pylori (Hp) employs a multi-component type IV secretion system (T4SS) to secrete the effector protein CagA into the cytosol of infected host cells. A longstanding challenge has been to identify the host cell receptor(s) involved. Two recent studies have independently unveiled human β(1) integrin as the receptor but are divided over which T4SS proteins bind to β(1) integrin. Here we revisit the two models in light of previous findings and recent progress in the field. More concerted efforts are required to fully understand the complex T4SS mechanisms that underpin Hp pathogenesis.
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Affiliation(s)
- Ralf Schuelein
- Department of Microbiology and Immunology, The University of Melbourne, Parkville, Australia
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Ang DKY, Oates CVL, Schuelein R, Kelly M, Sansom FM, Bourges D, Boon L, Hertzog PJ, Hartland EL, van Driel IR. Cutting edge: pulmonary Legionella pneumophila is controlled by plasmacytoid dendritic cells but not type I IFN. J Immunol 2010; 184:5429-33. [PMID: 20400697 DOI: 10.4049/jimmunol.1000128] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Plasmacytoid dendritic cells (pDCs) are well known as the major cell type that secretes type I IFN in response to viral infections. Their role in combating other classes of infectious organisms, including bacteria, and their mechanisms of action are poorly understood. We have found that pDCs play a significant role in the acute response to the intracellular bacterial pathogen Legionella pneumophila. pDCs were rapidly recruited to the lungs of L. pneumophila-infected mice, and depletion of pDCs resulted in increased bacterial load. The ability of pDCs to combat infection did not require type I IFN. This study points to an unappreciated role for pDCs in combating bacterial infections and indicates a novel mechanism of action for this cell type.
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Affiliation(s)
- Desmond K Y Ang
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Australia
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