Effects of individual Orsay virus proteins on the Intracellular Pathogen Response of C. elegans

In order to cause infection, pathogens must avoid destruction by the host immune system. However, how pathogens evolved to evade host immunity is not fully understood. Mammals have two systems of immunity, innate and adaptive, which are regulated by complex interactions between the two systems. In order to study innate immunity exclusively, the roundworm C. elegans is a useful invertebrate model because it lacks adaptive immunity and the complexities that arise from interactions between the two types of immunity. The goal of this project is to investigate whether the individual expression of the Orsay virus capsid and delta-fusion proteins can suppress the Intracellular Pathogen Response (IPR) in C. elegans. The IPR is an innate immune response activated by the Orsay virus. To investigate the effects of the viral proteins on the IPR, molecular cloning will be used to construct plasmids that will be microinjected into C. elegans, creating transgenic animals that overexpress each of the two Orsay proteins. We will then test the animals to observe the individual effects of the capsid protein and delta-fusion protein on IPR suppression. From this we will better understand how viruses evolved to evade the host immune system

Identifying Novel Triggers of the Intracellular Pathogen Response (IPR) in C. elegans

The intracellular pathogen response (IPR) is a cell signaling pathway found in C. elegans that is triggered when pathogenic microorganisms invade, and immune responses attempt to eliminate the threat. Due to the relative simplicity of C. elegans, they are an excellent model organism to analyze the cell signaling pathways triggered by various pathogens. They lack the complex immune systems of larger organisms, making it easier to study the involved cell signaling pathways. Past studies have shown that the IPR can also be triggered via intestinal wounding. Heat stress, viral infection, and proteasome stress are all known triggers of the IPR. The long-term goal of this project is to generate potential new triggers, the response of which will be compared to the response generated by known triggers. The IPR will be quantified by measuring nanoluciferase expression, which is driven by an IPR gene. The immediate goal of this project is to develop this nanoluciferase assay system to generate IPR activity data in a high-throughput fashion. We hope to eventually be able to relate our findings to similar pathways in humans and other vertebrates. While humans do not have the IPR that is found in C. elegans, they have similar pathways that perform equivalent functions. In particular, we are interested in how intestinal damage could be related to activation of innate immunity. This information could be used to gain a better understanding of gastrointestinal diseases, specifically inflammatory bowel diseases

Mitochondrial GTP metabolism controls reproductive aging in C. elegans

Healthy mitochondria are critical for reproduction. During aging, both reproductive fitness and mitochondrial homeostasis decline. Mitochondrial metabolism and dynamics are key factors in supporting mitochondrial homeostasis. However, how they are coupled to control reproductive health remains unclear. We report that mitochondrial GTP (mtGTP) metabolism acts through mitochondrial dynamics factors to regulate reproductive aging. We discovered that germline-only inactivation of GTP-but not ATP-specific succinyl-CoA synthetase (SCS) promotes reproductive longevity in Caenorhabditis elegans. We further identified an age-associated increase in mitochondrial clustering surrounding oocyte nuclei, which is attenuated by GTP-specific SCS inactivation. Germline-only induction of mitochondrial fission factors sufficiently promotes mitochondrial dispersion and reproductive longevity. Moreover, we discovered that bacterial inputs affect mtGTP levels and dynamics factors to modulate reproductive aging. These results demonstrate the significance of mtGTP metabolism in regulating oocyte mitochondrial homeostasis and reproductive longevity and identify mitochondrial fission induction as an effective strategy to improve reproductive health

Olfaction Modulates Reproductive Plasticity through Neuroendocrine Signaling in Caenorhabditis elegans

SummaryReproductive plasticity describes the ability of organisms to adjust parameters such as volume, rate, or timing of progeny production in order to maximize successful reproduction under different environmental conditions. Reproductive plasticity in response to environmental variation has been observed in a wide range of animals [1–4]; however, the mechanisms involved in translating environmental cues into reproductive outcomes remain unknown. Here, we show that olfaction modulates reproductive timing and senescence through neuroendocrine signaling in Caenorhabditis elegans. On their preferred diet, worms demonstrate an increased rate of reproduction and an early onset of reproductive aging. Perception of the preferred diet’s odor by AWB olfactory neurons elicits these adjustments by increasing germline proliferation, and optogenetic stimulation of AWB neurons is sufficient to accelerate reproductive timing in the absence of dietary inputs. Furthermore, AWB neurons act through neuropeptide signaling to regulate reproductive rate and senescence. These findings reveal a neuroendocrine nexus linking olfactory sensation and reproduction in response to environmental variation and indicate the significance of olfaction in the regulation of reproductive decline during aging

Alien Registration- Klimko, Joseph (Lewiston, Androscoggin County)

https://digitalmaine.com/alien_docs/27082/thumbnail.jp

Innate immune responses and permissiveness to ranavirus infection of peritoneal leukocytes in the frog Xenopus laevis.

Ranaviruses such as frog virus 3 ([FV3] family Iridoviridae) are increasingly prevalent pathogens that infect reptiles, amphibians, and fish worldwide. Whereas studies in the frog Xenopus laevis have revealed the critical involvement of CD8 T-cell and antibody responses in host resistance to FV3, little is known about the role played by innate immunity to infection with this virus. We have investigated the occurrence, composition, activation status, and permissiveness to infection of peritoneal leukocytes (PLs) in Xenopus adults during FV3 infection by microscopy, flow cytometry, and reverse transcription-PCR. The total number of PLs and the relative fraction of activated mononucleated macrophage-like cells significantly increase as early as 1 day postinfection (dpi), followed by NK cells at 3 dpi, before the peak of the T-cell response at 6 dpi. FV3 infection also induces a rapid upregulation of proinflammatory genes including arginase 1, interleukin-1beta, and tumor necrosis factor alpha. Although PLs are susceptible to FV3 infection, as evidenced by apoptotic cells, active FV3 transcription, and the detection of viral particles by electron microscopy, the infection is weaker (fewer infectious particles), more transitory, and involves a smaller fraction (less than 1%) of PLs than the kidney, the main site of infection. However, viral DNA remains detectable in PLs for at least 3 weeks postinfection, past the point of viral clearance observed in the kidneys. This suggests that although PLs are actively involved in anti-FV3 immune responses, some of these cells can be permissive and harbor quiescent, asymptomatic FV3

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

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. elegansIMPORTANCEC. 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

An Intracellular Pathogen Response Pathway Promotes Proteostasis in C. elegans

Maintenance of protein homeostasis, or proteostasis, is crucial for organismal health. Disruption of proteostasis can lead to the accumulation of protein aggregates, which are associated with aging and many human diseases such as Alzheimer's disease [1-3]. Through analysis of the C. elegans host response to intracellular infection, we describe here a novel response pathway that enhances proteostasis capacity and appears to act in parallel to well-studied proteostasis pathways. These findings are based on analysis of the transcriptional response to infection by the intracellular pathogen Nematocida parisii [4]. The response to N. parisii is strikingly similar to the response to infection by the Orsay virus, another natural intracellular pathogen of C. elegans, and is distinct from responses to extracellular pathogen infection [4-6]. We have therefore named this common transcriptional response 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 gene 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 appear independent of the well-studied heat shock and insulin signaling pathways, indicating that the IPR is a distinct pathway that protects animals from proteotoxic stress

Gene inactivations extending reproductive lifespan.

<p>32 gene inactivations extend reproductive lifespan more than 25% in the RNAi hypersensitive strain, <i>nre-1(hd20)lin-15b(hd126)</i> (A). 26 of those gene inactivations also significantly increase reproductive lifespan of wild type (<i>N2</i>) (B). The other six gene inactivations promote reproductive longevity only in the <i>nre-1(hd20)lin-15b(hd126)</i> strains. They may act in neurons or their RNAi inactivations are only effective in the RNAi hypersensitive background. The average of three independent experiments is shown, <i>p<0.05</i> except ^#.</p

Germline genetic inactivations that prolong reproductive lifespan.

<p>In the <i>rrf-1(pk1417)</i> mutant, RNAi predominantly operates in the germline. Ten of the identified genes increase reproductive lifespan when inactivated in the <i>rrf-1</i> mutants. The extension levels are comparable to that in wild type (<i>N2)</i>, except for <i>daf-2</i>, <i>nhx-2</i> and <i>moma-1</i>. The average of three independent experiments is shown, <i>p<0.05</i>.</p