scholarly journals An Alternative STAT Signaling Pathway Acts in Viral Immunity in Caenorhabditis elegans

mBio ◽  
2017 ◽  
Vol 8 (5) ◽  
Author(s):  
Mélanie Tanguy ◽  
Louise Véron ◽  
Przemyslaw Stempor ◽  
Julie Ahringer ◽  
Peter Sarkies ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Rna Interference ◽  
Caenorhabditis Elegans ◽  
Viral Infection ◽  
Defense Mechanisms ◽  
Rna Virus ◽  
Interferon Response ◽  
Rnai Pathway ◽  
C Elegans ◽  
Stat Pathway

ABSTRACT Across metazoans, innate immunity is vital in defending organisms against viral infection. In mammals, antiviral innate immunity is orchestrated by interferon signaling, activating the STAT transcription factors downstream of the JAK kinases to induce expression of antiviral effector genes. In the nematode Caenorhabditis elegans, which lacks the interferon system, the major antiviral response so far described is RNA interference (RNAi), but whether additional gene expression responses are employed is not known. Here we show that, despite the absence of both interferon and JAK, the C. elegans STAT homolog STA-1 orchestrates antiviral immunity. Intriguingly, mutants lacking STA-1 are less permissive to antiviral infection. Using gene expression analysis and chromatin immunoprecipitation, we show that, in contrast to the mammalian pathway, STA-1 acts mostly as a transcriptional repressor. Thus, STA-1 might act to suppress a constitutive antiviral response in the absence of infection. Additionally, using a reverse genetic screen, we identify the kinase SID-3 as a new component of the response to infection, which, along with STA-1, participates in the transcriptional regulatory network of the immune response. Our work uncovers novel physiological roles for two factors in viral infection: a SID protein acting independently of RNAi and a STAT protein acting in C. elegans antiviral immunity. Together, these results illustrate the complex evolutionary trajectory displayed by innate immune signaling pathways across metazoan organisms. IMPORTANCE Since innate immunity was discovered, a diversity of pathways has arisen as powerful first-line defense mechanisms to fight viral infection. RNA interference, reported mostly in invertebrates and plants, as well as the mammalian interferon response and JAK/STAT pathway are key in RNA virus innate immunity. We studied infection by the Orsay virus in Caenorhabditis elegans, where RNAi is known to be a potent antiviral defense. We show that, in addition to its RNAi pathway, C. elegans utilizes an alternative STAT pathway to control the levels of viral infection. We identify the transcription factor STA-1 and the kinase SID-3 as two components of this response. Our study defines C. elegans as a new example of the diversity of antiviral strategies. IMPORTANCE Since innate immunity was discovered, a diversity of pathways has arisen as powerful first-line defense mechanisms to fight viral infection. RNA interference, reported mostly in invertebrates and plants, as well as the mammalian interferon response and JAK/STAT pathway are key in RNA virus innate immunity. We studied infection by the Orsay virus in Caenorhabditis elegans, where RNAi is known to be a potent antiviral defense. We show that, in addition to its RNAi pathway, C. elegans utilizes an alternative STAT pathway to control the levels of viral infection. We identify the transcription factor STA-1 and the kinase SID-3 as two components of this response. Our study defines C. elegans as a new example of the diversity of antiviral strategies.

scholarly journals Caenorhabditis elegans RIG-I Homolog Mediates Antiviral RNA Interference Downstream of Dicer-Dependent Biogenesis of Viral Small Interfering RNAs

mBio ◽  
2017 ◽  
Vol 8 (2) ◽  
Author(s):  
Stephanie R. Coffman ◽  
Jinfeng Lu ◽  
Xunyang Guo ◽  
Jing Zhong ◽  
Hongshan Jiang ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Rna Interference ◽  
Caenorhabditis Elegans ◽  
Virus Infection ◽  
Rna Virus ◽  
Genetic Screen ◽  
Small Interfering Rnas ◽  
Forward Genetic Screen ◽  
C Elegans ◽  
Terminal Domains

ABSTRACT Dicer enzymes process virus-specific double-stranded RNA (dsRNA) into small interfering RNAs (siRNAs) to initiate specific antiviral defense by related RNA interference (RNAi) pathways in plants, insects, nematodes, and mammals. Antiviral RNAi in Caenorhabditis elegans requires Dicer-related helicase 1 (DRH-1), not found in plants and insects but highly homologous to mammalian retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), intracellular viral RNA sensors that trigger innate immunity against RNA virus infection. However, it remains unclear if DRH-1 acts analogously to initiate antiviral RNAi in C. elegans . Here, we performed a forward genetic screen to characterize antiviral RNAi in C. elegans . Using a mapping-by-sequencing strategy, we uncovered four loss-of-function alleles of drh-1 , three of which caused mutations in the helicase and C-terminal domains conserved in RLRs. Deep sequencing of small RNAs revealed an abundant population of Dicer-dependent virus-derived small interfering RNAs (vsiRNAs) in drh-1 single and double mutant animals after infection with Orsay virus, a positive-strand RNA virus. These findings provide further genetic evidence for the antiviral function of DRH-1 and illustrate that DRH-1 is not essential for the sensing and Dicer-mediated processing of the viral dsRNA replicative intermediates. Interestingly, vsiRNAs produced by drh-1 mutants were mapped overwhelmingly to the terminal regions of the viral genomic RNAs, in contrast to random distribution of vsiRNA hot spots when DRH-1 is functional. As RIG-I translocates on long dsRNA and DRH-1 exists in a complex with Dicer, we propose that DRH-1 facilitates the biogenesis of vsiRNAs in nematodes by catalyzing translocation of the Dicer complex on the viral long dsRNA precursors. IMPORTANCE The helicase and C-terminal domains of mammalian RLRs sense intracellular viral RNAs to initiate the interferon-regulated innate immunity against RNA virus infection. Both of the domains from human RIG-I can substitute for the corresponding domains of DRH-1 to mediate antiviral RNAi in C. elegans , suggesting an analogous role for DRH-1 as an intracellular dsRNA sensor to initiate antiviral RNAi. Here, we developed a forward genetic screen for the identification of host factors required for antiviral RNAi in C. elegans . Characterization of four distinct drh-1 mutants obtained from the screen revealed that DRH-1 did not function to initiate antiviral RNAi. We show that DRH-1 acted in a downstream step to enhance Dicer-dependent biogenesis of viral siRNAs in C. elegans . As mammals produce Dicer-dependent viral siRNAs to target RNA viruses, our findings suggest a possible role for mammalian RLRs and interferon signaling in the biogenesis of viral siRNAs.

scholarly journals Antiviral RNA Interference against Orsay Virus Is neither Systemic nor Transgenerational in Caenorhabditis elegans

2015 ◽  
Vol 89 (23) ◽  
pp. 12035-12046 ◽  
Author(s):  
Alyson Ashe ◽  
Peter Sarkies ◽  
Jérémie Le Pen ◽  
Mélanie Tanguy ◽  
Eric A. Miska
Keyword(s):  
Caenorhabditis Elegans ◽  
Virus Infection ◽  
Viral Infection ◽  
Rna Virus ◽  
Rnai Pathway ◽  
Content Type ◽  
C Elegans ◽  
Systemic Rnai ◽  
Endogenous Role ◽  
Orsay Virus

ABSTRACTAntiviral RNA-mediated silencing (RNA interference [RNAi]) acts as a powerful innate immunity defense in plants, invertebrates, and mammals. InCaenorhabditis elegans, RNAi is systemic; i.e., RNAi silencing signals can move between cells and tissues. Furthermore, RNAi effects can be inherited transgenerationally and may last for many generations. Neither the biological relevance of systemic RNAi nor transgenerational RNAi is currently understood. Here we examined the role of both pathways in the protection ofC. elegansfrom viral infection. We studied the Orsay virus, a positive-strand RNA virus related toNodaviridaeand the first and only virus known to infectC. elegans. Immunity to Orsay virus infection requires the RNAi pathway. Surprisingly, we found that genes required for systemic or transgenerational RNAi did not have a role in antiviral defense. Furthermore, we found that Orsay virus infection did not elicit a systemic RNAi response even when a target for RNAi was provided by using transgenes. Finally, we show that viral siRNAs, the effectors of RNAi, are not inherited to a level that provides any significant resistance to viral infection in the next generation. We conclude that systemic or transgenerational RNAi does not play a role in the defense against natural Orsay virus infection. Furthermore, our data suggest that there is a qualitative difference between experimental RNAi and antiviral RNAi. Our data are consistent with a model of systemic and transgenerational RNAi that requires a nuclear or germ line component that is lacking in almost all RNA virus infections.IMPORTANCESince its discovery inCaenorhabditis elegans, RNAi has proven a valuable scientific tool in many organisms. InC. elegans, exogenous RNAi spreads throughout the organism and can be passed between generations; however, there has been controversy as to the endogenous role(s) that the RNAi pathway plays. One endogenous role for which spreading both within the infected organism and between generations would be advantageous is a role in viral defense. In plants, antiviral RNAi is systemic and the spread of RNAi between cells provides protection against subsequent viral infection. Here we investigated this by using the only naturally occurring virus known to infectC. elegans, Orsay virus, and surprisingly found that, in contrast to the exogenous RNAi pathway, the antiviral RNAi response targeted against this virus does not spread systemically throughout the organism and cannot be passed between generations. These results suggest that there are differences between the two pathways that remain to be discovered.

scholarly journals A deletion polymorphism in the Caenorhabditis elegans RIG-I homolog disables viral RNA dicing and antiviral immunity

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Alyson Ashe ◽  
Tony Bélicard ◽  
Jérémie Le Pen ◽  
Peter Sarkies ◽  
Lise Frézal ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Genome Wide Association Study ◽  
Rna Virus ◽  
Rnai Pathway ◽  
Animal Cells ◽  
C Elegans ◽  
Base Pair Deletion ◽  
A Genome ◽  
Positive Strand Rna ◽  
Viral Recognition

RNA interference defends against viral infection in plant and animal cells. The nematode Caenorhabditis elegans and its natural pathogen, the positive-strand RNA virus Orsay, have recently emerged as a new animal model of host-virus interaction. Using a genome-wide association study in C. elegans wild populations and quantitative trait locus mapping, we identify a 159 base-pair deletion in the conserved drh-1 gene (encoding a RIG-I-like helicase) as a major determinant of viral sensitivity. We show that DRH-1 is required for the initiation of an antiviral RNAi pathway and the generation of virus-derived siRNAs (viRNAs). In mammals, RIG-I-domain containing proteins trigger an interferon-based innate immunity pathway in response to RNA virus infection. Our work in C. elegans demonstrates that the RIG-I domain has an ancient role in viral recognition. We propose that RIG-I acts as modular viral recognition factor that couples viral recognition to different effector pathways including RNAi and interferon responses.

scholarly journals New Role for DCR-1/Dicer in Caenorhabditis elegans Innate Immunity against the Highly Virulent Bacterium Bacillus thuringiensis DB27

2013 ◽  
Vol 81 (10) ◽  
pp. 3942-3957 ◽  
Author(s):  
Igor Iatsenko ◽  
Amit Sinha ◽  
Christian Rödelsperger ◽  
Ralf J. Sommer
Keyword(s):  
Innate Immunity ◽  
Caenorhabditis Elegans ◽  
Bacillus Thuringiensis ◽  
Defense Mechanisms ◽  
Content Type ◽  
Mirna Processing ◽  
C Elegans ◽  
Nuclear Autoantigenic Sperm Protein ◽  
Bacterium Bacillus ◽  
Underlying Mechanisms

ABSTRACTBacillus thuringiensisproduces toxins that target invertebrates, includingCaenorhabditis elegans. Virulence ofBacillusstrains is often highly specific, such thatB. thuringiensisstrain DB27 is highly pathogenic toC. elegansbut shows no virulence for another model nematode,Pristionchus pacificus. To uncover the underlying mechanisms of the differential responses of the two nematodes toB. thuringiensisDB27 and to reveal theC. elegansdefense mechanisms against this pathogen, we conducted a genetic screen forC. elegansmutants resistant toB. thuringiensisDB27. Here, we describe aB. thuringiensisDB27-resistantC. elegansmutant that is identical tonasp-1, which encodes theC. eleganshomolog of the nuclear-autoantigenic-sperm protein. Gene expression analysis indicated a substantial overlap between the genes downregulated in thenasp-1mutant and targets ofC. elegansdcr-1/Dicer, suggesting thatdcr-1is repressed innasp-1mutants, which was confirmed by quantitative PCR. Consistent with this, thenasp-1mutant exhibits RNA interference (RNAi) deficiency and reduced longevity similar to those of adcr-1mutant. Building on these surprising findings, we further explored a potential role fordcr-1inC. elegansinnate immunity. We show thatdcr-1mutant alleles deficient in microRNA (miRNA) processing, but not those deficient only in RNAi, are resistant toB. thuringiensisDB27. Furthermore,dcr-1overexpression rescues thenasp-1mutant's resistance, suggesting that repression ofdcr-1determines thenasp-1mutant's resistance. Additionally, we identified the collagen-encoding genecol-92as one of the downstream effectors ofnasp-1that play an important role in resistance to DB27. Taken together, these results uncover a previously unknown role for DCR-1/Dicer inC. elegansantibacterial immunity that is largely associated with miRNA processing.

scholarly journals Tumor Necrosis Factor-α-Induced Protein 8-Like 2 Negatively Regulates Innate Immunity Against RNA Virus by Targeting RIG-I in Macrophages

2021 ◽  
Vol 12 ◽  
Author(s):  
Ziqi Zou ◽  
Mengyao Li ◽  
Yunlian Zhou ◽  
Jiaying Li ◽  
Ting Pan ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Retinoic Acid ◽  
Viral Infection ◽  
Tumor Necrosis ◽  
Tumor Necrosis Factor Α ◽  
Rna Virus ◽  
Type I ◽  
Factor Α ◽  
Necrosis Factor ◽  
Inducible Gene

A systematic and flexible immunoregulatory network is required to ensure the proper outcome of antiviral immune signaling and maintain homeostasis during viral infection. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2), a novel immunoregulatory protein, has been extensively studied in inflammatory response, apoptosis, and cancer. However, the function of TIPE2 in antiviral innate immunity is poorly clarified. In this study, we reported that the expression of TIPE2 declined at the early period and then climbed up in macrophages under RNA virus stimulation. Knockout of TIPE2 in the macrophages enhanced the antiviral capacity and facilitated type I interferon (IFN) signaling after RNA viral infection both in vitro and in vivo. Consistently, overexpression of TIPE2 inhibited the production of type I IFNs and pro-inflammatory cytokines, and thus promoted the viral infection. Moreover, TIPE2 restrained the activation of TBK1 and IRF3 in the retinoic acid inducible gene-I (RIG-I)-like receptors (RLR) signaling pathway by directly interacting with retinoic acid inducible gene-I (RIG-I). Taken together, our results suggested that TIPE2 suppresses the type I IFN response induced by RNA virus by targeting RIG-I and blocking the activation of downstream signaling. These findings will provide new insights to reveal the immunological function of TIPE2 and may help to develop new strategies for the clinical treatment of RNA viral infections.

scholarly journals HCP-4/CENP-C Promotes the Prophase Timing of Centromere Resolution by Enabling the Centromere Association of HCP-6 in Caenorhabditis elegans

2005 ◽  
Vol 25 (7) ◽  
pp. 2583-2592 ◽  
Author(s):  
Landon L. Moore ◽  
Gerald Stanvitch ◽  
Mark B. Roth ◽  
David Rosen
Keyword(s):  
Rna Interference ◽  
Caenorhabditis Elegans ◽  
Holocentric Chromosomes ◽  
Kinetochore Protein ◽  
C Elegans ◽  
Kinetochore Assembly ◽  
Centromere Protein ◽  
Sister Centromere ◽  
Microtubule Capture

ABSTRACT Prior to microtubule capture, sister centromeres resolve from one another, coming to rest on opposite surfaces of the condensing chromosome. Subsequent assembly of sister kinetochores at each sister centromere generates a geometry favorable for equal levels of segregation of chromatids. The holocentric chromosomes of Caenorhabditis elegans are uniquely suited for the study of centromere resolution and subsequent kinetochore assembly. In C. elegans, only two proteins have been identified as being necessary for centromere resolution, the kinase AIR-2 (prophase only) and the centromere protein HCP-4/CENP-C. Here we found that the loss of proteins involved in chromosome cohesion bypassed the requirement for HCP-4/CENP-C but not for AIR-2. Interestingly, the loss of cohesin proteins also restored the localization of HCP-6 to the kinetochore. The loss of the condensin II protein HCP-6 or MIX-1/SMC2 impaired centromere resolution. Furthermore, the loss of HCP-6 or MIX-1/SMC2 resulted in no centromere resolution when either nocodazole or RNA interference (RNAi) of the kinetochore protein KNL-1 perturbed spindle-kinetochore interactions. This result suggests that normal prophase centromere resolution is mediated by condensin II proteins, which are actively recruited to sister centromeres to mediate the process of resolution.

scholarly journals Inducible Systemic RNA Silencing in Caenorhabditis elegans

2003 ◽  
Vol 14 (7) ◽  
pp. 2972-2983 ◽  
Author(s):  
Lisa Timmons ◽  
Hiroaki Tabara ◽  
Craig C. Mello ◽  
Andrew Z. Fire
Keyword(s):  
Rna Interference ◽  
Caenorhabditis Elegans ◽  
Rna Silencing ◽  
Molecular Mechanisms ◽  
Normal Animal ◽  
Cell Types ◽  
Animal Cells ◽  
Tissue Specific ◽  
C Elegans ◽  
Systemic Rna

Introduction of double-stranded RNA (dsRNA) can elicit a gene-specific RNA interference response in a variety of organisms and cell types. In many cases, this response has a systemic character in that silencing of gene expression is observed in cells distal from the site of dsRNA delivery. The molecular mechanisms underlying the mobile nature of RNA silencing are unknown. For example, although cellular entry of dsRNA is possible, cellular exit of dsRNA from normal animal cells has not been directly observed. We provide evidence that transgenic strains of Caenorhabditis elegans transcribing dsRNA from a tissue-specific promoter do not exhibit comprehensive systemic RNA interference phenotypes. In these same animals, modifications of environmental conditions can result in more robust systemic RNA silencing. Additionally, we find that genetic mutations can influence the systemic character of RNA silencing in C. elegans and can separate mechanisms underlying systemic RNA silencing into tissue-specific components. These data suggest that trafficking of RNA silencing signals in C. elegans is regulated by specific physiological and genetic factors.

scholarly journals DAF-16 and SMK-1 Contribute to Innate Immunity During Adulthood in Caenorhabditis elegans

2020 ◽  
Vol 10 (5) ◽  
pp. 1521-1539 ◽  
Author(s):  
Daniel R. McHugh ◽  
Elena Koumis ◽  
Paul Jacob ◽  
Jennifer Goldfarb ◽  
Michelle Schlaubitz-Garcia ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Immune System ◽  
Caenorhabditis Elegans ◽  
Host Defense ◽  
Insulin Signaling ◽  
Bacterial Pathogens ◽  
C Elegans ◽  
Link Type ◽  
Age Dependent ◽  
Over Time

Aging is accompanied by a progressive decline in immune function termed “immunosenescence”. Deficient surveillance coupled with the impaired function of immune cells compromises host defense in older animals. The dynamic activity of regulatory modules that control immunity appears to underlie age-dependent modifications to the immune system. In the roundworm Caenorhabditis elegans levels of PMK-1 p38 MAP kinase diminish over time, reducing the expression of immune effectors that clear bacterial pathogens. Along with the PMK-1 pathway, innate immunity in C. elegans is regulated by the insulin signaling pathway. Here we asked whether DAF-16, a Forkhead box (FOXO) transcription factor whose activity is inhibited by insulin signaling, plays a role in host defense later in life. While in younger C. elegansDAF-16 is inactive unless stimulated by environmental insults, we found that even in the absence of acute stress the transcriptional activity of DAF-16 increases in an age-dependent manner. Beginning in the reproductive phase of adulthood, DAF-16 upregulates a subset of its transcriptional targets, including genes required to kill ingested microbes. Accordingly, DAF-16 has little to no role in larval immunity, but functions specifically during adulthood to confer resistance to bacterial pathogens. We found that DAF-16-mediated immunity in adults requires SMK-1, a regulatory subunit of the PP4 protein phosphatase complex. Our data suggest that as the function of one branch of the innate immune system of C. elegans (PMK-1) declines over time, DAF-16-mediated immunity ramps up to become the predominant means of protecting adults from infection, thus reconfiguring immunity later in life.

scholarly journals ATP-binding Cassette Transporters Are Required for Efficient RNA Interference in Caenorhabditis elegans

2006 ◽  
Vol 17 (8) ◽  
pp. 3678-3688 ◽  
Author(s):  
Prema Sundaram ◽  
Benjamin Echalier ◽  
Wang Han ◽  
Dawn Hull ◽  
Lisa Timmons
Keyword(s):  
Rna Interference ◽  
Caenorhabditis Elegans ◽  
Abc Transporters ◽  
Transport Systems ◽  
Atp Binding ◽  
C Elegans ◽  
Steep Concentration Gradient ◽  
Conserved Gene ◽  
Membrane Transport Systems ◽  
Atp Binding Cassette

RNA interference (RNAi) is a conserved gene-silencing phenomenon that can be triggered by delivery of double-stranded RNA (dsRNA) to cells and is a widely exploited technology in analyses of gene function. Although a number of proteins that facilitate RNAi have been identified, current descriptions of RNAi and interrelated mechanisms are far from complete. Here, we report that the Caenorhabditis elegans gene haf-6 is required for efficient RNAi. HAF-6 is a member of the ATP-binding cassette (ABC) transporter gene superfamily. ABC transporters use ATP to translocate small molecule substrates across the membranes in which they reside, often against a steep concentration gradient. Collectively, ABC transporters are involved in a variety of activities, including protective or barrier mechanisms that export drugs or toxins from cells, organellar biogenesis, and mechanisms that protect against viral infection. HAF-6 is expressed predominantly in the intestine and germline and is localized to intracellular reticular organelles. We further demonstrate that eight additional ABC genes from diverse subfamilies are each required for efficient RNAi in C. elegans. Thus, the ability to mount a robust RNAi response to dsRNA depends upon the deployment of two ancient systems that respond to environmental assaults: RNAi mechanisms and membrane transport systems that use ABC proteins.

Loss of DNase II function in the gonad is associated with a higher expression of antimicrobial genes in Caenorhabditis elegans

2015 ◽  
Vol 470 (1) ◽  
pp. 145-154 ◽  
Author(s):  
Hsiang Yu ◽  
Huey-Jen Lai ◽  
Tai-Wei Lin ◽  
Chang-Shi Chen ◽  
Szecheng J. Lo
Keyword(s):  
Immune Response ◽  
Innate Immunity ◽  
Caenorhabditis Elegans ◽  
Innate Immune Response ◽  
Innate Immune ◽  
Dnase Ii ◽  
C Elegans ◽  
Elevated Expression

This study uncovered NUC-1 and CRN-7 function in germline apoptosis. Mutations of nuc-1 and crn-7 led to elevated expression of five innate-immunity-related genes and demonstrated that DNase II activity is associated with an innate immune response in C. elegans.

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