scholarly journals The Caenorhabditis elegans RIG-I Homolog DRH-1 Mediates the Intracellular Pathogen Response upon Viral Infection

2019 ◽  
Vol 94 (2) ◽  
Author(s):  
Jessica N. Sowa ◽  
Hongbing Jiang ◽  
Lakshmi Somasundaram ◽  
Eillen Tecle ◽  
Guorong Xu ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Polymerase Activity ◽  
Intracellular Pathogen ◽  
Content Type ◽  
C Elegans ◽  
Proteotoxic Stress ◽  
Rna Polymerase Activity ◽  
Pathogen Response ◽  
Orsay Virus ◽  
Recognition Receptor

ABSTRACT Mammalian retinoic acid-inducible gene I (RIG-I)-like receptors detect viral double-stranded RNA (dsRNA) and 5′-triphosphorylated RNA to activate the transcription of interferon genes and promote antiviral defense. The Caenorhabditis elegans RIG-I-like receptor DRH-1 promotes defense through antiviral RNA interference (RNAi), but less is known about its role in regulating transcription. Here, we describe a role for DRH-1 in directing a transcriptional response in C. elegans called the intracellular pathogen response (IPR), which is associated with increased pathogen resistance. The IPR includes a set of genes induced by diverse stimuli, including intracellular infection and proteotoxic stress. Previous work suggested that the proteotoxic stress caused by intracellular infections might be the common trigger of the IPR, but here, we demonstrate that different stimuli act through distinct pathways. Specifically, we demonstrate that DRH-1/RIG-I is required for inducing the IPR in response to Orsay virus infection but not in response to other triggers like microsporidian infection or proteotoxic stress. Furthermore, DRH-1 appears to be acting independently of its known role in RNAi. Interestingly, expression of the replication-competent Orsay virus RNA1 segment alone is sufficient to induce most of the IPR genes in a manner dependent on RNA-dependent RNA polymerase activity and on DRH-1. Altogether, these results suggest that DRH-1 is a pattern recognition receptor that detects viral replication products to activate the IPR stress/immune program in C. elegans. IMPORTANCE C. elegans lacks homologs of most mammalian pattern recognition receptors, and how nematodes detect pathogens is poorly understood. We show that the C. elegans RIG-I homolog DRH-1 mediates the induction of the intracellular pathogen response (IPR), a novel transcriptional defense program, in response to infection by the natural C. elegans viral pathogen Orsay virus. DRH-1 appears to act as a pattern recognition receptor to induce the IPR transcriptional defense program by sensing the products of viral RNA-dependent RNA polymerase activity. Interestingly, this signaling role of DRH-1 is separable from its previously known role in antiviral RNAi. In addition, we show that there are multiple host pathways for inducing the IPR, shedding light on the regulation of this novel transcriptional immune response.

scholarly journals The C. elegans RIG-I homolog drh-1 mediates the Intracellular Pathogen Response upon viral infection

2019 ◽  
Author(s):  
Jessica N. Sowa ◽  
Hongbing Jiang ◽  
Lakshmi Somasundaram ◽  
Guorong Xu ◽  
David Wang ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Polymerase Activity ◽  
Intracellular Pathogen ◽  
Rna Dependent Rna Polymerase ◽  
C Elegans ◽  
Proteotoxic Stress ◽  
Rna Polymerase Activity ◽  
Pathogen Response ◽  
Orsay Virus ◽  
Recognition Receptor

AbstractMammalian RIG-I-like receptors detect viral dsRNA and 5’ triphosphorylated RNA to activate transcription of interferon genes and promote antiviral defense. The C. elegans RIG-I-like receptor DRH-1 promotes defense through antiviral RNA interference, but less is known about its role in regulating transcription. Here we describe a role for drh-1 in directing a transcriptional response in C. elegans called the Intracellular Pathogen Response (IPR), which is associated with increased pathogen resistance. The IPR includes a set of genes induced by diverse stimuli including intracellular infection and proteotoxic stress. Previous work suggested that the proteotoxic stress caused by intracellular infections might be the common trigger of the IPR, but here we demonstrate that different stimuli act through distinct pathways. Specifically, we demonstrate that DRH-1/RIG-I is required for inducing the IPR in response to Orsay virus infection, but not in response to other triggers like microsporidian infection or proteotoxic stress. Furthermore, drh-1 appears to be acting independently of its known role in RNAi. Interestingly, expression of the replication competent Orsay virus RNA1 segment alone is sufficient to induce most of the IPR genes in a manner dependent on RNA dependent RNA polymerase activity and on drh-1. Altogether, these results suggest that DRH-1 is a pattern-recognition receptor that detects viral replication products to activate the IPR stress/immune program in C. elegans.ImportanceC. elegans lacks homologs of most mammalian pattern recognition receptors, and how nematodes detect pathogens is poorly understood. We show that the C. elegans RIG-I homolog drh-1 mediates induction of the Intracellular Pathogen Response (IPR), a novel transcriptional defense program, in response to infection by the natural C. elegans viral pathogen Orsay virus. drh-1 appears to act as a pattern-recognition receptor to induce the IPR transcriptional defense program by sensing the products of viral RNA-dependent RNA polymerase activity. Interestingly, this signaling role of drh-1 is separable from its previously known role in antiviral RNAi. In addition, we show that there are multiple host pathways for inducing the IPR, shedding light on the regulation of this novel transcriptional immune response.

scholarly journals Heat Stress Reduces the Susceptibility of Caenorhabditis elegans to Orsay Virus Infection

Genes ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1161
Author(s):  
Yuqing Huang ◽  
Mark G. Sterken ◽  
Koen van Zwet ◽  
Lisa van Sluijs ◽  
Gorben P. Pijlman ◽  
...  
Keyword(s):  
Heat Stress ◽  
Caenorhabditis Elegans ◽  
Virus Infection ◽  
Intracellular Pathogen ◽  
Potential Candidate ◽  
Molecular Responses ◽  
C Elegans ◽  
Pathogen Response ◽  
Orsay Virus ◽  
Natural Virus

The nematode Caenorhabditis elegans has been a versatile model for understanding the molecular responses to abiotic stress and pathogens. In particular, the response to heat stress and virus infection has been studied in detail. The Orsay virus (OrV) is a natural virus of C. elegans and infection leads to intracellular infection and proteostatic stress, which activates the intracellular pathogen response (IPR). IPR related gene expression is regulated by the genes pals-22 and pals-25, which also control thermotolerance and immunity against other natural pathogens. So far, we have a limited understanding of the molecular responses upon the combined exposure to heat stress and virus infection. We test the hypothesis that the response of C. elegans to OrV infection and heat stress are co-regulated and may affect each other. We conducted a combined heat-stress-virus infection assay and found that after applying heat stress, the susceptibility of C. elegans to OrV was decreased. This difference was found across different wild types of C. elegans. Transcriptome analysis revealed a list of potential candidate genes associated with heat stress and OrV infection. Subsequent mutant screens suggest that pals-22 provides a link between viral response and heat stress, leading to enhanced OrV tolerance of C. elegans after heat stress.

scholarly journals An intracellular pathogen response pathway promotes proteostasis in C. elegans

2017 ◽  
Author(s):  
Kirthi C. Reddy ◽  
Tal Dror ◽  
Jessica N. Sowa ◽  
Johan Panek ◽  
Kevin Chen ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Intracellular Pathogen ◽  
Forward Genetic Screen ◽  
C Elegans ◽  
Transcriptional Signature ◽  
Proteotoxic Stress ◽  
Ubiquitin Ligase Complex ◽  
Pathogen Response ◽  
Mutant Phenotypes ◽  
Increased Activity

SummaryMaintenance of proteostasis is critical for organismal health. Here we describe a novel pathway that promotes proteostasis, identified through the analysis of C. elegans genes upregulated by intracellular infection. We named this distinct transcriptional signature the Intracellular Pathogen Response (IPR), and it includes upregulation of several predicted ubiquitin ligase complex components such as the cullin cul-6. Through a forward genetic screen we found pals-22, a gene of previously unknown function, to be a repressor of the cul-6/Cullin gene and other IPR gene expression. Interestingly, pals-22 mutants have increased thermotolerance and reduced levels of stress-induced polyglutamine aggregates, likely due to upregulated IPR expression. We found the enhanced stress resistance of pals-22 mutants to be dependent on cul-6, suggesting that pals-22 mutants have increased activity of a CUL-6/Cullin-containing ubiquitin ligase complex. pals-22 mutant phenotypes are distinct from the well-studied heat shock and insulin signaling pathways, indicating that the IPR is a novel pathway that protects animals from proteotoxic stress.

scholarly journals Balancing selection of the Intracellular Pathogen Response in natural Caenorhabditis elegans populations

2019 ◽  
Author(s):  
Lisa van Sluijs ◽  
Kobus J. Bosman ◽  
Frederik Pankok ◽  
Tatiana Blokhina ◽  
Joost A. G. Riksen ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Caenorhabditis Elegans ◽  
Balancing Selection ◽  
Model Organism ◽  
Evolutionary Strategies ◽  
Intracellular Pathogen ◽  
C Elegans ◽  
Pathogen Response ◽  
Orsay Virus ◽  
Selection Of

AbstractBackgroundGenetic variation in host populations may lead to differential viral susceptibilities. Here, we investigate the role of natural genetic variation present for an antiviral pathway, the Intracellular Pathogen Response (IPR), underlying susceptibility to Orsay virus in the model organism Caenorhabditis elegans. The IPR involves transcriptional activity of 80 genes including the pals-genes. The pals-genes form an expanded gene family which hints they could be shaped by an evolutionary selective pressure. Here we examine the genetic variation in the pals-family for traces of selection and explore the molecular and phenotypic effects of having distinct pals-gene alleles.ResultsGenetic analysis of 330 world-wide C. elegans strains reveals that genetic diversity within the IPR-related pals-genes can be categorized in a few haplotypes worldwide. Importantly, two key-IPR regulators, pals-22 and pals-25, are in a genomic region carrying signatures of balancing selection. Therefore, distinct pals-22/pals-25 alleles have been maintained in C. elegans populations over time, which suggests different evolutionary strategies exist in IPR regulation. We investigated the IPR by infecting two C. elegans strains that represent distinct pals-22/pals-25 haplotypes, N2 and CB4856, with Orsay virus to determine their susceptibility and transcriptional response to infection. Our data suggests that regulatory genetic variation underlies constant high activity of IPR genes in CB4856 which could determine the host transcriptional defense. We found that CB4856 shows initially lower viral susceptibility than N2. High basal IPR expression levels might help counteract viral infection directly, whereas N2-like strains that need to activate the IPR genes first may have a slower response. Nevertheless, most wild strains harbor N2-like alleles for the pals-genes.ConclusionsOur work provides evidence for balancing genetic selection of immunity genes in C. elegans and illustrated how this may shape the transcriptional defense against pathogens. The transcriptional and genetic data presented in this study therefore provide a novel perspective on the functional diversity that can develop within a main antiviral response in natural host populations.

scholarly journals A cullin-RING ubiquitin ligase promotes thermotolerance as part of the intracellular pathogen response inCaenorhabditis elegans

2020 ◽  
Vol 117 (14) ◽  
pp. 7950-7960 ◽  
Author(s):  
Johan Panek ◽  
Spencer S. Gang ◽  
Kirthi C. Reddy ◽  
Robert J. Luallen ◽  
Amitkumar Fulzele ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Intracellular Pathogen ◽  
Intracellular Pathogens ◽  
Core Component ◽  
C Elegans ◽  
Proteotoxic Stress ◽  
Expression Of Genes ◽  
Core Components ◽  
Pathogen Response ◽  
Related Proteins

Intracellular pathogen infection leads to proteotoxic stress in host organisms. Previously we described a physiological program in the nematodeCaenorhabditis eleganscalled the intracellular pathogen response (IPR), which promotes resistance to proteotoxic stress and appears to be distinct from canonical proteostasis pathways. The IPR is controlled by PALS-22 and PALS-25, proteins of unknown biochemical function, which regulate expression of genes induced by natural intracellular pathogens. We previously showed that PALS-22 and PALS-25 regulate the mRNA expression of the predicted ubiquitin ligase component cullincul-6, which promotes thermotolerance inpals-22mutants. However, it was unclear whether CUL-6 acted alone, or together with other cullin-ring ubiquitin ligase components, which comprise a greatly expanded gene family inC. elegans. Here we use coimmunoprecipitation studies paired with genetic analysis to define the cullin-RING ligase components that act together with CUL-6 to promote thermotolerance. First, we identify a previously uncharacterized RING domain protein in the TRIM family we named RCS-1, which acts as a core component with CUL-6 to promote thermotolerance. Next, we show that the Skp-related proteins SKR-3, SKR-4, and SKR-5 act redundantly to promote thermotolerance with CUL-6. Finally, we screened F-box proteins that coimmunoprecipitate with CUL-6 and find that FBXA-158 and FBXA-75 promote thermotolerance. In summary, we have defined the three core components and two F-box adaptors of a cullin-RING ligase complex that promotes thermotolerance as part of the IPR inC. elegans, which adds to our understanding of how organisms cope with proteotoxic stress.

scholarly journals A cullin-RING ubiquitin ligase promotes thermotolerance as part of the Intracellular Pathogen Response in C. elegans

2019 ◽  
Author(s):  
Johan Panek ◽  
Spencer S. Gang ◽  
Kirthi C. Reddy ◽  
Robert J. Luallen ◽  
Amitkumar Fulzele ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Protein Quality ◽  
Transcriptional Response ◽  
Intracellular Pathogen ◽  
Protein Homeostasis ◽  
Pathogen Infection ◽  
C Elegans ◽  
Proteotoxic Stress ◽  
Expression Of Genes ◽  
Pathogen Response

AbstractIntracellular pathogen infection leads to proteotoxic stress in host organisms. Previously we described a physiological program in the nematode C. elegans called the Intracellular Pathogen Response (IPR), which promotes resistance to proteotoxic stress and appears to be distinct from canonical proteostasis pathways. The IPR is controlled by PALS-22 and PALS-25, proteins of unknown biochemical function, which regulate expression of genes induced by natural intracellular pathogens. We previously showed that PALS-22 and PALS-25 regulate the mRNA expression of the predicted ubiquitin ligase component cullin cul-6, which promotes thermotolerance in pals-22 mutants. However, it was unclear whether CUL-6 acted alone, or together with other ubiquitin ligase components. Here we use co-immunoprecipitation studies paired with genetic analysis to define the cullin-RING ligase components that act together with CUL-6 to promote thermotolerance. First, we identify a previously uncharacterized RING domain protein in the TRIM family we named RCS-1, which acts as a core component with CUL-6 to promote thermotolerance. Next, we show that the Skp-related proteins SKR-3, SKR-4 and SKR-5 act redundantly to promote thermotolerance with CUL-6. Finally, we screened F-box proteins that co-immunoprecipitate with CUL-6 and find that FBXA-158 promotes thermotolerance. In summary, we have defined the three core components and an F-box adaptor of a cullin-RING ligase complex that promotes thermotolerance as part of the IPR in C. elegans, which adds to our understanding of how organisms cope with proteotoxic stress.Significance StatementIntracellular pathogen infection in the nematode Caenorhabditis elegans induces a robust transcriptional response as the host copes with infection. This response program includes several ubiquitin ligase components that are predicted to function in protein quality control. In this study, we show that these infection-induced ubiquitin ligase components form a protein complex that promotes increased tolerance of acute heat stress, an indicator of improved protein homeostasis capacity. These findings show that maintaining protein homeostasis may be a critical component of a multifaceted approach allowing the host to deal with stress caused by intracellular infection.

scholarly journals An Intracellular Pathogen Response Pathway Promotes Proteostasis in C. elegans

2017 ◽  
Vol 27 (22) ◽  
pp. 3544-3553.e5 ◽  
Author(s):  
Kirthi C. Reddy ◽  
Tal Dror ◽  
Jessica N. Sowa ◽  
Johan Panek ◽  
Kevin Chen ◽  
...  
Keyword(s):  
Intracellular Pathogen ◽  
C Elegans ◽  
Pathogen Response

scholarly journals The predicted bZIP transcription factor ZIP-1 promotes resistance to intracellular infection in Caenorhabditis elegans

2021 ◽  
Author(s):  
Vladimir Lazetic ◽  
Fengting Wu ◽  
Lianne B Cohen ◽  
Kirthi C Reddy ◽  
Ya-Ting Chang ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Caenorhabditis Elegans ◽  
Rna Virus ◽  
Bzip Transcription Factor ◽  
Intestinal Cells ◽  
Intracellular Pathogen ◽  
Regulatory Pathways ◽  
Intracellular Infection ◽  
C Elegans ◽  
Orsay Virus

Defense against intracellular infection has been extensively studied in vertebrate hosts, but less is known about invertebrate hosts. For example, almost nothing is known about the transcription factors that induce defense against intracellular infection in the model nematode Caenorhabditis elegans. Two types of intracellular pathogens that naturally infect C. elegans are the Orsay virus, which is a positive-sense RNA virus, and microsporidia, which are fungal pathogens. Surprisingly, these molecularly distinct pathogens induce a common host transcriptional response called the Intracellular Pathogen Response (IPR). Here we describe zip-1 as an IPR regulator that functions downstream of all known IPR activating and regulatory pathways. zip-1 encodes a putative bZIP transcription factor of previously unknown function, and we show how zip-1 controls induction of a subset of genes upon IPR activation. ZIP-1 protein is expressed in the nuclei of intestinal cells, and is required in the intestine to upregulate IPR gene expression. Importantly, zip-1 promotes resistance to infection by the Orsay virus and by microsporidia in intestinal cells. Altogether, our results indicate that zip-1 represents a central hub for all triggers of the IPR, and that this transcription factor plays a protective role against intracellular pathogen infection in C. elegans.

scholarly journals Orsay δ Protein Is Required for Nonlytic Viral Egress

2018 ◽  
Vol 92 (14) ◽  
Author(s):  
Wang Yuan ◽  
Ying Zhou ◽  
Yanlin Fan ◽  
Yizhi J. Tao ◽  
Weiwei Zhong
Keyword(s):  
Rna Virus ◽  
Nonstructural Protein ◽  
Mutant Virus ◽  
Host Cells ◽  
Apical Surface ◽  
Content Type ◽  
C Elegans ◽  
Apical Side ◽  
Orsay Virus

ABSTRACTNonenveloped gastrointestinal viruses, such as human rotavirus, can exit infected cells from the apical surface without cell lysis. The mechanism of such nonlytic exit is poorly understood. The nonenveloped Orsay virus is an RNA virus infecting the intestine cells of the nematodeCaenorhabditis elegans. Dye staining results suggested that Orsay virus exits from the intestine of infected worms in a nonlytic manner. Therefore, the Orsay virus-C. eleganssystem provides an excellentin vivomodel to study viral exit. The Orsay virus genome encodes three proteins: RNA-dependent RNA polymerase, capsid protein (CP), and a nonstructural protein, δ. δ can also be expressed as a structural CP-δ fusion. We generated an ATG-to-CTG mutant virus that had a normal CP-δ fusion but could not produce free δ due to the lack of the start codon. This mutant virus showed a viral exit defect without obvious phenotypes in other steps of viral infection, suggesting that δ is involved in viral exit. Ectopically expressed free δ localized near the apical membrane of intestine cells inC. elegansand colocalized with ACT-5, an intestine-specific actin that is a component of the terminal web. Orsay virus infection rearranged ACT-5 apical localization. Reduction of the ACT-5 level via RNA interference (RNAi) significantly exacerbated the viral exit defect of the δ mutant virus, suggesting that δ and ACT-5 functionally interact to promote Orsay virus exit. Together, these data support a model in which the viral δ protein interacts with the actin network at the apical side of host intestine cells to mediate the polarized, nonlytic egress of Orsay virus.IMPORTANCEAn important step of the viral life cycle is how viruses exit from host cells to spread to other cells. Certain nonenveloped viruses can exit cultured cells in nonlytic ways; however, such nonlytic exit has not been demonstratedin vivo. In addition, it is not clear how such nonlytic exit is achieved mechanisticallyin vivo. Orsay virus is a nonenveloped RNA virus that infects the intestine cells of the nematodeC. elegans. It is currently the only virus known to naturally infectC. elegans. Using thisin vivomodel, we show that the δ protein encoded by Orsay virus facilitates the nonlytic exit of the virus, possibly by interacting with host actin on the apical side of worm intestine cells.

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