Osmosensory neurons modulate hypertonic stress resistance in C. elegans by controlling protein damage in non-neuronal cells
ABSTRACT: Protein function is controlled by the cellular proteostasis network. Proteostasis is energetically costly and those costs must be balanced with the energy needs of other physiological functions. Hypertonic stress causes widespread protein damage in C. elegans. Suppression and management of protein damage is essential for optimal survival under hypertonic conditions. ASH chemosensory neurons allow C. elegans to detect and avoid strongly hypertonic environments. We demonstrate that gene mutations that disrupt ASH mediated hypertonic avoidance behavior or genetic ablation of ASH neurons enhance survival during hypertonic stress. Enhanced survival is not due to altered systemic volume homeostasis or organic osmolyte accumulation. Instead, loss of ASH neuron function reduces protein damage in non-neuronal cells. Improved proteostasis capacity is due in part to upregulation of genes that play important roles in managing protein damage. We propose that inhibitory signaling from ASH neurons normally suppresses expression of genes required for non-neuronal cell proteostasis. Because all cells have the capacity to sense and respond to stressors, inhibitory neuronal signaling may be important for minimizing activation of cellular stress resistance and proteostasis pathways during short duration and less extreme stressors or stressors that can be avoided by behavioral changes. Neuronal regulation of systemic proteostasis allows the nervous system to monitor environmental variables and more effectively partition finite energy resources between different organismal processes. Our studies add to a growing body of work demonstrating that intercellular communication between neuronal and non-neuronal cells plays a critical role in integrating cellular stress resistance with other organismal physiological demands and associated energy costs. mRNA expression profiling of synchronized L4 stage wild-type N2 Bristol and VC1262 osm-9(ok1677) C. elegans strains under control (51mM NaCl) and hypertonic stress (200mM NaCl).
Project description:Protein function is controlled by the cellular proteostasis network. Proteostasis is energetically costly and those costs must be balanced with the energy needs of other physiological functions. Hypertonic stress causes widespread protein damage in C. elegans. Suppression and management of protein damage is essential for optimal survival under hypertonic conditions. ASH chemosensory neurons allow C. elegans to detect and avoid strongly hypertonic environments. We demonstrate that gene mutations that disrupt ASH mediated hypertonic avoidance behavior or genetic ablation of ASH neurons enhance survival during hypertonic stress. Enhanced survival is not due to altered systemic volume homeostasis or organic osmolyte accumulation. Instead, loss of ASH neuron function reduces protein damage in non-neuronal cells. Improved proteostasis capacity is due in part to upregulation of genes that play important roles in managing protein damage. We propose that inhibitory signaling from ASH neurons normally suppresses expression of genes required for non-neuronal cell proteostasis. Because all cells have the capacity to sense and respond to stressors, inhibitory neuronal signaling may be important for minimizing activation of cellular stress resistance and proteostasis pathways during short duration and less extreme stressors or stressors that can be avoided by behavioral changes. Neuronal regulation of systemic proteostasis allows the nervous system to monitor environmental variables and more effectively partition finite energy resources between different organismal processes. Our studies add to a growing body of work demonstrating that intercellular communication between neuronal and non-neuronal cells plays a critical role in integrating cellular stress resistance with other organismal physiological demands and associated energy costs. Overall design: mRNA expression profiling of synchronized L4 stage wild-type N2 Bristol and VC1262 osm-9(ok1677) C. elegans strains under control (51mM NaCl) and hypertonic stress (200mM NaCl).
Project description:Clarke2000 - One-hit model of cell death in
This one-hit model fits different
neuronal-death associated diseases for different animal
This model is described in the article:
A one-hit model of cell
death in inherited neuronal degenerations.
Clarke G, Collins RA, Leavitt BR,
Andrews DF, Hayden MR, Lumsden CJ, McInnes RR.
Nature 2000 Jul; 406(6792):
In genetic disorders associated with premature neuronal
death, symptoms may not appear for years or decades. This delay
in clinical onset is often assumed to reflect the occurrence of
age-dependent cumulative damage. For example, it has been
suggested that oxidative stress disrupts metabolism in
neurological degenerative disorders by the cumulative damage of
essential macromolecules. A prediction of the cumulative damage
hypothesis is that the probability of cell death will increase
over time. Here we show in contrast that the kinetics of
neuronal death in 12 models of photoreceptor degeneration,
hippocampal neurons undergoing excitotoxic cell death, a mouse
model of cerebellar degeneration and Parkinson's and
Huntington's diseases are all exponential and better explained
by mathematical models in which the risk of cell death remains
constant or decreases exponentially with age. These kinetics
argue against the cumulative damage hypothesis; instead, the
time of death of any neuron is random. Our findings are most
simply accommodated by a 'one-hit' biochemical model in which
mutation imposes a mutant steady state on the neuron and a
single event randomly initiates cell death. This model appears
to be common to many forms of neurodegeneration and has
implications for therapeutic strategies.
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Project description:Effective silencing by RNA-interference (RNAi) depends on mechanisms that amplify and propagate the silencing signal. In some organisms, small-interfering (si) RNAs are amplified from target mRNAs by RNA-dependent RNA polymerase (RdRP). Both RdRP recruitment and mRNA silencing require Argonaute proteins, which are generally thought to degrade RNAi targets by directly cleaving them. However in C. elegans, the enzymatic activity of the primary Argonaute, RDE-1, is not required for silencing activity. We show that RDE-1 can instead recruit an endoribonuclease, RDE-8, to target RNA. RDE-8 can cleave RNA in vitro and is needed for the production of 3′ uridylated fragments of target mRNA in vivo. We also find that RDE-8 promotes RdRP activity, thereby ensuring amplification of siRNAs. Together, our findings suggest a model in which RDE-8 cleaves target mRNAs to mediate silencing, while generating 3’ uridylated mRNA fragments to serve as templates for the RdRP-directed amplification of the silencing signal. We examined the role of rde-8 in C. elegans small RNA biogenesis pathways, including endogenous and exogenous RNAi pathways. We performed 3' RACE seq from the sel-1 target mRNA and correlate with small RNAs from wild type, rde-8 and rde-8 transgenic strains after sel-1(RNAi) for different lengths of time.
Project description:In the present study, we investigated the effect of CBM 588 on lifespan and multiple-stress resistance using Caenorhabditis elegans as a model animal. When adult C. elegans were fed a standard diet of Escherichia coli OP50 or CBM 588, the lifespan of the animals fed CBM 588 was significantly longer than that of animals fed OP50. Moreover, the worms fed CBM 588 were more resistant to certain stressors, including infections with pathogenic bacteria, UV irradiation, and the metal stressor Cu2+. CBM 588 failed to extend the lifespan of the daf-2/IR, daf-16/FOXO and skn-1/Nrf2 mutants. Transcriptional profiling comparing CBM 588-fed and control-fed animals suggested that DAF-16-dependent class II genes were regulated by CBM 588. In conclusion, CBM 588 extends the lifespan of C. elegans probably through regulation of the insulin/IGF-1 signaling (IIS) pathway and the Nrf2 transcription factor, and CBM 588 improves resistance to several stressors in C. elegans. Overall design: Transcriptional profiling of eight-day-old worms that were fed OP50 or CBM 588 for five days, by deep sequencing, using Illumina HiSeq.
Project description:The plasticity of ageing suggests that longevity may be controlled epigenetically by specific alterations in chromatin state. The link between chromatin and ageing has mostly focused on histone deacetylation by the Sir2 family1, 2, but less is known about the role of other histone modifications in longevity. Histone methylation has a crucial role in development and in maintaining stem cell pluripotency in mammals3. Regulators of histone methylation have been associated with ageing in worms4, 5, 6, 7 and flies8, but characterization of their role and mechanism of action has been limited. Here we identify the ASH-2 trithorax complex9, which trimethylates histone H3 at lysine 4 (H3K4), as a regulator of lifespan in Caenorhabditis elegans in a directed RNA interference (RNAi) screen in fertile worms. Deficiencies in members of the ASH-2 complex—ASH-2 itself, WDR-5 and the H3K4 methyltransferase SET-2—extend worm lifespan. Conversely, the H3K4 demethylase RBR-2 is required for normal lifespan, consistent with the idea that an excess of H3K4 trimethylation—a mark associated with active chromatin—is detrimental for longevity. Lifespan extension induced by ASH-2 complex deficiency requires the presence of an intact adult germline and the continuous production of mature eggs. ASH-2 and RBR-2 act in the germline, at least in part, to regulate lifespan and to control a set of genes involved in lifespan determination. These results indicate that the longevity of the soma is regulated by an H3K4 methyltransferase/demethylase complex acting in the C. elegans germline. There are 23 samples in total. ASH-2 knock-down increases lifespan in a germline dependent manner. We examined ASH-2 regulated genes that are dependent on the presence of an intact germline using WT or glp-1(e2141ts) mutant worms which develop only 5-15 meiotic germ cells treated with either empty vector (EV) or ash-2 RNAi. We examined gene expression at the L3 stage (when we observe changes in H3K4me3) and at a mid life stage (day 8). The majority of ASH-2 controlled genes were regulated in a germline dependent manner. Samples were collected in triplicate for each condition (but Day 8 N2 (WT) E.V. #3 was excluded from all analysis due to quality issues).
Project description:Higher order structure of interphase chromosomes and their spatial organization within the nucleus can have profound effects on regulation of gene expression. We show how compartmentalizing the genome by tethering heterochromatic regions to the nuclear lamina can affect gene expression during C. elegans dosage compensation. In this organism, the dosage compensation complex (DCC) binds both X chromosomes of hermaphrodites to repress gene expression two-fold, thus balancing gene expression between XX hermaphrodites and XO males. X chromosome structure is disrupted by mutations in DCC subunits. We found that X chromosome structure and subnuclear localization are also disrupted when the mechanisms that anchor heterochromatin to the nuclear lamina are defective. Strikingly, the heterochromatic left end of the X chromosome is less affected than the gene-rich middle region which lacks heterochromatic anchors. Our results suggest a model in which tethers at the left of the chromosome nucleate formation of a compact structure, which, by the action of the DCC, is propagated to the rest of the chromosome. These changes in X chromosome structure and subnuclear localization are accompanied by small, but significant levels of derepression of X-linked genes, without any observable defects in DCC localization and DCC-mediated changes in histone modification. RNA-seq profiles of C. elegans L1 wild type hermaphrodites, cec-4, met-2 set-25, and DPY-27 RNAi. RNA-seq profiles or C. elegans. Strains are N2 Bristol strain (wild type), RB2301 cec-4(ok3124) IV, and EKM99 met-2(n4256) set-25(n5021) III. Biological replicates for each strain/stage listed separately.
Project description:The aim of this study was to explore whether mitochondrial- and histone stress cause any common changes in global gene expression. For this experiment, we performed RNA sequencing from control RNAi, cco-1 RNAi (mitochondrial stress) and his-3 RNAi (histone stress) treated C. elegans. Nematodes were collected at L4 larval stage, and total RNA was extracted with TriPure Isolation Reagent (Roche). An Illumina Truseq stranded mRNA library was prepared for nine samples (three biological replicates for each sample). Single-end sequencing with 100 cycles was performed by running the nine samples on one lane of an Illumina Hiseq 2500, yielding a minimum of 26 million reads per sample. Although the two stressors were found to have divergent effects on global gene expression, some biological processes such as innate immunity, heat shock response and chromatin remodeler expression are commonly upregulated upon both mitochondrial- and histone stress. Overall design: Wild-type C. elegans was treated with control RNAi, cco-1 RNAi and his-3 RNAi, and gene expression was examined with RNA sequencing
Project description:The goal of this RNA-Seq analysis was to identify genes differentially expressed in a C. elegans strain overexpressing HSP-90 in the neurons compared to control (N2) animals. C. elegans overexpressing HSP-90 protein in the neurons activate transcellular chaperone signalling that enhances organismal proteostasis. This study aimed to identify components of the signalling pathway responsible for this effect. Overall design: Gene expression profile of L4 C. elegans wild type (N2) animals compared to L4 C. elegans overexpressing HSP-90::GFP in the neurons, using a neuron-specific promoter (F25B3.3p), grown at 20C. 3 replicates of each sample.
Project description:The unfolded protein response (UPR) maintains endoplasmic reticulum (ER) proteostasis through the activation of transcription factors such as XBP1s and ATF6. The functional consequences of these transcription factors for ER proteostasis remain poorly defined. Here, we describe methodology that enables orthogonal, small molecule-mediated activation of the UPR-associated transcription factors XBP1s and/or ATF6 in the same cell independent of stress. We employ transcriptomics and quantitative proteomics to evaluate ER proteostasis network remodeling owing to the XBP1s and/or ATF6 transcriptional programs. Furthermore, we demonstrate that the three ER proteostasis environments accessible by activating XBP1s and/or ATF6 differentially influence the folding, trafficking, and degradation of destabilized ER client proteins without globally affecting the endogenous proteome. Our data reveal how the ER proteostasis network is remodeled by the XBP1s and/or ATF6 transcriptional programs at the molecular level and demonstrate the potential for selectively restoring aberrant ER proteostasis of pathologic, destabilized proteins through arm-selective UPR-activation. The unfolded protein response adapts endoplasmic reticulum (ER) proteostasis via stress-responsive transcription factors including XBP1s and ATF6. Here, R. Luke Wiseman and colleagues implement technology for the orthogonal, ligand-dependent activation of XBP1s and/or ATF6 in a single cell. They characterize how XBP1s and/or ATF6 activation impacts ER proteostasis pathway composition and function. Adapted ER environments influence the proteostasis of destabilized protein variants without affecting the endogenous proteome. The work informs the development of proteostasis environment-adapting therapeutics for protein misfolding-related diseases. In order to activate both XBP1s and ATF6 in the same cell, we incorporated DHFR.ATF6 and tet-inducible XBP1s into a HEK293T-REx cell line stably expressing the tet-repressor. The HEK293DYG control cell line expresses tet-inducible eGFP and DHFR.YFP and is used as a control to demonstrate that the addition of doxycycline (dox) and trimethoprim (TMP) do not induce UPR genes. HEK293DYG cells were treated for 12 h with vehicle or 1 μg/mL dox and 10 μM TMP in biological triplicate. Cells were harvested and RNA was extracted using the RNeasy Mini Kit (Qiagen). Genomic DNA was removed by on-column digestion using the RNase-free DNase Set (Qiagen). Data from HEK293DYG cells showed no significant overlap in the ligand-treated transcriptomes obtained from HEK293DAX cells.