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Malmsheimer S, Grin I, Bohn E, Franz-Wachtel M, Macek B, Sahr T, Smollich F, Chetrit D, Meir A, Roy C, Buchrieser C, Wagner S. The T4bSS of Legionella features a two-step secretion pathway with an inner membrane intermediate for secretion of transmembrane effectors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.14.584949. [PMID: 38559167 PMCID: PMC10980071 DOI: 10.1101/2024.03.14.584949] [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
To promote intracellular survival and infection, Legionella spp. translocate hundreds of effector proteins into eukaryotic host cells using a type IV b protein secretion system (T4bSS). T4bSS are well known to translocate soluble as well as transmembrane domain-containing effector proteins (TMD-effectors) but the mechanisms of secretion are still poorly understood. Herein we investigated the secretion of hydrophobic TMD-effectors, of which about 80 were previously reported to be encoded by L. pneumophila. A proteomic analysis of fractionated membranes revealed that TMD-effectors are targeted to and inserted into the bacterial inner membranes of L. pneumophila independent of the presence of a functional T4bSS. While the T4bSS chaperones IcmS and IcmW were critical for secretion of all tested TMD-effectors, they did not influence inner membrane targeting of these proteins. As for soluble effector proteins, translocation of TMD-effectors into host cells depended on a C-terminal secretion signal and this signal needed to be presented towards the cytoplasmic side of the inner membrane. A different secretion behavior of TMD- and soluble effectors and the need for small periplasmic loops within TMD-effectors provided strong evidence that TMD-effectors are secreted in a two-step secretion process: Initially, an inner membrane intermediate is formed, that is extracted towards the cytoplasmic side, possibly by the help of the type IV coupling protein complex and subsequently secreted into eukaryotic host cells by the T4bSS core complex. Overall, our study highlights the amazing versatility of T4bSS to secrete soluble and TMD-effectors from different subcellular locations of the bacterial cell.
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Affiliation(s)
- Silke Malmsheimer
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
- Current address: Institut de Recherche en Infectiologie de Montpellier, Equipe Kremer, UMR 9004 - CNRS / UM, 1919 route de Mende, 34293 Montpellier cedex 5, France
| | - Iwan Grin
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Erwin Bohn
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Institute of Medical Microbiology and Hygiene, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Mirita Franz-Wachtel
- University of Tübingen, Proteome Center Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Boris Macek
- University of Tübingen, Proteome Center Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Tobias Sahr
- Institute Pasteur, Université Paris Cité, Biologie des Bactéries Intracellulaires, 75015 Paris, France
| | - Fabian Smollich
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - David Chetrit
- Yale University, Department of Microbial Pathogenesis, 295 Congress Avenue, New Haven, CT 06536-0812, USA
| | - Amit Meir
- Yale University, Department of Microbial Pathogenesis, 295 Congress Avenue, New Haven, CT 06536-0812, USA
- Birkbeck Institute of Structural and Molecular Biology, Birkbeck and UCL, Malet Street, London WC1E 7HX, UK
- Current address: University of Glasgow, MRC Centre for Virus Research, School of Infection and Immunity, Glasgow, UK
| | - Craig Roy
- Yale University, Department of Microbial Pathogenesis, 295 Congress Avenue, New Haven, CT 06536-0812, USA
| | - Carmen Buchrieser
- Institute Pasteur, Université Paris Cité, Biologie des Bactéries Intracellulaires, 75015 Paris, France
| | - Samuel Wagner
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
- Excellence Cluster "Controlling Microbes to Fight Infections" (CMFI), Elfriede-Aulhorn-Str. 6, 72076 Tébingen, Germany
- German Center for Infection Research (DZIF), partner-site Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
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2
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Wilkins AA, Schwarz B, Torres-Escobar A, Castore R, Landry L, Latimer B, Bohrnsen E, Bosio CM, Dragoi AM, Ivanov SS. The intracellular growth of the vacuolar pathogen Legionella pneumophila is dependent on the acyl chain composition of host membranes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.19.567753. [PMID: 38045297 PMCID: PMC10690232 DOI: 10.1101/2023.11.19.567753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Legionella pneumophila is an accidental human bacterial pathogen that infects and replicates within alveolar macrophages causing a severe atypical pneumonia known as Legionnaires' disease. As a prototypical vacuolar pathogen L. pneumophila establishes a unique endoplasmic reticulum (ER)-derived organelle within which bacterial replication takes place. Bacteria-derived proteins are deposited in the host cytosol and in the lumen of the pathogen-occupied vacuole via a type IVb (T4bSS) and a type II (T2SS) secretion system respectively. These secretion system effector proteins manipulate multiple host functions to facilitate intracellular survival of the bacteria. Subversion of host membrane glycerophospholipids (GPLs) by the internalized bacteria via distinct mechanisms feature prominently in trafficking and biogenesis of the Legionella -containing vacuole (LCV). Conventional GPLs composed of a glycerol backbone linked to a polar headgroup and esterified with two fatty acids constitute the bulk of membrane lipids in eukaryotic cells. The acyl chain composition of GPLs dictates phase separation of the lipid bilayer and therefore determines the physiochemical properties of biological membranes - such as membrane disorder, fluidity and permeability. In mammalian cells, fatty acids esterified in membrane GPLs are sourced endogenously from de novo synthesis or via internalization from the exogenous pool of lipids present in serum and other interstitial fluids. Here, we exploited the preferential utilization of exogenous fatty acids for GPL synthesis by macrophages to reprogram the acyl chain composition of host membranes and investigated its impact on LCV homeostasis and L. pneumophila intracellular replication. Using saturated fatty acids as well as cis - and trans - isomers of monounsaturated fatty acids we discovered that under conditions promoting lipid packing and membrane rigidification L. pneumophila intracellular replication was significantly reduced. Palmitoleic acid - a C16:1 monounsaturated fatty acid - that promotes membrane disorder when enriched in GPLs significantly increased bacterial replication within human and murine macrophages but not in axenic growth assays. Lipidome analysis of infected macrophages showed that treatment with exogenous palmitoleic acid resulted in membrane acyl chain reprogramming in a manner that promotes membrane disorder and live-cell imaging revealed that the consequences of increasing membrane disorder impinge on several LCV homeostasis parameters. Collectively, we provide experimental evidence that L. pneumophila replication within its intracellular niche is a function of the lipid bilayer disorder and hydrophobic thickness.
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3
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Role of mitochondria in regulating immune response during bacterial infection. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2023; 374:159-200. [PMID: 36858655 DOI: 10.1016/bs.ircmb.2022.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Mitochondria are dynamic organelles of eukaryotes involved in energy production and fatty acid oxidation. Besides maintaining ATP production, calcium signaling, cellular apoptosis, and fatty acid synthesis, mitochondria are also known as the central hub of the immune system as it regulates the innate immune pathway during infection. Mitochondria mediated immune functions mainly involve regulation of reactive oxygen species production, inflammasome activation, cytokine secretion, and apoptosis of infected cells. Recent findings indicate that cellular mitochondria undergo constant biogenesis, fission, fusion and degradation, and these dynamics regulate cellular immuno-metabolism. Several intracellular pathogens target and modulate these normal functions of mitochondria to facilitate their own survival and growth. De-regulation of mitochondrial functions and dynamics favors bacterial infection and pathogens are able to protect themselves from mitochondria mediated immune responses. Here, we will discuss how mitochondria mediated anti-bacterial immune pathways help the host to evade pathogenic insult. In addition, examples of bacterial pathogens modulating mitochondrial metabolism and dynamics will also be elaborated. Study of these interactions between the mitochondria and bacterial pathogens during infection will lead to a better understanding of the mitochondrial metabolism pathways and dynamics important for the establishment of bacterial diseases. In conclusion, detailed studies on how mitochondria regulate the immune response during bacterial infection can open up new avenues to develop mitochondria centric anti-bacterial therapeutics.
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4
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Brucella effectors NyxA and NyxB target SENP3 to modulate the subcellular localisation of nucleolar proteins. Nat Commun 2023; 14:102. [PMID: 36609656 PMCID: PMC9823007 DOI: 10.1038/s41467-022-35763-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 12/23/2022] [Indexed: 01/07/2023] Open
Abstract
The cell nucleus is a primary target for intracellular bacterial pathogens to counteract immune responses and hijack host signalling pathways to cause disease. Here we identify two Brucella abortus effectors, NyxA and NyxB, that interfere with host protease SENP3, and this facilitates intracellular replication of the pathogen. The translocated Nyx effectors directly interact with SENP3 via a defined acidic patch (identified from the crystal structure of NyxB), preventing nucleolar localisation of SENP3 at late stages of infection. By sequestering SENP3, the effectors promote cytoplasmic accumulation of nucleolar AAA-ATPase NVL and ribosomal protein L5 (RPL5) in effector-enriched structures in the vicinity of replicating bacteria. The shuttling of ribosomal biogenesis-associated nucleolar proteins is inhibited by SENP3 and requires the autophagy-initiation protein Beclin1 and the SUMO-E3 ligase PIAS3. Our results highlight a nucleomodulatory function of two Brucella effectors and reveal that SENP3 is a crucial regulator of the subcellular localisation of nucleolar proteins during Brucella infection, promoting intracellular replication of the pathogen.
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5
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Ondari E, Wilkins A, Latimer B, Dragoi AM, Ivanov SS. Cellular cholesterol licenses Legionella pneumophila intracellular replication in macrophages. MICROBIAL CELL (GRAZ, AUSTRIA) 2023; 10:1-17. [PMID: 36636491 PMCID: PMC9806796 DOI: 10.15698/mic2023.01.789] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 11/28/2022] [Accepted: 11/30/2022] [Indexed: 01/03/2023]
Abstract
Host membranes are inherently critical for niche homeostasis of vacuolar pathogens. Thus, intracellular bacteria frequently encode the capacity to regulate host lipogenesis as well as to modulate the lipid composition of host membranes. One membrane component that is often subverted by vacuolar bacteria is cholesterol - an abundant lipid that mammalian cells produce de novo at the endoplasmic reticulum (ER) or acquire exogenously from serum-derived lipoprotein carriers. Legionella pneumophila is an accidental human bacterial pathogen that infects and replicates within alveolar macrophages causing a severe atypical pneumonia known as Legionnaires' disease. From within a unique ER-derived vacuole L. pneumophila promotes host lipogenesis and experimental evidence indicates that cholesterol production might be one facet of this response. Here we investigated the link between cellular cholesterol and L. pneumophila intracellular replication and discovered that disruption of cholesterol biosynthesis or cholesterol trafficking lowered bacterial replication in infected cells. These growth defects were rescued by addition of exogenous cholesterol. Conversely, bacterial growth within cholesterol-leaden macrophages was enhanced. Importantly, the growth benefit of cholesterol was observed strictly in cellular infections and L. pneumophila growth kinetics in axenic cultures did not change in the presence of cholesterol. Microscopy analyses indicate that cholesterol regulates a step in L. pneumophila intracellular lifecycle that occurs after bacteria begin to replicate within an established intracellular niche. Collectively, we provide experimental evidence that cellular cholesterol promotes L. pneumophila replication within a membrane bound organelle in infected macrophages.
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Affiliation(s)
- Edna Ondari
- Department of Microbiology and Immunology, Louisiana State University Health - Shreveport, Shreveport, LA 71130
| | - Ashley Wilkins
- Department of Microbiology and Immunology, Louisiana State University Health - Shreveport, Shreveport, LA 71130
| | - Brian Latimer
- Innovative North Louisiana Experimental Therapeutics program (INLET), Feist-Weiller Cancer Center, Louisiana State University Health - Shreveport, Shreveport, LA 71130
| | - Ana-Maria Dragoi
- Department of Molecular and Cellular Physiology, Louisiana State University Health - Shreveport, Shreveport, LA 71130.,Innovative North Louisiana Experimental Therapeutics program (INLET), Feist-Weiller Cancer Center, Louisiana State University Health - Shreveport, Shreveport, LA 71130
| | - Stanimir S. Ivanov
- Department of Microbiology and Immunology, Louisiana State University Health - Shreveport, Shreveport, LA 71130.,* Corresponding Author: Stanimir S. Ivanov, Department of Microbiology and Immunology, Louisiana State University Health - Shreveport, Shreveport, LA 71130; E-mail:
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6
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Mahmud SA, Qureshi MA, Pellegrino MW. On the offense and defense: mitochondrial recovery programs amidst targeted pathogenic assault. FEBS J 2022; 289:7014-7037. [PMID: 34270874 PMCID: PMC9192128 DOI: 10.1111/febs.16126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/24/2021] [Accepted: 07/15/2021] [Indexed: 01/13/2023]
Abstract
Bacterial pathogens employ a variety of tactics to persist in their host and promote infection. Pathogens often target host organelles in order to benefit their survival, either through manipulation or subversion of their function. Mitochondria are regularly targeted by bacterial pathogens owing to their diverse cellular roles, including energy production and regulation of programmed cell death. However, disruption of normal mitochondrial function during infection can be detrimental to cell viability because of their essential nature. In response, cells use multiple quality control programs to mitigate mitochondrial dysfunction and promote recovery. In this review, we will provide an overview of mitochondrial recovery programs including mitochondrial dynamics, the mitochondrial unfolded protein response (UPRmt ), and mitophagy. We will then discuss the various approaches used by bacterial pathogens to target mitochondria, which result in mitochondrial dysfunction. Lastly, we will discuss how cells leverage mitochondrial recovery programs beyond their role in organelle repair, to promote host defense against pathogen infection.
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Affiliation(s)
- Siraje A Mahmud
- Department of Biology, University of Texas Arlington, TX, USA
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7
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Reversible modification of mitochondrial ADP/ATP translocases by paired Legionella effector proteins. Proc Natl Acad Sci U S A 2022; 119:e2122872119. [PMID: 35653564 DOI: 10.1073/pnas.2122872119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
SignificanceMitochondria are organelles of the central metabolism that produce ATP and play fundamental roles in eukaryotic cell function and thereby become targets for pathogenic bacteria to manipulate. We found that the intracellular bacterial pathogen, Legionella pneumophila, targets mitochondrial ADP/ATP translocases (ANTs), the function of which is linked to the mitochondrial ATP synthesis. This is achieved by a pair of effector proteins, Lpg0080 and Lpg0081, which have opposing enzymatic activities as an ADP ribosyltransferase (ART) and an ADP ribosylhydrolase (ARH), respectively, coordinately regulating the chemical modification of ANTs upon infection. Our structural analyses indicate that Lpg0081 is an ARH with a noncanonical macrodomain, whose folding topology is distinct from that of the canonical macrodomain of known eukaryotic, archaeal, and bacterial proteins.
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8
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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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9
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Fu J, Zhou M, Gritsenko MA, Nakayasu ES, Song L, Luo ZQ. Legionella pneumophila modulates host energy metabolism by ADP-ribosylation of ADP/ATP translocases. eLife 2022; 11:73611. [PMID: 35084332 PMCID: PMC8820735 DOI: 10.7554/elife.73611] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Accepted: 01/26/2022] [Indexed: 11/13/2022] Open
Abstract
The intracellular pathogen Legionella pneumophila delivers more than 330 effectors into host cells by its Dot/Icm secretion system. Those effectors direct the biogenesis of the Legionella-containing vacuole (LCV) that permits its intracellular survival and replication. It has long been documented that the LCV is associated with mitochondria and a number of Dot/Icm effectors have been shown to target to this organelle. Yet, the biochemical function and host cell target of most of these effectors remain unknown. Here, we found that the Dot/Icm substrate Ceg3 (Lpg0080) is a mono-ADP-ribosyltransferase that localizes to the mitochondria in host cells where it attacks ADP/ATP translocases by ADP-ribosylation, and blunts their ADP/ATP exchange activity. The modification occurs on the second arginine residue in the -RRRMMM- element, which is conserved among all known ADP/ATP carriers from different organisms. Our results reveal modulation of host energy metabolism as a virulence mechanism for L. pneumophila.
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Affiliation(s)
- Jiaqi Fu
- Department of Biological Science, Purdue University, West Lafayette, United States
| | - Mowei Zhou
- Environmental and Molecular Sciences Division, Pacific Northwest National Laboratory, Richland, United States
| | - Marina A Gritsenko
- Biological Science Division, Pacific Northwest National Laboratory, Richland, United States
| | - Ernesto S Nakayasu
- Biological Science Division, Pacific Northwest National Laboratory, Richland, United States
| | - Lei Song
- Department of Respiratory Medicine, Jilin University, Changchun, China
| | - Zhao-Qing Luo
- Department of Biological Science, Purdue University, West Lafayette, United States
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10
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Escoll P, Platon L, Dramé M, Sahr T, Schmidt S, Rusniok C, Buchrieser C. Reverting the mode of action of the mitochondrial F OF 1-ATPase by Legionella pneumophila preserves its replication niche. eLife 2021; 10:e71978. [PMID: 34882089 PMCID: PMC8718111 DOI: 10.7554/elife.71978] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 12/06/2021] [Indexed: 01/17/2023] Open
Abstract
Legionella pneumophila, the causative agent of Legionnaires' disease, a severe pneumonia, injects via a type 4 secretion system (T4SS) more than 300 proteins into macrophages, its main host cell in humans. Certain of these proteins are implicated in reprogramming the metabolism of infected cells by reducing mitochondrial oxidative phosphorylation (OXPHOS) early after infection. Here. we show that despite reduced OXPHOS, the mitochondrial membrane potential (Δψm) is maintained during infection of primary human monocyte-derived macrophages (hMDMs). We reveal that L. pneumophila reverses the ATP-synthase activity of the mitochondrial FOF1-ATPase to ATP-hydrolase activity in a T4SS-dependent manner, which leads to a conservation of the Δψm, preserves mitochondrial polarization, and prevents macrophage cell death. Analyses of T4SS effectors known to target mitochondrial functions revealed that LpSpl is partially involved in conserving the Δψm, but not LncP and MitF. The inhibition of the L. pneumophila-induced 'reverse mode' of the FOF1-ATPase collapsed the Δψm and caused cell death in infected cells. Single-cell analyses suggested that bacterial replication occurs preferentially in hMDMs that conserved the Δψm and showed delayed cell death. This direct manipulation of the mode of activity of the FOF1-ATPase is a newly identified feature of L. pneumophila allowing to delay host cell death and thereby to preserve the bacterial replication niche during infection.
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Affiliation(s)
- Pedro Escoll
- Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR 3525ParisFrance
| | - Lucien Platon
- Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR 3525ParisFrance
- Faculté des Sciences, Université de MontpellierMontpellierFrance
| | - Mariatou Dramé
- Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR 3525ParisFrance
- Faculté des Sciences, Université de ParisParisFrance
| | - Tobias Sahr
- Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR 3525ParisFrance
| | - Silke Schmidt
- Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR 3525ParisFrance
- Sorbonne Université, Collège doctoralParisFrance
| | - Christophe Rusniok
- Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR 3525ParisFrance
| | - Carmen Buchrieser
- Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR 3525ParisFrance
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11
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Voth K, Pasricha S, Chung IYW, Wibawa RR, Zainudin ENHE, Hartland EL, Cygler M. Structural and Functional Characterization of Legionella pneumophila Effector MavL. Biomolecules 2021; 11:biom11121802. [PMID: 34944446 PMCID: PMC8699189 DOI: 10.3390/biom11121802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 11/25/2021] [Accepted: 11/27/2021] [Indexed: 11/23/2022] Open
Abstract
Legionella pneumophila is a Gram-negative intracellular pathogen that causes Legionnaires’ disease in elderly or immunocompromised individuals. This bacterium relies on the Dot/Icm (Defective in organelle trafficking/Intracellular multiplication) Type IV Secretion System (T4SS) and a large (>330) set of effector proteins to colonize the host cell. The structural variability of these effectors allows them to disrupt many host processes. Herein, we report the crystal structure of MavL to 2.65 Å resolution. MavL adopts an ADP-ribosyltransferase (ART) fold and contains the distinctive ligand-binding cleft of ART proteins. Indeed, MavL binds ADP-ribose with Kd of 13 µM. Structural overlay of MavL with poly-(ADP-ribose) glycohydrolases (PARGs) revealed a pair of aspartate residues in MavL that align with the catalytic glutamates in PARGs. MavL also aligns with ADP-ribose “reader” proteins (proteins that recognize ADP-ribose). Since no glycohydrolase activity was observed when incubated in the presence of ADP-ribosylated PARP1, MavL may play a role as a signaling protein that binds ADP-ribose. An interaction between MavL and the mammalian ubiquitin-conjugating enzyme UBE2Q1 was revealed by yeast two-hybrid and co-immunoprecipitation experiments. This work provides structural and molecular insights to guide biochemical studies aimed at elucidating the function of MavL. Our findings support the notion that ubiquitination and ADP-ribosylation are global modifications exploited by L. pneumophila.
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Affiliation(s)
- Kevin Voth
- Department of Biochemistry, Microbiology & Immunology, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (K.V.); (I.Y.W.C.)
| | - Shivani Pasricha
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton 3168, Australia; (S.P.); (R.R.W.)
| | - Ivy Yeuk Wah Chung
- Department of Biochemistry, Microbiology & Immunology, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (K.V.); (I.Y.W.C.)
| | - Rachelia R. Wibawa
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton 3168, Australia; (S.P.); (R.R.W.)
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne 3000, Australia;
| | - Engku Nuraishah Huda E. Zainudin
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne 3000, Australia;
| | - Elizabeth L. Hartland
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton 3168, Australia; (S.P.); (R.R.W.)
- Department of Molecular and Translational Science, Monash University, Clayton 3168, Australia
- Correspondence: (E.L.H.); (M.C.)
| | - Miroslaw Cygler
- Department of Biochemistry, Microbiology & Immunology, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (K.V.); (I.Y.W.C.)
- Correspondence: (E.L.H.); (M.C.)
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12
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Horváthová L, Žárský V, Pánek T, Derelle R, Pyrih J, Motyčková A, Klápšťová V, Vinopalová M, Marková L, Voleman L, Klimeš V, Petrů M, Vaitová Z, Čepička I, Hryzáková K, Harant K, Gray MW, Chami M, Guilvout I, Francetic O, Franz Lang B, Vlček Č, Tsaousis AD, Eliáš M, Doležal P. Analysis of diverse eukaryotes suggests the existence of an ancestral mitochondrial apparatus derived from the bacterial type II secretion system. Nat Commun 2021; 12:2947. [PMID: 34011950 PMCID: PMC8134430 DOI: 10.1038/s41467-021-23046-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 03/22/2021] [Indexed: 12/14/2022] Open
Abstract
The type 2 secretion system (T2SS) is present in some Gram-negative eubacteria and used to secrete proteins across the outer membrane. Here we report that certain representative heteroloboseans, jakobids, malawimonads and hemimastigotes unexpectedly possess homologues of core T2SS components. We show that at least some of them are present in mitochondria, and their behaviour in biochemical assays is consistent with the presence of a mitochondrial T2SS-derived system (miT2SS). We additionally identified 23 protein families co-occurring with miT2SS in eukaryotes. Seven of these proteins could be directly linked to the core miT2SS by functional data and/or sequence features, whereas others may represent different parts of a broader functional pathway, possibly also involving the peroxisome. Its distribution in eukaryotes and phylogenetic evidence together indicate that the miT2SS-centred pathway is an ancestral eukaryotic trait. Our findings thus have direct implications for the functional properties of the early mitochondrion. Bacteria use the type 2 secretion system to secrete enzymes and toxins across the outer membrane to the environment. Here the authors analyse the T2SS pathway in three protist lineages and suggest that the early mitochondrion may have been capable of secreting proteins into the cytosol.
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Affiliation(s)
- Lenka Horváthová
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Vojtěch Žárský
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Tomáš Pánek
- Faculty of Science, Department of Biology and Ecology, University of Ostrava, Ostrava, Czech Republic.,Faculty of Science, Department of Zoology, Charles University, Prague 2, Czech Republic
| | - Romain Derelle
- School of Biosciences, University of Birmingham, Edgbaston, UK
| | - Jan Pyrih
- Laboratory of Molecular & Evolutionary Parasitology, RAPID group, School of Biosciences, University of Kent, Canterbury, UK.,Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Alžběta Motyčková
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Veronika Klápšťová
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Martina Vinopalová
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Lenka Marková
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Luboš Voleman
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Vladimír Klimeš
- Faculty of Science, Department of Biology and Ecology, University of Ostrava, Ostrava, Czech Republic
| | - Markéta Petrů
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Zuzana Vaitová
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Ivan Čepička
- Faculty of Science, Department of Zoology, Charles University, Prague 2, Czech Republic
| | - Klára Hryzáková
- Faculty of Science, Department of Genetics and Microbiology, Charles University, Prague 2, Czech Republic
| | - Karel Harant
- Faculty of Science, Proteomic core facility, Charles University, BIOCEV, Vestec, Czech Republic
| | - Michael W Gray
- Department of Biochemistry and Molecular Biology and Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, NS, Canada
| | - Mohamed Chami
- Center for Cellular Imaging and NanoAnalytics, University of Basel, Basel, Switzerland
| | - Ingrid Guilvout
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, CNRS UMR3528, Paris, France
| | - Olivera Francetic
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, CNRS UMR3528, Paris, France
| | - B Franz Lang
- Robert Cedergren Centre for Bioinformatics and Genomics, Département de Biochimie, Université de Montréal, Montreal, QC, Canada
| | - Čestmír Vlček
- Institute of Molecular Genetics, Czech Academy of Sciences, Prague 4, Czech Republic
| | - Anastasios D Tsaousis
- Laboratory of Molecular & Evolutionary Parasitology, RAPID group, School of Biosciences, University of Kent, Canterbury, UK
| | - Marek Eliáš
- Faculty of Science, Department of Biology and Ecology, University of Ostrava, Ostrava, Czech Republic.
| | - Pavel Doležal
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic.
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13
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Chung IYW, Li L, Tyurin O, Gagarinova A, Wibawa R, Li P, Hartland EL, Cygler M. Structural and functional study of Legionella pneumophila effector RavA. Protein Sci 2021; 30:940-955. [PMID: 33660322 DOI: 10.1002/pro.4057] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 02/15/2021] [Accepted: 02/20/2021] [Indexed: 01/20/2023]
Abstract
Legionella pneumophila is an intracellular pathogen that causes Legionnaire's disease in humans. This bacterium can be found in freshwater environments as a free-living organism, but it is also an intracellular parasite of protozoa. Human infection occurs when inhaled aerosolized pathogen comes into contact with the alveolar mucosa and replicates in alveolar macrophages. Legionella enters the host cell by phagocytosis and redirects the Legionella-containing phagosomes from the phagocytic maturation pathway. These nascent phagosomes fuse with ER-derived secretory vesicles and membranes forming the Legionella-containing vacuole. Legionella subverts many host cellular processes by secreting over 300 effector proteins into the host cell via the Dot/Icm type IV secretion system. The cellular function for many Dot/Icm effectors is still unknown. Here, we present a structural and functional study of L. pneumophila effector RavA (Lpg0008). Structural analysis revealed that the RavA consists of four ~85 residue long α-helical domains with similar folds, which show only a low level of structural similarity to other protein domains. The ~90 residues long C-terminal segment is predicted to be natively unfolded. We show that during L. pneumophila infection of human cells, RavA localizes to the Golgi apparatus and to the plasma membrane. The same localization is observed when RavA is expressed in human cells. The localization signal resides within the C-terminal sequence C409 WTSFCGLF417 . Yeast-two-hybrid screen using RavA as bait identified RAB11A as a potential binding partner. RavA is present in L. pneumophila strains but only distant homologs are found in other Legionella species, where the number of repeats varies.
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Affiliation(s)
- Ivy Y W Chung
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Lei Li
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Oleg Tyurin
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.,Symvivo Corporation, Burnaby, British Columbia, Canada
| | - Alla Gagarinova
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Raissa Wibawa
- 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, and Department of Molecular and Translational Science, Monash University, Clayton, Australia
| | - Pengfei 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, and Department of Molecular and Translational Science, Monash University, 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, and Department of Molecular and Translational Science, Monash University, Clayton, Australia
| | - Miroslaw Cygler
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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14
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Quarleri J, Cevallos C, Delpino MV. Apoptosis in infectious diseases as a mechanism of immune evasion and survival. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 125:1-24. [PMID: 33931136 DOI: 10.1016/bs.apcsb.2021.01.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In pluricellular organisms, apoptosis is indispensable for the development and homeostasis. During infection, apoptosis plays the main role in the elimination of infected cells. Infectious diseases control apoptosis, and this contributes to disease pathogenesis. Increased apoptosis may participate in two different ways. It can assist the dissemination of intracellular pathogens or induce immunosuppression to favor pathogen dissemination. In other conditions, apoptosis can benefit eradicate infectious agents from the host. Accordingly, bacteria, viruses, fungi, and parasites have developed strategies to inhibit host cell death by apoptosis to allow intracellular survival and persistence of the pathogen. The clarification of the intracellular signaling pathways, the receptors involved and the pathogen factors that interfere with apoptosis could disclose new therapeutic targets for blocking microbial actions on apoptotic pathways. In this review, we summarize the current knowledge on pathogen anti-apoptotic and apoptotic approaches and the mechanisms involving in disease.
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Affiliation(s)
- Jorge Quarleri
- Instituto de Investigaciones Biomédicas en Retrovirus y Sida (INBIRS), Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina
| | - Cintia Cevallos
- Instituto de Investigaciones Biomédicas en Retrovirus y Sida (INBIRS), Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina
| | - María Victoria Delpino
- Instituto de Inmunología, Genética y Metabolismo (INIGEM), Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina.
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15
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Abstract
Through coevolution with host cells, microorganisms have acquired mechanisms to avoid the detection by the host surveillance system and to use the cell's supplies to establish themselves. Indeed, certain pathogens have evolved proteins that imitate specific eukaryotic cell proteins, allowing them to manipulate host pathways, a phenomenon termed molecular mimicry. Bacterial "eukaryotic-like proteins" are a remarkable example of molecular mimicry. They are defined as proteins that strongly resemble eukaryotic proteins or that carry domains that are predominantly present in eukaryotes and that are generally absent from prokaryotes. The widest diversity of eukaryotic-like proteins known to date can be found in members of the bacterial genus Legionella, some of which cause a severe pneumonia in humans. The characterization of a number of these proteins shed light on their importance during infection. The subsequent identification of eukaryotic-like genes in the genomes of other amoeba-associated bacteria and bacterial symbionts suggested that eukaryotic-like proteins are a common means of bacterial evasion and communication, shaped by the continuous interactions between bacteria and their protozoan hosts. In this review, we discuss the concept of molecular mimicry using Legionella as an example and show that eukaryotic-like proteins effectively manipulate host cell pathways. The study of the function and evolution of such proteins is an exciting field of research that is leading us toward a better understanding of the complex world of bacterium-host interactions. Ultimately, this knowledge will teach us how host pathways are manipulated and how infections may possibly be tackled.
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16
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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 DOI: 10.1073/pnas.1902806116] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [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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17
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van de Vossenberg BTLH, Warris S, Nguyen HDT, van Gent-Pelzer MPE, Joly DL, van de Geest HC, Bonants PJM, Smith DS, Lévesque CA, van der Lee TAJ. Comparative genomics of chytrid fungi reveal insights into the obligate biotrophic and pathogenic lifestyle of Synchytrium endobioticum. Sci Rep 2019; 9:8672. [PMID: 31209237 PMCID: PMC6572847 DOI: 10.1038/s41598-019-45128-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/31/2019] [Indexed: 01/09/2023] Open
Abstract
Synchytrium endobioticum is an obligate biotrophic soilborne Chytridiomycota (chytrid) species that causes potato wart disease, and represents the most basal lineage among the fungal plant pathogens. We have chosen a functional genomics approach exploiting knowledge acquired from other fungal taxa and compared this to several saprobic and pathogenic chytrid species. Observations linked to obligate biotrophy, genome plasticity and pathogenicity are reported. Essential purine pathway genes were found uniquely absent in S. endobioticum, suggesting that it relies on scavenging guanine from its host for survival. The small gene-dense and intron-rich chytrid genomes were not protected for genome duplications by repeat-induced point mutation. Both pathogenic chytrids Batrachochytrium dendrobatidis and S. endobioticum contained the largest amounts of repeats, and we identified S. endobioticum specific candidate effectors that are associated with repeat-rich regions. These candidate effectors share a highly conserved motif, and show isolate specific duplications. A reduced set of cell wall degrading enzymes, and LysM protein expansions were found in S. endobioticum, which may prevent triggering plant defense responses. Our study underlines the high diversity in chytrids compared to the well-studied Ascomycota and Basidiomycota, reflects characteristic biological differences between the phyla, and shows commonalities in genomic features among pathogenic fungi.
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Affiliation(s)
- Bart T L H van de Vossenberg
- Wageningen University & Research, Droevendaalsesteeg 1, Plant Science Group, 6708PB, Wageningen, The Netherlands.
- Dutch National Plant Protection Organization, National Reference Centre, Geertjesweg 15, 6706EA, Wageningen, The Netherlands.
| | - Sven Warris
- Wageningen University & Research, Droevendaalsesteeg 1, Plant Science Group, 6708PB, Wageningen, The Netherlands
| | - Hai D T Nguyen
- Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, Canada
| | - Marga P E van Gent-Pelzer
- Wageningen University & Research, Droevendaalsesteeg 1, Plant Science Group, 6708PB, Wageningen, The Netherlands
| | - David L Joly
- Université de Moncton, 18 avenue Antonine-Maillet, Moncton, Canada
| | - Henri C van de Geest
- Wageningen University & Research, Droevendaalsesteeg 1, Plant Science Group, 6708PB, Wageningen, The Netherlands
| | - Peter J M Bonants
- Wageningen University & Research, Droevendaalsesteeg 1, Plant Science Group, 6708PB, Wageningen, The Netherlands
| | - Donna S Smith
- Canadian Food Inspection Agency, 93 Mount Edward Road, Charlottetown, Canada
| | - C André Lévesque
- Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, Canada
| | - Theo A J van der Lee
- Wageningen University & Research, Droevendaalsesteeg 1, Plant Science Group, 6708PB, Wageningen, The Netherlands
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18
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Naderer T, Fulcher MC. Targeting apoptosis pathways in infections. J Leukoc Biol 2019; 103:275-285. [PMID: 29372933 DOI: 10.1189/jlb.4mr0717-286r] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 08/29/2017] [Accepted: 09/13/2017] [Indexed: 11/24/2022] Open
Abstract
The programmed cell death pathway of apoptosis is essential for mammalian development and immunity as it eliminates unwanted and dangerous cells. As part of the cellular immune response, apoptosis removes the replicative niche of intracellular pathogens and enables the resolution of infections. To subvert apoptosis, pathogens have evolved a diverse range of mechanisms. In some circumstances, however, pathogens express effector molecules that induce apoptotic cell death. In this review, we focus on selected host-pathogen interactions that affect apoptotic pathways. We discuss how pathogens control the fate of host cells and how this determines the outcome of infections. Finally, small molecule inhibitors that activate apoptosis in cancer cells can also induce apoptotic cell death of infected cells. This suggests that targeting host death factors to kill infected cells is a potential therapeutic option to treat infectious diseases.
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Affiliation(s)
- Thomas Naderer
- Biomedicine Discovery Institute and Department of Biochemistry & Molecular Biology, Monash University, Clayton, Australia
| | - Maria Cecilia Fulcher
- Biomedicine Discovery Institute and Department of Biochemistry & Molecular Biology, Monash University, Clayton, Australia
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19
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Abstract
Mitochondria are essential and highly dynamic organelles whose morphology is determined by a steady-state balance between fusion and fission. Mitochondrial morphology and function are tightly connected. Because they are involved in many important cellular processes, including energy production, cell-autonomous immunity, and apoptosis, mitochondria present an attractive target for pathogens. Here, we explore the relationship between host cell mitochondria and intracellular bacteria, with a focus on mitochondrial morphology and function, as well as apoptosis. Modulation of apoptosis can allow bacteria to establish their replicative niche or support bacterial dissemination. Furthermore, bacteria can manipulate mitochondrial morphology and function through secreted effector proteins and can also contribute to the establishment of a successful infection, e.g., by favoring access to nutrients and/or evasion of the immune system.
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20
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Levanova N, Mattheis C, Carson D, To KN, Jank T, Frankel G, Aktories K, Schroeder GN. The Legionella effector LtpM is a new type of phosphoinositide-activated glucosyltransferase. J Biol Chem 2019; 294:2862-2879. [PMID: 30573678 PMCID: PMC6393602 DOI: 10.1074/jbc.ra118.005952] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 12/13/2018] [Indexed: 01/01/2023] Open
Abstract
Legionella pneumophila causes Legionnaires' disease, a severe form of pneumonia. L. pneumophila translocates more than 300 effectors into host cells via its Dot/Icm (Defective in organelle trafficking/Intracellular multiplication) type IV secretion system to enable its replication in target cells. Here, we studied the effector LtpM, which is encoded in a recombination hot spot in L. pneumophila Paris. We show that a C-terminal phosphoinositol 3-phosphate (PI3P)-binding domain, also found in otherwise unrelated effectors, targets LtpM to the Legionella-containing vacuole and to early and late endosomes. LtpM expression in yeast caused cytotoxicity. Sequence comparison and structural homology modeling of the N-terminal domain of LtpM uncovered a remote similarity to the glycosyltransferase (GT) toxin PaTox from the bacterium Photorhabdus asymbiotica; however, instead of the canonical DxD motif of GT-A type glycosyltransferases, essential for enzyme activity and divalent cation coordination, we found that a DxN motif is present in LtpM. Using UDP-glucose as sugar donor, we show that purified LtpM nevertheless exhibits glucohydrolase and autoglucosylation activity in vitro and demonstrate that PI3P binding activates LtpM's glucosyltransferase activity toward protein substrates. Substitution of the aspartate or the asparagine in the DxN motif abolished the activity of LtpM. Moreover, whereas all glycosyltransferase toxins and effectors identified so far depend on the presence of divalent cations, LtpM is active in their absence. Proteins containing LtpM-like GT domains are encoded in the genomes of other L. pneumophila isolates and species, suggesting that LtpM is the first member of a novel family of glycosyltransferase effectors employed to subvert hosts.
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Affiliation(s)
- Nadezhda Levanova
- From the Institute of Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany
| | - Corinna Mattheis
- the MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom, and
| | - Danielle Carson
- the MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom, and
| | - Ka-Ning To
- the MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom, and
| | - Thomas Jank
- From the Institute of Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany
| | - Gad Frankel
- the MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom, and
| | - Klaus Aktories
- From the Institute of Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany,
| | - Gunnar Neels Schroeder
- the MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom, and
- the Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry, and Biomedical Sciences, Queen's University Belfast, Belfast BT9 7BL, Northern Ireland, United Kingdom
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21
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The Galleria mellonella Infection Model for Investigating the Molecular Mechanisms of Legionella Virulence. Methods Mol Biol 2019; 1921:333-346. [PMID: 30694503 DOI: 10.1007/978-1-4939-9048-1_22] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Legionella species evolved virulence factors to exploit protozoa as replicative niches in the environment. Cell culture infection models demonstrated that many of these factors also enable the bacteria to thrive in human macrophages; however, these models do not recapitulate the complex interactions between macrophages, lung epithelial, and additional immune cells, which are crucial to control bacterial infections. Thus, suitable infection models are required to understand which bacterial factors are important to trigger disease. Guinea pigs and, most frequently, mice have been successfully used as mammalian model hosts; however, ethical and economic considerations impede their use in high-throughput screening studies of Legionella isolates or small molecule inhibitors.Here, we describe the larvae of the lepidopteran Galleria mellonella as insect model of Legionella pathogenesis. Larvae can be obtained from commercial suppliers in large numbers, maintained without the need of specialized equipment, and infected by injection. Although lacking the complexity of a mammalian immune system, the larvae mount humoral and cellular immune responses to infection. L. pneumophila strain 130b and other prototype isolates withstand these responses and use the Defective in organelle trafficking/Intracellular multiplication (Dot/Icm) type IV secretion system (T4SS ) to inject effectors enabling survival and replication in hemocytes, insect phagocytes, ultimately leading to the death of the larvae. Differences in virulence between L. pneumophila isolates or gene deletion mutants can be analyzed using indicators of larval health and immune induction, such as pigmentation, mobility, histopathology, and survival. Bacterial replication can be measured by plating hemolymph or by immunofluorescence microscopy of isolated circulating hemocytes from infected larvae. Combined, these straightforward experimental readouts make G. mellonella larvae a versatile model host to rapidly assess the virulence of different Legionella isolates and investigate the role of specific virulence factors in overcoming innate host defense mechanisms.
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22
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Brown AMV, Wasala SK, Howe DK, Peetz AB, Zasada IA, Denver DR. Comparative Genomics of Wolbachia- Cardinium Dual Endosymbiosis in a Plant-Parasitic Nematode. Front Microbiol 2018; 9:2482. [PMID: 30459726 PMCID: PMC6232779 DOI: 10.3389/fmicb.2018.02482] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/28/2018] [Indexed: 12/11/2022] Open
Abstract
Wolbachia and Cardinium are among the most important and widespread of all endosymbionts, occurring in nematodes and more than half of insect and arachnid species, sometimes as coinfections. These symbionts are of significant interest as potential biocontrol agents due to their abilities to cause major effects on host biology and reproduction through cytoplasmic incompatibility, sex ratio distortion, or obligate mutualism. The ecological and metabolic effects of coinfections are not well understood. This study examined a Wolbachia-Cardinium coinfection in the plant-parasitic nematode (PPN), Pratylenchus penetrans, producing the first detailed study of such a coinfection using fluorescence in situ hybridization (FISH), polymerase chain reaction (PCR), and comparative genomic analysis. Results from FISH and single-nematode PCR showed 123/127 individuals in a focal population carried Cardinium (denoted strain cPpe), and 48% were coinfected with Wolbachia strain wPpe. Both endosymbionts showed dispersed tissue distribution with highest densities in the anterior intestinal walls and gonads. Phylogenomic analyses confirmed an early place of cPpe and long distance from a sister strain in another PPN, Heterodera glycines, supporting a long history of both Cardinium and Wolbachia in PPNs. The genome of cPpe was 1.36 Mbp with 35.8% GC content, 1,131 predicted genes, 41% having no known function, and missing biotin and lipoate synthetic capacity and a plasmid present in other strains, despite having a slightly larger genome compared to other sequenced Cardinium. The larger genome revealed expansions of gene families likely involved in host-cellular interactions. More than 2% of the genes of cPpe and wPpe were identified as candidate horizontally transferred genes, with some of these from eukaryotes, including nematodes. A model of the possible Wolbachia-Cardinium interaction is proposed with possible complementation in function for pathways such as methionine and fatty acid biosynthesis and biotin transport.
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Affiliation(s)
- Amanda M V Brown
- Department of Biological Sciences, Texas Tech University, Lubbock, TX, United States
| | - Sulochana K Wasala
- Department of Integrative Biology, Oregon State University, Corvallis, OR, United States
| | - Dana K Howe
- Department of Integrative Biology, Oregon State University, Corvallis, OR, United States
| | - Amy B Peetz
- USDA-ARS Horticultural Crops Research Laboratory, Corvallis, OR, United States
| | - Inga A Zasada
- USDA-ARS Horticultural Crops Research Laboratory, Corvallis, OR, United States
| | - Dee R Denver
- Department of Integrative Biology, Oregon State University, Corvallis, OR, United States
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23
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Krampen L, Malmsheimer S, Grin I, Trunk T, Lührmann A, de Gier JW, Wagner S. Revealing the mechanisms of membrane protein export by virulence-associated bacterial secretion systems. Nat Commun 2018; 9:3467. [PMID: 30150748 PMCID: PMC6110835 DOI: 10.1038/s41467-018-05969-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 07/31/2018] [Indexed: 02/08/2023] Open
Abstract
Many bacteria export effector proteins fulfilling their function in membranes of a eukaryotic host. These effector membrane proteins appear to contain signals for two incompatible bacterial secretion pathways in the same protein: a specific export signal, as well as transmembrane segments that one would expect to mediate targeting to the bacterial inner membrane. Here, we show that the transmembrane segments of effector proteins of type III and type IV secretion systems indeed integrate in the membrane as required in the eukaryotic host, but that their hydrophobicity in most instances is just below the threshold required for mediating targeting to the bacterial inner membrane. Furthermore, we show that binding of type III secretion chaperones to both the effector’s chaperone-binding domain and adjacent hydrophobic transmembrane segments also prevents erroneous targeting. These results highlight the evolution of a fine discrimination between targeting pathways that is critical for the virulence of many bacterial pathogens. Many bacteria export effector proteins even when two incompatible signal sequences are present, one which would lead to export and the other to inner membrane targeting. Here the authors show that such proteins feature decreased hydrophobicity or cognate chaperone binding to prevent erroneous targeting.
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Affiliation(s)
- Lea Krampen
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076, Tübingen, Germany
| | - Silke Malmsheimer
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076, Tübingen, Germany
| | - Iwan Grin
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076, Tübingen, Germany
| | - Thomas Trunk
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076, Tübingen, Germany.,Section for Genetics and Evolutionary Biology, University of Oslo, Blindernveien 31, 0371, Oslo, Norway
| | - Anja Lührmann
- Institute of Microbiology, University Hospital Erlangen, Wasserturmstr. 3-5, 91054, Erlangen, Germany
| | - Jan-Willem de Gier
- Center for Biomembrane Research, Stockholm University, Svante-Arrhenius väg 16, SE-106 91, Stockholm, Sweden
| | - Samuel Wagner
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076, Tübingen, Germany. .,German Center for Infection Research (DZIF), Partner-site Tübingen, Elfriede-Aulhorn-Str. 6, 72076, Tübingen, Germany.
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24
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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: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [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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25
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Tucey TM, Verma J, Harrison PF, Snelgrove SL, Lo TL, Scherer AK, Barugahare AA, Powell DR, Wheeler RT, Hickey MJ, Beilharz TH, Naderer T, Traven A. Glucose Homeostasis Is Important for Immune Cell Viability during Candida Challenge and Host Survival of Systemic Fungal Infection. Cell Metab 2018; 27:988-1006.e7. [PMID: 29719235 PMCID: PMC6709535 DOI: 10.1016/j.cmet.2018.03.019] [Citation(s) in RCA: 136] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 12/18/2017] [Accepted: 03/26/2018] [Indexed: 12/20/2022]
Abstract
To fight infections, macrophages undergo a metabolic shift whereby increased glycolysis fuels antimicrobial inflammation and killing of pathogens. Here we demonstrate that the pathogen Candida albicans turns this metabolic reprogramming into an Achilles' heel for macrophages. During Candida-macrophage interactions intertwined metabolic shifts occur, with concomitant upregulation of glycolysis in both host and pathogen setting up glucose competition. Candida thrives on multiple carbon sources, but infected macrophages are metabolically trapped in glycolysis and depend on glucose for viability: Candida exploits this limitation by depleting glucose, triggering rapid macrophage death. Using pharmacological or genetic means to modulate glucose metabolism of host and/or pathogen, we show that Candida infection perturbs host glucose homeostasis in the murine candidemia model and demonstrate that glucose supplementation improves host outcomes. Our results support the importance of maintaining glucose homeostasis for immune cell survival during Candida challenge and for host survival in systemic infection.
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Affiliation(s)
- Timothy M Tucey
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton 3800, VIC, Australia
| | - Jiyoti Verma
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton 3800, VIC, Australia
| | - Paul F Harrison
- Bioinformatics Platform, Monash University, Clayton 3800, VIC, Australia
| | - Sarah L Snelgrove
- Centre for Inflammatory Diseases, Monash University Department of Medicine, Monash Medical Centre, Clayton 3168, VIC, Australia
| | - Tricia L Lo
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton 3800, VIC, Australia
| | - Allison K Scherer
- Department of Molecular & Biomedical Sciences, University of Maine, Orono, ME, USA
| | - Adele A Barugahare
- Bioinformatics Platform, Monash University, Clayton 3800, VIC, Australia
| | - David R Powell
- Bioinformatics Platform, Monash University, Clayton 3800, VIC, Australia
| | - Robert T Wheeler
- Department of Molecular & Biomedical Sciences, University of Maine, Orono, ME, USA
| | - Michael J Hickey
- Centre for Inflammatory Diseases, Monash University Department of Medicine, Monash Medical Centre, Clayton 3168, VIC, Australia
| | - Traude H Beilharz
- Development and Stem Cells Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton 3800, VIC, Australia
| | - Thomas Naderer
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton 3800, VIC, Australia.
| | - Ana Traven
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton 3800, VIC, Australia.
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26
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Escoll P, Buchrieser C. Metabolic reprogramming of host cells upon bacterial infection: Why shift to a Warburg-like metabolism? FEBS J 2018; 285:2146-2160. [PMID: 29603622 DOI: 10.1111/febs.14446] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Revised: 02/25/2018] [Accepted: 03/22/2018] [Indexed: 12/20/2022]
Abstract
The finding that the Warburg effect observed in proliferating cancer cells is also observed during immune responses renewed the interest in the study of metabolic reprogramming of immune cells, a field of investigation called immunometabolism. However, the specific mechanisms and processes underlying metabolic changes of host cells upon bacterial infection remain poorly understood. Several recent reports have reported that mammalian cells infected with intracellular bacteria have an altered metabolism that resembles the Warburg effect seen in cancer cells. In this Review, we will summarize current knowledge on metabolic reprogramming and discuss putative causes underlying the preferential remodelling of host cells to Warburg-like metabolic programs during infection by intracellular bacteria.
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Affiliation(s)
- Pedro Escoll
- Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France.,UMR 3525, CNRS, Paris, France
| | - Carmen Buchrieser
- Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France.,UMR 3525, CNRS, Paris, France
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27
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Schroeder GN. The Toolbox for Uncovering the Functions of Legionella Dot/Icm Type IVb Secretion System Effectors: Current State and Future Directions. Front Cell Infect Microbiol 2018; 7:528. [PMID: 29354599 PMCID: PMC5760550 DOI: 10.3389/fcimb.2017.00528] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 12/13/2017] [Indexed: 12/13/2022] Open
Abstract
The defective in organelle trafficking/intracellular multiplication (Dot/Icm) Type IVb secretion system (T4SS) is the essential virulence factor for the intracellular life style and pathogenicity of Legionella species. Screens demonstrated that an individual L. pneumophila strain can use the Dot/Icm T4SS to translocate an unprecedented number of more than 300 proteins into host cells, where these, so called Icm/Dot-translocated substrates (IDTS) or effectors, manipulate host cell functions to the benefit of the bacteria. Bioinformatic analysis of the pan-genus genome predicts at least 608 orthologous groups of putative effectors. Deciphering the function of these effectors is key to understanding Legionella pathogenesis; however, the analysis is challenging. Substantial functional redundancy renders classical, phenotypic screening of single gene deletion mutants mostly ineffective. Here, I review experimental approaches that were successfully used to identify, validate and functionally characterize T4SS effectors and highlight new methods, which promise to facilitate unlocking the secrets of Legionella's extraordinary weapons arsenal.
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Affiliation(s)
- Gunnar N Schroeder
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, United Kingdom
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28
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Gradowski M, Pawłowski K. The Legionella pneumophila effector Lpg1137 is a homologue of mitochondrial SLC25 carrier proteins, not of known serine proteases. PeerJ 2017; 5:e3849. [PMID: 28966893 PMCID: PMC5621508 DOI: 10.7717/peerj.3849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 09/01/2017] [Indexed: 01/08/2023] Open
Abstract
Many bacterial effector proteins that are delivered to host cells during infection are enzymes targeting host cell signalling. Recently, Legionella pneumophila effector Lpg1137 was experimentally characterised as a serine protease that cleaves human syntaxin 17. We present strong bioinformatic evidence that Lpg1137 is a homologue of mitochondrial carrier proteins and is not related to known serine proteases. We also discuss how this finding can be reconciled with the apparently contradictory experimental results.
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Affiliation(s)
- Marcin Gradowski
- Department of Experimental Design and Bioinformatics, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Warszawa, Poland
| | - Krzysztof Pawłowski
- Department of Experimental Design and Bioinformatics, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Warszawa, Poland.,Department of Translational Medicine, Clinical Sciences, Lund University, Lund, Sweden
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29
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Abstract
Enterohemorrhagic Escherichia coli (EHEC) is a diarrheagenic pathogen that colonizes the gut mucosa and induces attaching-and-effacing lesions. EHEC employs a type III secretion system (T3SS) to translocate 50 effector proteins that hijack and manipulate host cell signaling pathways, which allow bacterial colonization and subversion of immune responses and disease progression. The aim of this study was to characterize the T3SS effector EspW. We found espW in the sequenced O157:H7 and non-O157 EHEC strains as well as in Shigella boydii. Furthermore, a truncated version of EspW, containing the first 206 residues, is present in EPEC strains belonging to serotype O55:H7. Screening a collection of clinical EPEC isolates revealed that espW is present in 52% of the tested strains. We report that EspW modulates actin dynamics in a Rac1-dependent manner. Ectopic expression of EspW results in formation of unique membrane protrusions. Infection of Swiss cells with an EHEC espW deletion mutant induces a cell shrinkage phenotype that could be rescued by Rac1 activation via expression of the bacterial guanine nucleotide exchange factor, EspT. Furthermore, using a yeast two-hybrid screen, we identified the motor protein Kif15 as a potential interacting partner of EspW. Kif15 and EspW colocalized in cotransfected cells, while ectopically expressed Kif15 localized to the actin pedestals following EHEC infection. The data suggest that Kif15 recruits EspW to the site of bacterial attachment, which in turn activates Rac1, resulting in modifications of the actin cytoskeleton that are essential to maintain cell shape during infection.
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30
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Gunasinghe SD, Webb CT, Elgass KD, Hay ID, Lithgow T. Super-Resolution Imaging of Protein Secretion Systems and the Cell Surface of Gram-Negative Bacteria. Front Cell Infect Microbiol 2017; 7:220. [PMID: 28611954 PMCID: PMC5447050 DOI: 10.3389/fcimb.2017.00220] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 05/12/2017] [Indexed: 12/28/2022] Open
Abstract
Gram-negative bacteria have a highly evolved cell wall with two membranes composed of complex arrays of integral and peripheral proteins, as well as phospholipids and glycolipids. In order to sense changes in, respond to, and exploit their environmental niches, bacteria rely on structures assembled into or onto the outer membrane. Protein secretion across the cell wall is a key process in virulence and other fundamental aspects of bacterial cell biology. The final stage of protein secretion in Gram-negative bacteria, translocation across the outer membrane, is energetically challenging so sophisticated nanomachines have evolved to meet this challenge. Advances in fluorescence microscopy now allow for the direct visualization of the protein secretion process, detailing the dynamics of (i) outer membrane biogenesis and the assembly of protein secretion systems into the outer membrane, (ii) the spatial distribution of these and other membrane proteins on the bacterial cell surface, and (iii) translocation of effector proteins, toxins and enzymes by these protein secretion systems. Here we review the frontier research imaging the process of secretion, particularly new studies that are applying various modes of super-resolution microscopy.
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Affiliation(s)
- Sachith D Gunasinghe
- Infection and Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | - Chaille T Webb
- Infection and Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | | | - Iain D Hay
- Infection and Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | - Trevor Lithgow
- Infection and Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
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31
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An Y, Wang J, Li C, Revote J, Zhang Y, Naderer T, Hayashida M, Akutsu T, Webb GI, Lithgow T, Song J. SecretEPDB: a comprehensive web-based resource for secreted effector proteins of the bacterial types III, IV and VI secretion systems. Sci Rep 2017; 7:41031. [PMID: 28112271 PMCID: PMC5253721 DOI: 10.1038/srep41031] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 12/14/2016] [Indexed: 12/28/2022] Open
Abstract
Bacteria translocate effector molecules to host cells through highly evolved secretion systems. By definition, the function of these effector proteins is to manipulate host cell biology and the sequence, structural and functional annotations of these effector proteins will provide a better understanding of how bacterial secretion systems promote bacterial survival and virulence. Here we developed a knowledgebase, termed SecretEPDB (Bacterial Secreted Effector Protein DataBase), for effector proteins of type III secretion system (T3SS), type IV secretion system (T4SS) and type VI secretion system (T6SS). SecretEPDB provides enriched annotations of the aforementioned three classes of effector proteins by manually extracting and integrating structural and functional information from currently available databases and the literature. The database is conservative and strictly curated to ensure that every effector protein entry is supported by experimental evidence that demonstrates it is secreted by a T3SS, T4SS or T6SS. The annotations of effector proteins documented in SecretEPDB are provided in terms of protein characteristics, protein function, protein secondary structure, Pfam domains, metabolic pathway and evolutionary details. It is our hope that this integrated knowledgebase will serve as a useful resource for biological investigation and the generation of new hypotheses for research efforts aimed at bacterial secretion systems.
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Affiliation(s)
- Yi An
- College of Information Engineering, Northwest A&F University, Yangling 712100, China.,Monash Centre for Data Science, Faculty of Information Technology, Monash University, Melbourne, VIC 3800, Australia
| | - Jiawei Wang
- School of Electronic and Computer Engineering, Peking University, Beijing 100871, China
| | - Chen Li
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, VIC 3800, Australia
| | - Jerico Revote
- Monash Bioinformatics Platform, Monash University, Melbourne, VIC 3800, Australia
| | - Yang Zhang
- College of Information Engineering, Northwest A&F University, Yangling 712100, China
| | - Thomas Naderer
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC 3800, Australia
| | - Morihiro Hayashida
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Tatsuya Akutsu
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Geoffrey I Webb
- Monash Centre for Data Science, Faculty of Information Technology, Monash University, Melbourne, VIC 3800, Australia
| | - Trevor Lithgow
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, VIC 3800, Australia
| | - Jiangning Song
- Monash Centre for Data Science, Faculty of Information Technology, Monash University, Melbourne, VIC 3800, Australia.,Infection and Immunity Program, Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC 3800, Australia
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32
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Khan AA, Khan Z, Kalam MA, Khan AA. Inter-kingdom prediction certainty evaluation of protein subcellular localization tools: microbial pathogenesis approach for deciphering host microbe interaction. Brief Bioinform 2016; 19:12-22. [DOI: 10.1093/bib/bbw093] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Indexed: 12/19/2022] Open
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33
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Fielden LF, Kang Y, Newton HJ, Stojanovski D. Targeting mitochondria: how intravacuolar bacterial pathogens manipulate mitochondria. Cell Tissue Res 2016; 367:141-154. [PMID: 27515462 DOI: 10.1007/s00441-016-2475-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Accepted: 07/07/2016] [Indexed: 02/07/2023]
Abstract
Manipulation of host cell function by bacterial pathogens is paramount for successful invasion and creation of a niche conducive to bacterial replication. Mitochondria play a role in many important cellular processes including energy production, cellular calcium homeostasis, lipid metabolism, haeme biosynthesis, immune signalling and apoptosis. The sophisticated integration of host cell processes by the mitochondrion have seen it emerge as a key target during bacterial infection of human host cells. This review highlights the targeting and interaction of this dynamic organelle by intravacuolar bacterial pathogens and the way that the modulation of mitochondrial function might contribute to pathogenesis.
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Affiliation(s)
- Laura F Fielden
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Yilin Kang
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Hayley J Newton
- Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, VIC, 3000, Australia.
| | - Diana Stojanovski
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, 3010, Australia.
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34
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Naujoks J, Tabeling C, Dill BD, Hoffmann C, Brown AS, Kunze M, Kempa S, Peter A, Mollenkopf HJ, Dorhoi A, Kershaw O, Gruber AD, Sander LE, Witzenrath M, Herold S, Nerlich A, Hocke AC, van Driel I, Suttorp N, Bedoui S, Hilbi H, Trost M, Opitz B. IFNs Modify the Proteome of Legionella-Containing Vacuoles and Restrict Infection Via IRG1-Derived Itaconic Acid. PLoS Pathog 2016; 12:e1005408. [PMID: 26829557 PMCID: PMC4734697 DOI: 10.1371/journal.ppat.1005408] [Citation(s) in RCA: 183] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 12/30/2015] [Indexed: 11/21/2022] Open
Abstract
Macrophages can be niches for bacterial pathogens or antibacterial effector cells depending on the pathogen and signals from the immune system. Here we show that type I and II IFNs are master regulators of gene expression during Legionella pneumophila infection, and activators of an alveolar macrophage-intrinsic immune response that restricts bacterial growth during pneumonia. Quantitative mass spectrometry revealed that both IFNs substantially modify Legionella-containing vacuoles, and comparative analyses reveal distinct subsets of transcriptionally and spatially IFN-regulated proteins. Immune-responsive gene (IRG)1 is induced by IFNs in mitochondria that closely associate with Legionella-containing vacuoles, and mediates production of itaconic acid. This metabolite is bactericidal against intravacuolar L. pneumophila as well as extracellular multidrug-resistant Gram-positive and -negative bacteria. Our study explores the overall role IFNs play in inducing substantial remodeling of bacterial vacuoles and in stimulating production of IRG1-derived itaconic acid which targets intravacuolar pathogens. IRG1 or its product itaconic acid might be therapeutically targetable to fight intracellular and drug-resistant bacteria. Numerous intracellular bacterial pathogens replicate in specialized vacuoles within macrophages. We systematically study the molecular mechanism and the impact of macrophage-intrinsic antibacterial defense. Using L. pneumophila, an important cause of pneumonia and model organism for intracellular bacteria, we found that type I and II interferons critically modify the proteome of bacterial vacuoles to restrict infection. We identify IRG1 and demonstrate a bactericidal activity of its metabolite itaconic acid on bacteria in their vacuole. Moreover, our study provides evidence for the impact of this cell-autonomous defense pathway in alveolar macrophages to restrict lung infection. We speculate that vacuolar IRG1 or its product itaconic acid could serve as future therapeutic targets to fight intracellular and drug-resistant bacteria.
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Affiliation(s)
- Jan Naujoks
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Christoph Tabeling
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Brian D. Dill
- MRC Protein Phosphorylation Unit, University of Dundee, Dundee, United Kingdom
| | - Christine Hoffmann
- Max-von-Pettenkofer Institute, Ludwig Maximilian University, Munich, Germany
| | - Andrew S. Brown
- The Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Australia
| | - Mareike Kunze
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Stefan Kempa
- Integrative Metabolomics and Proteomics, Institute of Medical Systems Biology/Max-Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Andrea Peter
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | | | - Anca Dorhoi
- Max Planck Institute for Infection Biology, Berlin, Germany
| | - Olivia Kershaw
- Department of Veterinary Pathology, Free University Berlin, Berlin, Germany
| | - Achim D. Gruber
- Department of Veterinary Pathology, Free University Berlin, Berlin, Germany
| | - Leif E. Sander
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Martin Witzenrath
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Susanne Herold
- Medizinische Klinik II, University Giessen and Marburg Lung Center, Justus-Liebig-University Giessen, Giessen, Germany
| | - Andreas Nerlich
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Andreas C. Hocke
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Ian van Driel
- The Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Australia
| | - Norbert Suttorp
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
| | - Sammy Bedoui
- The Department of Microbiology and Immunology, The University of Melbourne, Melbourne, Australia
| | - Hubert Hilbi
- Max-von-Pettenkofer Institute, Ludwig Maximilian University, Munich, Germany
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Matthias Trost
- MRC Protein Phosphorylation Unit, University of Dundee, Dundee, United Kingdom
| | - Bastian Opitz
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité University Medicine Berlin, Berlin, Germany
- * E-mail:
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Targeting of host organelles by pathogenic bacteria: a sophisticated subversion strategy. Nat Rev Microbiol 2015; 14:5-19. [PMID: 26594043 DOI: 10.1038/nrmicro.2015.1] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Many bacterial pathogens have evolved the ability to subvert and exploit host functions in order to enter and replicate in eukaryotic cells. For example, bacteria have developed specific mechanisms to target eukaryotic organelles such as the nucleus, the mitochondria, the endoplasmic reticulum and the Golgi apparatus. In this Review, we highlight the most recent advances in our understanding of the mechanisms that bacterial pathogens use to target these organelles. We also discuss how these strategies allow bacteria to manipulate host functions and to ultimately enable bacterial infection.
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MavN is a Legionella pneumophila vacuole-associated protein required for efficient iron acquisition during intracellular growth. Proc Natl Acad Sci U S A 2015; 112:E5208-17. [PMID: 26330609 DOI: 10.1073/pnas.1511389112] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Iron is essential for the growth and virulence of most intravacuolar pathogens. The mechanisms by which microbes bypass host iron restriction to gain access to this metal across the host vacuolar membrane are poorly characterized. In this work, we identify a unique intracellular iron acquisition strategy used by Legionella pneumophila. The bacterial Icm/Dot (intracellular multiplication/defect in organelle trafficking) type IV secretion system targets the bacterial-derived MavN (more regions allowing vacuolar colocalization N) protein to the surface of the Legionella-containing vacuole where this putative transmembrane protein facilitates intravacuolar iron acquisition. The ΔmavN mutant exhibits a transcriptional iron-starvation signature before its growth is arrested during the very early stages of macrophage infection. This intracellular growth defect is rescued only by the addition of excess exogenous iron to the culture medium and not a variety of other metals. Consistent with MavN being a translocated substrate that plays an exclusive role during intracellular growth, the mutant shows no defect for growth in broth culture, even under severe iron-limiting conditions. Putative iron-binding residues within the MavN protein were identified, and point mutations in these residues resulted in defects specific for intracellular growth that are indistinguishable from the ΔmavN mutant. This model of a bacterial protein inserting into host membranes to mediate iron transport provides a paradigm for how intravacuolar pathogens can use virulence-associated secretion systems to manipulate and acquire host iron.
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Legionella pneumophila Effector LpdA Is a Palmitoylated Phospholipase D Virulence Factor. Infect Immun 2015. [PMID: 26216420 DOI: 10.1128/iai.00785-15] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Legionella pneumophila is a bacterial pathogen that thrives in alveolar macrophages, causing a severe pneumonia. The virulence of L. pneumophila depends on its Dot/Icm type IV secretion system (T4SS), which delivers more than 300 effector proteins into the host, where they rewire cellular signaling to establish a replication-permissive niche, the Legionella-containing vacuole (LCV). Biogenesis of the LCV requires substantial redirection of vesicle trafficking and remodeling of intracellular membranes. In order to achieve this, several T4SS effectors target regulators of membrane trafficking, while others resemble lipases. Here, we characterized LpdA, a phospholipase D effector, which was previously proposed to modulate the lipid composition of the LCV. We found that ectopically expressed LpdA was targeted to the plasma membrane and Rab4- and Rab14-containing vesicles. Subcellular targeting of LpdA required a C-terminal motif, which is posttranslationally modified by S-palmitoylation. Substrate specificity assays showed that LpdA hydrolyzed phosphatidylinositol, -inositol-3- and -4-phosphate, and phosphatidylglycerol to phosphatidic acid (PA) in vitro. In HeLa cells, LpdA generated PA at vesicles and the plasma membrane. Imaging of different phosphatidylinositol phosphate (PIP) and organelle markers revealed that while LpdA did not impact on membrane association of various PIP probes, it triggered fragmentation of the Golgi apparatus. Importantly, although LpdA is translocated inefficiently into cultured cells, an L. pneumophila ΔlpdA mutant displayed reduced replication in murine lungs, suggesting that it is a virulence factor contributing to L. pneumophila infection in vivo.
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Rana A, Kumar D, Rub A, Akhter Y. Proteome-scale identification and characterization of mitochondria targeting proteins of Mycobacterium avium subspecies paratuberculosis: Potential virulence factors modulating host mitochondrial function. Mitochondrion 2015; 23:42-54. [PMID: 26048556 DOI: 10.1016/j.mito.2015.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/21/2015] [Accepted: 05/04/2015] [Indexed: 02/03/2023]
Abstract
Mycobacterium avium subsp. paratuberculosis is the etiological agent of Johne's Disease among ruminants. During the course of infection, it expresses a number of proteins for its successful persistence inside the host that cause variety of physiological abnormalities in the host. Mitochondrion is one of the attractive targets for pathogenic bacteria. Employing a proteome-wide sequence and structural signature based approach we have identified 46 M. avium subsp. paratuberculosis proteins as potential targets for the host mitochondrial targeting. These may act as virulence factors modulating mitochondrial physiology for bacterial survival and immune evasion inside the host cells.
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Affiliation(s)
- Aarti Rana
- School of Life Sciences, Central University of Himachal Pradesh, Shahpur, District-Kangra, 176206 Himachal Pradesh, India
| | - Devender Kumar
- School of Life Sciences, Central University of Himachal Pradesh, Shahpur, District-Kangra, 176206 Himachal Pradesh, India
| | - Abdur Rub
- Infection and Immunity Lab, Department of Biotechnology, Jamia Millia Islamia (A Central University), New Delhi 110025, India
| | - Yusuf Akhter
- School of Life Sciences, Central University of Himachal Pradesh, Shahpur, District-Kangra, 176206 Himachal Pradesh, India.
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Finsel I, Hilbi H. Formation of a pathogen vacuole according to Legionella pneumophila: how to kill one bird with many stones. Cell Microbiol 2015; 17:935-50. [PMID: 25903720 DOI: 10.1111/cmi.12450] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 04/13/2015] [Accepted: 04/17/2015] [Indexed: 12/12/2022]
Abstract
Legionella species are ubiquitous, waterborne bacteria that thrive in numerous ecological niches. Yet, in contrast to many other environmental bacteria, Legionella spp. are also able to grow intracellularly in predatory protozoa. This feature mainly accounts for the pathogenicity of Legionella pneumophila, which causes the majority of clinical cases of a severe pneumonia termed Legionnaires' disease. The pathomechanism underlying L. pneumophila infection is based on macrophage resistance, which in turn is largely defined by the opportunistic pathogen's resistance towards amoebae. L. pneumophila replicates in macrophages or amoebae in a unique membrane-bound compartment, the Legionella-containing vacuole (LCV). LCV formation requires the bacterial intracellular multiplication/defective for organelle trafficking (Icm/Dot) type IV secretion system and involves a plethora of translocated effector proteins, which subvert pivotal processes in the host cell. Of the ca. 300 different experimentally validated Icm/Dot substrates, about 50 have been studied and attributed a cellular function to date. The versatility and ingenuity of these effectors' mode of actions is striking. In this review, we summarize insight into the cellular functions and biochemical activities of well-characterized L. pneumophila effector proteins and the host pathways they target. Recent studies not only substantially increased our knowledge about pathogen-host interactions, but also shed light on novel biological mechanisms.
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Affiliation(s)
- Ivo Finsel
- Max von Pettenkofer Institute, Ludwig-Maximilians University, Munich, Germany
| | - Hubert Hilbi
- Max von Pettenkofer Institute, Ludwig-Maximilians University, Munich, Germany.,Institute of Medical Microbiology, University of Zürich, Zürich, Switzerland
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So EC, Mattheis C, Tate EW, Frankel G, Schroeder GN. Creating a customized intracellular niche: subversion of host cell signaling by Legionella type IV secretion system effectors. Can J Microbiol 2015; 61:617-35. [PMID: 26059316 DOI: 10.1139/cjm-2015-0166] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The Gram-negative facultative intracellular pathogen Legionella pneumophila infects a wide range of different protozoa in the environment and also human alveolar macrophages upon inhalation of contaminated aerosols. Inside its hosts, it creates a defined and unique compartment, termed the Legionella-containing vacuole (LCV), for survival and replication. To establish the LCV, L. pneumophila uses its Dot/Icm type IV secretion system (T4SS) to translocate more than 300 effector proteins into the host cell. Although it has become apparent in the past years that these effectors subvert a multitude of cellular processes and allow Legionella to take control of host cell vesicle trafficking, transcription, and translation, the exact function of the vast majority of effectors still remains unknown. This is partly due to high functional redundancy among the effectors, which renders conventional genetic approaches to elucidate their role ineffective. Here, we review the current knowledge about Legionella T4SS effectors, highlight open questions, and discuss new methods that promise to facilitate the characterization of T4SS effector functions in the future.
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Affiliation(s)
- Ernest C So
- a MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, SW7 2AZ, UK.,b Department of Chemistry, South Kensington Campus, Imperial College, London, SW7 2AZ, UK
| | - Corinna Mattheis
- a MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | - Edward W Tate
- b Department of Chemistry, South Kensington Campus, Imperial College, London, SW7 2AZ, UK
| | - Gad Frankel
- a MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | - Gunnar N Schroeder
- a MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
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The Legionella Kinase LegK2 Targets the ARP2/3 Complex To Inhibit Actin Nucleation on Phagosomes and Allow Bacterial Evasion of the Late Endocytic Pathway. mBio 2015; 6:e00354-15. [PMID: 25944859 PMCID: PMC4436068 DOI: 10.1128/mbio.00354-15] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
UNLABELLED Legionella pneumophila, the etiological agent of legionellosis, replicates within phagocytic cells. Crucial to biogenesis of the replicative vacuole is the Dot/Icm type 4 secretion system, which translocates a large number of effectors into the host cell cytosol. Among them is LegK2, a protein kinase that plays a key role in Legionella infection. Here, we identified the actin nucleator ARP2/3 complex as a target of LegK2. LegK2 phosphorylates the ARPC1B and ARP3 subunits of the ARP2/3 complex. LegK2-dependent ARP2/3 phosphorylation triggers global actin cytoskeleton remodeling in cells, and it impairs actin tail formation by Listeria monocytogenes, a well-known ARP2/3-dependent process. During infection, LegK2 is addressed to the Legionella-containing vacuole surface and inhibits actin polymerization on the phagosome, as revealed by legK2 gene inactivation. Consequently, LegK2 prevents late endosome/lysosome association with the phagosome and finally contributes to remodeling of the bacterium-containing phagosome into a replicative niche. The inhibition of actin polymerization by LegK2 and its effect on endosome trafficking are ARP2/3 dependent since it can be phenocopied by a specific chemical inhibitor of the ARP2/3 complex. Thus, LegK2-ARP2/3 interplay highlights an original mechanism of bacterial virulence with an unexpected role in local actin remodeling that allows bacteria to control vesicle trafficking in order to escape host defenses. IMPORTANCE Deciphering the individual contribution of each Dot/Icm type 4 secretion system substrate to the intracellular life-style of L. pneumophila remains the principal challenge in understanding the molecular basis of Legionella virulence. Our finding that LegK2 is a Dot/Icm effector that inhibits actin polymerization on the Legionella-containing vacuole importantly contributes to the deciphering of the molecular mechanisms evolved by Legionella to counteract the endocytic pathway. Indeed, our results highlight the essential role of LegK2 in preventing late endosomes from fusing with the phagosome. More generally, this work is the first demonstration of local actin remodeling as a mechanism used by bacteria to control organelle trafficking. Further, by characterizing the role of the bacterial protein kinase LegK2, we reinforce the concept that posttranslational modifications are key strategies used by pathogens to evade host cell defenses.
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42
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Lobet E, Letesson JJ, Arnould T. Mitochondria: a target for bacteria. Biochem Pharmacol 2015; 94:173-85. [PMID: 25707982 DOI: 10.1016/j.bcp.2015.02.007] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 02/12/2015] [Accepted: 02/12/2015] [Indexed: 01/12/2023]
Abstract
Eukaryotic cells developed strategies to detect and eradicate infections. The innate immune system, which is the first line of defence against invading pathogens, relies on the recognition of molecular patterns conserved among pathogens. Pathogen associated molecular pattern binding to pattern recognition receptor triggers the activation of several signalling pathways leading to the establishment of a pro-inflammatory state required to control the infection. In addition, pathogens evolved to subvert those responses (with passive and active strategies) allowing their entry and persistence in the host cells and tissues. Indeed, several bacteria actively manipulate immune system or interfere with the cell fate for their own benefit. One can imagine that bacterial effectors can potentially manipulate every single organelle in the cell. However, the multiple functions fulfilled by mitochondria especially their involvement in the regulation of innate immune response, make mitochondria a target of choice for bacterial pathogens as they are not only a key component of the central metabolism through ATP production and synthesis of various biomolecules but they also take part to cell signalling through ROS production and control of calcium homeostasis as well as the control of cell survival/programmed cell death. Furthermore, considering that mitochondria derived from an ancestral bacterial endosymbiosis, it is not surprising that a special connection does exist between this organelle and bacteria. In this review, we will discuss different mitochondrial functions that are affected during bacterial infection as well as different strategies developed by bacterial pathogens to subvert functions related to calcium homeostasis, maintenance of redox status and mitochondrial morphology.
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Affiliation(s)
- Elodie Lobet
- Laboratory of Biochemistry and Cellular Biology (URBC), NAmur Research Institute for LIfe Science (NARILIS), University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
| | - Jean-Jacques Letesson
- Research Unit in Microorganisms Biology, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
| | - Thierry Arnould
- Laboratory of Biochemistry and Cellular Biology (URBC), NAmur Research Institute for LIfe Science (NARILIS), University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
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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] [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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Robertson P, Abdelhady H, Garduño RA. The many forms of a pleomorphic bacterial pathogen-the developmental network of Legionella pneumophila. Front Microbiol 2014; 5:670. [PMID: 25566200 PMCID: PMC4273665 DOI: 10.3389/fmicb.2014.00670] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 11/18/2014] [Indexed: 01/18/2023] Open
Abstract
Legionella pneumophila is a natural intracellular bacterial parasite of free-living freshwater protozoa and an accidental human pathogen that causes Legionnaires' disease. L. pneumophila differentiates, and does it in style. Recent experimental data on L. pneumophila's differentiation point at the existence of a complex network that involves many developmental forms. We intend readers to: (i) understand the biological relevance of L. pneumophila's forms found in freshwater and their potential to transmit Legionnaires' disease, and (ii) learn that the common depiction of L. pneumophila's differentiation as a biphasic developmental cycle that alternates between a replicative and a transmissive form is but an oversimplification of the actual process. Our specific objectives are to provide updates on the molecular factors that regulate L. pneumophila's differentiation (Section The Differentiation Process and Its Regulation), and describe the developmental network of L. pneumophila (Section Dissecting Lp's Developmental Network), which for clarity's sake we have dissected into five separate developmental cycles. Finally, since each developmental form seems to contribute differently to the human pathogenic process and the transmission of Legionnaires' disease, readers are presented with a challenge to develop novel methods to detect the various L. pneumophila forms present in water (Section Practical Implications), as a means to improve our assessment of risk and more effectively prevent legionellosis outbreaks.
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Affiliation(s)
- Peter Robertson
- Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada
| | - Hany Abdelhady
- Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada
| | - Rafael A Garduño
- Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada ; Division of Infectious Diseases, Department of Medicine, Dalhousie University Halifax, NS, Canada
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Comparative in-silico genome analysis of Leishmania (Leishmania) donovani: A step towards its species specificity. Meta Gene 2014; 2:782-98. [PMID: 25606461 PMCID: PMC4287845 DOI: 10.1016/j.mgene.2014.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 09/12/2014] [Accepted: 10/04/2014] [Indexed: 12/24/2022] Open
Abstract
Comparative genome analysis of recently sequenced Leishmania (L.) donovani was unexplored so far. The present study deals with the complete scanning of L. (L.) donovani genome revealing its interspecies variations. 60 distinctly present genes in L. (L.) donovani were identified when the whole genome was compared with Leishmania (L.) infantum. Similarly 72, 159, and 265 species specific genes were identified in L. (L.) donovani when compared to Leishmania (L.) major, Leishmania (L.) mexicana and Leishmania (Viannia) braziliensis respectively. The cross comparison of L. (L.) donovani in parallel with the other sequenced species of leishmanial led to the identification of 55 genes which are highly specific and expressed exclusively in L. (L.) donovani. We found mainly the discrepancies of surface proteins such as amastins, proteases, and peptidases. Also 415 repeat containing proteins in L. (L.) donovani and their differential distribution in other leishmanial species were identified which might have a potential role during pathogenesis. The genes identified can be evaluated as drug targets for anti-leishmanial treatment, exploring the scope for extensive future investigations. Comparative genome analysis identifies 55 species specific L. (L.) donovani genes. Discrepancies of surface proteins such as amastins, proteases, and peptidases are identified in L. (L.) donovani. Apical Membrane Antigen (AMA1) might be a novel factor which helps L. (L.) donovani invasion. Novel A2 and amastin genes in L. (L.) donovani genome are identified. Our study identifies differential gene distribution in L. (L.) donovani with respect to other leishmanial species.
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46
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Speir M, Vince JE, Naderer T. Programmed cell death in Legionella infection. Future Microbiol 2014; 9:107-18. [DOI: 10.2217/fmb.13.139] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
ABSTRACT: The causative agent of Legionnaires’ disease, Legionella pneumophila, resides within alveolar macrophages by exporting 295 bacterial virulence proteins (effectors) to modulate host cell processes. This leads to the formation of a unique vacuolar niche and the suppression of macrophage cell death pathways, which, in turn, promote bacterial survival and allow sufficient time for replication. However, once nutrients within the vacuole are depleted, Legionella must act to induce host cell death in order to facilitate bacterial egress and reinfect new cells. Intracellular Legionella also evade detection by the host cell’s innate immune system, which seeks to destroy invading pathogens by activating inflammasome complexes, thereby promoting proinflammatory cytokine activation and pyroptotic cell death. Understanding how different forms of programmed cell death contribute to Legionella infectivity and are manipulated by Legionella effector proteins will be important for identifying novel antibacterial therapeutic targets.
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Affiliation(s)
- Mary Speir
- Department of Biochemistry & Molecular Biology, Monash University, Clayton, 3800 Victoria, Australia
| | - James E Vince
- The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, 3052 Victoria, Australia
| | - Thomas Naderer
- Department of Biochemistry & Molecular Biology, Monash University, Clayton, 3800 Victoria, Australia
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Overexpression in E. coli and Purification of the L. pneumophila Lpp2981 Protein. Mol Biotechnol 2013; 56:157-65. [DOI: 10.1007/s12033-013-9691-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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48
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The Dot/Icm effector SdhA is necessary for virulence of Legionella pneumophila in Galleria mellonella and A/J mice. Infect Immun 2013; 81:2598-605. [PMID: 23649096 DOI: 10.1128/iai.00296-13] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Legionella pneumophila is an intracellular bacterium that resides within amoebae and macrophages in a specialized compartment termed the Legionella-containing vacuole (LCV). As well as providing an intracellular niche for replication, the LCV helps to prevent the release of bacterial components into the cytoplasm. Recognition of these components as danger signals by the host activates immune responses leading to clearance of the bacterium. Here, we examined the role of two important virulence factors of L. pneumophila, the potent danger signal flagellin and the translocated Dot/Icm type IVB secretion system effector SdhA, which is crucial to maintain LCV integrity, in the Galleria mellonella infection model. We demonstrate that flagellin expression does not contribute to virulence, replication, or induction of clearance mechanisms. Conversely, SdhA expression is important for virulence. We found that in the absence of SdhA, the LCV in hemocytes showed signs of instability and leakage. Furthermore, in contrast to wild-type L. pneumophila, a ΔsdhA mutant caused a transient depletion of hemocytes and reduced mortality. Analysis of the ΔsdhA mutant in the A/J mouse model also showed a significant replication defect. Together, our data underline the crucial importance of SdhA in infection across different model organisms.
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49
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Sun EW, Wagner ML, Maize A, Kemler D, Garland-Kuntz E, Xu L, Luo ZQ, Hollenbeck PJ. Legionella pneumophila infection of Drosophila S2 cells induces only minor changes in mitochondrial dynamics. PLoS One 2013; 8:e62972. [PMID: 23638172 PMCID: PMC3640039 DOI: 10.1371/journal.pone.0062972] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 03/28/2013] [Indexed: 12/02/2022] Open
Abstract
During infection of cells by Legionella pneumophila, the bacterium secretes a large number of effector proteins into the host cell cytoplasm, allowing it to alter many cellular processes and make the vacuole and the host cell into more hospitable environments for bacterial replication. One major change induced by infection is the recruitment of ER-derived vesicles to the surface of the vacuole, where they fuse with the vacuole membrane and prevent it from becoming an acidified, degradative compartment. However, the recruitment of mitochondria to the region of the vacuole has also been suggested by ultrastructural studies. In order to test this idea in a controlled and quantitative experimental system, and to lay the groundwork for a genome-wide screen for factors involved in mitochondrial recruitment, we examined the behavior of mitochondria during the early stages of Legionella pneumophila infection of Drosophila S2 cells. We found that the density of mitochondria near vacuoles formed by infection with wild type Legionella was not different from that found in dotA– mutant-infected cells during the first 4 hours after infection. We then examined 4 parameters of mitochondrial motility in infected cells: velocity of movement, duty cycle of movement, directional persistence and net direction. In the 4 hours following infection, most of these measures were indistinguishable between wild type and dotA−.infection. However, wild type Legionella did induce a modest shift in the velocity distribution toward faster movement compared dotA− infection, and a small downward shift in the duty cycle distribution. In addition, wild type infection produced mitochondrial movement that was biased in the direction of the bacterial vacuole relative to dotA-, although not enough to cause a significant accumulation within 10 um of the vacuole. We conclude that in this host cell, mitochondria are not strongly recruited to the vacuole, nor is their motility dramatically affected.
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Affiliation(s)
- Elizabeth Wen Sun
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Monica L. Wagner
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Amanda Maize
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Doris Kemler
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Elisabeth Garland-Kuntz
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Li Xu
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Zhao-Qing Luo
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Peter J. Hollenbeck
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
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Vogrin AJ, Mousnier A, Frankel G, Hartland EL. Subcellular localization of legionella Dot/Icm effectors. Methods Mol Biol 2013; 954:333-44. [PMID: 23150406 DOI: 10.1007/978-1-62703-161-5_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The translocation of effector proteins by the Dot/Icm type IV secretion system is central to the ability of Legionella pneumophila to persist and replicate within eukaryotic cells. The subcellular localization of translocated Dot/Icm proteins in host cells provides insight into their function. Through co-staining with host cell markers, effector proteins may be localized to specific subcellular compartments and membranes, which frequently reflects their host cell target and mechanism of action. In this chapter, we describe protocols to (1) localize effector proteins within cells by ectopic expression using green fluorescent protein fusions and (2) localize effector proteins within infected cells using epitope-tagged effector proteins and immuno-fluorescence microscopy.
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Affiliation(s)
- Adam J Vogrin
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, VIC, Australia
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