301
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Phagocytosis of apoptotic cells in homeostasis. Nat Immunol 2015; 16:907-17. [PMID: 26287597 DOI: 10.1038/ni.3253] [Citation(s) in RCA: 534] [Impact Index Per Article: 59.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Accepted: 07/17/2015] [Indexed: 02/07/2023]
Abstract
Human bodies collectively turn over about 200 billion to 300 billion cells every day. Such turnover is an integral part of embryonic and postnatal development, as well as routine tissue homeostasis. This process involves the induction of programmed cell death in specific cells within the tissues and the specific recognition and removal of dying cells by a clearance 'crew' composed of professional, non-professional and specialized phagocytes. In the past few years, considerable progress has been made in identifying many features of apoptotic cell clearance. Some of these new observations challenge the way dying cells themselves are viewed, as well as how healthy cells interact with and respond to dying cells. Here we focus on the homeostatic removal of apoptotic cells in tissues.
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302
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Huerta V, Ramos Y, Yero A, Pupo D, Martín D, Toledo P, Fleitas N, Gallien S, Martín AM, Márquez GJ, Pérez-Riverol Y, Sarría M, Guirola O, González LJ, Domon B, Chinea G. Novel interactions of domain III from the envelope glycoprotein of dengue 2 virus with human plasma proteins. J Proteomics 2015; 131:205-213. [PMID: 26546555 DOI: 10.1016/j.jprot.2015.11.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 10/16/2015] [Accepted: 11/02/2015] [Indexed: 11/24/2022]
Abstract
UNLABELLED Blood cells and plasma are important media for the four serotypes of dengue virus (DENV1-4) spreading into an infected person. Thus, interactions with human plasma proteins are expected to be decisive in the course of the viral infection. Affinity purification followed by MS analysis (AP/MS) was used to isolate and identify plasma-derived proteins capable to interact with a recombinant protein comprising the domain III of the envelope protein of DENV2 (DIIIE2). The elution of the AP potently inhibits DENV2 infection. Twenty-nine proteins were identified using a label-free approach as specifically captured by DIIIE2. Of these, a direct interaction with C reactive protein, thrombin and Inter-alpha-inhibitor complexes was confirmed by ELISA. Results provide further evidence of a significant representation of proteins from complement and coagulation cascades on DENV2 interactome in human plasma and stand out the domain III of the viral envelope protein as participant on these interactions. A functional clustering analysis highlights the presence of three structural motifs among putative DIIIE2-binding proteins: hydroxylation and EGF-like calcium-binding- and Gla domains. BIOLOGICAL SIGNIFICANCE Early cycles of dengue virus replication take place in human blood cells. Thus, the characterization of the interactome of dengue virus proteins in human plasma can lead to the identification of pivotal interactions for the infection that can eventually constitute the target for the development of methods to control dengue virus-caused disease. In this work we identified 29 proteins from human plasma that potentially interact with the envelope protein of dengue 2 virus either directly or through co-complex formation. C reactive protein, thrombin and Inter-alpha-inhibitor complexes were validated as interactors of the domain III of the envelope protein of dengue 2. Results highlight the presence of three structural motifs among putative DIIIE2-binding proteins: hydroxylation and EGF-like calcium-binding- and Gla domains. This finding together with the participation of domain III of the envelope protein on the interactions with human plasma proteins should contribute to a better understanding of dengue virus interactome in human plasma. Such knowledge can contribute to the development of more effective treatments to infected persons.
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Affiliation(s)
- Vivian Huerta
- Center for Genetic Engineering and Biotechnology, Cuba.
| | - Yassel Ramos
- Center for Genetic Engineering and Biotechnology, Cuba
| | - Alexis Yero
- Center for Genetic Engineering and Biotechnology, Cuba
| | - Dianne Pupo
- Center for Genetic Engineering and Biotechnology, Cuba
| | - Dayron Martín
- Center for Genetic Engineering and Biotechnology, Cuba
| | | | | | | | | | | | | | - Mónica Sarría
- Center for Genetic Engineering and Biotechnology, Cuba
| | | | | | - Bruno Domon
- Luxembourg Clinical Proteomics Center, Luxembourg
| | - Glay Chinea
- Center for Genetic Engineering and Biotechnology, Cuba
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303
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Virion-associated phosphatidylethanolamine promotes TIM1-mediated infection by Ebola, dengue, and West Nile viruses. Proc Natl Acad Sci U S A 2015; 112:14682-7. [PMID: 26575624 DOI: 10.1073/pnas.1508095112] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phosphatidylserine (PS) receptors contribute to two crucial biological processes: apoptotic clearance and entry of many enveloped viruses. In both cases, they recognize PS exposed on the plasma membrane. Here we demonstrate that phosphatidylethanolamine (PE) is also a ligand for PS receptors and that this phospholipid mediates phagocytosis and viral entry. We show that a subset of PS receptors, including T-cell immunoglobulin (Ig) mucin domain protein 1 (TIM1), efficiently bind PE. We further show that PE is present in the virions of flaviviruses and filoviruses, and that the PE-specific cyclic peptide lantibiotic agent Duramycin efficiently inhibits the entry of West Nile, dengue, and Ebola viruses. The inhibitory effect of Duramycin is specific: it inhibits TIM1-mediated, but not L-SIGN-mediated, virus infection, and it does so by blocking virus attachment to TIM1. We further demonstrate that PE is exposed on the surface of apoptotic cells, and promotes their phagocytic uptake by TIM1-expressing cells. Together, our data show that PE plays a key role in TIM1-mediated virus entry, suggest that disrupting PE association with PS receptors is a promising broad-spectrum antiviral strategy, and deepen our understanding of the process by which apoptotic cells are cleared.
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304
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The TAM receptor Mertk protects against neuroinvasive viral infection by maintaining blood-brain barrier integrity. Nat Med 2015; 21:1464-72. [PMID: 26523970 PMCID: PMC4674389 DOI: 10.1038/nm.3974] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 09/16/2015] [Indexed: 12/12/2022]
Abstract
The TAM receptors Tyro3, Axl, and Mertk are receptor tyrosine kinases that dampen host innate immune responses following engagement with their ligands, Gas6 and Protein S, which recognize phosphatidylserine on apoptotic cells. In a form of apoptotic mimicry, many enveloped viruses display phosphatidylserine on the outer leaflet of their membranes, enabling TAM receptor activation and down-regulation of antiviral responses. Accordingly, we hypothesized that a deficiency of TAM receptors would enhance antiviral responses and protect against viral infection. Unexpectedly, mice lacking Mertk and/or Axl but not Tyro3 exhibited greater vulnerability to infection with neuroinvasive West Nile and La Crosse viruses. This phenotype was associated with increased blood-brain barrier permeability, which enhanced virus entry into and infection of the brain. Activation of Mertk synergized with IFN-β to tighten cell junctions and prevent virus transit across brain microvascular endothelial cells. Because TAM receptors restrict pathogenesis of neuroinvasive viruses, these findings have implications for TAM antagonists that are currently in clinical development.
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305
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Abstract
Hepatitis A virus (HAV) is an ancient and ubiquitous human pathogen recovered previously only from primates. The sole species of the genus Hepatovirus, existing in both enveloped and nonenveloped forms, and with a capsid structure intermediate between that of insect viruses and mammalian picornaviruses, HAV is enigmatic in its origins. We conducted a targeted search for hepatoviruses in 15,987 specimens collected from 209 small mammal species globally and discovered highly diversified viruses in bats, rodents, hedgehogs, and shrews, which by pairwise sequence distance comprise 13 novel Hepatovirus species. Near-complete genomes from nine of these species show conservation of unique hepatovirus features, including predicted internal ribosome entry site structure, a truncated VP4 capsid protein lacking N-terminal myristoylation, a carboxyl-terminal pX extension of VP1, VP2 late domains involved in membrane envelopment, and a cis-acting replication element within the 3D(pol) sequence. Antibodies in some bat sera immunoprecipitated and neutralized human HAV, suggesting conservation of critical antigenic determinants. Limited phylogenetic cosegregation among hepatoviruses and their hosts and recombination patterns are indicative of major hepatovirus host shifts in the past. Ancestral state reconstructions suggest a Hepatovirus origin in small insectivorous mammals and a rodent origin of human HAV. Patterns of infection in small mammals mimicked those of human HAV in hepatotropism, fecal shedding, acute nature, and extinction of the virus in a closed host population. The evolutionary conservation of hepatovirus structure and pathogenesis provide novel insight into the origins of HAV and highlight the utility of analyzing animal reservoirs for risk assessment of emerging viruses.
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306
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Patent Highlights June–July 2015. Pharm Pat Anal 2015. [DOI: 10.4155/ppa.15.27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.
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307
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The Phosphatidylserine and Phosphatidylethanolamine Receptor CD300a Binds Dengue Virus and Enhances Infection. J Virol 2015; 90:92-102. [PMID: 26468529 DOI: 10.1128/jvi.01849-15] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 09/28/2015] [Indexed: 12/27/2022] Open
Abstract
UNLABELLED Dengue virus (DENV) is the etiological agent of the major human arboviral disease. We previously demonstrated that the TIM and TAM families of phosphatidylserine (PtdSer) receptors involved in the phagocytosis of apoptotic cells mediate DENV entry into target cells. We show here that human CD300a, a recently identified phospholipid receptor, also binds directly DENV particles and enhances viral entry. CD300a facilitates infection of the four DENV serotypes, as well as of other mosquito-borne viruses such as West Nile virus and Chikungunya virus. CD300a acts as an attachment factor that enhances DENV internalization through clathrin-mediated endocytosis. CD300a recognizes predominantly phosphatidylethanolamine (PtdEth) and to a lesser extent PtdSer associated with viral particles. Mutation of residues in the IgV domain critical for phospholipid binding abrogate CD300a-mediated enhancement of DENV infection. Finally, we show that CD300a is expressed at the surface of primary macrophages and anti-CD300a polyclonal antibodies partially inhibited DENV infection of these cells. Overall, these data indicate that CD300a is a novel DENV binding receptor that recognizes PtdEth and PtdSer present on virions and enhance infection. IMPORTANCE Dengue disease, caused by dengue virus (DENV), has emerged as the most important mosquito-borne viral disease of humans and is a major global health concern. The molecular bases of DENV-host cell interactions during virus entry are poorly understood, hampering the discovery of new targets for antiviral intervention. We recently discovered that the TIM and TAM proteins, two receptor families involved in the phosphatidylserine (PtdSer)-dependent phagocytic removal of apoptotic cells, interact with DENV particles-associated PtdSer through a mechanism that mimics the recognition of apoptotic cells and mediate DENV infection. In this study, we show that CD300a, a novel identified phospholipid receptor, mediates DENV infection. CD300a-dependent DENV infection relies on the direct recognition of phosphatidylethanolamine and to a lesser extent PtdSer associated with viral particles. This study provides novel insights into the mechanisms that mediate DENV entry and reinforce the concept that DENV uses an apoptotic mimicry strategy for viral entry.
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308
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The phospholipid code: a key component of dying cell recognition, tumor progression and host-microbe interactions. Cell Death Differ 2015; 22:1893-905. [PMID: 26450453 DOI: 10.1038/cdd.2015.122] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/05/2015] [Accepted: 08/06/2015] [Indexed: 02/06/2023] Open
Abstract
A significant effort is made by the cell to maintain certain phospholipids at specific sites. It is well described that proteins involved in intracellular signaling can be targeted to the plasma membrane and organelles through phospholipid-binding domains. Thus, the accumulation of a specific combination of phospholipids, denoted here as the 'phospholipid code', is key in initiating cellular processes. Interestingly, a variety of extracellular proteins and pathogen-derived proteins can also recognize or modify phospholipids to facilitate the recognition of dying cells, tumorigenesis and host-microbe interactions. In this article, we discuss the importance of the phospholipid code in a range of physiological and pathological processes.
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309
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Segawa K, Nagata S. An Apoptotic 'Eat Me' Signal: Phosphatidylserine Exposure. Trends Cell Biol 2015; 25:639-650. [PMID: 26437594 DOI: 10.1016/j.tcb.2015.08.003] [Citation(s) in RCA: 475] [Impact Index Per Article: 52.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 08/08/2015] [Accepted: 08/17/2015] [Indexed: 12/19/2022]
Abstract
Apoptosis and the clearance of apoptotic cells are essential processes in animal development and homeostasis. For apoptotic cells to be cleared, they must display an 'eat me' signal, most likely phosphatidylserine (PtdSer) exposure, which prompts phagocytes to engulf the cells. PtdSer, which is recognized by several different systems, is normally confined to the cytoplasmic leaflet of the plasma membrane by a 'flippase'; apoptosis activates a 'scramblase' that quickly exposes PtdSer on the cell surface. The molecules that flip and scramble phospholipids at the plasma membrane have recently been identified. Here we discuss recent findings regarding the molecular mechanisms of apoptotic PtdSer exposure and the clearance of apoptotic cells.
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Affiliation(s)
- Katsumori Segawa
- Laboratory of Biochemistry and Immunology, WPI Immunology Frontier Research Center, Osaka University, 3-1 Yamada-oka, Suita 565-0871, Japan
| | - Shigekazu Nagata
- Laboratory of Biochemistry and Immunology, WPI Immunology Frontier Research Center, Osaka University, 3-1 Yamada-oka, Suita 565-0871, Japan.
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310
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Abstract
Many flaviviruses are significant human pathogens that are transmitted by mosquitoes and ticks. Although effective vaccines are available for yellow fever virus, Japanese encephalitic virus, and tick-borne encephalitis virus, these and other flaviviruses still cause thousands of human deaths and millions of illnesses each year. No clinically approved antiviral therapy is available for flavivirus treatment. To meet this unmet medical need, industry and academia have taken multiple approaches to develop antiflavivirus therapy, among which targeting viral entry has been actively pursued in the past decade. Here we review the current knowledge of flavivirus entry and its use for small molecule drug discovery. Inhibitors of two major steps of flaviviral entry have been reported: (i) molecules that block virus-receptor interaction; (ii) compounds that prevent conformational change of viral envelope protein during virus-host membrane fusion. We also discuss the advantages and disadvantages of targeting viral entry for treatment of flavivirus infection as compared to targeting viral replication proteins.
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Affiliation(s)
| | - Pei-Yong Shi
- Novartis Institute for Tropical Diseases, Singapore
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311
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Hamel R, Dejarnac O, Wichit S, Ekchariyawat P, Neyret A, Luplertlop N, Perera-Lecoin M, Surasombatpattana P, Talignani L, Thomas F, Cao-Lormeau VM, Choumet V, Briant L, Desprès P, Amara A, Yssel H, Missé D. Biology of Zika Virus Infection in Human Skin Cells. J Virol 2015; 89:8880-96. [PMID: 26085147 PMCID: PMC4524089 DOI: 10.1128/jvi.00354-15] [Citation(s) in RCA: 840] [Impact Index Per Article: 93.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 06/08/2015] [Indexed: 12/22/2022] Open
Abstract
UNLABELLED Zika virus (ZIKV) is an emerging arbovirus of the Flaviviridae family, which includes dengue, West Nile, yellow fever, and Japanese encephalitis viruses, that causes a mosquito-borne disease transmitted by the Aedes genus, with recent outbreaks in the South Pacific. Here we examine the importance of human skin in the entry of ZIKV and its contribution to the induction of antiviral immune responses. We show that human dermal fibroblasts, epidermal keratinocytes, and immature dendritic cells are permissive to the most recent ZIKV isolate, responsible for the epidemic in French Polynesia. Several entry and/or adhesion factors, including DC-SIGN, AXL, Tyro3, and, to a lesser extent, TIM-1, permitted ZIKV entry, with a major role for the TAM receptor AXL. The ZIKV permissiveness of human skin fibroblasts was confirmed by the use of a neutralizing antibody and specific RNA silencing. ZIKV induced the transcription of Toll-like receptor 3 (TLR3), RIG-I, and MDA5, as well as several interferon-stimulated genes, including OAS2, ISG15, and MX1, characterized by strongly enhanced beta interferon gene expression. ZIKV was found to be sensitive to the antiviral effects of both type I and type II interferons. Finally, infection of skin fibroblasts resulted in the formation of autophagosomes, whose presence was associated with enhanced viral replication, as shown by the use of Torin 1, a chemical inducer of autophagy, and the specific autophagy inhibitor 3-methyladenine. The results presented herein permit us to gain further insight into the biology of ZIKV and to devise strategies aiming to interfere with the pathology caused by this emerging flavivirus. IMPORTANCE Zika virus (ZIKV) is an arbovirus belonging to the Flaviviridae family. Vector-mediated transmission of ZIKV is initiated when a blood-feeding female Aedes mosquito injects the virus into the skin of its mammalian host, followed by infection of permissive cells via specific receptors. Indeed, skin immune cells, including dermal fibroblasts, epidermal keratinocytes, and immature dendritic cells, were all found to be permissive to ZIKV infection. The results also show a major role for the phosphatidylserine receptor AXL as a ZIKV entry receptor and for cellular autophagy in enhancing ZIKV replication in permissive cells. ZIKV replication leads to activation of an antiviral innate immune response and the production of type I interferons in infected cells. Taken together, these results provide the first general insights into the interaction between ZIKV and its mammalian host.
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MESH Headings
- Aedes/virology
- Animals
- Autophagy/immunology
- Cell Adhesion Molecules/genetics
- Cell Adhesion Molecules/metabolism
- Cells, Cultured
- Chlorocebus aethiops
- Cytokines/biosynthesis
- DEAD Box Protein 58
- DEAD-box RNA Helicases/genetics
- DEAD-box RNA Helicases/metabolism
- Dendritic Cells/immunology
- Dendritic Cells/virology
- Fibroblasts/virology
- Flaviviridae/immunology
- Flaviviridae/physiology
- Flaviviridae Infections/immunology
- Flaviviridae Infections/virology
- HEK293 Cells
- Hepatitis A Virus Cellular Receptor 1
- Humans
- Insect Vectors/virology
- Interferon-Induced Helicase, IFIH1
- Interferon-beta/biosynthesis
- Interferon-beta/immunology
- Keratinocytes/virology
- Lectins, C-Type/genetics
- Lectins, C-Type/metabolism
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Myxovirus Resistance Proteins/biosynthesis
- Phagosomes/immunology
- Proto-Oncogene Proteins/genetics
- Proto-Oncogene Proteins/metabolism
- RNA Interference
- RNA, Small Interfering
- Receptor Protein-Tyrosine Kinases/genetics
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, Immunologic
- Receptors, Virus/genetics
- Receptors, Virus/metabolism
- Skin/immunology
- Skin/virology
- Toll-Like Receptor 3/genetics
- Toll-Like Receptor 3/immunology
- Toll-Like Receptor 3/metabolism
- Toll-Like Receptor 7/immunology
- Ubiquitins/biosynthesis
- Vero Cells
- Virus Internalization
- Virus Replication
- Axl Receptor Tyrosine Kinase
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Affiliation(s)
- Rodolphe Hamel
- Laboratoire MIVEGEC, UMR 224 IRD/CNRS/UM, Montpellier, France
| | - Ophélie Dejarnac
- INSERM, U944, Laboratoire de Pathologie et Virologie Moléculaire, Paris, France
| | | | | | - Aymeric Neyret
- Centre d'Étude d'Agents Pathogènes et Biotechnologies pour la Santé, CNRS-UMR 5236/UM, Montpellier, France
| | - Natthanej Luplertlop
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | | | | | - Loïc Talignani
- Laboratoire MIVEGEC, UMR 224 IRD/CNRS/UM, Montpellier, France
| | - Frédéric Thomas
- Laboratoire MIVEGEC, UMR 224 IRD/CNRS/UM, Montpellier, France
| | | | - Valérie Choumet
- Environment and Infectious Risks Unit, Institut Pasteur, Paris, France
| | - Laurence Briant
- Centre d'Étude d'Agents Pathogènes et Biotechnologies pour la Santé, CNRS-UMR 5236/UM, Montpellier, France
| | - Philippe Desprès
- Département Infections et Epidémiologie, Institut Pasteur, Paris, France, and UMR PIMIT (I2T Team), Université de La Réunion, INSERM U1187, CNRS 9192, IRD 249, GIP-CYROI, Saint Clotilde, La Réunion, France
| | - Ali Amara
- INSERM, U944, Laboratoire de Pathologie et Virologie Moléculaire, Paris, France
| | - Hans Yssel
- Centre d'Immunologie et des Maladies Infectieuses, INSERM, U1135, Sorbonne Universités, UPMC, APHP Hôpital Pitié-Salpêtrière, Paris, France
| | - Dorothée Missé
- Laboratoire MIVEGEC, UMR 224 IRD/CNRS/UM, Montpellier, France
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312
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Read SA, Tay ES, Shahidi M, O’Connor KS, Booth DR, George J, Douglas MW. Hepatitis C Virus Driven AXL Expression Suppresses the Hepatic Type I Interferon Response. PLoS One 2015; 10:e0136227. [PMID: 26313459 PMCID: PMC4551482 DOI: 10.1371/journal.pone.0136227] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Accepted: 07/30/2015] [Indexed: 01/06/2023] Open
Abstract
Treatment of chronic hepatitis C virus (HCV) infection is evolving rapidly with the development of novel direct acting antivirals (DAAs), however viral clearance remains intimately linked to the hepatic innate immune system. Patients demonstrating a high baseline activation of interferon stimulated genes (ISGs), termed interferon refractoriness, are less likely to mount a strong antiviral response and achieve viral clearance when placed on treatment. As a result, suppressor of cytokine signalling (SOCS) 3 and other regulators of the IFN response have been identified as key candidates for the IFN refractory phenotype due to their regulatory role on the IFN response. AXL is a receptor tyrosine kinase that has been identified as a key regulator of interferon (IFN) signalling in myeloid cells of the immune system, but has not been examined in the context of chronic HCV infection. Here, we show that AXL is up-regulated following HCV infection, both in vitro and in vivo and is likely induced by type I/III IFNs and inflammatory signalling pathways. AXL inhibited type IFNα mediated ISG expression resulting in a decrease in its antiviral efficacy against HCV in vitro. Furthermore, patients possessing the favourable IFNL3 rs12979860 genotype associated with treatment response, showed lower AXL expression in the liver and a stronger induction of AXL in the blood, following their first dose of IFN. Together, these data suggest that elevated AXL expression in the liver may mediate an IFN-refractory phenotype characteristic of patients possessing the unfavourable rs12979860 genotype, which is associated with lower rates of viral clearance.
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Affiliation(s)
- Scott A. Read
- Storr Liver Centre, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, Australia
| | - Enoch S. Tay
- Storr Liver Centre, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, Australia
| | - Mahsa Shahidi
- Storr Liver Centre, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, Australia
| | - Kate S. O’Connor
- Centre for Immunology and Allergy Research, University of Sydney at Westmead Hospital, Westmead, Australia
| | - David R. Booth
- Centre for Immunology and Allergy Research, University of Sydney at Westmead Hospital, Westmead, Australia
| | - Jacob George
- Storr Liver Centre, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, Australia
| | - Mark W. Douglas
- Storr Liver Centre, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, Australia
- Centre for Infectious Diseases and Microbiology, Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney at Westmead Hospital, Westmead, Australia
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313
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Zenarruzabeitia O, Vitallé J, Eguizabal C, Simhadri VR, Borrego F. The Biology and Disease Relevance of CD300a, an Inhibitory Receptor for Phosphatidylserine and Phosphatidylethanolamine. THE JOURNAL OF IMMUNOLOGY 2015; 194:5053-60. [PMID: 25980030 DOI: 10.4049/jimmunol.1500304] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The CD300a inhibitory receptor belongs to the CD300 family of cell surface molecules that regulate a diverse array of immune cell processes. The inhibitory signal of CD300a depends on the phosphorylation of tyrosine residues embedded in ITIMs of the cytoplasmic tail. CD300a is broadly expressed on myeloid and lymphoid cells, and its expression is differentially regulated depending on the cell type. The finding that CD300a recognizes phosphatidylserine and phosphatidylethanolamine, two aminophospholipids exposed on the outer leaflet of dead and activated cells, has shed new light on its role in the modulation of immune functions and in its participation in the host response to several diseases states, such as infectious diseases, cancer, allergy, and chronic inflammatory diseases. This review summarizes the literature on CD300a expression, regulation, signaling pathways, and ligand interaction, as well as its role in fine tuning immune cell functions and its clinical relevance.
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Affiliation(s)
| | - Joana Vitallé
- Immunopathology Group, BioCruces Health Research Institute, Barakaldo 48903, Spain
| | - Cristina Eguizabal
- Cell Therapy and Stem Cell Group, Basque Center for Transfusion and Human Tissues, Galdakao 48960, Spain
| | - Venkateswara R Simhadri
- Division of Biotechnology Review and Research-I, Office of Biotechnology Products Review and Research, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993; and
| | - Francisco Borrego
- Immunopathology Group, BioCruces Health Research Institute, Barakaldo 48903, Spain; Ikerbasque, Basque Foundation for Science 48903, Bilbao, Spain
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314
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Hackett BA, Yasunaga A, Panda D, Tartell MA, Hopkins KC, Hensley SE, Cherry S. RNASEK is required for internalization of diverse acid-dependent viruses. Proc Natl Acad Sci U S A 2015; 112:7797-802. [PMID: 26056282 PMCID: PMC4485095 DOI: 10.1073/pnas.1424098112] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Viruses must gain entry into cells to establish infection. In general, viruses enter either at the plasma membrane or from intracellular endosomal compartments. Viruses that use endosomal pathways are dependent on the cellular factors that control this process; however, these genes have proven to be essential for endogenous cargo uptake, and thus are of limited value for therapeutic intervention. The identification of genes that are selectively required for viral uptake would make appealing drug targets, as their inhibition would block an early step in the life cycle of diverse viruses. At this time, we lack pan-antiviral therapeutics, in part because of our lack of knowledge of such cellular factors. RNAi screening has begun to reveal previously unknown genes that play roles in viral infection. We identified dRNASEK in two genome-wide RNAi screens performed in Drosophila cells against West Nile and Rift Valley Fever viruses. Here we found that ribonuclease kappa (RNASEK) is essential for the infection of human cells by divergent and unrelated positive- and negative-strand-enveloped viruses from the Flaviviridae, Togaviridae, Bunyaviridae, and Orthomyxoviridae families that all enter cells from endosomal compartments. In contrast, RNASEK was dispensable for viruses, including parainfluenza virus 5 and Coxsackie B virus, that enter at the plasma membrane. RNASEK is dispensable for attachment but is required for uptake of these acid-dependent viruses. Furthermore, this requirement appears specific, as general endocytic uptake of transferrin is unaffected in RNASEK-depleted cells. Therefore, RNASEK is a potential host cell Achilles' heel for viral infection.
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Affiliation(s)
- Brent A Hackett
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
| | - Ari Yasunaga
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
| | - Debasis Panda
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
| | - Michael A Tartell
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
| | - Kaycie C Hopkins
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
| | | | - Sara Cherry
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104;
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315
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Abstract
Viral apoptotic mimicry, defined by the exposure of phosphatidylserine on the pathogen surface, is emerging as a common theme used by enveloped viruses to promote infection. In this Progress article, Amara and Mercer discuss how viruses acquire phosphatidylserine and how this mimicry might facilitate cell entry and evasion of the immune response. As opportunistic pathogens, viruses have evolved many elegant strategies to manipulate host cells for infectious entry and replication. Viral apoptotic mimicry, defined by the exposure of phosphatidylserine — a marker for apoptosis — on the pathogen surface, is emerging as a common theme used by enveloped viruses to promote infection. Focusing on the four best described examples (vaccinia virus, dengue virus, Ebola virus and pseudotyped lentivirus), we summarize our current understanding of apoptotic mimicry as a mechanism for virus entry, binding and immune evasion. We also describe recent examples of non-enveloped viruses that use this mimicry strategy, and discuss future directions and how viral apoptotic mimicry could be targeted therapeutically.
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Affiliation(s)
- Ali Amara
- Institut National de la Santé et de la Recherche Médicale U944 and Centre National de la Recherche Scientifique UMR 7212, Laboratoire de Pathologie et Virologie Moléculaire, Institut Universitaire d'Hématologie, Université Paris Diderot, Sorbonne Paris Cité, Hôpital Saint-Louis, 1 avenue Claude Vellefaux, 75010 Paris, France
| | - Jason Mercer
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
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316
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Castilla V, Piccini LE, Damonte EB. Dengue virus entry and trafficking: perspectives as antiviral target for prevention and therapy. Future Virol 2015. [DOI: 10.2217/fvl.15.35] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
ABSTRACT Dengue virus (DENV) is the etiological agent of the most important human viral infection transmitted by mosquitoes in the world. In spite of the serious health threat that dengue represents, at present there are no vaccine or antiviral agents available and treatment of patients consists of supportive therapy. This review will focus on the process of DENV entry into the host cell as a potential target for antiviral therapy. The recent advances in the knowledge of viral and cellular molecules and mechanisms involved in binding, internalization and trafficking of DENV into the host cell until virion uncoating are discussed, together with an overview of the strategies and compounds evaluated for development of antiviral agents targeted to DENV entry.
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Affiliation(s)
- Viviana Castilla
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellón 2, Piso 4, 1428 Buenos Aires, Argentina
| | - Luana E Piccini
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellón 2, Piso 4, 1428 Buenos Aires, Argentina
| | - Elsa B Damonte
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellón 2, Piso 4, 1428 Buenos Aires, Argentina
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317
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Affiliation(s)
- Sven Moller-Tank
- Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America
- Gene Therapy Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Wendy Maury
- Gene Therapy Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail:
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318
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Interaction between TIM-1 and NPC1 Is Important for Cellular Entry of Ebola Virus. J Virol 2015; 89:6481-93. [PMID: 25855742 DOI: 10.1128/jvi.03156-14] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Accepted: 04/03/2015] [Indexed: 01/06/2023] Open
Abstract
UNLABELLED Multiple host molecules are known to be involved in the cellular entry of filoviruses, including Ebola virus (EBOV); T-cell immunoglobulin and mucin domain 1 (TIM-1) and Niemann-Pick C1 (NPC1) have been identified as attachment and fusion receptors, respectively. However, the molecular mechanisms underlying the entry process have not been fully understood. We found that TIM-1 and NPC1 colocalized and interacted in the intracellular vesicles where EBOV glycoprotein (GP)-mediated membrane fusion occurred. Interestingly, a TIM-1-specific monoclonal antibody (MAb), M224/1, prevented GP-mediated membrane fusion and also interfered with the binding of TIM-1 to NPC1, suggesting that the interaction between TIM-1 and NPC1 is important for filovirus membrane fusion. Moreover, MAb M224/1 efficiently inhibited the cellular entry of viruses from all known filovirus species. These data suggest a novel mechanism underlying filovirus membrane fusion and provide a potential cellular target for antiviral compounds that can be universally used against filovirus infections. IMPORTANCE Filoviruses, including Ebola and Marburg viruses, cause rapidly fatal diseases in humans and nonhuman primates. There are currently no approved vaccines or therapeutics for filovirus diseases. In general, the cellular entry step of viruses is one of the key mechanisms to develop antiviral strategies. However, the molecular mechanisms underlying the entry process of filoviruses have not been fully understood. In this study, we demonstrate that TIM-1 and NPC1, which serve as attachment and fusion receptors for filovirus entry, interact in the intracellular vesicles where Ebola virus GP-mediated membrane fusion occurs and that this interaction is important for filovirus infection. We found that filovirus infection and GP-mediated membrane fusion in cultured cells were remarkably suppressed by treatment with a TIM-1-specific monoclonal antibody that interfered with the interaction between TIM-1 and NPC1. Our data provide new insights for the development of antiviral compounds that can be universally used against filovirus infections.
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319
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Dubayle J, Vialle S, Schneider D, Pontvianne J, Mantel N, Adam O, Guy B, Talaga P. Site-specific characterization of envelope protein N-glycosylation on Sanofi Pasteur's tetravalent CYD dengue vaccine. Vaccine 2015; 33:1360-8. [PMID: 25660649 DOI: 10.1016/j.vaccine.2015.01.047] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 01/09/2015] [Accepted: 01/11/2015] [Indexed: 01/16/2023]
Abstract
Recently, several virus studies have shown that protein glycosylation play a fundamental role in the virus-host cell interaction. Glycosylation characterization of the envelope proteins in both insect and mammalian cell-derived dengue virus (DENV) has established that two potential glycosylation residues, the asparagine 67 and 153 can potentially be glycosylated. Moreover, it appears that the glycosylation of these two residues can influence dramatically the virus production and the infection spreading in either mosquito or mammalian cells. The Sanofi Pasteur tetravalent dengue vaccine (CYD) consists of four chimeric viruses produced in mammalian vero cells. As DENV, the CYDs are able to infect human monocyte-derived dendritic cells in vitro via C-type lectins cell-surface molecules. Despite the importance of this interaction, the specific glycosylation pattern of the DENV has not been clearly documented so far. In this paper, we investigated the structure of the N-linked glycans in the four CYD serotypes. Using MALDI-TOF analysis, the N-linked glycans of CYDs were found to be a mix of high-mannose, hybrid and complex glycans. Site-specific N-glycosylation analysis of CYDs using nanoLC-ESI-MS/MS demonstrates that both asparagine residues 67 and 153 are glycosylated. Predominant glycoforms at asparagine 67 are high mannose-type structures while mainly complex- and hybrid-type structures are detected at asparagine 153. In vitro studies have shown that the immunological consequences of infection by the CYD dengue viruses 1-4 versus the wild type parents are comparable in human monocyte-derived dendritic cells. Our E-protein glycan characterizations of CYD are consistent with those observations from the wild type parents and thus support in vitro studies. In addition, these data provide new insights for the role of glycans in the dengue virus-host cell interactions.
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Affiliation(s)
- Jean Dubayle
- Research and Development Department, Sanofi Pasteur, Campus Mérieux, 1541 Avenue Marcel Mérieux, 69280 Marcy L'Etoile, France.
| | - Sandrine Vialle
- Research and Development Department, Sanofi Pasteur, Campus Mérieux, 1541 Avenue Marcel Mérieux, 69280 Marcy L'Etoile, France
| | - Diane Schneider
- Research and Development Department, Sanofi Pasteur, Campus Mérieux, 1541 Avenue Marcel Mérieux, 69280 Marcy L'Etoile, France
| | - Jérémy Pontvianne
- Research and Development Department, Sanofi Pasteur, Campus Mérieux, 1541 Avenue Marcel Mérieux, 69280 Marcy L'Etoile, France
| | - Nathalie Mantel
- Research and Development Department, Sanofi Pasteur, Campus Mérieux, 1541 Avenue Marcel Mérieux, 69280 Marcy L'Etoile, France
| | - Olivier Adam
- Research and Development Department, Sanofi Pasteur, Campus Mérieux, 1541 Avenue Marcel Mérieux, 69280 Marcy L'Etoile, France
| | - Bruno Guy
- Research and Development Department, Sanofi Pasteur, Campus Mérieux, 1541 Avenue Marcel Mérieux, 69280 Marcy L'Etoile, France
| | - Philippe Talaga
- Research and Development Department, Sanofi Pasteur, Campus Mérieux, 1541 Avenue Marcel Mérieux, 69280 Marcy L'Etoile, France
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320
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Rothlin CV, Carrera-Silva EA, Bosurgi L, Ghosh S. TAM receptor signaling in immune homeostasis. Annu Rev Immunol 2015; 33:355-91. [PMID: 25594431 DOI: 10.1146/annurev-immunol-032414-112103] [Citation(s) in RCA: 307] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The TAM receptor tyrosine kinases (RTKs)-TYRO3, AXL, and MERTK-together with their cognate agonists GAS6 and PROS1 play an essential role in the resolution of inflammation. Deficiencies in TAM signaling have been associated with chronic inflammatory and autoimmune diseases. Three processes regulated by TAM signaling may contribute, either independently or collectively, to immune homeostasis: the negative regulation of the innate immune response, the phagocytosis of apoptotic cells, and the restoration of vascular integrity. Recent studies have also revealed the function of TAMs in infectious diseases and cancer. Here, we review the important milestones in the discovery of these RTKs and their ligands and the studies that underscore the functional importance of this signaling pathway in physiological immune settings and disease.
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321
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Cruz-Oliveira C, Freire JM, Conceição TM, Higa LM, Castanho MARB, Da Poian AT. Receptors and routes of dengue virus entry into the host cells. FEMS Microbiol Rev 2014; 39:155-70. [PMID: 25725010 DOI: 10.1093/femsre/fuu004] [Citation(s) in RCA: 209] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Dengue is the most prevalent arthropod-borne viral disease, caused by dengue virus, a member of the Flaviviridae family. Its worldwide incidence is now a major health problem, with 2.5 billion people living in risk areas. In this review, we integrate the structural rearrangements of each viral protein and their functions in all the steps of virus entry into the host cells. We describe in detail the putative receptors and attachment factors in mammalian and mosquito cells, and the recognition of viral immunocomplexes via Fcγ receptor in immune cells. We also discuss that virus internalization might occur through distinct entry pathways, including clathrin-mediated or non-classical clathrin-independent endocytosis, depending on the host cell and virus serotype or strain. The implications of viral maturation in virus entry are also explored. Finally, we discuss the mechanisms of viral genome access to the cytoplasm. This includes the role of low pH-induced conformational changes in the envelope protein that mediate membrane fusion, and original insights raised by our recent work that supports the hypothesis that capsid protein would also be an active player in this process, acting on viral genome translocation into the cytoplasm.
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Affiliation(s)
- Christine Cruz-Oliveira
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil
| | - João Miguel Freire
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisbon, Portugal
| | - Thaís M Conceição
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil
| | - Luiza M Higa
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil
| | - Miguel A R B Castanho
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisbon, Portugal
| | - Andrea T Da Poian
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil
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322
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Cerny D, Haniffa M, Shin A, Bigliardi P, Tan BK, Lee B, Poidinger M, Tan EY, Ginhoux F, Fink K. Selective susceptibility of human skin antigen presenting cells to productive dengue virus infection. PLoS Pathog 2014; 10:e1004548. [PMID: 25474532 PMCID: PMC4256468 DOI: 10.1371/journal.ppat.1004548] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 11/01/2014] [Indexed: 12/11/2022] Open
Abstract
Dengue is a growing global concern with 390 million people infected each year. Dengue virus (DENV) is transmitted by mosquitoes, thus host cells in the skin are the first point of contact with the virus. Human skin contains several populations of antigen-presenting cells which could drive the immune response to DENV in vivo: epidermal Langerhans cells (LCs), three populations of dermal dendritic cells (DCs), and macrophages. Using samples of normal human skin we detected productive infection of CD14+ and CD1c+ DCs, LCs and dermal macrophages, which was independent of DC-SIGN expression. LCs produced the highest viral titers and were less sensitive to IFN-β. Nanostring gene expression data showed significant up-regulation of IFN-β, STAT-1 and CCL5 upon viral exposure in susceptible DC populations. In mice infected intra-dermally with DENV we detected parallel populations of infected DCs originating from the dermis and migrating to the skin-draining lymph nodes. Therefore dermal DCs may simultaneously facilitate systemic spread of DENV and initiate the adaptive anti-viral immune response. Dengue virus (DENV) is transmitted by mosquitoes with skin as point of entry for the virus. Here, we investigated DENV infection in primary human skin cells and their initial immune response. Using skin from normal human donors for infection with DENV in vitro we identified antigen-presenting cells (APCs) as main targets of DENV. Further analysis showed that only distinct subsets of dendritic cells (DCs) and macrophages were infected and efficiently produced viral progeny. Langerhans cells were most susceptible to infection despite lacking DC-SIGN, a previously described DENV receptor. Infection of the other DC subsets and macrophages was also independent of DC-SIGN expression. Genes of the interferon pathway and CCL5, a chemokine attracting immune cells to sites of inflammation, were highly up-regulated in the infected DC subsets. Using a mouse infection model, we showed that murine dermal DCs were also susceptible to DENV and migrated to draining lymph nodes. At the same time infiltrating monocytes differentiated into monocyte-derived cells at the site of infection and became an additional target for DENV in vivo. These data demonstrate that DENV differentially infects and activates primary human skin APCs and that infected cell types individually contribute to inflammation and the adaptive response.
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Affiliation(s)
- Daniela Cerny
- Singapore Immunology Network, Agency for Science, Technology and Research, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Muzlifah Haniffa
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Amanda Shin
- Singapore Immunology Network, Agency for Science, Technology and Research, Singapore
| | - Paul Bigliardi
- Institute of Molecular Biology, Agency for Science, Technology and Research, Singapore
- Division of Rheumatology, University Medicine Cluster, National University Health System, Singapore
| | - Bien Keem Tan
- Department of Plastic Surgery, Singapore General Hospital, Singapore
| | - Bernett Lee
- Singapore Immunology Network, Agency for Science, Technology and Research, Singapore
| | - Michael Poidinger
- Singapore Immunology Network, Agency for Science, Technology and Research, Singapore
| | - Ern Yu Tan
- Department of General Surgery, Tan Tock Seng Hospital, Singapore
| | - Florent Ginhoux
- Singapore Immunology Network, Agency for Science, Technology and Research, Singapore
| | - Katja Fink
- Singapore Immunology Network, Agency for Science, Technology and Research, Singapore
- * E-mail:
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323
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Graham DK, DeRyckere D, Davies KD, Earp HS. The TAM family: phosphatidylserine sensing receptor tyrosine kinases gone awry in cancer. Nat Rev Cancer 2014; 14:769-85. [PMID: 25568918 DOI: 10.1038/nrc3847] [Citation(s) in RCA: 498] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The TYRO3, AXL (also known as UFO) and MERTK (TAM) family of receptor tyrosine kinases (RTKs) are aberrantly expressed in multiple haematological and epithelial malignancies. Rather than functioning as oncogenic drivers, their induction in tumour cells predominately promotes survival, chemoresistance and motility. The unique mode of maximal activation of this RTK family requires an extracellular lipid–protein complex. For example, the protein ligand, growth arrest-specific protein 6 (GAS6), binds to phosphatidylserine (PtdSer) that is externalized on apoptotic cell membranes, which activates MERTK on macrophages. This triggers engulfment of apoptotic material and subsequent anti-inflammatory macrophage polarization. In tumours, autocrine and paracrine ligands and apoptotic cells are abundant, which provide a survival signal to the tumour cell and favour an anti-inflammatory, immunosuppressive microenvironment. Thus, TAM kinase inhibition could stimulate antitumour immunity, reduce tumour cell survival, enhance chemosensitivity and diminish metastatic potential.
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324
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Tsai TT, Chuang YJ, Lin YS, Chang CP, Wan SW, Lin SH, Chen CL, Lin CF. Antibody-dependent enhancement infection facilitates dengue virus-regulated signaling of IL-10 production in monocytes. PLoS Negl Trop Dis 2014; 8:e3320. [PMID: 25412261 PMCID: PMC4239119 DOI: 10.1371/journal.pntd.0003320] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 10/06/2014] [Indexed: 12/20/2022] Open
Abstract
Background Interleukin (IL)-10 levels are increased in dengue virus (DENV)-infected patients with severe disorders. A hypothetical intrinsic pathway has been proposed for the IL-10 response during antibody-dependent enhancement (ADE) of DENV infection; however, the mechanisms of IL-10 regulation remain unclear. Principle Finding We found that DENV infection and/or attachment was sufficient to induce increased expression of IL-10 and its downstream regulator suppressor of cytokine signaling 3 in human monocytic THP-1 cells and human peripheral blood monocytes. IL-10 production was controlled by activation of cyclic adenosine monophosphate response element-binding (CREB), primarily through protein kinase A (PKA)- and phosphoinositide 3-kinase (PI3K)/PKB-regulated pathways, with PKA activation acting upstream of PI3K/PKB. DENV infection also caused glycogen synthase kinase (GSK)-3β inactivation in a PKA/PI3K/PKB-regulated manner, and inhibition of GSK-3β significantly increased DENV-induced IL-10 production following CREB activation. Pharmacological inhibition of spleen tyrosine kinase (Syk) activity significantly decreased DENV-induced IL-10 production, whereas silencing Syk-associated C-type lectin domain family 5 member A caused a partial inhibition. ADE of DENV infection greatly increased IL-10 expression by enhancing Syk-regulated PI3K/PKB/GSK-3β/CREB signaling. We also found that viral load, but not serotype, affected the IL-10 response. Finally, modulation of IL-10 expression could affect DENV replication. Significance These results demonstrate that, in monocytes, IL-10 production is regulated by ADE through both an extrinsic and an intrinsic pathway, all involving a Syk-regulated PI3K/PKB/GSK-3β/CREB pathway, and both of which impact viral replication. IL-10 has multiple cellular functions, including anti-inflammatory and immunomodulatory effects. Clinical studies have demonstrated that the serum levels of IL-10 are significantly increased in DENV-infected patients with severe disorders. However, the molecular mechanism underlying DENV-induced IL-10 production is still unresolved. In this study, we demonstrate a molecular mechanism for DENV-induced IL-10 production, which may be exacerbated by ADE through Fcγ receptor-mediated extrinsic and intrinsic pathways, leading to IL-10/SOCS3-mediated advantages for viral replication. With or without Fcγ receptor- or CLEC5A-mediated DENV infection, a common Syk/PKA-regulated PI3K/PKB activation results in a decrease in GSK-3β activity followed by an increase in CREB-mediated IL-10 expression not only in THP-1 monocytic cells but also in human monocytes. Taken together, we demonstrate a potential regulation and a pathological role for ADE-induced IL-10 overproduction during DENV replication. Therefore, inhibiting immunosuppression by targeting the IL-10 pathways identified in this study may help to prevent the progression of severe dengue diseases.
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Affiliation(s)
- Tsung-Ting Tsai
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Yi-Jui Chuang
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Yee-Shin Lin
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Chih-Peng Chang
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Shu-Wen Wan
- Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Sheng-Hsiang Lin
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chia-Ling Chen
- Center of Translational Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chiou-Feng Lin
- Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
- Department of Microbiology and Immunology, College of Medicine, Taipei Medical University, Taipei, Taiwan
- * E-mail:
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325
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Microparticles provide a novel biomarker to predict severe clinical outcomes of dengue virus infection. J Virol 2014; 89:1587-607. [PMID: 25410854 DOI: 10.1128/jvi.02207-14] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
UNLABELLED Shedding of microparticles (MPs) is a consequence of apoptotic cell death and cellular activation. Low levels of circulating MPs in blood help maintain homeostasis, whereas increased MP generation is linked to many pathological conditions. Herein, we investigated the role of MPs in dengue virus (DENV) infection. Infection of various susceptible cells by DENV led to apoptotic death and MP release. These MPs harbored a viral envelope protein and a nonstructural protein 1 (NS1) on their surfaces. Ex vivo analysis of clinical specimens from patients with infections of different degrees of severity at multiple time points revealed that MPs generated from erythrocytes and platelets are two major MP populations in the circulation of DENV-infected patients. Elevated levels of red blood cell-derived MPs (RMPs) directly correlated with DENV disease severity, whereas a significant decrease in platelet-derived MPs was associated with a bleeding tendency. Removal by mononuclear cells of complement-opsonized NS1-anti-NS1 immune complexes bound to erythrocytes via complement receptor type 1 triggered MP shedding in vitro, a process that could explain the increased levels of RMPs in severe dengue. These findings point to the multiple roles of MPs in dengue pathogenesis. They offer a potential novel biomarker candidate capable of differentiating dengue fever from the more serious dengue hemorrhagic fever. IMPORTANCE Dengue is the most important mosquito-transmitted viral disease in the world. No vaccines or specific treatments are available. Rapid diagnosis and immediate treatment are the keys to achieve a positive outcome. Dengue virus (DENV) infection, like some other medical conditions, changes the level and composition of microparticles (MPs), tiny bag-like structures which are normally present at low levels in the blood of healthy individuals. This study investigated how MPs in culture and patients' blood are changed in response to DENV infection. Infection of cells led to programmed cell death and MP release. In patients' blood, the majority of MPs originated from red blood cells and platelets. Decreased platelet-derived MPs were associated with a bleeding tendency, while increased levels of red blood cell-derived MPs (RMPs) correlated with more severe disease. Importantly, the level of RMPs during the early acute phase could serve as a biomarker to identify patients with potentially severe disease who require immediate care.
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326
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Kimani SG, Geng K, Kasikara C, Kumar S, Sriram G, Wu Y, Birge RB. Contribution of Defective PS Recognition and Efferocytosis to Chronic Inflammation and Autoimmunity. Front Immunol 2014; 5:566. [PMID: 25426118 PMCID: PMC4226236 DOI: 10.3389/fimmu.2014.00566] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Accepted: 10/23/2014] [Indexed: 12/14/2022] Open
Abstract
The rapid and efficient clearance of apoptotic cells results in the elimination of auto-antigens and provides a strong anti-inflammatory and immunosuppressive signal to prevent autoimmunity. While professional and non-professional phagocytes utilize a wide array of surface receptors to recognize apoptotic cells, the recognition of phosphatidylserine (PS) on apoptotic cells by PS receptors on phagocytes is the emblematic signal for efferocytosis in metazoans. PS-dependent efferocytosis is associated with the production of anti-inflammatory factors such as IL-10 and TGF-β that function, in part, to maintain tolerance to auto-antigens. In contrast, when apoptotic cells fail to be recognized and processed for degradation, auto-antigens persist, such as self-nucleic acids, which can trigger immune activation leading to autoantibody production and autoimmunity. Despite the fact that genetic mouse models clearly demonstrate that loss of PS receptors can lead to age-dependent auto-immune diseases reminiscent of systemic lupus erythematosus (SLE), the link between PS and defective clearance in chronic inflammation and human autoimmunity is not well delineated. In this perspective, we review emerging questions developing in the field that may be of relevance to SLE and human autoimmunity.
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Affiliation(s)
- Stanley Gititu Kimani
- Department of Biochemistry and Molecular Biology, Rutgers School of Biomedical and Health Sciences - Cancer Center , Newark, NJ , USA
| | - Ke Geng
- Department of Biochemistry and Molecular Biology, Rutgers School of Biomedical and Health Sciences - Cancer Center , Newark, NJ , USA
| | - Canan Kasikara
- Department of Biochemistry and Molecular Biology, Rutgers School of Biomedical and Health Sciences - Cancer Center , Newark, NJ , USA
| | - Sushil Kumar
- Department of Biochemistry and Molecular Biology, Rutgers School of Biomedical and Health Sciences - Cancer Center , Newark, NJ , USA
| | - Ganapathy Sriram
- Department of Biochemistry and Molecular Biology, Rutgers School of Biomedical and Health Sciences - Cancer Center , Newark, NJ , USA
| | - Yi Wu
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, First Affiliated Hospital, Soochow University , Suzhou , China ; Sol Sherry Thrombosis Research Center, Temple University School of Medicine , Philadelphia, PA , USA
| | - Raymond B Birge
- Department of Biochemistry and Molecular Biology, Rutgers School of Biomedical and Health Sciences - Cancer Center , Newark, NJ , USA
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Kuroda M, Fujikura D, Noyori O, Kajihara M, Maruyama J, Miyamoto H, Yoshida R, Takada A. A polymorphism of the TIM-1 IgV domain: implications for the susceptibility to filovirus infection. Biochem Biophys Res Commun 2014; 455:223-8. [PMID: 25449273 PMCID: PMC7124303 DOI: 10.1016/j.bbrc.2014.10.144] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 10/29/2014] [Indexed: 01/17/2023]
Abstract
TIM-1 genes were compared among African green monkey kidney cell lines. Vero E6-derived TIM-1 has increased potential to promote filovirus entry. The IgV domain is primarily involved in TIM-1-mediated filovirus entry. A single amino acid in the IgV domain is crucial for the increased ability of TIM-1. TIM-1 polymorphism may affect the cell susceptibility to filovirus infection.
Filoviruses, including Ebola and Marburg viruses, cause severe hemorrhagic fever in humans and nonhuman primates with mortality rates of up to 90%. Human T-cell immunoglobulin and mucin domain 1 (TIM-1) is one of the host proteins that have been shown to promote filovirus entry into cells. In this study, we cloned TIM-1 genes from three different African green monkey kidney cell lines (Vero E6, COS-1, and BSC-1) and found that TIM-1 of Vero E6 had a 23-amino acid deletion and 6 amino acid substitutions compared with those of COS-1 and BSC-1. Interestingly, Vero E6 TIM-1 had a greater ability to promote the infectivity of vesicular stomatitis viruses pseudotyped with filovirus glycoproteins than COS-1-derived TIM-1. We further found that the increased ability of Vero E6 TIM-1 to promote virus infectivity was most likely due to a single amino acid difference between these TIM-1s. These results suggest that a polymorphism of the TIM-1 molecules is one of the factors that influence cell susceptibility to filovirus infection, providing a new insight into the molecular basis for the filovirus host range.
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Affiliation(s)
- Makoto Kuroda
- Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo 001-0020, Japan
| | - Daisuke Fujikura
- Division of Infection and Immunity, Hokkaido University Research Center for Zoonosis Control, Sapporo 001-0020, Japan
| | - Osamu Noyori
- Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo 001-0020, Japan
| | - Masahiro Kajihara
- Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo 001-0020, Japan
| | - Junki Maruyama
- Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo 001-0020, Japan
| | - Hiroko Miyamoto
- Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo 001-0020, Japan
| | - Reiko Yoshida
- Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo 001-0020, Japan
| | - Ayato Takada
- Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo 001-0020, Japan; Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 001-0020, Japan; School of Veterinary Medicine, The University of Zambia, P.O. Box 32379, Lusaka, Zambia.
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328
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Sensing of immature particles produced by dengue virus infected cells induces an antiviral response by plasmacytoid dendritic cells. PLoS Pathog 2014; 10:e1004434. [PMID: 25340500 PMCID: PMC4207819 DOI: 10.1371/journal.ppat.1004434] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 08/29/2014] [Indexed: 11/19/2022] Open
Abstract
Dengue virus (DENV) is the leading cause of mosquito-borne viral illness and death in humans. Like many viruses, DENV has evolved potent mechanisms that abolish the antiviral response within infected cells. Nevertheless, several in vivo studies have demonstrated a key role of the innate immune response in controlling DENV infection and disease progression. Here, we report that sensing of DENV infected cells by plasmacytoid dendritic cells (pDCs) triggers a robust TLR7-dependent production of IFNα, concomitant with additional antiviral responses, including inflammatory cytokine secretion and pDC maturation. We demonstrate that unlike the efficient cell-free transmission of viral infectivity, pDC activation depends on cell-to-cell contact, a feature observed for various cell types and primary cells infected by DENV, as well as West Nile virus, another member of the Flavivirus genus. We show that the sensing of DENV infected cells by pDCs requires viral envelope protein-dependent secretion and transmission of viral RNA. Consistently with the cell-to-cell sensing-dependent pDC activation, we found that DENV structural components are clustered at the interface between pDCs and infected cells. The actin cytoskeleton is pivotal for both this clustering at the contacts and pDC activation, suggesting that this structural network likely contributes to the transmission of viral components to the pDCs. Due to an evolutionarily conserved suboptimal cleavage of the precursor membrane protein (prM), DENV infected cells release uncleaved prM containing-immature particles, which are deficient for membrane fusion function. We demonstrate that cells releasing immature particles trigger pDC IFN response more potently than cells producing fusion-competent mature virus. Altogether, our results imply that immature particles, as a carrier to endolysosome-localized TLR7 sensor, may contribute to regulate the progression of dengue disease by eliciting a strong innate response.
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329
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Hsieh SC, Wu YC, Zou G, Nerurkar VR, Shi PY, Wang WK. Highly conserved residues in the helical domain of dengue virus type 1 precursor membrane protein are involved in assembly, precursor membrane (prM) protein cleavage, and entry. J Biol Chem 2014; 289:33149-60. [PMID: 25326389 DOI: 10.1074/jbc.m114.610428] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The envelope and precursor membrane (prM) proteins of dengue virus (DENV) are present on the surface of immature virions. During maturation, prM protein is cleaved by furin protease into pr peptide and membrane (M) protein. Although previous studies mainly focusing on the pr region have identified several residues important for DENV replication, the functional role of M protein, particularly the α-helical domain (MH), which is predicted to undergo a large conformational change during maturation, remains largely unknown. In this study, we investigated the role of nine highly conserved MH domain residues in the replication cycle of DENV by site-directed mutagenesis in a DENV1 prME expression construct and found that alanine substitutions introduced to four highly conserved residues at the C terminus and one at the N terminus of the MH domain greatly affect the production of both virus-like particles and replicon particles. Eight of the nine alanine mutants affected the entry of replicon particles, which correlated with the impairment in prM cleavage. Moreover, seven mutants were found to have reduced prM-E interaction at low pH, which may inhibit the formation of smooth immature particles and exposure of prM cleavage site during maturation, thus contributing to inefficient prM cleavage. Taken together, these results are the first report showing that highly conserved MH domain residues, located at 20-38 amino acids downstream from the prM cleavage site, can modulate the prM cleavage, maturation of particles, and virus entry. The highly conserved nature of these residues suggests potential targets of antiviral strategy.
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Affiliation(s)
- Szu-Chia Hsieh
- From the Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813 and
| | - Yi-Chieh Wu
- From the Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813 and
| | - Gang Zou
- the Wadsworth Center, New York State Department of Health, Albany, New York 12208
| | - Vivek R Nerurkar
- From the Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813 and
| | - Pei-Yong Shi
- the Wadsworth Center, New York State Department of Health, Albany, New York 12208
| | - Wei-Kung Wang
- From the Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813 and
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330
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Lew ED, Oh J, Burrola PG, Lax I, Zagórska A, Través PG, Schlessinger J, Lemke G. Differential TAM receptor-ligand-phospholipid interactions delimit differential TAM bioactivities. eLife 2014; 3. [PMID: 25265470 PMCID: PMC4206827 DOI: 10.7554/elife.03385] [Citation(s) in RCA: 197] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 09/28/2014] [Indexed: 12/22/2022] Open
Abstract
The TAM receptor tyrosine kinases Tyro3, Axl, and Mer regulate key features of cellular physiology, yet the differential activities of the TAM ligands Gas6 and Protein S are poorly understood. We have used biochemical and genetic analyses to delineate the rules for TAM receptor–ligand engagement and find that the TAMs segregate into two groups based on ligand specificity, regulation by phosphatidylserine, and function. Tyro3 and Mer are activated by both ligands but only Gas6 activates Axl. Optimal TAM signaling requires coincident TAM ligand engagement of both its receptor and the phospholipid phosphatidylserine (PtdSer): Gas6 lacking its PtdSer-binding ‘Gla domain’ is significantly weakened as a Tyro3/Mer agonist and is inert as an Axl agonist, even though it binds to Axl with wild-type affinity. In two settings of TAM-dependent homeostatic phagocytosis, Mer plays a predominant role while Axl is dispensable, and activation of Mer by Protein S is sufficient to drive phagocytosis. DOI:http://dx.doi.org/10.7554/eLife.03385.001 Cells send out and receive signals to communicate with other cells. Detecting these signals is largely carried out by proteins called receptors that span the cell surface membrane. These proteins typically have extracellular domains outside of the cell that can bind to specific signaling molecules and an intracellular domain inside the cell that relays the information inwards to trigger a response. Three such receptor proteins are collectively known as the TAM receptors. Each day, many billions of cells in the human body die and are engulfed by other cells and broken down so that their building blocks can be reused. TAM receptors are required for this process; and the TAM receptors also help prevent the immune system from going out of control, which would damage the body's own tissues. Two different signaling proteins, called Gas6 and Protein S, can bind to and activate TAM receptors. Both of the signaling proteins can also bind to a phospholipid molecule that is found on the surface membrane of dead cells. However, it is not known if all three TAM receptors bind to both signaling proteins equally, and the importance of the phospholipid-binding domain in the signaling proteins remains unclear. To shed light on the workings of these receptors, Lew et al. created mouse cells that each only express one out of the three TAM receptors. These cells were then exposed to intact Gas6 and Protein S, or shortened versions that lacked the phospholipid-binding domain. Lew et al. found that Gas6 could trigger a response through all three TAM receptors but that Protein S was specific for only two out of the three receptors. Signaling proteins with or without their phospholipid-binding domains bound equally well to the receptors, but the maximum level of response was only triggered when both signaling proteins were intact and the phospholipid molecule was present. This is important since the phospholipid can be thought of as an ‘eat-me’ signal by which the dead cells are recognized by the TAM receptor-expressing cells that will engulf them. Using mice that only produce a TAM receptor called Mer, Lew et al. show that Protein S alone can trigger the process that engulfs and breaks down cells in a living organism. These data and previous work suggest that two TAM receptors—including Mer—are involved in the daily engulfment of dying cells, whereas the third mediates this process during infection and tissue damage. Molecules that inhibit or activate the function of TAM receptors are currently being developed to treat cancer and other diseases. By revealing which receptors respond to which signaling molecules, the findings of Lew et al. will serve to guide these efforts. DOI:http://dx.doi.org/10.7554/eLife.03385.002
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Affiliation(s)
- Erin D Lew
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States
| | - Jennifer Oh
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States
| | - Patrick G Burrola
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States
| | - Irit Lax
- Department of Pharmacology, Yale University School of Medicine, New Haven, United States
| | - Anna Zagórska
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States
| | - Paqui G Través
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States
| | - Joseph Schlessinger
- Department of Pharmacology, Yale University School of Medicine, New Haven, United States
| | - Greg Lemke
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States
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331
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Moller-Tank S, Maury W. Phosphatidylserine receptors: enhancers of enveloped virus entry and infection. Virology 2014; 468-470:565-580. [PMID: 25277499 PMCID: PMC4252826 DOI: 10.1016/j.virol.2014.09.009] [Citation(s) in RCA: 138] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Revised: 07/15/2014] [Accepted: 09/08/2014] [Indexed: 12/23/2022]
Abstract
A variety of both RNA and DNA viruses envelop their capsids in a lipid bilayer. One of the more recently appreciated benefits this envelope is incorporation of phosphatidylserine (PtdSer). Surface exposure of PtdSer disguises viruses as apoptotic bodies; tricking cells into engulfing virions. This mechanism is termed apoptotic mimicry. Several PtdSer receptors have been identified to enhance virus entry and we have termed this group of proteins PtdSer-mediated virus entry enhancing receptors or PVEERs. These receptors enhance entry of a range of enveloped viruses. Internalization of virions by PVEERs provides a broad mechanism of entry with little investment by the virus itself. PVEERs may allow some viruses to attach to cells, thereby making viral glycoprotein/cellular receptor interactions more probable. Alternatively, other viruses may rely entirely on PVEERs for internalization into endosomes. This review provides an overview of PtdSer receptors that serve as PVEERs and the biology behind virion/PVEER interaction. Phosphatidylserine (PtdSer) receptors can mediate entry of enveloped viruses. PtdSer is present on the outer leaflet of the virion envelope. PtdSer receptors are expressed on a variety of primary cells and cell lines. Characteristics of PtdSer receptors that mediate virus entry are defined.
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Affiliation(s)
- Sven Moller-Tank
- Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
| | - Wendy Maury
- Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA.
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332
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Mazzon M, Mercer J. Lipid interactions during virus entry and infection. Cell Microbiol 2014; 16:1493-502. [PMID: 25131438 PMCID: PMC4265854 DOI: 10.1111/cmi.12340] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 07/26/2014] [Accepted: 08/01/2014] [Indexed: 12/14/2022]
Abstract
For entry and infection viruses have developed numerous strategies to subjugate indispensable cellular factors and functions. Host cell lipids and cellular lipid synthesis machinery are no exception. Not only do viruses exploit existing lipid signalling and modifications for virus entry and trafficking, they also reprogram lipid synthesis, metabolism, and compartmentalization for assembly and egress. Here we review these various concepts and highlight recent progress in understanding viral interactions with host cell lipids during entry and assembly.
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Affiliation(s)
- Michela Mazzon
- MRC-Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
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333
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Zagórska A, Través PG, Lew ED, Dransfield I, Lemke G. Diversification of TAM receptor tyrosine kinase function. Nat Immunol 2014; 15:920-8. [PMID: 25194421 PMCID: PMC4169336 DOI: 10.1038/ni.2986] [Citation(s) in RCA: 301] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 08/05/2014] [Indexed: 12/12/2022]
Abstract
The clearance of apoptotic cells is critical for both tissue homeostasis and the resolution of inflammation. We found that the TAM receptor tyrosine kinases Axl and Mer had distinct roles as phagocytic receptors in these two settings, in which they exhibited divergent expression, regulation and activity. Mer acted as a tolerogenic receptor in resting macrophages and during immunosuppression. In contrast, Axl was an inflammatory response receptor whose expression was induced by proinflammatory stimuli. Axl and Mer differed in their ligand specificities, ligand-receptor complex formation in tissues, and receptor shedding upon activation. These differences notwithstanding, phagocytosis by either protein was strictly dependent on receptor activation triggered by bridging of TAM receptor-ligand complexes to the 'eat-me' signal phosphatidylserine on the surface of apoptotic cells.
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Affiliation(s)
- Anna Zagórska
- Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA
| | - Paqui G Través
- Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA
| | - Erin D Lew
- Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA
| | - Ian Dransfield
- MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, UK
| | - Greg Lemke
- 1] Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA. [2] Immunobiology and Microbial Pathogenesis Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA
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334
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Abstract
Accumulating evidence indicates that T-cell immunoglobulin (Ig) and mucin domain (TIM) proteins play critical roles in viral infections. Herein, we report that the TIM-family proteins strongly inhibit HIV-1 release, resulting in diminished viral production and replication. Expression of TIM-1 causes HIV-1 Gag and mature viral particles to accumulate on the plasma membrane. Mutation of the phosphatidylserine (PS) binding sites of TIM-1 abolishes its ability to block HIV-1 release. TIM-1, but to a much lesser extent PS-binding deficient mutants, induces PS flipping onto the cell surface; TIM-1 is also found to be incorporated into HIV-1 virions. Importantly, TIM-1 inhibits HIV-1 replication in CD4-positive Jurkat cells, despite its capability of up-regulating CD4 and promoting HIV-1 entry. In addition to TIM-1, TIM-3 and TIM-4 also block the release of HIV-1, as well as that of murine leukemia virus (MLV) and Ebola virus (EBOV); knockdown of TIM-3 in differentiated monocyte-derived macrophages (MDMs) enhances HIV-1 production. The inhibitory effects of TIM-family proteins on virus release are extended to other PS receptors, such as Axl and RAGE. Overall, our study uncovers a novel ability of TIM-family proteins to block the release of HIV-1 and other viruses by interaction with virion- and cell-associated PS. Our work provides new insights into a virus-cell interaction that is mediated by TIMs and PS receptors.
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335
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The composition of West Nile virus lipid envelope unveils a role of sphingolipid metabolism in flavivirus biogenesis. J Virol 2014; 88:12041-54. [PMID: 25122799 DOI: 10.1128/jvi.02061-14] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
West Nile virus (WNV) is an emerging zoonotic mosquito-borne flavivirus responsible for outbreaks of febrile illness and meningoencephalitis. The replication of WNV takes place on virus-modified membranes from the endoplasmic reticulum of the host cell, and virions acquire their envelope by budding into this organelle. Consistent with this view, the cellular biology of this pathogen is intimately linked to modifications of the intracellular membranes, and the requirement for specific lipids, such as cholesterol and fatty acids, has been documented. In this study, we evaluated the impact of WNV infection on two important components of cellular membranes, glycerophospholipids and sphingolipids, by mass spectrometry of infected cells. A significant increase in the content of several glycerophospholipids (phosphatidylcholine, plasmalogens, and lysophospholipids) and sphingolipids (ceramide, dihydroceramide, and sphingomyelin) was noticed in WNV-infected cells, suggesting that these lipids have functional roles during WNV infection. Furthermore, the analysis of the lipid envelope of WNV virions and recombinant virus-like particles revealed that their envelopes had a unique composition. The envelopes were enriched in sphingolipids (sphingomyelin) and showed reduced levels of phosphatidylcholine, similar to sphingolipid-enriched lipid microdomains. Inhibition of neutral sphingomyelinase (which catalyzes the hydrolysis of sphingomyelin into ceramide) by either pharmacological approaches or small interfering RNA-mediated silencing reduced the release of flavivirus virions as well as virus-like particles, suggesting a role of sphingomyelin-to-ceramide conversion in flavivirus budding and confirming the importance of sphingolipids in the biogenesis of WNV. Importance: West Nile virus (WNV) is a neurotropic flavivirus spread by mosquitoes that can infect multiple vertebrate hosts, including humans. There is no specific vaccine or therapy against this pathogen licensed for human use. Since the multiplication of this virus is associated with rearrangements of host cell membranes, we analyzed the effect of WNV infection on different cellular lipids that constitute important membrane components. The levels of multiple lipid species were increased in infected cells, pointing to the induction of major alterations of cellular lipid metabolism by WNV infection. Interestingly, certain sphingolipids, which were increased in infected cells, were also enriched in the lipid envelope of the virus, thus suggesting a potential role during virus assembly. We further verified the role of sphingolipids in the production of WNV by means of functional analyses. This study provides new insight into the formation of flavivirus infectious particles and the involvement of sphingolipids in the WNV life cycle.
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336
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Abstract
Dengue virus (DENV) is an emerging mosquito-borne human pathogen that affects millions of individuals each year by causing severe and potentially fatal syndromes. Despite intense research efforts, no approved vaccine or antiviral therapy is yet available. Overcoming this limitation requires detailed understanding of the intimate relationship between the virus and its host cell, providing the basis to devise optimal prophylactic and therapeutic treatment options. With the advent of novel high-throughput technologies including functional genomics, transcriptomics, proteomics, and lipidomics, new important insights into the DENV replication cycle and the interaction of this virus with its host cell have been obtained. In this chapter, we provide a comprehensive overview on the current status of the DENV research field, covering every step of the viral replication cycle with a particular focus on virus-host cell interaction. We will also review specific chemical inhibitors targeting cellular factors and processes of relevance for the DENV replication cycle and their possible exploitation for the development of next generation antivirals.
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337
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Abstract
Of the many pathogens that infect humans and animals, a large number use cells of the host organism as protected sites for replication. To reach the relevant intracellular compartments, they take advantage of the endocytosis machinery and exploit the network of endocytic organelles for penetration into the cytosol or as sites of replication. In this review, we discuss the endocytic entry processes used by viruses and bacteria and compare the strategies used by these dissimilar classes of pathogens.
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Affiliation(s)
- Pascale Cossart
- Institut Pasteur, Unité des Interactions Bactéries-Cellules, Paris F-75015, France; INSERM U604, Paris F-75015, France; and INRA, USC2020, Paris F-75015, France
| | - Ari Helenius
- Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
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338
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Tsou WI, Nguyen KQN, Calarese DA, Garforth SJ, Antes AL, Smirnov SV, Almo SC, Birge RB, Kotenko SV. Receptor tyrosine kinases, TYRO3, AXL, and MER, demonstrate distinct patterns and complex regulation of ligand-induced activation. J Biol Chem 2014; 289:25750-63. [PMID: 25074926 DOI: 10.1074/jbc.m114.569020] [Citation(s) in RCA: 165] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
TYRO3, AXL, and MER receptors (TAMs) are three homologous type I receptor-tyrosine kinases that are activated by endogenous ligands, protein S (PROS1) and growth arrest-specific gene 6 (GAS6). These ligands can either activate TAMs as soluble factors, or, in turn, opsonize phosphatidylserine (PS) on apoptotic cells (ACs) and serve as bridging molecules between ACs and TAMs. Abnormal expression and activation of TAMs have been implicated in promoting proliferation and survival of cancer cells, as well as in suppressing anti-tumor immunity. Despite the fact that TAM receptors share significant similarity, little is known about the specificity of interaction between TAM receptors and their ligands, particularly in the context of ACs, and about the functional diversity of TAM receptors. To study ligand-mediated activation of TAMs, we generated a series of reporter cell lines expressing chimeric TAM receptors. Using this system, we found that each TAM receptor has a unique pattern of interaction with and activation by GAS6 and PROS1, which is also differentially affected by the presence of ACs, PS-containing lipid vesicles and enveloped virus. We also demonstrated that γ-carboxylation of ligands is essential for the full activation of TAMs and that soluble immunoglobulin-like TAM domains act as specific ligand antagonists. These studies demonstrate that, despite their similarity, TYRO3, AXL, and MER are likely to perform distinct functions in both immunoregulation and the recognition and removal of ACs.
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Affiliation(s)
- Wen-I Tsou
- From the Department of Biochemistry and Molecular Biology, University Hospital Cancer Center and Center for Immunity and Inflammation, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Newark, New Jersey 07103, and
| | - Khanh-Quynh N Nguyen
- From the Department of Biochemistry and Molecular Biology, University Hospital Cancer Center and
| | | | | | - Anita L Antes
- From the Department of Biochemistry and Molecular Biology, University Hospital Cancer Center and
| | - Sergey V Smirnov
- From the Department of Biochemistry and Molecular Biology, University Hospital Cancer Center and Center for Immunity and Inflammation, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Newark, New Jersey 07103, and
| | - Steve C Almo
- the Department of Biochemistry and Albert Einstein Cancer Center, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461
| | - Raymond B Birge
- From the Department of Biochemistry and Molecular Biology, University Hospital Cancer Center and
| | - Sergei V Kotenko
- From the Department of Biochemistry and Molecular Biology, University Hospital Cancer Center and Center for Immunity and Inflammation, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Newark, New Jersey 07103, and
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339
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Progress in the identification of dengue virus entry/fusion inhibitors. BIOMED RESEARCH INTERNATIONAL 2014; 2014:825039. [PMID: 25157370 PMCID: PMC4135166 DOI: 10.1155/2014/825039] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 05/09/2014] [Indexed: 01/12/2023]
Abstract
Dengue fever, a reemerging disease, is putting nearly 2.5 billion people at risk worldwide. The number of infections and the geographic extension of dengue fever infection have increased in the past decade. The disease is caused by the dengue virus, a flavivirus that uses mosquitos Aedes sp. as vectors. The disease has several clinical manifestations, from the mild cold-like illness to the more serious hemorrhagic dengue fever and dengue shock syndrome. Currently, there is no approved drug for the treatment of dengue disease or an effective vaccine to fight the virus. Therefore, the search for antivirals against dengue virus is an active field of research. As new possible receptors and biological pathways of the virus biology are discovered, new strategies are being undertaken to identify possible antiviral molecules. Several groups of researchers have targeted the initial step in the infection as a potential approach to interfere with the virus. The viral entry process is mediated by viral proteins and cellular receptor molecules that end up in the endocytosis of the virion, the fusion of both membranes, and the release of viral RNA in the cytoplasm. This review provides an overview of the targets and progress that has been made in the quest for dengue virus entry inhibitors.
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340
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Kwissa M, Nakaya HI, Onlamoon N, Wrammert J, Villinger F, Perng GC, Yoksan S, Pattanapanyasat K, Chokephaibulkit K, Ahmed R, Pulendran B. Dengue virus infection induces expansion of a CD14(+)CD16(+) monocyte population that stimulates plasmablast differentiation. Cell Host Microbe 2014; 16:115-27. [PMID: 24981333 PMCID: PMC4116428 DOI: 10.1016/j.chom.2014.06.001] [Citation(s) in RCA: 169] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 04/11/2014] [Accepted: 05/19/2014] [Indexed: 12/28/2022]
Abstract
Dengue virus (DENV) infection induces the expansion of plasmablasts, which produce antibodies that can neutralize DENV but also enhance disease upon secondary infection with another DENV serotype. To understand how these immune responses are generated, we used a systems biological approach to analyze immune responses to dengue in humans. Transcriptomic analysis of whole blood revealed that genes encoding proinflammatory mediators and type I interferon-related proteins were associated with high DENV levels during initial symptomatic disease. Additionally, CD14(+)CD16(+) monocytes increased in the blood. Similarly, in a nonhuman primate model, DENV infection boosted CD14(+)CD16(+) monocyte numbers in the blood and lymph nodes. Upon DENV infection in vitro, monocytes upregulated CD16 and mediated differentiation of resting B cells to plasmablasts as well as immunoglobulin G (IgG) and IgM secretion. These findings provide a detailed picture of innate responses to dengue and highlight a role for CD14(+)CD16(+) monocytes in promoting plasmablast differentiation and anti-DENV antibody responses.
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Affiliation(s)
- Marcin Kwissa
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Helder I Nakaya
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Department of Pathology & Laboratory Medicine, School of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Nattawat Onlamoon
- Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Jens Wrammert
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Department of Microbiology and Immunology, School of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Francois Villinger
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Division of Pathology at Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Guey Chuen Perng
- Department of Microbiology and Immunology, Medical College, National Cheng Kung University, Tainan 70101, Taiwan; Center of Infectious Disease and Signaling Research, Medical College, National Cheng Kung University, Tainan 70101, Taiwan
| | - Sutee Yoksan
- Insitute of Molecular Biosciences, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Kovit Pattanapanyasat
- Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Kulkanya Chokephaibulkit
- Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Rafi Ahmed
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Department of Microbiology and Immunology, School of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Bali Pulendran
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Department of Pathology & Laboratory Medicine, School of Medicine, Emory University, Atlanta, GA 30322, USA.
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341
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Characterization of the ectodomain of the envelope protein of dengue virus type 4: expression, membrane association, secretion and particle formation in the absence of precursor membrane protein. PLoS One 2014; 9:e100641. [PMID: 24950216 PMCID: PMC4065094 DOI: 10.1371/journal.pone.0100641] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 05/29/2014] [Indexed: 01/08/2023] Open
Abstract
Background The envelope (E) of dengue virus (DENV) is the major target of neutralizing antibodies and vaccine development. After biosynthesis E protein forms a heterodimer with precursor membrane (prM) protein. Recent reports of infection enhancement by anti-prM monoclonal antibodies (mAbs) suggest anti-prM responses could be potentially harmful. Previously, we studied a series of C-terminal truncation constructs expressing DENV type 4 prM/E or E proteins and found the ectodomain of E protein alone could be recognized by all 12 mAbs tested, suggesting E protein ectodomain as a potential subunit immunogen without inducing anti-prM response. The characteristics of DENV E protein ectodomain in the absence of prM protein remains largely unknown. Methodology/Principal Findings In this study, we investigated the expression, membrane association, glycosylation pattern, secretion and particle formation of E protein ectodomain of DENV4 in the presence or absence of prM protein. E protein ectodomain associated with membrane in or beyond trans-Golgi and contained primarily complex glycans, whereas full-length E protein associated with ER membrane and contained high mannose glycans. In the absence of prM protein, E protein ectodomain can secrete as well as form particles of approximately 49 nm in diameter, as revealed by sucrose gradient ultracentrifugation with or without detergent and electron microscopy. Mutational analysis revealed that the secretion of E protein ectodomain was affected by N-linked glycosylation and could be restored by treatment with ammonia chloride. Conclusions/Significance Considering the enhancement of DENV infectivity by anti-prM antibodies, our findings provide new insights into the expression and secretion of E protein ectodomain in the absence of prM protein and contribute to future subunit vaccine design.
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342
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Abstract
UNLABELLED The production of neutralizing antibodies (NAbs) is a correlate of protection for many human vaccines, including currently licensed vaccines against flaviviruses. NAbs are typically measured using a plaque reduction neutralization test (PRNT). Despite its extensive use, parameters that impact the performance of the PRNT have not been investigated from a mechanistic perspective. The results of a recent phase IIb clinical trial of a tetravalent dengue virus (DENV) vaccine suggest that NAbs, as measured using a PRNT performed with Vero cells, do not correlate with protection. This surprising finding highlights the importance of understanding how well the PRNT captures the complexity of the NAb response to DENV. In this study, we demonstrated that the structural heterogeneity of flaviviruses arising from inefficient virion maturation impacts the results of neutralization assays in a cell type-dependent manner. Neutralization titers of several monoclonal antibodies were significantly reduced when assayed on Vero cells compared to Raji cells expressing DC-SIGNR. This pattern can be explained by differences in the efficiency with which partially mature flaviviruses attach to each cell type, rather than a differential capacity of antibody to block infection. Vero cells are poorly permissive to the fraction of virions that are most sensitive to neutralization. Analysis of sera from recipients of live-attenuated monovalent DENV vaccine candidates revealed a strong correlation between the sensitivity of serum antibodies to the maturation state of DENV and cell type-dependent patterns of neutralization. Cross-reactive patterns of neutralization may be underrepresented by the "gold-standard" PRNT that employs Vero cells. IMPORTANCE Cell type-dependent patterns of neutralization describe a differential capacity of antibodies to inhibit virus infection when assayed on multiple cellular substrates. In this study, we established a link between antibodies that neutralize infection in a cell type-dependent fashion and those sensitive to the maturation state of the flavivirus virion. We demonstrated that cell type-dependent neutralization reflects a differential capacity to measure neutralization of viruses that are incompletely mature. Partially mature virions that most efficiently bind maturation state-sensitive antibodies are poorly represented by assays typically used in support of flavivirus vaccine development. The selection of cellular substrate for neutralization assays may significantly impact evaluation of the neutralization potency of the polyclonal response. These data suggest that current assays do not adequately capture the full complexity of the neutralizing antibody response and may hinder the identification of correlates of protection following flavivirus vaccination.
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343
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Listeria monocytogenes exploits efferocytosis to promote cell-to-cell spread. Nature 2014; 509:230-4. [PMID: 24739967 PMCID: PMC4151619 DOI: 10.1038/nature13168] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 02/21/2014] [Indexed: 11/08/2022]
Abstract
Efferocytosis, the process by which dying or dead cells are removed by phagocytosis, has an important role in development, tissue homeostasis and innate immunity. Efferocytosis is mediated, in part, by receptors that bind to exofacial phosphatidylserine (PS) on cells or cellular debris after loss of plasma membrane asymmetry. Here we show that a bacterial pathogen, Listeria monocytogenes, can exploit efferocytosis to promote cell-to-cell spread during infection. These bacteria can escape the phagosome in host cells by using the pore-forming toxin listeriolysin O (LLO) and two phospholipase C enzymes. Expression of the cell surface protein ActA allows L. monocytogenes to activate host actin regulatory factors and undergo actin-based motility in the cytosol, eventually leading to formation of actin-rich protrusions at the cell surface. Here we show that protrusion formation is associated with plasma membrane damage due to LLO's pore-forming activity. LLO also promotes the release of bacteria-containing protrusions from the host cell, generating membrane-derived vesicles with exofacial PS. The PS-binding receptor TIM-4 (encoded by the Timd4 gene) contributes to efficient cell-to-cell spread by L. monocytogenes in macrophages in vitro and growth of these bacteria is impaired in Timd4(-/-) mice. Thus, L. monocytogenes promotes its dissemination in a host by exploiting efferocytosis. Our results indicate that PS-targeted therapeutics may be useful in the fight against infections by L. monocytogenes and other bacteria that use similar strategies of cell-to-cell spread during infection.
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344
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Abstract
UNLABELLED T-cell immunoglobulin and mucin domain 1 (TIM-1) and other TIM family members were recently identified as phosphatidylserine (PtdSer)-mediated virus entry-enhancing receptors (PVEERs). These proteins enhance entry of Ebola virus (EBOV) and other viruses by binding PtdSer on the viral envelope, concentrating virus on the cell surface, and promoting subsequent internalization. The PtdSer-binding activity of the immunoglobulin-like variable (IgV) domain is essential for both virus binding and internalization by TIM-1. However, TIM-3, whose IgV domain also binds PtdSer, does not effectively enhance virus entry, indicating that other domains of TIM proteins are functionally important. Here, we investigate the domains supporting enhancement of enveloped virus entry, thereby defining the features necessary for a functional PVEER. Using a variety of chimeras and deletion mutants, we found that in addition to a functional PtdSer-binding domain PVEERs require a stalk domain of sufficient length, containing sequences that promote an extended structure. Neither the cytoplasmic nor the transmembrane domain of TIM-1 is essential for enhancing virus entry, provided the protein is still plasma membrane bound. Based on these defined characteristics, we generated a mimic lacking TIM sequences and composed of annexin V, the mucin-like domain of α-dystroglycan, and a glycophosphatidylinositol anchor that functioned as a PVEER to enhance transduction of virions displaying Ebola, Chikungunya, Ross River, or Sindbis virus glycoproteins. This identification of the key features necessary for PtdSer-mediated enhancement of virus entry provides a basis for more effective recognition of unknown PVEERs. IMPORTANCE T-cell immunoglobulin and mucin domain 1 (TIM-1) and other TIM family members are recently identified phosphatidylserine (PtdSer)-mediated virus entry-enhancing receptors (PVEERs). These proteins enhance virus entry by binding the phospholipid, PtdSer, present on the viral membrane. While it is known that the PtdSer binding is essential for the PVEER function of TIM-1, TIM-3 shares this binding activity but does not enhance virus entry. No comprehensive studies have been done to characterize the other domains of TIM-1. In this study, using a variety of chimeric proteins and deletion mutants, we define the features necessary for a functional PVEER. With these features in mind, we generated a TIM-1 mimic using functionally similar domains from other proteins. This mimic, like TIM-1, effectively enhanced transduction. These studies provide insight into the key features necessary for PVEERs and will allow for more effective identification of unknown PVEERs.
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345
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Lam SK. Challenges in reducing dengue burden; diagnostics, control measures and vaccines. Expert Rev Vaccines 2014; 12:995-1010. [PMID: 24053394 DOI: 10.1586/14760584.2013.824712] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Dengue is a major public health concern worldwide, with the number of infections increasing globally. The illness imposes the greatest economic and human burden on developing countries that have limited resources to deal with the scale of the problem. No cure for dengue exists; treatment is limited to rehydration therapy, and with vector control strategies proving to be relatively ineffective, a vaccine is an urgent priority. Despite the numerous challenges encountered in the development of a dengue vaccine, several vaccine candidates have shown promise in clinical development and it is believed that a vaccination program would be at least as cost-effective as current vector control programs. The lead candidate vaccine is a tetravalent, live attenuated, recombinant vaccine, which is currently in Phase III clinical trials. Vaccine introduction is a complex process that requires consideration and is discussed here. This review discusses the epidemiology, burden and pathogenesis of dengue, as well as the vaccine candidates currently in clinical development.
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Affiliation(s)
- Sai Kit Lam
- Office of the Vice-Chancellor, University of Malaya, Jalan Pantai Baru, 50603, Kuala Lumpur, Malaysia +60 17 8800044 +60 37 7259635
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346
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Shibata T, Habiel DM, Coelho AL, Kunkel SL, Lukacs NW, Hogaboam CM. Axl receptor blockade ameliorates pulmonary pathology resulting from primary viral infection and viral exacerbation of asthma. THE JOURNAL OF IMMUNOLOGY 2014; 192:3569-81. [PMID: 24659691 DOI: 10.4049/jimmunol.1302766] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Viruses use Tyro3, Axl, and Mertk (TAM) receptor tyrosine kinases to infect and modulate the immune properties of various cell types, which led us to investigate whether TAM receptor activation affected primary viral infection and viral exacerbation of asthma in experimental models. In these lung-specific models, we observed that Axl was the most abundantly induced TAM receptor protein. During primary respiratory syncytial virus (RSV) infection, anti-Axl mAb treatment significantly increased the number of IFN-γ-producing T cells and NK cells and significantly suppressed RSV replication and whole lung levels of IL-4 and IL-13. Intrapulmonary H1N1 infection induced lethal pulmonary inflammation, but anti-Axl mAb treatment of infected mice significantly increased the number of IFN-β-producing macrophages and dendritic cells and significantly suppressed neutrophil infiltration. Consequently, the lethal effect of H1N1 infection in this model was significantly reduced in the mAb-treated group compared with the IgG control-treated group. Targeting Axl also inhibited airway hyperresponsiveness, IL-4 and IL-13 production, and goblet cell metaplasia in an Aspergillus fumigatus-induced asthma model. Finally, infection of mice with RSV during fungal asthma significantly exacerbated airway inflammation, goblet cell metaplasia, and airway remodeling, but all of these features in this viral exacerbation model were ameliorated by anti-Axl mAb treatment. Taken together, these results demonstrate that Axl modulates the pulmonary immune response during viral and/or allergic pathology, and they also suggest that targeting this TAM receptor might provide a novel therapeutic approach in these infectious diseases.
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Affiliation(s)
- Takehiko Shibata
- Immunology Program, Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109
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347
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Bhattacharyya S, Zagórska A, Lew ED, Shrestha B, Rothlin CV, Naughton J, Diamond MS, Lemke G, Young JAT. Enveloped viruses disable innate immune responses in dendritic cells by direct activation of TAM receptors. Cell Host Microbe 2014; 14:136-47. [PMID: 23954153 DOI: 10.1016/j.chom.2013.07.005] [Citation(s) in RCA: 157] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 05/21/2013] [Accepted: 06/14/2013] [Indexed: 01/21/2023]
Abstract
Upon activation by the ligands Gas6 and Protein S, Tyro3/Axl/Mer (TAM) receptor tyrosine kinases promote phagocytic clearance of apoptotic cells and downregulate immune responses initiated by Toll-like receptors and type I interferons (IFNs). Many enveloped viruses display the phospholipid phosphatidylserine on their membranes, through which they bind Gas6 and Protein S and engage TAM receptors. We find that ligand-coated viruses activate TAM receptors on dendritic cells (DCs), dampen type I IFN signaling, and thereby evade host immunity and promote infection. Upon virus challenge, TAM-deficient DCs display type I IFN responses that are elevated in comparison to wild-type cells. As a consequence, TAM-deficient DCs are relatively resistant to infection by flaviviruses and pseudotyped retroviruses, but infection can be restored with neutralizing type I IFN antibodies. Correspondingly, a TAM kinase inhibitor antagonizes the infection of wild-type DCs. Thus, TAM receptors are engaged by viruses in order to attenuate type I IFN signaling and represent potential therapeutic targets.
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Affiliation(s)
- Suchita Bhattacharyya
- Nomis Center for Immunobiology and Microbial Pathogenesis, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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348
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Cosset FL, Dreux M. HCV transmission by hepatic exosomes establishes a productive infection. J Hepatol 2014; 60:674-5. [PMID: 24512825 DOI: 10.1016/j.jhep.2013.10.015] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 10/09/2013] [Accepted: 10/10/2013] [Indexed: 12/04/2022]
Affiliation(s)
- François-Loïc Cosset
- CIRI - International Center for Infectiology Research, Team EVIR, Université de Lyon, Lyon, France; Inserm, U1111, Lyon, France; Ecole Normale Supérieure de Lyon, Lyon, France; Université Lyon 1, Centre International de Recherche en Infectiologie, Lyon, France; CNRS, UMR5308, Lyon, France; LabEx Ecofect, Université de Lyon, Lyon, France.
| | - Marlène Dreux
- CIRI - International Center for Infectiology Research, Team EVIR, Université de Lyon, Lyon, France; Inserm, U1111, Lyon, France; Ecole Normale Supérieure de Lyon, Lyon, France; Université Lyon 1, Centre International de Recherche en Infectiologie, Lyon, France; CNRS, UMR5308, Lyon, France; LabEx Ecofect, Université de Lyon, Lyon, France.
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349
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Targeting host factors to treat West Nile and dengue viral infections. Viruses 2014; 6:683-708. [PMID: 24517970 PMCID: PMC3939478 DOI: 10.3390/v6020683] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 02/03/2014] [Accepted: 02/04/2014] [Indexed: 01/15/2023] Open
Abstract
West Nile (WNV) and Dengue (DENV) viruses are major arboviral human pathogens belonging to the genus Flavivirus. At the current time, there are no approved prophylactics (e.g., vaccines) or specific therapeutics available to prevent or treat human infections by these pathogens. Due to their minimal genome, these viruses require many host molecules for their replication and this offers a therapeutic avenue wherein host factors can be exploited as treatment targets. Since several host factors appear to be shared by many flaviviruses the strategy may result in pan-flaviviral inhibitors and may also attenuate the rapid emergence of drug resistant mutant viruses. The scope of this strategy is greatly enhanced by the recent en masse identification of host factors impacting on WNV and DENV infection. Excellent proof-of-principle experimental demonstrations for host-targeted control of infection and infection-induced pathogenesis have been reported for both WNV and DENV. These include exploiting not only those host factors supporting infection, but also targeting host processes contributing to pathogenesis and innate immune responses. While these early studies validated the host-targeting approach, extensive future investigations spanning a range of aspects are needed for a successful deployment in humans.
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350
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Abstract
UNLABELLED We recently demonstrated that a soluble protein, Gas6, can facilitate viral entry by bridging viral envelope phosphatidylserine to Axl, a receptor tyrosine kinase expressed on target cells. The interaction between phosphatidylserine, Gas6, and Axl was originally shown to be a molecular mechanism through which phagocytes recognize phosphatidylserine exposed on dead cells. Since our initial report, several groups have confirmed that Axl/Gas6, as well as other phosphatidylserine receptors, facilitate entry of dengue, West Nile, and Ebola viruses. Virus binding by viral envelope phosphatidylserine is now a viral entry mechanism generalized to many families of viruses. In addition to Axl/Gas6, various molecules are known to recognize phosphatidylserine; however, the effects of these molecules on virus binding and entry have not been comprehensively evaluated and compared. In this study, we examined most of the known human phosphatidylserine-recognizing molecules, including MFG-E8, TIM-1, -3, and -4, CD300a, BAI1, and stabilin-1 and -2, for their abilities to facilitate virus binding and infection. Using pseudotyped lentiviral vectors, we found that a soluble phosphatidylserine-binding protein, MFG-E8, enhances transduction. Cell surface receptors TIM-1 and -4 also enhance virus binding/transduction. The extent of enhancement by these molecules varies, depending on the type of pseudotyping envelope proteins. Mutated MFG-E8, which binds viral envelope phosphatidylserine without bridging virus to cells, but, surprisingly, not annexin V, which has been used to block phagocytosis of dead cells by concealing phosphatidylserine, efficiently blocks these phosphatidylserine-dependent viral entry mechanisms. These results provide insight into understanding the role of viral envelope phosphatidylserine in viral infection. IMPORTANCE Envelope phosphatidylserine has previously been shown to be important for replication of various envelope viruses, but details of this mechanism(s) were unclear. We were the first to report that a bifunctional serum protein, Gas6, bridges envelope phosphatidylserine to a cell surface receptor, Axl. Recent studies demonstrated that many envelope viruses, including vaccinia, dengue, West Nile, and Ebola viruses, utilize Axl/Gas6 to facilitate their entry, suggesting that the phosphatidylserine-mediated viral entry mechanism can be shared by various enveloped viruses. In addition to Axl/Gas6, various molecules are known to recognize phosphatidylserine; however, the effects of these molecules on virus binding and entry have not been comprehensively evaluated and compared. In this study, we examined most human phosphatidylserine-recognizing molecules for their abilities to facilitate viral infection. The results provide insights into the role(s) of envelope phosphatidylserine in viral infection, which can be applicable to the development of novel antiviral reagents that block phosphatidylserine-mediated viral entry.
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