51
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Mitchell G, Isberg RR. Innate Immunity to Intracellular Pathogens: Balancing Microbial Elimination and Inflammation. Cell Host Microbe 2018; 22:166-175. [PMID: 28799902 DOI: 10.1016/j.chom.2017.07.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Recent excitement regarding immune clearance of intracellular microorganisms has focused on two systems that maintain cellular homeostasis. One system includes cellular autophagy components that mediate degradation of pathogens in membrane-bound compartments, in a process termed xenophagy. The second system is driven by interferon-regulated GTPases that promote rupture of pathogen-containing vacuoles and microbial degradation. In the case of xenophagy, pathogen sequestration and compartmentalization suppress inflammation. In contrast, interferon-driven events can lead to exposure of pathogen-associated molecular patterns to the host cytosol with consequent inflammasome activation. Paradoxically, signals and factors involved in xenophagy also mobilize interferon-regulated GTPases, which drive the inflammatory response, indicating considerable cross-talk between these pathways. How these responses are prioritized remains to be understood. In this review, we describe mechanisms of intracellular pathogen clearance that rely on the autophagy machinery and interferon-regulated GTPases, and speculate how these pathways engage each other to balance pathogen elimination with inflammation.
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Affiliation(s)
- Gabriel Mitchell
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA.
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52
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Abstract
Interferon effector functions and autophagy are evolutionarily conserved arms of cell-autonomous immunity that restrict replication of intracellular pathogens. In this issue of Cell Host and Microbe, Biering et al., (2017) demonstrate how host cells co-opt sequential action of autophagy proteins and IFN-inducible GTPases to inhibit replication of positive-sense RNA viruses.
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53
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Cadwell K, Debnath J. Beyond self-eating: The control of nonautophagic functions and signaling pathways by autophagy-related proteins. J Cell Biol 2018; 217:813-822. [PMID: 29237720 PMCID: PMC5839790 DOI: 10.1083/jcb.201706157] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 11/16/2017] [Accepted: 11/17/2017] [Indexed: 12/12/2022] Open
Abstract
The identification of conserved autophagy-related proteins (ATGs) that mediate bulk degradation of cytosolic material laid the foundation for breakthroughs linking autophagy to a litany of physiological processes and disease conditions. Recent discoveries are revealing that these same ATGs orchestrate processes that are related to, and yet clearly distinct from, classic autophagy. Autophagy-related functions include secretion, trafficking of phagocytosed material, replication and egress of viral particles, and regulation of inflammatory and immune signaling cascades. Here, we define common processes dependent on ATGs, and discuss the challenges in mechanistically separating autophagy from these related pathways. Elucidating the molecular events that distinguish how individual ATGs function promises to improve our understanding of the origin of diseases ranging from autoimmunity to cancer.
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Affiliation(s)
- Ken Cadwell
- Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, NY
- Department of Microbiology, New York University School of Medicine, New York, NY
| | - Jayanta Debnath
- Department of Pathology and Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA
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54
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Coppens I. How Toxoplasma and malaria parasites defy first, then exploit host autophagic and endocytic pathways for growth. Curr Opin Microbiol 2017; 40:32-39. [DOI: 10.1016/j.mib.2017.10.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 09/15/2017] [Accepted: 10/15/2017] [Indexed: 02/07/2023]
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55
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Schille S, Crauwels P, Bohn R, Bagola K, Walther P, van Zandbergen G. LC3-associated phagocytosis in microbial pathogenesis. Int J Med Microbiol 2017; 308:228-236. [PMID: 29169848 DOI: 10.1016/j.ijmm.2017.10.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 10/26/2017] [Accepted: 10/31/2017] [Indexed: 12/18/2022] Open
Abstract
Phagocytosis is essential for uptake and elimination of pathogenic microorganisms. Autophagy is a highly conserved mechanism for incorporation of cellular constituents to replenish nutrients by degradation. Recently, parts of the autophagy machinery - above all microtubule-associated protein 1 light chain 3 (LC3) - were found to be specifically recruited to phagosomal membranes resulting in phagosome-lysosome fusion and efficient degradation of internalized cargo in a process termed LC3-associated phagocytosis (LAP). Many pathogenic bacterial, fungal and parasitic microorganisms reside within LAP-targeted single-membrane phagosomes or vacuoles after infection of host cells. In this minireview we describe the state of knowledge on the interaction of pathogens with LAP or LAP-like pathways and report on various pathogens that have evolved strategies to circumvent degradation in LAP compartments.
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Affiliation(s)
- Stefan Schille
- Department of Immunology, Paul-Ehrlich-Institut, Paul-Ehrlich-Straße 51-59, 63225 Langen, Germany
| | - Peter Crauwels
- Department of Immunology, Paul-Ehrlich-Institut, Paul-Ehrlich-Straße 51-59, 63225 Langen, Germany
| | - Rebecca Bohn
- Department of Immunology, Paul-Ehrlich-Institut, Paul-Ehrlich-Straße 51-59, 63225 Langen, Germany
| | - Katrin Bagola
- Department of Immunology, Paul-Ehrlich-Institut, Paul-Ehrlich-Straße 51-59, 63225 Langen, Germany
| | - Paul Walther
- Central Facility for EM, Ulm University, Ulm, Germany
| | - Ger van Zandbergen
- Department of Immunology, Paul-Ehrlich-Institut, Paul-Ehrlich-Straße 51-59, 63225 Langen, Germany; Institute for Immunology, University Medicine Mainz, Langenbeckstraße 1, 55131 Mainz, Germany.
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56
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Abstract
The cellular degradative pathway of autophagy has a fundamental role in immunity. Here, we review the function of autophagy and autophagy proteins in inflammation. We discuss how the autophagy machinery controls the burden of infectious agents while simultaneously limiting inflammatory pathologies, which often involves processes that are distinct from conventional autophagy. Among the newly emerging processes we describe are LC3-associated phagocytosis and targeting by autophagy proteins, both of which require many of the same proteins that mediate conventional autophagy. We also discuss how autophagy contributes to differentiation of myeloid and lymphoid cell types, coordinates multicellular immunity, and facilitates memory responses. Together, these functions establish an intimate link between autophagy, mucosal immunity, and chronic inflammatory diseases. Finally, we offer our perspective on current challenges and barriers to translation.
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Affiliation(s)
- Yu Matsuzawa-Ishimoto
- Kimmel Center for Biology and Medicine at the Skirball Institute and.,Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA; ,
| | - Seungmin Hwang
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637, USA;
| | - Ken Cadwell
- Kimmel Center for Biology and Medicine at the Skirball Institute and.,Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA; ,
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57
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Saeij JP, Frickel EM. Exposing Toxoplasma gondii hiding inside the vacuole: a role for GBPs, autophagy and host cell death. Curr Opin Microbiol 2017; 40:72-80. [PMID: 29141239 PMCID: PMC7004510 DOI: 10.1016/j.mib.2017.10.021] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 10/24/2017] [Indexed: 11/28/2022]
Abstract
The intracellular parasite Toxoplasma gondii resides inside a vacuole, which shields it from the host’s intracellular defense mechanisms. The cytokine interferon gamma (IFNγ) upregulates host cell effector pathways that are able to destroy the vacuole, restrict parasite growth and induce host cell death. Interferon-inducible GTPases such as the Guanylate Binding Proteins (GBPs), autophagy proteins and ubiquitin-driven mechanisms play important roles in Toxoplasma control in mice and partly also in humans. The host inflammasome is regulated by GBPs in response to bacterial infection in murine cells and may also respond to Toxoplasma infection. Elucidation of murine Toxoplasma defense mechanisms are guiding studies on human cells, while inevitably leading to the discovery of human-specific pathways that often function in a cell type-dependent manner.
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Affiliation(s)
- Jeroen P Saeij
- School of Veterinary Medicine, Department of Pathology, Microbiology and Immunology, University of California, Davis, Davis, CA 95616, USA.
| | - Eva-Maria Frickel
- The Francis Crick Institute, Host-Toxoplasma Interaction Laboratory, 1 Midland Road, London NW1 1AT, UK.
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58
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Brasil TR, Freire-de-Lima CG, Morrot A, Vetö Arnholdt AC. Host- Toxoplasma gondii Coadaptation Leads to Fine Tuning of the Immune Response. Front Immunol 2017; 8:1080. [PMID: 28955329 PMCID: PMC5601305 DOI: 10.3389/fimmu.2017.01080] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 08/21/2017] [Indexed: 12/22/2022] Open
Abstract
Toxoplasma gondii has successfully developed strategies to evade host's immune response and reach immune privileged sites, which remains in a controlled environment inside quiescent tissue cysts. In this review, we will approach several known mechanisms used by the parasite to modulate mainly the murine immune system at its favor. In what follows, we review recent findings revealing interference of host's cell autonomous immunity and cell signaling, gene expression, apoptosis, and production of microbicide molecules such as nitric oxide and oxygen reactive species during parasite infection. Modulation of host's metalloproteinases of extracellular matrix is also discussed. These immune evasion strategies are determinant to parasite dissemination throughout the host taking advantage of cells from the immune system to reach brain and retina, crossing crucial hosts' barriers.
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Affiliation(s)
- Thaís Rigueti Brasil
- Laboratório de Biologia do Reconhecer, Universidade Estadual do Norte Fluminense, Rio de Janeiro, Brazil
| | | | - Alexandre Morrot
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.,Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
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59
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Yuan J, Han R, Esther A, Wu Q, Yang J, Yan W, Ji X, Liu Y, Li Y, Yao W, Ni C. Polymorphisms in autophagy related genes and the coal workers' pneumoconiosis in a Chinese population. Gene 2017; 632:36-42. [PMID: 28844669 DOI: 10.1016/j.gene.2017.08.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2017] [Revised: 07/24/2017] [Accepted: 08/23/2017] [Indexed: 01/09/2023]
Abstract
Autophagy is an evolutionary conserved intracellular degradation/recycling system that is essential for cellular homeostasis. Dysregulation of this process leads to a number of disorders, including pulmonary fibrosis. However, the genetic association between singe nucleotide polymorphisms of autophagy related genes (ATGs) and the risk of coal workers' pneumoconiosis has not been reported yet. Total of 7 SNPs in ATGs (ATG16, ATG12, ATG5, ATG10) were investigated for their roles in CWP by a case-control study which including 705 CWP patients and 703 control subjects. Genotyping were performed by the Sequenom Mass ARRAY system. Luciferase assays were taken to test the effects of rs26538 C>T on the activity of ATG12 in the promoter. Our data showed that ATG10 rs1864182 GT genotype was associated with a decreased risk of CWP compared with TT genotype (OR=0.42, 95% CI=0.33-0.54, P=0.001). Another 2 SNPs (rs26538, rs510432) were also with the marked decreases in the risk of CWP under recessive models (OR=0.58, 95% CI=0.40-0.83, P=0.002 for rs26538; OR=0.74, 95% CI=0.57-0.97, P=0.040 for rs510432). Luciferase assays in two different cell lines revealed that the rs26538 C>T substitution could reduce the expression of ATG12. Taken together, we identified three SNPs in ATGs, which implicated the development of CWP. Further studies are warranted to validate these findings.
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Affiliation(s)
- Jiali Yuan
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Ruhui Han
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Ayaaba Esther
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Qiuyun Wu
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Jingjin Yang
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Weiwen Yan
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Xiaoming Ji
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Yi Liu
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Yan Li
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Wenxi Yao
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China
| | - Chunhui Ni
- Department of Occupational Medicine and Environmental Health, School of Public Health, Nanjing Medical University, Nanjing 210029, China.
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60
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Biering SB, Choi J, Halstrom RA, Brown HM, Beatty WL, Lee S, McCune BT, Dominici E, Williams LE, Orchard RC, Wilen CB, Yamamoto M, Coers J, Taylor GA, Hwang S. Viral Replication Complexes Are Targeted by LC3-Guided Interferon-Inducible GTPases. Cell Host Microbe 2017; 22:74-85.e7. [PMID: 28669671 PMCID: PMC5591033 DOI: 10.1016/j.chom.2017.06.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 04/14/2017] [Accepted: 06/08/2017] [Indexed: 12/22/2022]
Abstract
All viruses with positive-sense RNA genomes replicate on membranous structures in the cytoplasm called replication complexes (RCs). RCs provide an advantageous microenvironment for viral replication, but it is unknown how the host immune system counteracts these structures. Here we show that interferon-gamma (IFNG) disrupts the RC of murine norovirus (MNV) via evolutionarily conserved autophagy proteins and the induction of IFN-inducible GTPases, which are known to destroy the membrane of vacuoles containing bacteria, protists, or fungi. The MNV RC was marked by the microtubule-associated-protein-1-light-chain-3 (LC3) conjugation system of autophagy and then targeted by immunity-related GTPases (IRGs) and guanylate-binding proteins (GBPs) upon their induction by IFNG. Further, the LC3 conjugation system and the IFN-inducible GTPases were necessary to inhibit MNV replication in mice and human cells. These data suggest that viral RCs can be marked and antagonized by a universal immune defense mechanism targeting diverse pathogens replicating in cytosolic membrane structures.
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Affiliation(s)
- Scott B Biering
- Committee on Microbiology, University of Chicago, Chicago, IL 60637, USA
| | - Jayoung Choi
- Department of Pathology, University of Chicago, Chicago, IL 60637, USA
| | - Rachel A Halstrom
- Department of Pathology, University of Chicago, Chicago, IL 60637, USA
| | - Hailey M Brown
- Committee on Immunology, University of Chicago, Chicago, IL 60637, USA
| | - Wandy L Beatty
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Sanghyun Lee
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Broc T McCune
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Erin Dominici
- Department of Pathology, University of Chicago, Chicago, IL 60637, USA
| | - Lelia E Williams
- Biological Sciences Collegiate Division, University of Chicago, Chicago, IL 60637, USA
| | - Robert C Orchard
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Craig B Wilen
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Masahiro Yamamoto
- Laboratory of Immunoparasitology, World Premier International Research Center Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
| | - Jörn Coers
- Departments of Medicine, Molecular Genetics and Microbiology, and Immunology, Duke University Medical Center, Durham, NC 27710, USA
| | - Gregory A Taylor
- Departments of Medicine, Molecular Genetics and Microbiology, and Immunology, Duke University Medical Center, Durham, NC 27710, USA; GRECC, Durham VA Health Care System, Durham, NC 27705, USA
| | - Seungmin Hwang
- Committee on Microbiology, University of Chicago, Chicago, IL 60637, USA; Department of Pathology, University of Chicago, Chicago, IL 60637, USA; Committee on Immunology, University of Chicago, Chicago, IL 60637, USA.
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61
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Scutigliani EM, Kikkert M. Interaction of the innate immune system with positive-strand RNA virus replication organelles. Cytokine Growth Factor Rev 2017; 37:17-27. [PMID: 28709747 PMCID: PMC7108334 DOI: 10.1016/j.cytogfr.2017.05.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 05/15/2017] [Indexed: 02/08/2023]
Abstract
All +RNA viruses induce replication organelles to shield viral RNA from innate immune surveillance. Recent literature suggests that non-self or aberrant-self membrane structures can be tagged with LC3 or ubiquitin. Interferon-induced GTPases then recognize these tags and destroy the membrane structures, thereby exposing PAMPs. More research will have to indicate whether this is a general antiviral mechanism affecting +RNA virus infections.
The potential health risks associated with (re-)emerging positive-strand RNA (+RNA) viruses emphasizes the need for understanding host-pathogen interactions for these viruses. The innate immune system forms the first line of defense against pathogenic organisms like these and is responsible for detecting pathogen-associated molecular patterns (PAMPs). Viral RNA is a potent inducer of antiviral innate immune signaling, provoking an antiviral state by directing expression of interferons (IFNs) and pro-inflammatory cytokines. However, +RNA viruses developed various methods to avoid detection and downstream signaling, including isolation of viral RNA replication in membranous viral replication organelles (ROs). These structures therefore play a central role in infection, and consequently, loss of RO integrity might simultaneously result in impaired viral replication and enhanced antiviral signaling. This review summarizes the first indications that the innate immune system indeed has tools to disrupt viral ROs and other non- or aberrant-self membrane structures, and may do this by marking these membranes with proteins such as microtubule-associated protein 1A/1B-light chain 3 (LC3) and ubiquitin, resulting in the recruitment of IFN-inducible GTPases. Further studies should evaluate whether this process forms a general effector mechanism in +RNA virus infection, thereby creating the opportunity for development of novel antiviral therapies.
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Affiliation(s)
- Enzo Maxim Scutigliani
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Marjolein Kikkert
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.
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62
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Wacker R, Eickel N, Schmuckli-Maurer J, Annoura T, Niklaus L, Khan SM, Guan JL, Heussler VT. LC3-association with the parasitophorous vacuole membrane of Plasmodium berghei liver stages follows a noncanonical autophagy pathway. Cell Microbiol 2017; 19. [PMID: 28573684 DOI: 10.1111/cmi.12754] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 05/23/2017] [Accepted: 05/31/2017] [Indexed: 12/22/2022]
Abstract
Eukaryotic cells can employ autophagy to defend themselves against invading pathogens. Upon infection by Plasmodium berghei sporozoites, the host hepatocyte targets the invader by labelling the parasitophorous vacuole membrane (PVM) with the autophagy marker protein LC3. Until now, it has not been clear whether LC3 recruitment to the PVM is mediated by fusion of autophagosomes or by direct incorporation. To distinguish between these possibilities, we knocked out genes that are essential for autophagosome formation and for direct LC3 incorporation into membranes. The CRISPR/Cas9 system was employed to generate host cell lines deficient for either FIP200, a member of the initiation complex for autophagosome formation, or ATG5, responsible for LC3 lipidation and incorporation of LC3 into membranes. Infection of these knockout cell lines with P. berghei sporozoites revealed that LC3 recruitment to the PVM indeed depends on functional ATG5 and the elongation machinery, but not on FIP200 and the initiation complex, suggesting a direct incorporation of LC3 into the PVM. Importantly, in P. berghei-infected ATG5-/- host cells, lysosomes still accumulated at the PVM, indicating that the recruitment of lysosomes follows an LC3-independent pathway.
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Affiliation(s)
- Rahel Wacker
- Institute of Cell Biology, University of Bern, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Nina Eickel
- Institute of Cell Biology, University of Bern, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | | | - Takeshi Annoura
- Department of Parasitology, National Institute of Infectious Diseases (NIID), Tokyo, Japan
| | - Livia Niklaus
- Institute of Cell Biology, University of Bern, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Shahid M Khan
- Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Jun-Lin Guan
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
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63
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Essential role for GABARAP autophagy proteins in interferon-inducible GTPase-mediated host defense. Nat Immunol 2017; 18:899-910. [PMID: 28604719 DOI: 10.1038/ni.3767] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 05/08/2017] [Indexed: 12/15/2022]
Abstract
Mammalian autophagy-related 8 (Atg8) homologs consist of LC3 proteins and GABARAPs, all of which are known to be involved in canonical autophagy. In contrast, the roles of Atg8 homologs in noncanonical autophagic processes are not fully understood. Here we show a unique role of GABARAPs, in particular gamma-aminobutyric acid (GABA)-A-receptor-associated protein-like 2 (Gabarapl2; also known as Gate-16), in interferon-γ (IFN-γ)-mediated antimicrobial responses. Cells that lacked GABARAPs but not LC3 proteins and mice that lacked Gate-16 alone were defective in the IFN-γ-induced clearance of vacuolar pathogens such as Toxoplasma. Gate-16 but not LC3b specifically associated with the small GTPase ADP-ribosylation factor 1 (Arf1) to mediate uniform distribution of interferon-inducible GTPases. The lack of GABARAPs reduced Arf1 activation, which led to formation of interferon-inducible GTPase-containing aggregates and hampered recruitment of interferon-inducible GTPases to vacuolar pathogens. Thus, GABARAPs are uniquely required for antimicrobial host defense through cytosolic distribution of interferon-inducible GTPases.
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64
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Latré de Laté P, Pineda M, Harnett M, Harnett W, Besteiro S, Langsley G. Apicomplexan autophagy and modulation of autophagy in parasite-infected host cells. Biomed J 2017; 40:23-30. [PMID: 28411879 PMCID: PMC6138587 DOI: 10.1016/j.bj.2017.01.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 01/05/2017] [Accepted: 01/11/2017] [Indexed: 11/18/2022] Open
Abstract
Apicomplexan parasites are responsible for a number of important human pathologies. Obviously, as Eukaryotes they share a number of cellular features and pathways with their respective host cells. One of them is autophagy, a process involved in the degradation of the cell's own components. These intracellular parasites nonetheless seem to present a number of original features compared to their very evolutionarily distant host cells. In mammals and other metazoans, autophagy has been identified as an important contributor to the defence against microbial pathogens. Thus, host autophagy also likely plays a key role in the control of apicomplexan parasites, although its potential manipulation and subversion by intracellular parasites creates a complex interplay in the regulation of host and parasite autophagy. In this mini-review, we summarise current knowledge on autophagy in both parasites and their host cells, in the context of infection by three Apicomplexa: Plasmodium, Toxoplasma, and Theileria.
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Affiliation(s)
- Perle Latré de Laté
- Inserm U1016, Cnrs UMR8104, Cochin Institute, Paris, France; Comparative Cellbiology of Apicomplexan Parasites, Faculty of Medicine, Paris-Descartes University, Paris, France
| | - Miguel Pineda
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow, UK
| | - Margaret Harnett
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow, UK.
| | - William Harnett
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | | | - Gordon Langsley
- Inserm U1016, Cnrs UMR8104, Cochin Institute, Paris, France; Comparative Cellbiology of Apicomplexan Parasites, Faculty of Medicine, Paris-Descartes University, Paris, France.
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65
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The Toxoplasma Parasitophorous Vacuole: An Evolving Host-Parasite Frontier. Trends Parasitol 2017; 33:473-488. [PMID: 28330745 DOI: 10.1016/j.pt.2017.02.007] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/20/2017] [Accepted: 02/24/2017] [Indexed: 01/17/2023]
Abstract
The parasitophorous vacuole is a unique replicative niche for apicomplexan parasites, including Toxoplasma gondii. Derived from host plasma membrane, the vacuole is rendered nonfusogenic with the host endolysosomal system. Toxoplasma secretes numerous proteins to modify the forming vacuole, enable nutrient uptake, and set up mechanisms of host subversion. Here we describe the pathways of host-parasite interaction at the parasitophorous vacuole employed by Toxoplasma and host, leading to the intricate balance of host defence versus parasite survival.
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66
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Krishnamurthy S, Konstantinou EK, Young LH, Gold DA, Saeij JPJ. The human immune response to Toxoplasma: Autophagy versus cell death. PLoS Pathog 2017; 13:e1006176. [PMID: 28278184 PMCID: PMC5344534 DOI: 10.1371/journal.ppat.1006176] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Affiliation(s)
- Shruthi Krishnamurthy
- Department of Pathology, Microbiology and Immunology, University of California Davis, Davis, California, United States of America
| | - Eleni K. Konstantinou
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Lucy H. Young
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Daniel A. Gold
- Department of Pathology, Microbiology and Immunology, University of California Davis, Davis, California, United States of America
| | - Jeroen P. J. Saeij
- Department of Pathology, Microbiology and Immunology, University of California Davis, Davis, California, United States of America
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Antiviral Innate Immune Response Interferes with the Formation of Replication-Associated Membrane Structures Induced by a Positive-Strand RNA Virus. mBio 2016; 7:mBio.01991-16. [PMID: 27923923 PMCID: PMC5142621 DOI: 10.1128/mbio.01991-16] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Infection with nidoviruses like corona- and arteriviruses induces a reticulovesicular network of interconnected endoplasmic reticulum (ER)-derived double-membrane vesicles (DMVs) and other membrane structures. This network is thought to accommodate the viral replication machinery and protect it from innate immune detection. We hypothesized that the innate immune response has tools to counteract the formation of these virus-induced replication organelles in order to inhibit virus replication. Here we have investigated the effect of type I interferon (IFN) treatment on the formation of arterivirus-induced membrane structures. Our approach involved ectopic expression of arterivirus nonstructural proteins nsp2 and nsp3, which induce DMV formation in the absence of other viral triggers of the interferon response, such as replicating viral RNA. Thus, this setup can be used to identify immune effectors that specifically target the (formation of) virus-induced membrane structures. Using large-scale electron microscopy mosaic maps, we found that IFN-β treatment significantly reduced the formation of the membrane structures. Strikingly, we also observed abundant stretches of double-membrane sheets (a proposed intermediate of DMV formation) in IFN-β-treated samples, suggesting the disruption of DMV biogenesis. Three interferon-stimulated gene products, two of which have been reported to target the hepatitis C virus replication structures, were tested for their possible involvement, but none of them affected membrane structure formation. Our study reveals the existence of a previously unknown innate immune mechanism that antagonizes the viral hijacking of host membranes. It also provides a solid basis for further research into the poorly understood interactions between the innate immune system and virus-induced replication structures. IMPORTANCE Viruses with a positive-strand RNA genome establish a membrane-associated replication organelle by hijacking and remodeling intracellular host membranes, a process deemed essential for their efficient replication. It is unknown whether the cellular innate immune system can detect and/or inhibit the formation of these membrane structures, which could be an effective mechanism to delay viral RNA replication. In this study, using an expression system that closely mimics the formation of arterivirus replication structures, we show for the first time that IFN-β treatment clearly reduces the amount of induced membrane structures. Moreover, drastic morphological changes were observed among the remaining structures, suggesting that their biogenesis was impaired. Follow-up experiments suggested that host cells contain a hitherto unknown innate antiviral mechanism, which targets this common feature of positive-strand RNA virus replication. Our study provides a strong basis for further research into the interaction of the innate immune system with membranous viral replication organelles.
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Abstract
Autophagy has broad functions in immunity, ranging from cell-autonomous defence to coordination of complex multicellular immune responses. The successful resolution of infection and avoidance of autoimmunity necessitates efficient and timely communication between autophagy and pathways that sense the immune environment. The recent literature indicates that a variety of immune mediators induce or repress autophagy. It is also becoming increasingly clear that immune signalling cascades are subject to regulation by autophagy, and that a return to homeostasis following a robust immune response is critically dependent on this pathway. Importantly, examples of non-canonical forms of autophagy in mediating immunity are pervasive. In this article, the progress in elucidating mechanisms of crosstalk between autophagy and inflammatory signalling cascades is reviewed. Improved mechanistic understanding of the autophagy machinery offers hope for treating infectious and inflammatory diseases.
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Affiliation(s)
- Ken Cadwell
- grid.137628.90000 0004 1936 8753and the Department of Microbiology, Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, 10016 New York USA
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Choi J, Biering SB, Hwang S. Quo vadis? Interferon-inducible GTPases go to their target membranes via the LC3-conjugation system of autophagy. Small GTPases 2016; 8:199-207. [PMID: 27428166 PMCID: PMC5680725 DOI: 10.1080/21541248.2016.1213090] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Many intracellular pathogens survive and replicate within vacuole-like structures in the cytoplasm. It has been unclear how the host immune system controls such pathogen-containing vacuoles. Interferon-inducible GTPases are dynamin-like GTPases that target the membranes of pathogen-containing vacuoles. Upon their oligomerization on the membrane, the vacuole structure disintegrates and the pathogen gets exposed to the hostile cytoplasm. What has been obscure is how the immune system detects and directs the GTPases to these pathogen shelters. Using a common protist parasite of mice, Toxoplasma gondii, we found that the LC3 conjugation system of autophagy is necessary and sufficient for targeting the interferon-inducible GTPases to membranes. We dubbed this process Targeting by AutophaGy proteins (TAG). In canonical autophagy, the LC3 conjugation system is required to form membrane-bound autophagosomes, which encircle and deliver cytosolic materials to lysosomes for degradation. In TAG, however, the conjugation system is required to mark the membranes of pathogen-containing vacuoles with ubiquitin-like LC3 homologs, which function as molecular beacons to recruit the GTPases to their target membranes. Our data suggest that the LC3 conjugation system of autophagy plays an essential role in detecting and marking pathogen-containing vacuoles for immune effector targeting by the host immune system.
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Affiliation(s)
- Jayoung Choi
- a Department of Pathology , The University of Chicago , Chicago , IL , USA
| | - Scott B Biering
- b Committee on Microbiology, The University of Chicago , Chicago , IL , USA
| | - Seungmin Hwang
- a Department of Pathology , The University of Chicago , Chicago , IL , USA.,b Committee on Microbiology, The University of Chicago , Chicago , IL , USA
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