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A Chlamydial Plasmid-Dependent Secretion System for the Delivery of Virulence Factors to the Host Cytosol. mBio 2021; 12:e0117921. [PMID: 34101486 PMCID: PMC8262877 DOI: 10.1128/mbio.01179-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Chlamydia are obligate intracellular Gram-negative bacteria distinguished by a unique developmental biology confined within a parasitophorous vacuole termed an inclusion. The chlamydial plasmid is a central virulence factor in the pathogenesis of infection. Plasmid gene protein 4 (Pgp4) regulates the expression of plasmid gene protein 3 (Pgp3) and chromosomal glycogen synthase (GlgA), virulence factors secreted from the inclusion to the host cytosol by an unknown mechanism. Here, we identified a plasmid-dependent secretion system for the cytosolic delivery of Pgp3 and GlgA. The secretion system consisted of a segregated population of globular structures originating from midcycle reticulate bodies. Globular structures contained the Pgp4-regulated proteins CT143, CT144, and CT050 in addition to Pgp3 and GlgA. Genetic replacement of Pgp4 with Pgp3 or GlgA negated the formation of globular structures, resulting in retention of Pgp3 and GlgA in chlamydial organisms. The generation of globular structures and secretion of virulence factors occurred independently of type 2 and type 3 secretion systems. Globular structures were enriched with lipopolysaccharide but lacked detectable major outer membrane protein and heat shock protein 60, implicating them as outer membrane vesicles. Thus, we have discovered a novel chlamydial plasmid-dependent secretion system that transports virulence factor cargo from the chlamydial inclusion to the host cytosol.
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2
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Bugalhão JN, Mota LJ. The multiple functions of the numerous Chlamydia trachomatis secreted proteins: the tip of the iceberg. MICROBIAL CELL 2019; 6:414-449. [PMID: 31528632 PMCID: PMC6717882 DOI: 10.15698/mic2019.09.691] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Chlamydia trachomatis serovars are obligate intracellular bacterial pathogens mainly causing ocular and urogenital infections that affect millions of people worldwide and which can lead to blindness or sterility. They reside and multiply intracellularly within a membrane-bound vacuolar compartment, known as inclusion, and are characterized by a developmental cycle involving two morphologically and physiologically distinct chlamydial forms. Completion of the developmental cycle involves the secretion of > 70 C. trachomatis proteins that function in the host cell cytoplasm and nucleus, in the inclusion membrane and lumen, and in the extracellular milieu. These proteins can, for example, interfere with the host cell cytoskeleton, vesicular and non-vesicular transport, metabolism, and immune signalling. Generally, this promotes C. trachomatis invasion into, and escape from, host cells, the acquisition of nutrients by the chlamydiae, and evasion of cell-autonomous, humoral and cellular innate immunity. Here, we present an in-depth review on the current knowledge and outstanding questions about these C. trachomatis secreted proteins.
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Affiliation(s)
- Joana N Bugalhão
- UCIBIO, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Luís Jaime Mota
- UCIBIO, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal
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3
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Make It a Sweet Home: Responses of Chlamydia trachomatis to the Challenges of an Intravacuolar Lifestyle. Microbiol Spectr 2019; 7. [PMID: 30848236 DOI: 10.1128/microbiolspec.bai-0005-2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Intravacuolar development has been adopted by several bacteria that grow inside a host cell. Remaining in a vacuole, as opposed to breaching the cytosol, protects the bacteria from some aspects of the cytosolic innate host defense and allows them to build an environment perfectly adapted to their needs. However, this raises new challenges: the host resources are separated from the bacteria by a lipid bilayer that is nonpermeable to most nutrients. In addition, the area of this lipid bilayer needs to expand to accommodate bacterial multiplication. This requires building material and energy that are not directly invested in bacterial growth. This article describes the strategies acquired by the obligate intracellular pathogen Chlamydia trachomatis to circumvent the difficulties raised by an intravacuolar lifestyle. We start with an overview of the origin and composition of the vacuolar membrane. Acquisition of host resources is largely, although not exclusively, mediated by interactions with membranous compartments of the eukaryotic cell, and we describe how the inclusion modifies the architecture of the cell and distribution of the neighboring compartments. The second part of this review describes the four mechanisms characterized so far by which the bacteria acquire resources from the host: (i) transport/diffusion across the vacuole membrane, (ii) fusion of this membrane with host compartments, (iii) direct transfer of lipids at membrane contact sites, and (iv) engulfment by the vacuole membrane of large cytoplasmic entities.
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Olson MG, Jorgenson LM, Widner RE, Rucks EA. Proximity Labeling of the Chlamydia trachomatis Inclusion Membrane. Methods Mol Biol 2019; 2042:245-278. [PMID: 31385281 DOI: 10.1007/978-1-4939-9694-0_17] [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: 01/09/2023]
Abstract
In the study of intracellular bacteria that reside within a membrane-bound vacuole, there are many questions related to how prokaryotic or eukaryotic transmembrane or membrane-associated proteins are organized and function within the membranes of these pathogen-containing vacuoles. Yet this host-pathogen interaction interface has proven difficult to experimentally resolve. For example, one method to begin to understand protein function is to determine the protein-binding partners; however, examining protein-protein interactions of hydrophobic transmembrane proteins is not widely successful using standard immunoprecipitation or coimmunoprecipitation techniques. In these scenarios, the lysis conditions that maintain protein-protein interactions are not compatible with solubilizing hydrophobic membrane proteins. In this chapter, we outline two proximity labeling systems to circumvent these issues to study (1) eukaryotic proteins that localize to the membrane-bound inclusion formed by Chlamydia trachomatis using BioID, and (2) chlamydial proteins that are inserted into the inclusion membrane using APEX2. BioID is a promiscuous biotin ligase to tag proximal proteins with biotin. APEX2 is an ascorbate peroxidase that creates biotin-phenoxyl radicals to label proximal proteins with biotin or 3,3'-diaminobenzidine intermediates for examination of APEX2 labeling of subcellular structures using transmission electron microscopy. We present how these methods were originally conceptualized and developed, so that the user can understand the strengths and limitations of each proximity labeling system. We discuss important considerations regarding experimental design, which include careful consideration of background conditions and statistical analysis of mass spectrometry results. When applied in the appropriate context with adequate controls, these methods can be powerful tools toward understanding membrane interfaces between intracellular pathogens and their hosts.
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Affiliation(s)
- Macy G Olson
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Lisa M Jorgenson
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Ray E Widner
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Elizabeth A Rucks
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, USA.
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5
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Prusty BK, Chowdhury SR, Gulve N, Rudel T. Peptidase Inhibitor 15 (PI15) Regulates Chlamydial CPAF Activity. Front Cell Infect Microbiol 2018; 8:183. [PMID: 29900129 PMCID: PMC5989220 DOI: 10.3389/fcimb.2018.00183] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 05/11/2018] [Indexed: 12/11/2022] Open
Abstract
Obligate intracellular pathogenic Chlamydia trachomatis express several serine proteases whose roles in chlamydial development and pathogenicity are not completely understood. The chlamydial protease CPAF is expressed during the replicative phase of the chlamydial developmental cycle and is secreted into the lumen of the Chlamydia-containing vacuole called inclusion. How the secreted protease is activated in the inclusion lumen is currently not fully understood. We have identified human serine peptidase inhibitor PI15 as a potential host factor involved in the regulation of CPAF activation. Silencing expression as well as over expression of PI15 affected normal development of Chlamydia. PI15 was transported into the chlamydial inclusion lumen where it co-localized with CPAF aggregates. We show that PI15 binds to the CPAF zymogen and potentially induces CPAF protease activity at low concentrations. However, at high concentrations PI15 inhibits CPAF activity possibly by blocking its protease domain. Our findings shed light on a new aspect of chlamydial host co-evolution which involves the recruitment of host cell proteins into the inclusion to control the activation of bacterial proteases like CPAF that are important for the normal development of Chlamydia.
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Affiliation(s)
- Bhupesh K Prusty
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
| | | | - Nitish Gulve
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
| | - Thomas Rudel
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
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VanCleave TT, Pulsifer AR, Connor MG, Warawa JM, Lawrenz MB. Impact of Gentamicin Concentration and Exposure Time on Intracellular Yersinia pestis. Front Cell Infect Microbiol 2017; 7:505. [PMID: 29312891 PMCID: PMC5732358 DOI: 10.3389/fcimb.2017.00505] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 11/22/2017] [Indexed: 11/27/2022] Open
Abstract
The study of intracellular bacterial pathogens in cell culture hinges on inhibiting extracellular growth of the bacteria in cell culture media. Aminoglycosides, like gentamicin, were originally thought to poorly penetrate eukaryotic cells, and thus, while inhibiting extracellular bacteria, these antibiotics had limited effect on inhibiting the growth of intracellular bacteria. This property led to the development of the antibiotic protection assay to study intracellular pathogens in vitro. More recent studies have demonstrated that aminoglycosides slowly penetrate eukaryotic cells and can even reach intracellular concentrations that inhibit intracellular bacteria. Therefore, important considerations, such as antibiotic concentration, incubation time, and cell type need to be made when designing the antibiotic protection assay to avoid potential false positive/negative observations. Yersinia pestis, which causes the human disease known as the plague, is a facultative intracellular pathogen that can infect and replicate in macrophages. Y. pestis is sensitive to gentamicin and this antibiotic is often employed in the antibiotic protection assay to study the Y. pestis intracellular life cycle. However, a large variety of gentamicin concentrations and incubation periods have been reported in the Y. pestis literature without a clear characterization of the potential influences that variations in the gentamicin protection assay could have on intracellular growth of this pathogen. This raised concerns that variations in the gentamicin protection assay could influence phenotypes and reproducibility of data. To provide a better understanding of the potential consequences that variations in the gentamicin protection assay could have on Y. pestis, we systematically examined the impact of multiple variables of the gentamicin protection assay on Y. pestis intracellular survival in macrophages. We found that prolonged incubation periods with low concentrations of gentamicin, or short incubation periods with higher concentrations of the antibiotic, have a dramatic impact on intracellular growth. Furthermore, the degree of sensitivity of intracellular Y. pestis to gentamicin was also cell type dependent. These data highlight the importance to empirically establish cell type specific gentamicin protection assays to avoid potential artificial data in Y. pestis intracellular studies.
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Affiliation(s)
- Tiva T VanCleave
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
| | - Amanda R Pulsifer
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
| | - Michael G Connor
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
| | - Jonathan M Warawa
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
| | - Matthew B Lawrenz
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
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Soupene E, Kuypers FA. Phosphatidylserine decarboxylase CT699, lysophospholipid acyltransferase CT775, and acyl-ACP synthase CT776 provide membrane lipid diversity to Chlamydia trachomatis. Sci Rep 2017; 7:15767. [PMID: 29150677 PMCID: PMC5693948 DOI: 10.1038/s41598-017-16116-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 11/07/2017] [Indexed: 02/08/2023] Open
Abstract
De novo lipid synthesis and scavenging of fatty acids (FA) are processes essential for the formation of the membrane of the human pathogen Chlamydia trachomatis (C.t.). Host FA are assimilated via esterification by the bacterial acyl-acyl carrier protein (ACP) synthase AasC but inhibitors of the host acyl-CoA synthetase enymes ACSL also impaired growth of C.t. in human cells. In E. coli, activity of AasC was sensitive to triacsin C and rosiglitazone G. The absence of a triacsin C-insensitive pathway and the increased inhibition by rosiglitazone G confirmed the sensitivity of the bacterial acyl-ACP synthase to these drugs in infected human cells. We found no evidence that the human ACSL enzymes are required for lipid formation by C.t. The broad substrate specificity of acyltransferase CT775 provides C.t. with the capacity to incorporate straight-chain and bacterial specific branched-chain fatty acids. CT775 accepts both acyl-ACP and acyl-CoA as acyl donors and, 1- or 2-acyl isomers of lysophosphoplipids as acyl acceptors. The enzyme responsible for remodeling of human phosphatidylserine to bacterial phosphatidylethanolamine was identified as CT699. These findings provide evidence that the pathogen has the ability to extend the lipid diversity of its membrane.
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Affiliation(s)
- Eric Soupene
- Children's Hospital Oakland Research Institute, Oakland, CA, USA.
| | - Frans A Kuypers
- Children's Hospital Oakland Research Institute, Oakland, CA, USA
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8
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Broad recruitment of mGBP family members to Chlamydia trachomatis inclusions. PLoS One 2017; 12:e0185273. [PMID: 28945814 PMCID: PMC5612764 DOI: 10.1371/journal.pone.0185273] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 09/08/2017] [Indexed: 12/22/2022] Open
Abstract
Chlamydia, the most common sexually transmitted pathogen, is an exquisitely adapted Gram-negative obligate intracellular bacterium. Intracellular Chlamydia trachomatis replicate in a specialized vacuole, termed inclusion, which shields the bacterium from antimicrobial immunity of the host cells and acts as a signalling interface. Previously it was shown that members of the interferon induced guanylate binding protein (mGBP) family, in particular murine GBP1 and mGBP2, were found to accumulate at the bacterial inclusions, similar to previously published recruitment of GBPs to the parasitophorous vacuole of Toxoplasma gondii. Here, we provide a wide comparison of mGBPs roles within the host cell in the context of Chlamydia and Toxoplasma infection. By confocal microscopy on fixed and living infected cells we show localization of mGBP3, mGBP6, mGBP7, mGBP9, and mGBP10, in addition to mGBP1 and mGBP2, at chlamydia inclusions. In time lapse videos using GFP expressing Chlamydia we show rapid and transient dynamics of mGBP9 accumulation onto chlamydia inclusions. Taken together this study reveals a broad activation of mGBP recruitment towards Chlamydia trachomatis inclusions after infection and provides evidence for time limited action of mGBP9 at the chlamydia inclusion.
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Abstract
Chlamydia spp. are important causes of human disease for which no effective vaccine exists. These obligate intracellular pathogens replicate in a specialized membrane compartment and use a large arsenal of secreted effectors to survive in the hostile intracellular environment of the host. In this Review, we summarize the progress in decoding the interactions between Chlamydia spp. and their hosts that has been made possible by recent technological advances in chlamydial proteomics and genetics. The field is now poised to decipher the molecular mechanisms that underlie the intimate interactions between Chlamydia spp. and their hosts, which will open up many exciting avenues of research for these medically important pathogens.
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10
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Recuero-Checa MA, Sharma M, Lau C, Watkins PA, Gaydos CA, Dean D. Chlamydia trachomatis growth and development requires the activity of host Long-chain Acyl-CoA Synthetases (ACSLs). Sci Rep 2016; 6:23148. [PMID: 26988341 PMCID: PMC4796813 DOI: 10.1038/srep23148] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 02/25/2016] [Indexed: 11/17/2022] Open
Abstract
The obligate-intracellular pathogen Chlamydia trachomatis (Ct) has undergone considerable genome reduction with consequent dependence on host biosynthetic pathways, metabolites and enzymes. Long-chain acyl-CoA synthetases (ACSLs) are key host-cell enzymes that convert fatty acids (FA) into acyl-CoA for use in metabolic pathways. Here, we show that the complete host ACSL family [ACSL1 and ACSL3-6] translocates into the Ct membrane-bound vacuole, termed inclusion, and remains associated with membranes of metabolically active forms of Ct throughout development. We discovered that three different pharmacologic inhibitors of ACSL activity independently impede Ct growth in a dose-dependent fashion. Using an FA competition assay, host ACSLs were found to activate Ct branched-chain FAs, suggesting that one function of the ACSLs is to activate Ct FAs and host FAs (recruited from the cytoplasm) within the inclusion. Because the ACSL inhibitors can deplete lipid droplets (LD), we used a cell line where LD synthesis was switched off to evaluate whether LD deficiency affects Ct growth. In these cells, we found no effect on growth or on translocation of ACSLs into the inclusion. Our findings support an essential role for ACSL activation of host-cell and bacterial FAs within the inclusion to promote Ct growth and development, independent of LDs.
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Affiliation(s)
- Maria A. Recuero-Checa
- Center for Immunobiology and Vaccine Development, UCSF Benioff Children’s Hospital Oakland Research Institute, Oakland, CA, 94609, USA
- Department of Infectious Disease, Johns Hopkins University, Baltimore, MD, 21205, USA
| | - Manu Sharma
- Center for Immunobiology and Vaccine Development, UCSF Benioff Children’s Hospital Oakland Research Institute, Oakland, CA, 94609, USA
| | - Constance Lau
- Center for Immunobiology and Vaccine Development, UCSF Benioff Children’s Hospital Oakland Research Institute, Oakland, CA, 94609, USA
| | - Paul A. Watkins
- Hugo W. Moser Research Institute at Kennedy Krieger, Baltimore, MD, 21205, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Charlotte A. Gaydos
- Department of Infectious Disease, Johns Hopkins University, Baltimore, MD, 21205, USA
| | - Deborah Dean
- Center for Immunobiology and Vaccine Development, UCSF Benioff Children’s Hospital Oakland Research Institute, Oakland, CA, 94609, USA
- Department of Bioengineering, University of California at Berkeley and San Francisco, CA, USA
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11
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Gehre L, Gorgette O, Perrinet S, Prevost MC, Ducatez M, Giebel AM, Nelson DE, Ball SG, Subtil A. Sequestration of host metabolism by an intracellular pathogen. eLife 2016; 5:e12552. [PMID: 26981769 PMCID: PMC4829429 DOI: 10.7554/elife.12552] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 03/15/2016] [Indexed: 01/22/2023] Open
Abstract
For intracellular pathogens, residence in a vacuole provides a shelter against cytosolic host defense to the cost of limited access to nutrients. The human pathogen Chlamydia trachomatis grows in a glycogen-rich vacuole. How this large polymer accumulates there is unknown. We reveal that host glycogen stores shift to the vacuole through two pathways: bulk uptake from the cytoplasmic pool, and de novo synthesis. We provide evidence that bacterial glycogen metabolism enzymes are secreted into the vacuole lumen through type 3 secretion. Our data bring strong support to the following scenario: bacteria co-opt the host transporter SLC35D2 to import UDP-glucose into the vacuole, where it serves as substrate for de novo glycogen synthesis, through a remarkable adaptation of the bacterial glycogen synthase. Based on these findings we propose that parasitophorous vacuoles not only offer protection but also provide a microorganism-controlled metabolically active compartment essential for redirecting host resources to the pathogens.
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Affiliation(s)
- Lena Gehre
- Unité de Biologie cellulaire de l'infection microbienne, Institut Pasteur, Paris, France.,CNRS UMR3691, Paris, France
| | - Olivier Gorgette
- Plate-forme de Microscopie Ultrastructurale, Imagopole, Institut Pasteur, Paris, France
| | - Stéphanie Perrinet
- Unité de Biologie cellulaire de l'infection microbienne, Institut Pasteur, Paris, France.,CNRS UMR3691, Paris, France
| | | | - Mathieu Ducatez
- Unité de Glycobiologie Structurale et Fonctionnelle - CNRS UMR8576, Université de Lille, Lille, France
| | - Amanda M Giebel
- Department of Biology, Indiana University Bloomington, Bloomington, United States
| | - David E Nelson
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, United States
| | - Steven G Ball
- Unité de Glycobiologie Structurale et Fonctionnelle - CNRS UMR8576, Université de Lille, Lille, France
| | - Agathe Subtil
- Unité de Biologie cellulaire de l'infection microbienne, Institut Pasteur, Paris, France.,CNRS UMR3691, Paris, France
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Truchan HK, Cockburn CL, Hebert KS, Magunda F, Noh SM, Carlyon JA. The Pathogen-Occupied Vacuoles of Anaplasma phagocytophilum and Anaplasma marginale Interact with the Endoplasmic Reticulum. Front Cell Infect Microbiol 2016; 6:22. [PMID: 26973816 PMCID: PMC4771727 DOI: 10.3389/fcimb.2016.00022] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 02/08/2016] [Indexed: 11/13/2022] Open
Abstract
The genus Anaplasma consists of tick-transmitted obligate intracellular bacteria that invade white or red blood cells to cause debilitating and potentially fatal infections. A. phagocytophilum, a human and veterinary pathogen, infects neutrophils to cause granulocytic anaplasmosis. A. marginale invades bovine erythrocytes. Evidence suggests that both species may also infect endothelial cells in vivo. In mammalian and arthropod host cells, A. phagocytophilum and A. marginale reside in host cell derived pathogen-occupied vacuoles (POVs). While it was recently demonstrated that the A. phagocytophilum-occupied vacuole (ApV) intercepts membrane traffic from the trans-Golgi network, it is unclear if it or the A. marginale-occupied vacuole (AmV) interacts with other secretory organelles. Here, we demonstrate that the ApV and AmV extensively interact with the host endoplasmic reticulum (ER) in endothelial, myeloid, and/or tick cells. ER lumen markers, calreticulin, and protein disulfide isomerase, and the ER membrane marker, derlin-1, were pronouncedly recruited to the peripheries of both POVs. ApV association with the ER initiated early and continued throughout the infection cycle. Both the ApV and AmV interacted with the rough ER and smooth ER. However, only derlin-1-positive rough ER derived vesicles were delivered into the ApV lumen where they localized with intravacuolar bacteria. Transmission electron microscopy identified multiple ER-POV membrane contact sites on the cytosolic faces of both species' vacuoles that corresponded to areas on the vacuoles' lumenal faces where intravacuolar Anaplasma organisms closely associated. A. phagocytophilum is known to hijack Rab10, a GTPase that regulates ER dynamics and morphology. Yet, ApV-ER interactions were unhindered in cells in which Rab10 had been knocked down, demonstrating that the GTPase is dispensable for the bacterium to parasitize the ER. These data establish the ApV and AmV as pathogen-host interfaces that directly engage the ER in vertebrate and invertebrate host cells and evidence the conservation of ER parasitism between two Anaplasma species.
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Affiliation(s)
- Hilary K Truchan
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine Richmond, VA, USA
| | - Chelsea L Cockburn
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine Richmond, VA, USA
| | - Kathryn S Hebert
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine Richmond, VA, USA
| | - Forgivemore Magunda
- Program in Vector Borne Diseases, Department of Veterinary Microbiology and Pathology, Washington State UniversityPullman, WA, USA; The Paul G. Allen School for Global Animal Health, Washington State UniversityPullman, WA, USA
| | - Susan M Noh
- Program in Vector Borne Diseases, Department of Veterinary Microbiology and Pathology, Washington State UniversityPullman, WA, USA; Animal Disease Research Unit, Agricultural Research Service, U. S. Department of AgriculturePullman, WA, USA
| | - Jason A Carlyon
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine Richmond, VA, USA
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13
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Membrane contact sites between pathogen-containing compartments and host organelles. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:895-899. [PMID: 26825687 DOI: 10.1016/j.bbalip.2016.01.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 01/20/2016] [Accepted: 01/25/2016] [Indexed: 11/23/2022]
Abstract
Intracellular pathogens survive and replicate within specialised membrane-bound compartments that can be considered as pseudo-organelles. Using the obligate intracellular bacterium Chlamydia as an illustrative example, we consider the modes of lipid transport between pathogen-containing compartments and host organelles, including the formation of static membrane contact sites. We discuss how lipid scavenging can be mediated via the reprogramming of cellular transporters at these interfaces and describe recent data suggesting that pathogen effectors modulate the formation of specific membrane contacts. Further study of these emerging mechanisms is likely to yield new insights into the cell biology of lipid transport and organelle communication, which highlights potential new targets and strategies for future therapeutics. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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