301
|
The N-terminal region of IFITM3 modulates its antiviral activity by regulating IFITM3 cellular localization. J Virol 2012; 86:13697-707. [PMID: 23055554 DOI: 10.1128/jvi.01828-12] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Interferon-inducible transmembrane (IFITM) protein family members IFITM1, -2, and -3 restrict the infection of multiple enveloped viruses. Significant enrichment of a minor IFITM3 allele was recently reported for patients who were hospitalized for seasonal and 2009 H1N1 pandemic flu. This IFITM3 allele lacks the region corresponding to the first amino-terminal 21 amino acids and is unable to inhibit influenza A virus. In this study, we found that deleting this 21-amino-acid region relocates IFITM3 from the endosomal compartments to the cell periphery. This finding likely underlies the lost inhibition of influenza A virus that completes its entry exclusively within endosomes at low pH. Yet, wild-type IFITM3 and the mutant with the 21-amino-acid deletion inhibit HIV-1 replication equally well. Given the pH-independent nature of HIV-1 entry, our results suggest that IFITM3 can inhibit viruses that enter cells via different routes and that its N-terminal region is specifically required for controlling pH-dependent viruses.
Collapse
|
302
|
Abstract
Interferon-induced transmembrane (IFITM) proteins are a family of viral restriction factors that inhibit the entry processes of several pathogenic viruses, including influenza A virus (IAV), in vitro. Here we report that IAV-infected knockout mice lacking the Ifitm locus on chromosome 7 exhibited accelerated disease progression, greater mortality, and higher pulmonary and systemic viral burdens as compared to wild type controls. We further observed that the phenotype of Ifitm3-specific knockout mice was indistinguishable from that of mice lacking the entire Ifitm locus. Ifitm3 was expressed by IAV target cells including alveolar type II pneumocytes and tracheal/bronchial respiratory epithelial cells. Robust Ifitm3 expression was also observed in several tissues in the absence of infection. Among murine Ifitm promoters, only that of Ifitm3 could be induced by type I and II interferons. Ifitm3 could also be upregulated by the gp130 cytokines IL-6 and oncostatin M on cells expressing appropriate receptors, suggesting that multiple cytokine signals could contribute to Ifitm3 expression in a cell or tissue-specific manner. Collectively, these findings establish a central role for Ifitm3 in limiting acute influenza in vivo, and provide further insight into Ifitm3 expression and regulation. The human genome contains many genes devoted to combating viral infections. Some of these genes encode a family of proteins called interferon-induced transmembrane (IFITM) proteins which were recently discovered to inhibit infection by influenza A viruses in cell culture experiments. Here we show that genetically engineered mice lacking the murine equivalents of the human IFITM genes are more susceptible to influenza than mice with a full complement of these genes. In addition, deletion of one of these genes alone, Ifitm3, made mice equally susceptible to infection, showing that the Ifitm3 protein plays a central role in the control of influenza A virus in living animals. We also show that murine Ifitm proteins are expressed on cells targeted by influenza A viruses and that the control of their expression in animals is more complex than suggested by previous cell culture studies.
Collapse
|
303
|
Chen Z, Zhang L, Ying S. SAMHD1: a novel antiviral factor in intrinsic immunity. Future Microbiol 2012; 7:1117-26. [DOI: 10.2217/fmb.12.81] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Some intracellular/membranous factors exert intrinsic immunity against viral pathogens. Most recently, SAMHD1 has been shown to be one of these factors. SAMHD1 is a nucleus-localized protein, and mutations in the gene are associated with Aicardi–Goutières syndrome. As a triphosphohydrolase, it depletes the intracellular pool of dNTPs in myeloid cells, such as macrophages and dendritic cells, to a low level that establishes a precursor-deficient environment for the synthesis of lentiviral cDNA, thereby restricting viral replication in these host cells. However, some viruses evolve Vpx to recruit SAMHD1 onto the CRL4DCAF1 E3 ubiquitin ligase in the cytoplasm for proteasome-dependent degradation, by which these viruses relieve SAMHD1-mediated restriction of primate lentivirus infection. In this review, we describe the latest knowledge of SAMHD1 biology.
Collapse
Affiliation(s)
- Zhangming Chen
- Department of Immunology, Anhui Medical University, Hefei, Anhui Province 230032, China
| | - Linjie Zhang
- Department of Immunology, Anhui Medical University, Hefei, Anhui Province 230032, China
| | - Songcheng Ying
- Department of Immunology, Anhui Medical University, Hefei, Anhui Province 230032, China
| |
Collapse
|
304
|
Lee SY, Yu JI, Chae SC. Associations of IFITM3 haplotypes with rheumatoid arthritis in a Korean population. Genes Genomics 2012. [DOI: 10.1007/s13258-011-0241-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
305
|
Hepatitis C virus infection modulates expression of interferon stimulatory gene IFITM1 by upregulating miR-130A. J Virol 2012; 86:10221-5. [PMID: 22787204 DOI: 10.1128/jvi.00882-12] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We have examined the underlying mechanism of hepatitis C virus (HCV)-mediated IFITM1 regulation. IFITM1 is a potential target of miR-130a. Our results demonstrated that miR-130a expression was significantly higher in HCV-infected hepatocytes and liver biopsy specimens than in controls. Introduction of anti-miR-130a in hepatocytes increased IFITM1 expression. Hepatocytes stably expressing IFITM1 reduced HCV replication. Together, these results suggested that HCV infection of hepatocytes upregulates miR-130a and that use of anti-miR-130a may have potential for restriction of HCV replication.
Collapse
|
306
|
Lau SLY, Yuen ML, Kou CYC, Au KW, Zhou J, Tsui SKW. Interferons induce the expression of IFITM1 and IFITM3 and suppress the proliferation of rat neonatal cardiomyocytes. J Cell Biochem 2012; 113:841-7. [PMID: 22021094 PMCID: PMC7166870 DOI: 10.1002/jcb.23412] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Cardiovascular diseases have been one of the leading killers among the human population worldwide. During the heart development, cardiomyocytes undergo a transition from hyperplastic to hypertrophic growth with an unclear underlying mechanism. In this study, we aim to investigate how interferons differentially stimulate the interferon-inducible transmembrane (IFITM) family proteins and further be involved in the process of heart development. The expression levels of three IFITM family members, IFITM1, IFITM2, and IFITM3 were investigated during Sprague-Dawley rat myocardial development and differentiation of H9C2 cardiomyocytes. The effects of interferon-α, -β, and -γ on DNA synthesis in H9C2 cells were also characterized. Up-regulation of IFITM1 and IFITM3 were observed during the heart development of Sprague-Dawley rat and the differentiation of H9C2 cells. Moreover, interferon-α and -β induce the expression of IFITM3 while interferon-γ up-regulates IFITM1. Finally, interferon-α and -β were demonstrated to inhibit DNA synthesis during H9C2 cell differentiation. Our results indicated interferons are potentially involved in the differentiation and cell proliferation during heart development.
Collapse
Affiliation(s)
- Samantha Lai-Yee Lau
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | | | | | | | | | | |
Collapse
|
307
|
HIV-1 infection of human macrophages directly induces viperin which inhibits viral production. Blood 2012; 120:778-88. [PMID: 22677126 DOI: 10.1182/blood-2012-01-407395] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Macrophages are key target cells for HIV-1. HIV-1(BaL) induced a subset of interferon-stimulated genes in monocyte-derived macrophages (MDMs), which differed from that in monocyte-derived dendritic cells and CD4 T cells, without inducing any interferons. Inhibition of type I interferon induction was mediated by HIV-1 inhibition of interferon-regulated factor (IRF3) nuclear translocation. In MDMs, viperin was the most up-regulated interferon-stimulated genes, and it significantly inhibited HIV-1 production. HIV-1 infection disrupted lipid rafts via viperin induction and redistributed viperin to CD81 compartments, the site of HIV-1 egress by budding in MDMs. Exogenous farnesol, which enhances membrane protein prenylation, reversed viperin-mediated inhibition of HIV-1 production. Mutagenesis analysis in transfected cell lines showed that the internal S-adenosyl methionine domains of viperin were essential for its antiviral activity. Thus viperin may contribute to persistent noncytopathic HIV-1 infection of macrophages and possibly to biologic differences with HIV-1-infected T cells.
Collapse
|
308
|
Abstract
CD56+ T cells, the crucial component of the host innate immune system, play an important role in defense against viral infections. We investigated the noncytolytic anti-HIV-1 activity of primary CD56+ T cells. SNs collected from CD56+ T cell cultures inhibited HIV-1 infection and replication. This CD56+ T SN-mediated anti-HIV-1 activity was broad-spectrum, as CD56+ T SNs could inhibit infections by laboratory-adapted and clinical strains of HIV-1. The antibody to IFN-γ could partially block the CD56+ T SN-mediated anti-HIV effect. Investigation of mechanism(s) of the CD56+ T cell action on HIV-1 showed that although CD56+ T SN had little effect on HIV-1 entry coreceptor CCR5 expression, CD56+ T SN induced the expression of CC-chemokines, the ligands for CCR5. The antibodies to CC-chemokines also significantly blocked CD56+ T SN-mediated anti-HIV activity. Furthermore, CD56+ T SN up-regulated the expression of STAT-1/-2 and enhanced the expression of IRF1, -3, -7, and -9, resulting in the induction of endogenous IFN-α/β expression in macrophages. Moreover, CD56+ T SN up-regulated intracellular expression of APOBEC3G/3F, the recently identified HIV-1 restriction factors. These findings provide compelling evidence that CD56+ T cells may have a critical role in innate immunity against HIV-1 infection.
Collapse
Affiliation(s)
- Wei Hou
- Animal Biosafety Level 3 Laboratory/Center for Animal Experiment, Wuhan University, Wuhan, P. R. China
| | | | | |
Collapse
|
309
|
Thippeshappa R, Ruan H, Kimata JT. Breaking Barriers to an AIDS Model with Macaque-Tropic HIV-1 Derivatives. BIOLOGY 2012; 1:134-64. [PMID: 23336082 PMCID: PMC3546514 DOI: 10.3390/biology1020134] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 06/14/2012] [Accepted: 06/18/2012] [Indexed: 12/15/2022]
Abstract
The development of an animal model of human immunodeficiency virus type 1 (HIV-1)/AIDS that is suitable for preclinical testing of antiretroviral therapy, vaccines, curative strategies, and studies of pathogenesis has been hampered by the human-specific tropism of HIV-1. Although simian immunodeficiency virus (SIV) or HIV-1/SIV chimeric viruses (SHIVs)-rhesus macaque models are excellent surrogates for AIDS research, the genetic differences between SIV or SHIV and HIV-1 limit their utility as model systems. The identification of innate retro viral restriction factors has increased our understanding about blockades to HIV-1 replication in macaques and provided a guide for the construction of macaque-tropic HIV-1 clones. However, while these viruses replicate in macaque cells in vitro, they are easily controlled and have not caused AIDS in host animals, indicating that we may not fully understand the restrictive barriers of innate immunity. In this review, we discuss recent findings regarding HIV-1 restriction factors, particularly as they apply to cross-species transmission of primate lentiviruses and the development of a macaque model of HIV-1/AIDS.
Collapse
Affiliation(s)
| | | | - Jason T. Kimata
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (R.T.); (H.R.)
| |
Collapse
|
310
|
Hickford D, Frankenberg S, Shaw G, Renfree MB. Evolution of vertebrate interferon inducible transmembrane proteins. BMC Genomics 2012; 13:155. [PMID: 22537233 PMCID: PMC3424830 DOI: 10.1186/1471-2164-13-155] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Accepted: 04/26/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Interferon inducible transmembrane proteins (IFITMs) have diverse roles, including the control of cell proliferation, promotion of homotypic cell adhesion, protection against viral infection, promotion of bone matrix maturation and mineralisation, and mediating germ cell development. Most IFITMs have been well characterised in human and mouse but little published data exists for other animals. This study characterised IFITMs in two distantly related marsupial species, the Australian tammar wallaby and the South American grey short-tailed opossum, and analysed the phylogeny of the IFITM family in vertebrates. RESULTS Five IFITM paralogues were identified in both the tammar and opossum. As in eutherians, most marsupial IFITM genes exist within a cluster, contain two exons and encode proteins with two transmembrane domains. Only two IFITM genes, IFITM5 and IFITM10, have orthologues in both marsupials and eutherians. IFITM5 arose in bony fish and IFITM10 in tetrapods. The bone-specific expression of IFITM5 appears to be restricted to therian mammals, suggesting that its specialised role in bone production is a recent adaptation specific to mammals. IFITM10 is the most highly conserved IFITM, sharing at least 85% amino acid identity between birds, reptiles and mammals and suggesting an important role for this presently uncharacterised protein. CONCLUSIONS Like eutherians, marsupials also have multiple IFITM genes that exist in a gene cluster. The differing expression patterns for many of the paralogues, together with poor sequence conservation between species, suggests that IFITM genes have acquired many different roles during vertebrate evolution.
Collapse
Affiliation(s)
- Danielle Hickford
- ARC Centre of Excellence for Kangaroo Genomics, Department of Zoology, The University of Melbourne, Victoria, 3010, Australia
| | - Stephen Frankenberg
- ARC Centre of Excellence for Kangaroo Genomics, Department of Zoology, The University of Melbourne, Victoria, 3010, Australia
| | - Geoff Shaw
- ARC Centre of Excellence for Kangaroo Genomics, Department of Zoology, The University of Melbourne, Victoria, 3010, Australia
| | - Marilyn B Renfree
- ARC Centre of Excellence for Kangaroo Genomics, Department of Zoology, The University of Melbourne, Victoria, 3010, Australia
| |
Collapse
|
311
|
Abstract
Interferons (IFNs) induce the expression of hundreds of genes as part of an elaborate antimicrobial programme designed to combat infection in all nucleated cells - a process termed cell-autonomous immunity. As described in this Review, recent genomic and subgenomic analyses have begun to assign functional properties to novel IFN-inducible effector proteins that restrict bacteria, protozoa and viruses in different subcellular compartments and at different stages of the pathogen life cycle. Several newly described host defence factors also participate in canonical oxidative and autophagic pathways by spatially coordinating their activities to enhance microbial killing. Together, these IFN-induced effector networks help to confer vertebrate host resistance to a vast and complex microbial world.
Collapse
Affiliation(s)
- John D MacMicking
- Section of Microbial Pathogenesis, Boyer Centre for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
| |
Collapse
|
312
|
Yount JS, Karssemeijer RA, Hang HC. S-palmitoylation and ubiquitination differentially regulate interferon-induced transmembrane protein 3 (IFITM3)-mediated resistance to influenza virus. J Biol Chem 2012; 287:19631-41. [PMID: 22511783 DOI: 10.1074/jbc.m112.362095] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The interferon (IFN)-induced transmembrane protein 3 (IFITM3) is a cellular restriction factor that inhibits infection by influenza virus and many other pathogenic viruses. IFITM3 prevents endocytosed virus particles from accessing the host cytoplasm although little is known regarding its regulatory mechanisms. Here we demonstrate that IFITM3 localization to and antiviral remodeling of endolysosomes is differentially regulated by S-palmitoylation and lysine ubiquitination. Although S-palmitoylation enhances IFITM3 membrane affinity and antiviral activity, ubiquitination decreases localization with endolysosomes and decreases antiviral activity. Interestingly, autophagy reportedly induced by IFITM3 expression is also negatively regulated by ubiquitination. However, the canonical ATG5-dependent autophagy pathway is not required for IFITM3 activity, indicating that virus trafficking from endolysosomes to autophagosomes is not a prerequisite for influenza virus restriction. Our characterization of IFITM3 ubiquitination sites also challenges the dual-pass membrane topology predicted for this protein family. We thus evaluated topology by N-linked glycosylation site insertion and protein lipidation mapping in conjunction with cellular fractionation and fluorescence imaging. Based on these studies, we propose that IFITM3 is predominantly an intramembrane protein where both the N and C termini face the cytoplasm. In sum, by characterizing S-palmitoylation and ubiquitination of IFITM3, we have gained a better understanding of the trafficking, activity, and intramembrane topology of this important IFN-induced effector protein.
Collapse
Affiliation(s)
- Jacob S Yount
- Laboratory of Chemical Biology and Microbial Pathogenesis, The Rockefeller University, New York, New York 10065, USA
| | | | | |
Collapse
|
313
|
Wee YS, Roundy KM, Weis JJ, Weis JH. Interferon-inducible transmembrane proteins of the innate immune response act as membrane organizers by influencing clathrin and v-ATPase localization and function. Innate Immun 2012; 18:834-45. [PMID: 22467717 DOI: 10.1177/1753425912443392] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The innate response interferon-inducible transmembrane (Ifitm) proteins have been characterized as influencing proliferation, signaling complexes and restricting virus infections. Treatment of cells lacking these proteins (IfitmDel) with IFN-β resulted in the loss of clathrin from membrane compartments and the inhibition of clathrin-mediated phagocytosis, suggesting a molecular interaction between clathrin and Ifitm proteins. The pH of endosomes of IfitmDel cells, with or without IFN activation, was neutralized, suggesting the function of the vacular ATPase proton pumps in such cells was compromised. Co-immunoprecipitation of Ifitm3 with Atp6v0b demonstrated a direct interaction between the Ifitm proteins and the v-ATPase. These data suggest that the Ifitm proteins help stabilize v-ATPase complexes in cellular membranes which, in turn, facilitates the appropriate subcellular localization of clathrin.
Collapse
Affiliation(s)
- Yin Shen Wee
- The Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT 84124, USA
| | | | | | | |
Collapse
|
314
|
Chan YK, Huang IC, Farzan M. IFITM proteins restrict antibody-dependent enhancement of dengue virus infection. PLoS One 2012; 7:e34508. [PMID: 22479637 PMCID: PMC3316688 DOI: 10.1371/journal.pone.0034508] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 03/05/2012] [Indexed: 11/19/2022] Open
Abstract
Interferon-inducible transmembrane (IFITM) proteins restrict the entry processes of several pathogenic viruses, including the flaviviruses West Nile virus and dengue virus (DENV). DENV infects cells directly or via antibody-dependent enhancement (ADE) in Fc-receptor-bearing cells, a process thought to contribute to severe disease in a secondary infection. Here we investigated whether ADE-mediated DENV infection bypasses IFITM-mediated restriction or whether IFITM proteins can be protective in a secondary infection. We observed that IFITM proteins restricted ADE-mediated and direct infection with comparable efficiencies in a myelogenous leukemia cell line. Our data suggest that IFITM proteins can contribute to control of secondary DENV infections.
Collapse
Affiliation(s)
- Ying Kai Chan
- New England Primate Research Center, Department of Microbiology and Immunobiology, Harvard Medical School, Southborough, Massachusetts, United States of America
- * E-mail: (YKC); (MF)
| | | | - Michael Farzan
- New England Primate Research Center, Department of Microbiology and Immunobiology, Harvard Medical School, Southborough, Massachusetts, United States of America
- * E-mail: (YKC); (MF)
| |
Collapse
|
315
|
Sällman Almén M, Bringeland N, Fredriksson R, Schiöth HB. The dispanins: a novel gene family of ancient origin that contains 14 human members. PLoS One 2012; 7:e31961. [PMID: 22363774 PMCID: PMC3282796 DOI: 10.1371/journal.pone.0031961] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 01/16/2012] [Indexed: 11/19/2022] Open
Abstract
The Interferon induced transmembrane proteins (IFITM) are a family of transmembrane proteins that is known to inhibit cell invasion of viruses such as HIV-1 and influenza. We show that the IFITM genes are a subfamily in a larger family of transmembrane (TM) proteins that we call Dispanins, which refers to a common 2TM structure. We mined the Dispanins in 36 eukaryotic species, covering all major eukaryotic groups, and investigated their evolutionary history using Bayesian and maximum likelihood approaches to infer a phylogenetic tree. We identified ten human genes that together with the known IFITM genes form the Dispanin family. We show that the Dispanins first emerged in eukaryotes in a common ancestor of choanoflagellates and metazoa, and that the family later expanded in vertebrates where it forms four subfamilies (A-D). Interestingly, we also find that the family is found in several different phyla of bacteria and propose that it was horizontally transferred to eukaryotes from bacteria in the common ancestor of choanoflagellates and metazoa. The bacterial and eukaryotic sequences have a considerably conserved protein structure. In conclusion, we introduce a novel family, the Dispanins, together with a nomenclature based on the evolutionary origin.
Collapse
Affiliation(s)
- Markus Sällman Almén
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala, Sweden
- * E-mail:
| | - Nathalie Bringeland
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala, Sweden
| | - Robert Fredriksson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala, Sweden
| | - Helgi B. Schiöth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala, Sweden
| |
Collapse
|
316
|
Strobl B, Leitner NR, Müller M. Multifaceted Antiviral Actions of Interferon-stimulated Gene Products. JAK-STAT SIGNALING : FROM BASICS TO DISEASE 2012. [PMCID: PMC7121797 DOI: 10.1007/978-3-7091-0891-8_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Interferons (IFNs) are extremely powerful cytokines for the host defence against viral infections. Binding of IFNs to their receptors activates the JAK/STAT signalling pathway with the Janus kinases JAK1, 2 and TYK2 and the signal transducer and activators of transcription (STAT) 1 and STAT2. Depending on the cellular setting, additional STATs (STAT3-6) and additional signalling pathways are activated. The actions of IFNs on infected cells and the surrounding tissue are mediated by the induction of several hundred IFN-stimulated genes (ISGs). Since the cloning of the first ISGs, considerable progress has been made in describing antiviral effector proteins and their many modes of action. Effector proteins individually target distinct steps in the viral life cycle, including blocking virus entry, inhibition of viral transcription and translation, modification of viral nucleic acids and proteins and, interference with virus assembly and budding. Novel pathways of viral inhibition are constantly being elucidated and, additionally, unanticipated functions of known antiviral effector proteins are discovered. Herein, we outline IFN-induced antiviral pathways and review recent developments in this fascinating area of research.
Collapse
|
317
|
Abstract
PURPOSE OF REVIEW The early stage of HIV-1 infection is when the virus is most vulnerable, and should therefore offer the best opportunity for therapeutic interventions. This review addresses the recent progress in the understanding of innate immune responses against HIV-1 with focus on the potential targets for prevention of viral acquisition, replication and dissemination. RECENT FINDINGS Research indicates that the host-derived factor trappin-2/elafin is protective against HIV, whereas semen-derived enhancer of viral infection and defensins 5 and 6 enhance viral transmission. Further, studies suggest that stimulation of TLR4 and inhibition of TLR7-9 pathways may be HIV suppressive. The regulation and function of viral restriction factors tetherin and APOBEC3G have been investigated and a molecule mimicking the premature uncoating achieved by TRIM5α, PF74, has been identified. Chloroquine has been shown to inhibit plasmacytoid dendritic cell activation and suppress negative modulators of T-cell responses. Blockade of HMBG1 has been found to restore natural-killer-cell-mediated killing of infected dendritic cells, normally suppressed by HIV-1. Interestingly, when used as adjuvants, EAT-2 and heat shock protein gp96 reportedly enhance innate immune responses. SUMMARY Several targets for innate immunity-mediated therapeutics have been identified. Nonetheless, more research is required to unveil their underlying mechanisms and interactions before testing these molecules in clinical trials.
Collapse
|
318
|
Abstract
PURPOSE OF REVIEW Acute HIV-1 infection (AHI) is composed of the eclipse phase, during which the transmitted virus struggles to avoid eradication and achieve amplification/spread; the expansion phase when virus disseminates and undergoes exponential replication associated with extensive CD4⁺ T-cell destruction; and the containment phase when set-point levels of viremia and immune activation are established. The importance of interactions between HIV-1 and innate responses in determining events throughout AHI is increasingly recognized, and is reviewed here. RECENT FINDINGS During the eclipse phase, HIV-1 subverts dendritic cell functions to promote its replication at mucosal sites and employs multiple strategies to minimize control by type 1 interferons. Systemic virus dissemination is associated with widespread activation of innate responses which fuels HIV-1 replication. To minimize the protective effects of innate responses, HIV-1 resists control by natural killer cells and may impair innate regulation of adaptive responses. Innate responses remain chronically activated after HIV-1 containment which is thought to drive HIV-1 pathogenesis. SUMMARY Innate responses are pivotal determinants of events at all stages of AHI. Increased understanding of mechanisms involved in innate control of HIV-1 and pathways regulating innate activation during HIV-1 infection could facilitate development of novel approaches to combating this infection.
Collapse
|
319
|
Raychoudhuri A, Shrivastava S, Steele R, Kim H, Ray R, Ray RB. ISG56 and IFITM1 proteins inhibit hepatitis C virus replication. J Virol 2011; 85:12881-9. [PMID: 21976647 PMCID: PMC3233139 DOI: 10.1128/jvi.05633-11] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 09/28/2011] [Indexed: 12/11/2022] Open
Abstract
Hepatitis C virus (HCV) often leads to persistent infection. Interferon (IFN) and IFN-stimulated genes (ISGs) are amplified during HCV infection but fail to eliminate virus from the liver in a large number of infected patients. We have observed previously that HCV infection induces IFN-β production in immortalized human hepatocytes (IHH) as early as 24 h after infection, although virus replication is not inhibited. To gain insights on possible countermeasures of virus for the suppression of host antiviral response, the cellular transcriptional profiles of ISGs were examined after various treatments of IHH. The majority of ISGs were upregulated in IFN-treated IHH from the level for mock-treated cells. However, the comparison of ISG expression in IFN-treated IHH and IFN-pretreated, HCV genotype 2a-infected IHH indicated that virus infection suppresses the upregulation of a subset of effector molecules, including ISG56 and IFITM1. Similar results were observed for HCV-infected Huh7 cells. Subsequent study suggested that the exogenous expression of ISG56 or IFITM1 inhibits HCV replication in IHH or Huh7 cells, and the knockdown of these genes enhanced HCV replication. Further characterization revealed that the overexpression of these ISGs does not block HCV pseudotype entry into Huh7 cells. Taken together, our results demonstrated that ISG56 and IFITM1 serve as important molecules to restrict HCV infection, and they may have implications in the development of therapeutic modalities.
Collapse
Affiliation(s)
| | | | | | - Hangeun Kim
- Internal Medicine, Saint Louis University, St. Louis, Missouri
| | - Ranjit Ray
- Internal Medicine, Saint Louis University, St. Louis, Missouri
| | | |
Collapse
|
320
|
IFITM3 inhibits influenza A virus infection by preventing cytosolic entry. PLoS Pathog 2011; 7:e1002337. [PMID: 22046135 PMCID: PMC3203188 DOI: 10.1371/journal.ppat.1002337] [Citation(s) in RCA: 298] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 09/13/2011] [Indexed: 01/01/2023] Open
Abstract
To replicate, viruses must gain access to the host cell's resources. Interferon (IFN) regulates the actions of a large complement of interferon effector genes (IEGs) that prevent viral replication. The interferon inducible transmembrane protein family members, IFITM1, 2 and 3, are IEGs required for inhibition of influenza A virus, dengue virus, and West Nile virus replication in vitro. Here we report that IFN prevents emergence of viral genomes from the endosomal pathway, and that IFITM3 is both necessary and sufficient for this function. Notably, viral pseudoparticles were inhibited from transferring their contents into the host cell cytosol by IFN, and IFITM3 was required and sufficient for this action. We further demonstrate that IFN expands Rab7 and LAMP1-containing structures, and that IFITM3 overexpression is sufficient for this phenotype. Moreover, IFITM3 partially resides in late endosomal and lysosomal structures, placing it in the path of invading viruses. Collectively our data are consistent with the prediction that viruses that fuse in the late endosomes or lysosomes are vulnerable to IFITM3's actions, while viruses that enter at the cell surface or in the early endosomes may avoid inhibition. Multiple viruses enter host cells through the late endocytic pathway, and many of these invaders are attenuated by IFN. Therefore these findings are likely to have significance for the intrinsic immune system's neutralization of a diverse array of threats. Influenza epidemics exact a great toll on world health. Thus research to identify new anti-influenza virus strategies would be useful. Each of our cells contains antiviral factors that work to inhibit infection. A large component of this antiviral program is regulated by the interferon family of signaling molecules. Here, we seek to better understand how one of these antiviral factors, IFITM3, contributes to both baseline, as well as interferon-induced, antagonism of influenza A viral infection. We found that interferon prevents influenza A virus from entering our cells by blocking the virus' fusion with the cellular membrane. Furthermore, we learned that IFITM3 is required for this antiviral action of interferon, and that high levels of IFITM3 alone can produce a similar viral inhibition. Together, these results improve our understanding of how IFITM3 serves to defend us against viral invasion at a very early stage of infection.
Collapse
|
321
|
|
322
|
Shaw ML. The host interactome of influenza virus presents new potential targets for antiviral drugs. Rev Med Virol 2011; 21:358-69. [PMID: 21823192 PMCID: PMC3207218 DOI: 10.1002/rmv.703] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 06/14/2011] [Accepted: 06/21/2011] [Indexed: 12/26/2022]
Abstract
Increasing antiviral drug resistance is a major concern for treating influenza, especially in a pandemic setting when the availability of a protective vaccine is uncertain. Resistance is often an issue with drugs directed at viral proteins and for small RNA viruses; there are also a limited number of viral proteins that are amenable to inhibition by a small molecule. A new approach that is gaining support is that cellular proteins, which facilitate virus replication, may be used as alternative targets. Whereas drugs directed at viral proteins tend to be virus-specific, drugs directed at host targets have the potential to have broad-spectrum antiviral activity as many viruses may share a dependency on that host function. For influenza virus, we have very limited knowledge of which cellular factors are involved in virus replication, let alone which of these have suitable properties to serve as drug targets. Through the use of high-throughput RNA interference screens, several studies have addressed this gap in our knowledge. The resulting datasets provide new insight into host pathways that are involved in the influenza virus replication cycle and identify specific host factors in these pathways that may serve as potential targets for future antiviral drug development.
Collapse
Affiliation(s)
- Megan L Shaw
- Department of Microbiology, Mount Sinai School of Medicine, New York, NY 10029, USA.
| |
Collapse
|
323
|
MicroRNA: implications in HIV, a brief overview. J Neurovirol 2011; 17:416-23. [PMID: 21786074 DOI: 10.1007/s13365-011-0046-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Revised: 06/27/2011] [Accepted: 06/29/2011] [Indexed: 10/18/2022]
Abstract
MicroRNAs (miRNAs) are 20-22 nucleotide length noncoding RNA molecules that represent key regulators of many normal cellular functions. miRNAs undergo two processing steps which transform a long primary transcript into the mature miRNA. Available literatures demonstrate the association between alterations in the expression of miRNAs and the progression of numerous human disorders. Even though significant advances have been made, many fundamental questions about their expression and function still remain unanswered. Identifying factors that block the negative action of drugs of abuse on the miRNAs could help in identifying new therapeutic strategies. In this review, we briefly discuss the importance of miRNAs on HIV, strategies used by virus to avoid the cells' antiviral miRNA defenses, and how HIV might control and regulate host cell genes by encoding viral miRNAs.
Collapse
|
324
|
Münk C, Sommer AF, König R. Systems-biology approaches to discover anti-viral effectors of the human innate immune response. Viruses 2011; 3:1112-30. [PMID: 21994773 PMCID: PMC3185791 DOI: 10.3390/v3071112] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 06/26/2011] [Accepted: 06/29/2011] [Indexed: 12/31/2022] Open
Abstract
Virus infections elicit an immediate innate response involving antiviral factors. The activities of some of these factors are, in turn, blocked by viral countermeasures. The ensuing battle between the host and the viruses is crucial for determining whether the virus establishes a foothold and/or induces adaptive immune responses. A comprehensive systems-level understanding of the repertoire of anti-viral effectors in the context of these immediate virus-host responses would provide significant advantages in devising novel strategies to interfere with the initial establishment of infections. Recent efforts to identify cellular factors in a comprehensive and unbiased manner, using genome-wide siRNA screens and other systems biology “omics” methodologies, have revealed several potential anti-viral effectors for viruses like Human immunodeficiency virus type 1 (HIV-1), Hepatitis C virus (HCV), West Nile virus (WNV), and influenza virus. This review describes the discovery of novel viral restriction factors and discusses how the integration of different methods in systems biology can be used to more comprehensively identify the intimate interactions of viruses and the cellular innate resistance.
Collapse
Affiliation(s)
- Carsten Münk
- Clinic for Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich Heine-University, Düsseldorf 40225, Germany; E-Mail:
| | - Andreas F.R. Sommer
- Research Group “Host-Pathogen Interactions”, Paul-Ehrlich-Institut, Langen 63225, Germany; E-Mail:
| | - Renate König
- Research Group “Host-Pathogen Interactions”, Paul-Ehrlich-Institut, Langen 63225, Germany; E-Mail:
- Infectious and Inflammatory Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +49-6103-774019; Fax: +49-6103-771255
| |
Collapse
|
325
|
Meyerson NR, Sawyer SL. Two-stepping through time: mammals and viruses. Trends Microbiol 2011; 19:286-94. [PMID: 21531564 DOI: 10.1016/j.tim.2011.03.006] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 03/08/2011] [Accepted: 03/16/2011] [Indexed: 12/14/2022]
Abstract
Recent studies have identified ancient virus genomes preserved as fossils within diverse animal genomes. These fossils have led to the revelation that a broad range of mammalian virus families are older and more ubiquitous than previously appreciated. Long-term interactions between viruses and their hosts often develop into genetic arms races where both parties continually jockey for evolutionary dominance. It is difficult to imagine how mammalian hosts have kept pace in the evolutionary race against rapidly evolving viruses over large expanses of time, given their much slower evolutionary rates. However, recent data has begun to reveal the evolutionary strategy of slowly-evolving hosts. We review these data and suggest a modified arms race model where the evolutionary possibilities of viruses are relatively constrained. Such a model could allow more accurate forecasting of virus evolution.
Collapse
Affiliation(s)
- Nicholas R Meyerson
- Section of Molecular Genetics and Microbiology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | | |
Collapse
|