| 1. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 2. |
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| 3. |
- Arkblad, Eva L, et al.
(författare)
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A Caenorhabditis elegans mutant lacking functional nicotinamide nucleotide transhydrogenase displays increased sensitivity to oxidative stress.
- 2005
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Ingår i: Free radical biology & medicine. - : Elsevier BV. - 0891-5849. ; 38:11, s. 1518-25
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Tidskriftsartikel (refereegranskat)abstract
- Proton-translocating mitochondrial nicotinamide nucleotide transhydrogenase (NNT) was investigated regarding its physiological role in Caenorhabditis elegans. NNT catalyzes the reduction of NADP(+) by NADH driven by the electrochemical proton gradient, Deltap, and is thus a potentially important source of mitochondrial NADPH. Mitochondrial detoxification of reactive oxygen species (ROS) by glutathione-dependent peroxidases depends on NADPH for regeneration of reduced glutathione. Transhydrogenase may therefore be directly involved in the defense against oxidative stress. nnt-1 deletion mutants of C. elegans, nnt-1(sv34), were isolated and shown to grow essentially as wild type under normal laboratory conditions, but with a strongly lowered GSH/GSSG ratio. Under conditions of oxidative stress, caused by the superoxide-generating agent methyl viologen, growth of worms lacking nnt-1 activity was severely impaired. A similar result was obtained by using RNAi. Reintroducing nnt-1 in the nnt-1(sv34) knockout mutant led to a partial rescue of growth under oxidative stress conditions. These results provide evidence for the first time that nnt-1 is important in the defense against mitochondrial oxidative stress.
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| 4. |
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| 5. |
- Chen, Changchun, 1979-, et al.
(författare)
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Defects in tRNA modification associated with neurological and developmental dysfunctions in Caenorhabditis elegans elongator mutants
- 2009
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Ingår i: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404. ; 5:7, s. e1000561-
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Tidskriftsartikel (refereegranskat)abstract
- Elongator is a six subunit protein complex, conserved from yeast to humans. Mutations in the human Elongator homologue, hELP1, are associated with the neurological disease familial dysautonomia. However, how Elongator functions in metazoans, and how the human mutations affect neural functions is incompletely understood. Here we show that in Caenorhabditis elegans, ELPC-1 and ELPC-3, components of the Elongator complex, are required for the formation of the 5-carbamoylmethyl and 5-methylcarboxymethyl side chains of wobble uridines in tRNA. The lack of these modifications leads to defects in translation in C. elegans. ELPC-1::GFP and ELPC-3::GFP reporters are strongly expressed in a subset of chemosensory neurons required for salt chemotaxis learning. elpc-1 or elpc-3 gene inactivation causes a defect in this process, associated with a posttranscriptional reduction of neuropeptide and a decreased accumulation of acetylcholine in the synaptic cleft. elpc-1 and elpc-3 mutations are synthetic lethal together with those in tuc-1, which is required for thiolation of tRNAs having the 5'methylcarboxymethyl side chain. elpc-1; tuc-1 and elpc-3; tuc-1 double mutants display developmental defects. Our results suggest that, by its effect on tRNA modification, Elongator promotes both neural function and development.
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| 6. |
- Chotard, Laëtitia, et al.
(författare)
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TBC-2 regulates RAB-5/RAB-7-mediated endosomal trafficking in Caenorhabditis elegans
- 2010
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Ingår i: Molecular Biology of the Cell. - : American Society for Cell Biology. - 1059-1524 .- 1939-4586. ; 21:13, s. 2285-2296
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Tidskriftsartikel (refereegranskat)abstract
- During endosome maturation the early endosomal Rab5 GTPase is replaced with the late endosomal Rab7 GTPase. It has been proposed that active Rab5 can recruit and activate Rab7, which in turn could inactivate and remove Rab5. However, many of the Rab5 and Rab7 regulators that mediate endosome maturation are not known. Here, we identify Caenorhabditis elegans TBC-2, a conserved putative Rab GTPase-activating protein (GAP), as a regulator of endosome to lysosome trafficking in several tissues. We show that tbc-2 mutant animals accumulate enormous RAB-7-positive late endosomes in the intestine containing refractile material. RAB-5, RAB-7, and components of the homotypic fusion and vacuole protein sorting (HOPS) complex, a RAB-7 effector/putative guanine nucleotide exchange factor (GEF), are required for the tbc-2(-) intestinal phenotype. Expression of activated RAB-5 Q78L in the intestine phenocopies the tbc-2(-) large late endosome phenotype in a RAB-7 and HOPS complex-dependent manner. TBC-2 requires the catalytic arginine-finger for function in vivo and displays the strongest GAP activity on RAB-5 in vitro. However, TBC-2 colocalizes primarily with RAB-7 on late endosomes and requires RAB-7 for membrane localization. Our data suggest that TBC-2 functions on late endosomes to inactivate RAB-5 during endosome maturation.
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| 7. |
- Dongre, Mitesh, et al.
(författare)
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Flagella-mediated secretion of a novel Vibrio cholerae cytotoxin affecting both vertebrate and invertebrate hosts
- 2018
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Ingår i: Communications Biology. - : Springer Nature Publishing AG. - 2399-3642. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- Using Caenorhabditis elegans as an infection host model for Vibrio cholerae predator interactions, we discovered a bacterial cytotoxin, MakA, whose function as a virulence factor relies on secretion via the flagellum channel in a proton motive force-dependent manner. The MakA protein is expressed from the polycistronic makDCBA (motility-associated killing factor) operon. Bacteria expressing makDCBA induced dramatic changes in intestinal morphology leading to a defecation defect, starvation and death in C. elegans. The Mak proteins also promoted V. cholerae colonization of the zebrafish gut causing lethal infection. A structural model of purified MakA at 1.9 Å resolution indicated similarities to members of a superfamily of bacterial toxins with unknown biological roles. Our findings reveal an unrecognized role for V. cholerae flagella in cytotoxin export that may contribute both to environmental spread of the bacteria by promoting survival and proliferation in encounters with predators, and to pathophysiological effects during infections.
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| 8. |
- Elle, Ida C, et al.
(författare)
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Tissue- and paralogue-specific functions of acyl-CoA-binding proteins in lipid metabolism in Caenorhabditis elegans
- 2011
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 437:2, s. 231-241
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Tidskriftsartikel (refereegranskat)abstract
- ACBP (acyl-CoA-binding protein) is a small primarily cytosolic protein that binds acyl-CoA esters with high specificity and affinity. ACBP has been identified in all eukaryotic species, indicating that it performs a basal cellular function. However, differential tissue expression and the existence of several ACBP paralogues in many eukaryotic species indicate that these proteins serve distinct functions. The nematode Caenorhabditis elegans expresses seven ACBPs: four basal forms and three ACBP domain proteins. We find that each of these paralogues is capable of complementing the growth of ACBP-deficient yeast cells, and that they exhibit distinct temporal and tissue expression patterns in C. elegans. We have obtained loss-of-function mutants for six of these forms. All single mutants display relatively subtle phenotypes; however, we find that functional loss of ACBP-1 leads to reduced triacylglycerol (triglyceride) levels and aberrant lipid droplet morphology and number in the intestine. We also show that worms lacking ACBP-2 show a severe decrease in the β-oxidation of unsaturated fatty acids. A quadruple mutant, lacking all basal ACBPs, is slightly developmentally delayed, displays abnormal intestinal lipid storage, and increased β-oxidation. Collectively, the present results suggest that each of the ACBP paralogues serves a distinct function in C. elegans.
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| 9. |
- Friberg, Josefin, 1974-
(författare)
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The control of growth and metabolism in Caenorhabditis elegans
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The control of growth is a poorly understood aspect of animal development. This thesis focuses on body size regulation in Caenorhabditis elegans, and in particular, how worms grow to a certain size. In C. elegans, a key regulator of size is the TGFβ homologue DBL-1. Mutations that deplete the worm of DBL-1 result in a small body size, whereas overexpression of the gene renders long animals. The small mutants have the same number of cells as wild type suggesting that some or all cells are smaller. DBL-1 activates a TGFβ receptor leading to the nuclear localization of three Smad proteins which then initiate a transcriptional program for size control whose targets are mainly unknown. In order to learn more about how body size in C. elegans is regulated, we set up EMS mutagenesis screens to identify new loci that caused a long phenotype. A subset of the genes we have identified might function in the TGFβ signaling pathway regulating growth while others likely function in parallel pathways. One gene that we found in this screen, lon-3, encodes a cuticle collagen that genetically lies downstream of the DBL-1 TGFβ signaling pathway. Interestingly, loss of function mutations in lon-3 result in a Lon phenotype, whereas increasing the amount of LON-3 protein cause the worms to be dumpy, i.e. shorter, but slightly fatter than wild type. LON-3 is expressed in the hypodermis, the tissue from which the cuticle is synthesized and in which TGFβ signaling, regulating body size, has its focus. This study and previous work have shown that DBL-1 may affect body volume via effects on hypodermal nuclear ploidy, however this is unaffected in lon-3 mutants. Consistent with this finding, the volume of lon-3 mutant worms is not different from wild type. Taken together, our results suggest that another mechanism, by which TGFβ signaling can regulate body length, is by altering the shape of the cuticle via its effect on lon-3 and possibly other cuticle collagens. Studies in worms, flies and mice show that body size and nutrient allocation are closely connected. p70 S6-kinase (S6K) is a known regulator of cell and body size that also plays a role in metabolism. In mice and flies S6K mutants are much smaller than wild type. Our work on the worm homolog, rsks-1, shows that in worms as well, this gene is important for growth regulation and cell size. However, this effect seems to be at least in part independent of DBL-1 TGFβ signaling. Furthermore, rsks-1mutants have a 50 % increase in the amount of stored fat. Fatty acid metabolism has been shown to play an important role in environmental adaptation, especially in regards to temperature changes. Consistent with this idea, rsks-1 mutants appear to have difficulties in adjusting to such changes, reflected in a much-decreased fecundity at 15 and 25 °C compared to their cultivation temperature (20 °C). Within the nervous system the gene is specifically expressed in a subset of the chemosensory neurons that, when nutrients are abundant, secrete signals that promote growth. Intriguingly, this expression seems to be negatively regulated by insulin- like signaling, in contrast to the positive regulation of S6K by insulin in Drosophila and mice. Taken together we show that rsks-1 is an important regulator of growth and fat metabolism in Caenorhabditis elegans.
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| 10. |
- Gaur, Rahul, et al.
(författare)
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Diet-dependent depletion of queuosine in tRNAs in Caenorhabditis elegans does not lead to a developmental block.
- 2007
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Ingår i: J Biosci. - 0250-5991. ; 32:4, s. 747-54
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Tidskriftsartikel (refereegranskat)abstract
- Queuosine (Q), a hypermodified nucleoside,occurs at the wobble position of transfer RNAs (tRNAs)with GUN anticodons. In eubacteria, absence of Q affects messenger RNA (mRNA) translation and reduces the virulence of certain pathogenic strains. In animal cells,changes in the abundance of Q have been shown to correlate with diverse phenomena including stress tolerance, cell proliferation and tumour growth but the function of Q in animals is poorly understood. Animals are thought to obtain Q (or its analogues) as a micronutrient from dietary sources such as gut micro flora. However,the difficulty of maintaining animals under bacteria-free conditions on Q-deficient diets has severely hampered the study of Q metabolism and function in animals. In this study,we show that as in higher animals, tRNAs in the nematode Caenorhabditis elegans are modified by Q and its sugar derivatives. When the worms were fed on Q-deficient Escherichia coli, Q modification was absent from the worm tRNAs suggesting that C.elegans lacks a de novo pathway of Q biosynthesis. The inherent advantages of C.elegans as a model organism, and the simplicity of conferring a Q-deficient phenotype on it make it an ideal system to investigate the function of Q modification in tRNA.
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| 11. |
- Goergen, Philip, 1986-
(författare)
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The Molecular Mechanism of Aggression and Feeding Behaviour in Drosophila melanogaster
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Obesity is a complex disorder which has become a growing health concern. Twin studies have demonstrated a strong genetic component to the development of obesity and genome wide association studies have identified several genetic loci associated with it. However, most of these loci are still poorly understood in a functional context. Interestingly, many of the hormones and neurobiological messengers responsible for regulating feeding behaviour and metabolism are also linked to controlling aggression, but it is still not understood how they interact to maintain metabolic homeostasis. In this thesis, the model organism Drosophila melanogaster was employed to dissect the molecular mechanisms of the genetic cascades regulating aggressive behaviour and metabolic homeostasis.In paper I and II, the role of transcription factor AP-2 (TfAP-2) and Tiwaz Twz, Drosophila homologues of two human obesity-linked genes were investigated in aggression and feeding behaviour. Paper I demonstrated that TfAP-2 and Twz genetically interact in octopaminergic neurons to modulate male aggression by controlling the expression of genes necessary for octopamine (fly analogue of noradrenaline) production and secretion. Moreover, it was revealed that octopamine in turn regulates aggression through the Drosophila cholecystokinin (CCK) satiation hormone homologue Drosulfakinin (Dsk). Paper II revealed that TfAP-2 and Twz also initiate feeding through regulation of octopamine poduction and secretion. Octopamine then induces Dsk expression leading to inhibition of feeding.Paper III established that the activity of the small GTPase Ras-related C3 botulinum toxin substrate 2 (Rac2) is required in Drosophila for the proper regulation of metabolic homeostasis, as well as overt behaviours. Rac2 mutants were starvation susceptible, had less lipids and exhibited disrupted feeding behaviour. Moreover, they displayed aberrant aggression and courtship behaviour towards conspecifics.Paper IV studied Protein kinase D (PKD), the homologue of a third obesity-linked gene PRKD1, and another kinase Stretchin-Mlck (Strn-Mlck). Reducing PKD transcript levels in the insulin producing cells led to flies with increased starvation susceptibility, decreased levels of lipids and diminished insulin signalling compared to controls. Reduced Strn-Mlck expression resulted in a starvation phenotype and slight reduction in insulin signalling and lipid content. These findings imply a function for PKD and Strn-Mlck in insulin release.
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| 12. |
- Herdenberg, Carl, et al.
(författare)
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LRIG proteins regulate lipid metabolism via BMP signaling and affect the risk of type 2 diabetes
- 2021
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Leucine-rich repeats and immunoglobulin-like domains (LRIG) proteins have been implicated as regulators of growth factor signaling; however, the possible redundancy among mammalian LRIG1, LRIG2, and LRIG3 has hindered detailed elucidation of their physiological functions. Here, we show that Lrig-null mouse embryonic fibroblasts (MEFs) are deficient in adipogenesis and bone morphogenetic protein (BMP) signaling. In contrast, transforming growth factor-beta (TGF-β) and receptor tyrosine kinase (RTK) signaling appeared unaltered in Lrig-null cells. The BMP signaling defect was rescued by ectopic expression of LRIG1 or LRIG3 but not by expression of LRIG2. Caenorhabditis elegans with mutant LRIG/sma-10 variants also exhibited a lipid storage defect. Human LRIG1 variants were strongly associated with increased body mass index (BMI) yet protected against type 2 diabetes; these effects were likely mediated by altered adipocyte morphology. These results demonstrate that LRIG proteins function as evolutionarily conserved regulators of lipid metabolism and BMP signaling and have implications for human disease.
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| 13. |
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| 14. |
- Kao, Gautam, et al.
(författare)
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C. elegans SUR-6/PR55 cooperates with LET-92/protein phosphatase 2A and promotes Raf activity independently of inhibitory Akt phosphorylation sites
- 2004
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Ingår i: Development. - Cambridge : Company of Biologists Limited. - 0950-1991 .- 1477-9129. ; 131:4, s. 755-765
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Tidskriftsartikel (refereegranskat)abstract
- Protein phosphatase 2A (PP2A) can both positively and negatively influence the Ras/Raf/MEK/ERK signaling pathway, but its relevant substrates are largely unknown. In C. elegans, the PR55/B regulatory subunit of PP2A, which is encoded by sur-6, positively regulates Ras-mediated vulval induction and acts at a step between Ras and Raf. We show that the catalytic subunit (C) of PP2A, which is encoded by let-92, also positively regulates vulval induction. Therefore SUR-6/PR55 and LET-92/PP2A-C probably act together to dephosphorylate a Ras pathway substrate. PP2A has been proposed to activate the Raf kinase by removing inhibitory phosphates from Ser259 from Raf-1 or from equivalent Akt phosphorylation sites in other Raf family members. However, we find that mutant forms ofC. elegans LIN-45 RAF that lack these sites still require sur-6. Therefore, SUR-6 must influence Raf activity via a different mechanism. SUR-6 and KSR (kinase suppressor of Ras) function at a similar step in Raf activation but our genetic analysis suggests that KSR activity is intact in sur-6 mutants. We identify the kinase PAR-1 as a negative regulator of vulval induction and show that it acts in opposition to SUR-6 and KSR-1. In addition to their roles in Ras signaling, SUR-6/PR55 and LET-92/PP2A-C cooperate to control mitotic progression during early embryogenesis.
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| 15. |
- Korta, Dorota Z, et al.
(författare)
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S6K links cell fate, cell cycle and nutrient response in C. elegans germline stem/progenitor cells.
- 2012
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Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 139:5, s. 859-870
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Tidskriftsartikel (refereegranskat)abstract
- Coupling of stem/progenitor cell proliferation and differentiation to organismal physiological demands ensures the proper growth and homeostasis of tissues. However, in vivo mechanisms underlying this control are poorly characterized. We investigated the role of ribosomal protein S6 kinase (S6K) at the intersection of nutrition and the establishment of a stem/progenitor cell population using the C. elegans germ line as a model. We find that rsks-1 (which encodes the worm homolog of mammalian p70S6K) is required germline-autonomously for proper establishment of the germline progenitor pool. In the germ line, rsks-1 promotes cell cycle progression and inhibits larval progenitor differentiation, promotes growth of adult tumors and requires a conserved TOR phosphorylation site. Loss of rsks-1 and ife-1 (eIF4E) together reduces the germline progenitor pool more severely than either single mutant and similarly to reducing the activity of let-363 (TOR) or daf-15 (RAPTOR). Moreover, rsks-1 acts in parallel with the glp-1 (Notch) and daf-2 (insulin-IGF receptor) pathways, and does not share the same genetic dependencies with its role in lifespan control. We show that overall dietary restriction and amino acid deprivation cause germline defects similar to a subset of rsks-1 mutant phenotypes. Consistent with a link between diet and germline proliferation via rsks-1, loss of rsks-1 renders the germ line largely insensitive to the effects of dietary restriction. Our studies establish the C. elegans germ line as an in vivo model to understand TOR-S6K signaling in proliferation and differentiation and suggest that this pathway is a key nutrient-responsive regulator of germline progenitors.
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| 16. |
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| 17. |
- Leitz, Guenther, et al.
(författare)
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Stress response in Caenorhabditis elegans caused by optical tweezers : wavelength, power, and time dependence
- 2002
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Ingår i: Biophysical Journal. - : Biophysical Society. - 0006-3495 .- 1542-0086. ; 82:4, s. 2224-2231
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Tidskriftsartikel (refereegranskat)abstract
- Optical tweezers have emerged as a powerful technique for micromanipulation of living cells. Although the technique often has been claimed to be nonintrusive, evidence has appeared that this is not always the case. This work presents evidence that near-infrared continuous-wave laser light from optical tweezers can produce stress in Caenorhabditis elegans. A transgenic strain of C. elegans, carrying an integrated heat-shock-responsive reporter gene, has been exposed to laser light under a variety of illumination conditions. It was found that gene expression was most often induced by light of 760 nm, and least by 810 nm. The stress response increased with laser power and irradiation time. At 810 nm, significant gene expression could be observed at 360 mW of illumination, which is more than one order of magnitude above that normally used in optical tweezers. In the 700-760-nm range, the results show that the stress response is caused by photochemical processes, whereas at 810 nm, it mainly has a photothermal origin. These results give further evidence that the 700-760-nm wavelength region is unsuitable for optical tweezers and suggest that work at 810 nm at normal laser powers does not cause stress at the cellular level.
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| 18. |
- Navarro-Gonzalez, Carmen, et al.
(författare)
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Mutations in the Caenorhabditis elegans orthologs of human genes required for mitochondrial tRNA modification cause similar electron transport chain defects but different nuclear responses
- 2017
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Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- Several oxidative phosphorylation (OXPHOS) diseases are caused by defects in the post-transcriptional modification of mitochondrial tRNAs (mt-tRNAs). Mutations in MTO1 or GTPBP3 impair the modification of the wobble uridine at position 5 of the pyrimidine ring and cause heart failure. Mutations in TRMU affect modification at position 2 and cause liver disease. Presently, the molecular basis of the diseases and why mutations in the different genes lead to such different clinical symptoms is poorly understood. Here we use Caenorhabditis elegans as a model organism to investigate how defects in the TRMU, GTPBP3 and MTO1 orthologues (designated as mttu-1, mtcu-1, and mtcu-2, respectively) exert their effects. We found that whereas the inactivation of each C. elegans gene is associated with a mild OXPHOS dysfunction, mutations in mtcu-1 or mtcu-2 cause changes in the expression of metabolic and mitochondrial stress response genes that are quite different from those caused by mttu-1 mutations. Our data suggest that retrograde signaling promotes defect-specific metabolic reprogramming, which is able to rescue the OXPHOS dysfunction in the single mutants by stimulating the oxidative tricarboxylic acid cycle flux through complex II. This adaptive response, however, appears to be associated with a biological cost since the single mutant worms exhibit thermosensitivity and decreased fertility and, in the case of mttu-1, longer reproductive cycle. Notably, mttu-1 worms also exhibit increased lifespan. We further show that mtcu-1; mttu-1 and mtcu-2; mttu-1 double mutants display severe growth defects and sterility. The animal models presented here support the idea that the pathological states in humans may initially develop not as a direct consequence of a bioenergetic defect, but from the cell's maladaptive response to the hypomodification status of mt-tRNAs. Our work highlights the important association of the defect-specific metabolic rewiring with the pathological phenotype, which must be taken into consideration in exploring specific therapeutic interventions.
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| 19. |
- Nilsson, Lars, et al.
(författare)
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C. elegans TAT-6, a putative aminophospholipid translocase, is expressed in sujc cells in the hermaphrodite gonad
- 2021
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Ingår i: microPublication biology. - : Caltech Library. - 2578-9430.
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Tidskriftsartikel (refereegranskat)abstract
- In healthy eukaryotic cells, the two leaflets that make up plasma membranes are highly asymmetric with respect to the lipids they contain. In both unicellular eukaryotes and metazoans, the asymmetry in the distribution of aminophospholipids is maintained by P4-family transmembrane ATPases, which catalyze the movement of selected phospholipids from the outer leaflet to the inner. C. elegans has six P4-family ATPases, TAT-1 - TAT-6. TAT-1 - TAT-5 are expressed in many tissues and cells. Here we report that, in contrast, TAT-6 is much less broadly expressed and that, within the somatic gonad, expression of TAT-6 reporters is restricted to the spermathecal-uterine core cell (sujc) cells.
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| 20. |
- Nilsson, Lars, et al.
(författare)
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Caenorhabditis elegans num-1 negatively regulates endocytic recycling
- 2008
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Ingår i: Genetics. - : Oxford University Press (OUP). - 1943-2631. ; 179, s. 375-387
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Tidskriftsartikel (refereegranskat)abstract
- Much of the material taken into cells by endocytosis is rapidly returned to the plasma membrane by the endocytic recycling pathway. Although recycling is vital for the correct localization of cell membrane receptors and lipids, the molecular mechanisms that regulate recycling are only partially understood. Here we show that in C. elegans, endocytic recycling is inhibited by NUM-1A, the nematode Numb homologue. NUM-1A::GFP fusion protein is localized to the baso-lateral surfaces of many polarized epithelial cells including the hypodermis and the intestine. We show that increased NUM-1A levels cause morphological defects in these cells similar to those caused by loss-of-function mutations in rme-1, a positive regulator of recycling both in C. elegans and mammals. We describe the isolation of worms lacking num-1A activity and show that, consistent with a model in which NUM-1A negatively regulates recycling in the intestine, loss of num-1A function bypasses the requirement for RME-1. Genetic epistasis analysis with rab-10, which is required at an early part of the recycling pathway, suggests that loss of num-1A function does not affect the uptake of material by endocytosis but rather inhibits baso-lateral recycling downstream of rab-10.
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| 21. |
- Nilsson, Lars, et al.
(författare)
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Caenorhabditis elegans Numb Inhibits Endocytic Recycling by Binding TAT-1 Aminophospholipid Translocase
- 2011
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Ingår i: Traffic. - Malden : Wiley-Blackwell. - 1398-9219 .- 1600-0854. ; 12:12, s. 1839-1849
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Tidskriftsartikel (refereegranskat)abstract
- Numb regulates endocytosis in many metazoans, but the mechanism by which it functions is not completely understood. Here we report that the Caenorhabditis ele-gans Numb ortholog, NUM-1A, a regulator of endocytic recycling, binds the C isoform of transbilayer amphipath transporter-1 (TAT-1), a P4 family adenosine triphosphatase and putative aminophospholipid translocase that is required for proper endocytic trafficking. We demonstrate that TAT-1 is differentially spliced during development and that TAT-1C-specific splicing occurs in the intestine where NUM-1A is known to function. NUM-1A and TAT-1C colocalize in vivo. We have mapped the binding site to an NXXF motif in TAT-1C. This motif is not required for TAT-1C function but is required for NUM-1A's ability to inhibit recycling. We demonstrate that num-1A and tat-1 defects are both suppressed by the loss of the activity of PSSY-1, a phosphatidylserine (PS) synthase. PS is mislocalized in intestinal cells with defects in tat-1 or num-1A function. We propose that NUM-1A inhibits recycling by inhibiting TAT-1C's ability to translocate PS across the membranes of recycling endosomes.
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Pu, Longjun, 1990-
(författare)
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A molecular exploration of sensory responses in c. elegans
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sensation provides a pivotal ability, allowing animals to survive in complex environments. The cues sensed by animals are represented by external stimuli and internal signals. However, the mechanisms mediating sensations in molecular and cellular level are still not well-studied. In this thesis, by using free-living nematodes C. elegans with relatively simple nerve system, we are trying to get better understandings of molecular mechanisms by which animals sense and interpret external cues and internal signals.G protein-coupled receptors (GPCRs), as one of the major families of transmembrane proteins, participate in a variety of physiological responses to both external stimuli and internal cues. Previous studies have shown that GPCR signals are broadly involved in many processes in C. elegans, such as olfactory sensing, nociceptive responses, social behavior, pathogen responses, and mating. However, the complexity and diversity of GPCRs pose significant challenges to systematic dissection of their function as well as identification of receptor-ligand pairs which play crucial roles for animals´ sensory behaviors. Interestingly, the genome of C. elegans encodes one of the largest GPCR repertoires among any sequenced organisms, indicating a dramatical expansion and high degree of gene redundancy. To comprehensively dissect GPCR signaling in C. elegans and gain more insights into their roles in sensations, we developed an approach by employing CRISPR/Cas9-based gene editing to mutate closely related GPCRs and neuropeptide genes (internal signals) in a single strain on a genome-wide scale, resulting in disrupting nearly all the GPCR and neuropeptide genes (more than 1800 genes in total) and eliminating high degree of gene redundancy as well. Then using these two genetic libraries, we successfully identified neuropeptide (FLP -1) and cognate receptors (DMSR-4, DMSR-7 and DMSR-8) required for hypoxia-evoked locomotory responses, obtained a set of novel regulators of the pathogen-induced immune response including FMI-1 and DOP-6, and especially identified receptors (SRX-64) in AWA neurons for the volatile odorant pyrazine and redundant receptors (SRX-1, SRX-2 and SRX-3) in AWCOFF neuron for 2,3-pentanedione.In nature, animals often experience and sense constantly changing gas environments. And human bodies also generate internal gas as gasotransmitters for signal transduction, such as CO, NO and H2S. For the mechanism governing sensory and adaptive responses to different gaseous cues, extensive studies are still needed. Here, taking advantage of the robust locomotory responses to H2S in C. elegans, we delineated the molecular mechanisms of H2S sensation and adaptation. We found that C. elegans exhibited transiently increased locomotory and turning activity as a strategy to escape the noxious H2S. The behavioral responses to H2S were modulated by a complex network of signaling pathways, ranging from cyclic GMP signaling in ciliated sensory neurons, calcineurin, nuclear hormone receptors, to the major starvation regulators such as insulin and TGF-β signaling. Prolonged exposure to H2S robustly evoked H2S detoxification and reprogrammed gene expression, where genes involved in iron homeostasis, including ftn-1 and smf-3, were robustly modified, implying that labile iron levels are affected by H2S. In addition, the roles of labile iron for modulating H2S response were further investigated by using genetic studies and chemical applications. Interestingly, the response to H2S was substantially affected by the ambient O2 levels and their prior experience in low O2 environments, suggesting an intricate interplay between O2 and H2S sensing. The crosstalk is often seen between different experiences and sensations. In addition to the interplay between O2 and H2S sensing, we found hypoxia challenge could induce food leaving behavior in C. elegans. The alteration of food behavior by hypoxia experience was independent of the known mechanisms involved in O2 response, including pathways in acute hypoxia and HIF-1 signaling for chronic hypoxia response. The robust failure of induced food avoidance in egl-3 and egl-21 mutants suggested that neuropeptidergic signaling was required for this response. And future work is needed for comprehensively understanding the roles of neuropeptide signaling in the crosstalk between hypoxia experience and food leaving behavior.In summary, our studies shed light on the molecular and cellular mechanisms of how animals sense and interpret the signals, allowing them to survive in a complex environment niche. More specifically, 1) we demonstrated the dissection of genetic landscape of GPCR signaling through phenotypic profiling in C. elegans. And as a powerful genetic resource, our libraries can greatly expedite the analyses of GPCR signaling in multiple additional contexts. 2) we provided molecular insights into how C. elegans detects and adapts its response to H2S and modulates behaviors through ambient environment and experience.
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| 27. |
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| 28. |
- Rahmani, Shapour, et al.
(författare)
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EGL-4 promotes turning behavior of C. elegans males during mating
- 2021
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Ingår i: microPublication biology. - : Caltech Library. - 2578-9430.
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Tidskriftsartikel (refereegranskat)abstract
- During mating, C. elegans males whose tails have reached the head or tail of their intended mates are able to switch to scanning the other side by performing a turn during which the male's tail curls ventrally all the while keeping in contact with the hermaphrodite. The ability to execute turns efficiently is dependent upon serotonergic neurons in the posterior ventral nerve cord that stimulate diagonal muscles by activating a serotonin receptor, SER-1. Here we show that turning behavior is abnormal in males lacking a cGMP-dependent protein kinase, EGL-4. egl-4 mutant males are also resistant to ventral tail curling induced by exogenous serotonin.
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| 29. |
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| 30. |
- Rahmani, Shapour, 1975-
(författare)
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Studies on lipid transport and extracellular vesicle production in Caenorhabditis elegans ciliated neurons
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The cilium is a protrusion of cell membrane. Both the protein and lipid contents of cilia are different from those of other parts of the cell membrane. While the transport of proteins into and out of cilia has been intensively studied, much less is known about how the lipid content of ciliary membranes is regulated. TAT-6 is a P4-family ATPase that is expressed in C. elegans ciliated neurons whose endings are exposed to the environment. To study the function of TAT-6 and that other translocases in lipid transport in C. elegans ciliated neurons, I developed a technique to allow labelling of cilia with lipids. For the first time I used fusogenic liposomes to study the roles of all the TAT proteins in this organism in maintaining the lipid asymmetry in this organelle. Assessment the cilia with these liposomes showed that TAT-5 and TAT-1 translocase activities promote the transport of phosphatidylethanolamine (PE) and phosphatidylserine (PS) respectively and TAT-6 has an overlapping function in transporting both phospholipds. In C. elegans males, certain ciliated neurons release extracellular vesicles (EVs). The cilium is a site of EV biogenesis and shedding. I found that ciliated neurons in tat-6 mutant males produced significantly fewer EVs than those in wild type. tat-1, tat-5 and pad-1 mutants, however, produced far more EVs than those in wild type. PPK-3, CUP-5 and LMP-1 are proteins necessary for endolysosomal trafficking and lysosomes biogenesis, a process in which TAT-1 has previously been shown to function in C. elegans intestinal cells. I found that, like tat-1 mutants, ppk-3, lmp-1 and cup-5 mutant males release significantly greater numbers of EVs from cilia compared with wild-type. I found that increasing and decreasing the cGMP signaling cause defects in the response and turning behavior in male C. elegans respectively. Exposing wild-type males to high levels of 8-Bromoguanosine 3′,5′-cyclic monophosphate strongly reduced response behavior. Males mutant for odr-3, which encodes a G protein were defective in response. Overall my investigations indicate that the regulation of lipid asymmetry and phospholipid transport is required for proper cilia function in C. elegans, that intercellular trafficking and lipid composition have important roles in EVs biogenesis, and that different TAT proteins can affect the size and number of EVs produced. I also showed that in male animals, cGMP is one of the mediators in mating transduction signal and that a high level of cGMP inhibits mating response behavior in male C. elegans.
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| 31. |
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| 32. |
- Rohn, Isabelle, et al.
(författare)
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Selenium species-dependent toxicity, bioavailability and metabolic transformations in Caenorhabditis elegans
- 2018
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Ingår i: Metallomics. - : Royal Society of Chemistry. - 1756-5901 .- 1756-591X. ; 10:6, s. 818-827
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Tidskriftsartikel (refereegranskat)abstract
- The essential micronutrient selenium (Se) is required for various systemic functions, but its beneficial range is narrow and overexposure may result in adverse health effects. Additionally, the chemical form of the ingested selenium contributes crucially to its health effects. While small Se species play a major role in Se metabolism, their toxicological effects, bioavailability and metabolic transformations following elevated uptake are poorly understood. Utilizing the tractable invertebrate Caenorhabditis elegans allowed for an alternative approach to study species-specific characteristics of organic and inorganic Se forms in vivo, revealing remarkable species-dependent differences in the toxicity and bioavailability of selenite, selenomethionine (SeMet) and Se-methylselenocysteine (MeSeCys). An inverse relationship was found between toxicity and bioavailability of the Se species, with the organic species displaying a higher bioavailability than the inorganic form, yet being less toxic. Quantitative Se speciation analysis with HPLC/mass spectrometry revealed a partial metabolism of SeMet and MeSeCys. In SeMet exposed worms, identified metabolites were Se-adenosylselenomethionine (AdoSeMet) and Se-adenosylselenohomocysteine (AdoSeHcy), while worms exposed to MeSeCys produced Se-methylselenoglutathione (MeSeGSH) and -glutamyl-MeSeCys (-Glu-MeSeCys). Moreover, the possible role of the sole selenoprotein in the nematode, thioredoxin reductase-1 (TrxR-1), was studied comparing wildtype and trxr-1 deletion mutants. Although a lower basal Se level was detected in trxr-1 mutants, Se toxicity and bioavailability following acute exposure was indistinguishable from wildtype worms. Altogether, the current study demonstrates the suitability of C. elegans as a model for Se species dependent toxicity and metabolism, while further research is needed to elucidate TrxR-1 function in the nematode.
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| 33. |
- Rohn, Isabelle, et al.
(författare)
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Treatment of Caenorhabditis elegans with Small Selenium Species Enhances Antioxidant Defense Systems
- 2019
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Ingår i: Molecular Nutrition & Food Research. - : WILEY. - 1613-4125 .- 1613-4133. ; 63:9
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Tidskriftsartikel (refereegranskat)abstract
- ScopeSmall selenium (Se) species play a key role in Se metabolism and act as dietary sources of the essential trace element. However, they are redox-active and trigger pro- and antioxidant responses. As health outcomes are strongly species-dependent, species-specific characteristics of Se compounds are tested in vivo. Methods and resultsIn the model organism Caenorhabditis elegans (C. elegans), immediate and sustained effects of selenite, selenomethionine (SeMet), and Se-methylselenocysteine (MeSeCys) are studied regarding their bioavailability, incorporation into proteins, as well as modulation of the cellular redox status. While all tested Se compounds are bioavailable, only SeMet persistently accumulates and is non-specifically incorporated into proteins. However, the protection toward chemically-induced formation of reactive species is independent of the applied Se compound. Increased thioredoxin reductase (TXNRD) activity and changes in mRNA expression levels of antioxidant proteins indicate the activation of cellular defense mechanisms. However, in txnrd-1 deletion mutants, no protective effects of the Se species are observed anymore, which is also reflected by differential gene expression data. ConclusionSe species protect against chemically-induced reactive species formation. The identified immediate and sustained systemic effects of Se species give rise to speculations on possible benefits facing subsequent periods of inadequate Se intake.
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| 34. |
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| 35. |
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| 36. |
- Sheng, Ming, et al.
(författare)
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Aberrant Fat Metabolism in Caenorhabditis elegans Mutants with Defects in the Defecation Motor Program
- 2015
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Ingår i: PLOS ONE. - : PLOS one. - 1932-6203. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- The molecular mechanisms by which dietary fatty acids are absorbed by the intestine, and the way in which the process is regulated are poorly understood. In a genetic screen for mutations affecting fat accumulation in the intestine of Caenorhabditis elegans, nematode worms, we have isolated mutations in the aex-5 gene, which encodes a Kex2/subtilisinfamily, Ca2+-sensitive proprotein convertase known to be required for maturation of certain neuropeptides, and for a discrete step in an ultradian rhythmic phenomenon called the defecation motor program. We demonstrate that aex-5 mutants have markedly lower steadystate levels of fat in the intestine, and that this defect is associated with a significant reduction in the rate at which labeled fatty acid derivatives are taken up from the intestinal lumen. Other mutations affecting the defecation motor program also affect steady-state levels of triglycerides, suggesting that the program is required per se for the proper accumulation of neutral lipids. Our results suggest that an important function of the defecation motor program in C. elegans is to promote the uptake of an important class of dietary nutrients. They also imply that modulation of the program might be one way in which worms adjust nutrient uptake in response to altered metabolic status.
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| 37. |
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| 38. |
- Sheng, Ming, et al.
(författare)
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Fourier transform infrared microspectroscopy for the analysis of the biochemical composition of C. elegans worms
- 2016
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Ingår i: Worm. - : Taylor & Francis. - 2162-4054. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Changes in intermediary metabolism have profound effects on many aspects of C. elegans biology including growth, development and behavior. However, many traditional biochemical techniques for analyzing chemical composition require relatively large amounts of starting material precluding the analysis of mutants that cannot be grown in large amounts as homozygotes. Here we describe a technique for detecting changes in the chemical compositions of C. elegans worms by Fourier transform infrared microspectroscopy. We demonstrate that the technique can be used to detect changes in the relative levels of carbohydrates, proteins and lipids in one and the same worm. We suggest that Fourier transform infrared microspectroscopy represents a useful addition to the arsenal of techniques for metabolic studies of C. elegans worms.
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| 39. |
- Sheng, Ming, 1981-
(författare)
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Regulation of energy balance in Caenorhabditis elegans
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Obesity is a medical condition in which excess body fat has been accumulated. It is most commonly caused by imbalance between energy intake and energy expenditure (lack of physical activity and lower metabolic rate, etc.). The control of energy metabolism involves multiple tissues and signalling pathways and there is a great need for further understanding of these different interactions.In this study, I use Caenorhabditis elegans to study these complex pathways at the level of a whole organism. The downstream target of mTOR, p70 S6 kinase (S6K), has been implicated in the phosphorylation of multiple substrates and the regulation of growth and metabolism. In this study the worm homolog of S6K, rsks-1, found to be important for fat metabolism. Previous work in our lab found that RSKS-1::GFP is expressed at high levels in a set of sensory neurons and upregulated in ASJ, ASE and BAG sensory neurons in starved worms or mutants with low insulin activity. In this study, I found that the upregulation of rsks-1 expression was affected by serotonin, but not by the other neurotransmitters. Combined with the result that rsks-1 is required for the expression of TGFβ and insulin in ASI, rsks-1 may control dietary sensing by affecting insulin and TGFβ signalling within nervous system. Quantification of fat accumulation by TLC/GC revealed that in comparison to wild type worms, rsks-1 mutants have more than two-fold higher levels of triglycerides. This was confirmed by FT-IR microspectroscopy analysis. rsks-1 mutants also contain disproportionately high levels of C16:1n9 and C18:1n9 lipids compared with wild type worms. Genetic analysis has shown that rsks-1 acts either downstream of, or in parallel to the insulin and TGFβ pathways to affect fat levels. My studies showed that rsks-1 affects fat metabolism by influencing mRNA levels of genes encoding proteins in the β-oxidation pathway. Combined with defects in dietary sensing, fatty acid absorption, fertility and mitochondria function, the loss of rsks-1 activity induced much more energy storage than wild type by making a profound metabolic shift. These results are consistent with the metabolomics data analysis. Tissue specific RNAi showed that rsks-1 was required in many different tissues to regulate fat metabolism. Taken together, it can be concluded that RSKS-1 activity is needed for co-ordination of metabolic states in C. elegans. In order to understand more about the physiology behind fat accumulation, I analysed a mutant, aex-5, that has significantly lowered lipid levels. I found that this defect is associated with a significant reduction in the rate at which dietary fatty acids are taken up from the intestinal lumen. The aex-5 gene, which encodes a Kex2/subtilisin-family, Ca2+-sensitive proprotein convertase, is required for a discrete step in an ultraradian rhythmic phenomenon called the defecation motor program (DMP). Combined with other results, we conclude that aex-5 and other defecation genes may affect fat uptake by promoting the correct distribution of acidity within the intestinal lumen.This dissertation also described how to use Fourier transform infrared (FT-IR) microspectroscopy to detect lipids, proteins and carbohydrates directly in single worm. In conclusion, in this thesis I have uncovered several components that play roles in dietary sensing, fatty acid synthesis, adiposity regulation and fatty acid absorption in C. elegans.
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| 40. |
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| 41. |
- Stenvall, Jörgen, et al.
(författare)
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Selenoprotein TRXR-1 and GSR-1 are essential for removal of old cuticle during molting in Caenorhabditis elegans
- 2011
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 108:3, s. 1064-1069
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Tidskriftsartikel (refereegranskat)abstract
- Selenoproteins, in particular thioredoxin reductase, have been implicated in countering oxidative damage occurring during aging but the molecular functions of these proteins have not been extensively investigated in different animal models. Here we demonstrate that TRXR-1 thioredoxin reductase, the sole selenoprotein in Caenorhabditis elegans, does not protect against acute oxidative stress but functions instead together with GSR-1 glutathione reductase to promote the removal of old cuticle during molting. We show that the oxidation state of disulfide groups in the cuticle is tightly regulated during the molting cycle, and that when trxr-1 and gsr-1 function is reduced, disulfide groups in the cuticle remain oxidized. A selenocysteine-to-cysteine TRXR-1 mutant fails to rescue molting defects. Furthermore, worms lacking SELB-1, the C. elegans homolog of Escherichia coli SelB or mammalian EFsec, a translation elongation factor known to be specific for selenocysteine in E. coli, fail to incorporate selenocysteine, and display the same phenotype as those lacking trxr-1. Thus, TRXR-1 function in the reduction of old cuticle is strictly selenocysteine dependent in the nematode. Exogenously supplied reduced glutathione reduces disulfide groups in the cuticle and induces apolysis, the separation of old and new cuticle, strongly suggesting that molting involves the regulated reduction of cuticle components driven by TRXR-1 and GSR-1. Using dauer larvae, we demonstrate that aged worms have a decreased capacity to molt, and decreased expression of GSR-1. Together, our results establish a function for the selenoprotein TRXR-1 and GSR-1 in the removal of old cuticle from the surface of epidermal cells.
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| 42. |
- Tiensuu, Teresa, 1970-
(författare)
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Cell fate specification by Ras-mediated cell signalling in C. elegans
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Induction of vulval fates in the C. elegans hermaphrodite is mediated by a conserved RTK/Ras/MAP kinase signalling pathway, in which the core components can be placed into a linear genetic and biochemical pathway. However, the events that occur downstream of this pathway are not yet well understood. This thesis describes studies on three genes, lin-1, lin-25 and sur-2 that function genetically downstream of the RTK/Ras/MAP kinase pathway in vulva induction. lin-1 encodes an ETS protein that appears to be a direct target of the RTK/Ras/MAP kinase pathway during the induction of vulval fates. To understand more in detail how Ras signalling in C. elegans affects cell fate specification we have analysed the effects of lin-1 mutations on various Ras-mediated cell fate specification events. Our results show that lin-1, besides its function in vulval induction, functions in most other Ras-mediated cell fate specification events in C. elegans, and that lin-1 appears to have a negative function in a majority of these events. Two other genes, lin-25 and sur-2, also function genetically downstream of the RTK/Ras/MAP kinase pathway during induction of vulval fates. Previously, two different models have been proposed for the function of these genes (I) that they function together with a gene in the homeotic cluster to specify the identity of the vulval precursor cells or (II) that they constitute components of the RTK/Ras/MAP kinase signalling pathway. To help clarify the role of lin-25 and sur-2, we have caried out studies of the effects of lin-25 and sur-2 mutations on other cells in the worm in which the RTK/Ras/MAP kinase pathway functions. The results exclude the possibility that lin-25 and sur-2 solely function in vulva induction and suggest that the two genes are intimately involved in Ras-mediated signalling. In addition we show that the major focus for lin-25 during vulval induction is in the vulva precursor cells themselves. Furthermore, results presented here suggest that LIN-25 and SUR-2 function together in the same process in the cell. We show here by both genetic and immunological experiments that LIN-25 is associated with Mediator in C. elegans, a multiprotein complex required for transcriptional regulation. Taken together, these results suggest that lin-25 and sur-2 function in regulating transcription of genes in response to Ras signalling.
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| 43. |
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| 44. |
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| 45. |
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| 46. |
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| 47. |
- Tuck, Simon
(författare)
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The control of cell growth and body size in Caenorhabditis elegans
- 2014
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827 .- 1090-2422. ; 321:1, s. 71-76
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Forskningsöversikt (refereegranskat)abstract
- One of the most important ways in which animal species vary is in their size. Individuals of the largest animal ever thought to have lived, the blue whale (Balaenoptera musculus), can reach a weight of 190 t and a length of over 30 m. At the other extreme, among the smallest multicellular animals are males of the parasitic wasp, Dicopomorpha echmepterygis, which even as adults are just 140 mu m in length. In terms of volume, these species differ by more than 14 orders of magnitude. Since size has such profound effects on an organism's ecology, anatomy and physiology, an important task for evolutionary biology and ecology is to account for why organisms grow to their characteristic sizes. Equally, a full description of an organism's development must include an explanation of how its growth and body size are regulated. Here I review research on how these processes are controlled in the nematode, Caenorhabditis elegans. Analyses of small and long mutants have revealed that in the worm, DBL-1, a ligand in the TGF beta superfamily family, promotes growth in a dose-dependent manner. DBL-1 signaling affects body size by stimulating the growth of syncytial hypodermal cells rather than controlling cell division. Signals from chemosensory neurons and from the gonad also modulate body size, in part, independently of DBL-1-mediated signaling. Organismal size and morphology is heavily influenced by the cuticle, which acts as the exoskeleton. Finally, I summarize research on several genes that appear to regulate body size by cell autonomously regulating cell growth throughout the worm.
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| 48. |
- Vaitkevicius, Karolis, et al.
(författare)
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A Vibrio cholerae protease needed for killing of Caenorhabditis elegans has a role in protection from natural predator grazing
- 2006
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 103:24, s. 9280-9285
-
Tidskriftsartikel (refereegranskat)abstract
- Vibrio cholerae is the causal bacterium of the diarrheal disease cholera, and its growth and survival are thought to be curtailed by bacteriovorous predators, e.g., ciliates and flagellates. We explored Caenorhabditis elegans as a test organism after finding that V. cholerae can cause lethal infection of this nematode. By reverse genetics we identified an extracellular protease, the previously uncharacterized PrtV protein, as being necessary for killing. The killing effect is associated with the colonization of bacteria within the Caenorhabditis elegans intestine. We also show that PrtV is essential for V. cholerae in the bacterial survival from grazing by the flagellate Cafeteria roenbergensis and the ciliate Tetrahymena pyriformis. The PrtV protein appears to have an indirect role in the interaction of V. cholerae with mammalian host cells as judged from tests with tight monolayers of human intestinal epithelial cells. Our results demonstrate a key role for PrtV in V. cholerae interaction with grazing predators, and we establish Caenorhabditis elegans as a convenient organism for identification of V. cholerae factors involved in host interactions and environmental persistence.
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| 49. |
- Zhao, Lina, 1990-
(författare)
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Oxygen sensing in Caenorhabditis elegans
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sufficient supply of oxygen (O2) to tissue is essential for survival of aerobicanimals. In mammals, there are constant homeostatic regulation mechanisms that act on different time scales to maintain optimal O2 delivery to tissues. The ability to detect and respond to acute oxygen shortages is indispensable to aerobic life. However, the molecular mechanisms and circuits underlying this capacity are poorly understood.We characterize the locomotory response of feeding Caenorhabditis elegans (C. elegans) to 1% O2. Acute hypoxia triggers a bout of turning maneuvers followed by a persistent switch to rapid forward movement as animals seek to avoid and escape hypoxia. Increasing cGMP signaling inhibits escape from 1% O2, and that cGMP activates the protein kinase G, EGL-4, which in turn enhances neuroendocrine secretion to inhibit acute response to 1% O2. A primary source of cGMP is the guanylyl cyclase, GCY-28. In addition, increasing mitochondrial reactive oxygen species (ROS), abrogate acute hypoxia response. Up-regulation of mitochondrial ROS increases cGMP levels, which contribute to the reduced hypoxia response. Our results implicate ROS and precise regulation of intracellular cGMP in the modulation of acute response to hypoxia by C. elegans.In addition, we found that FMRFamide-related peptides FLP-1 plays a role in hypoxia evoked locomotory response. Our data showed that FLP-1 secretion from AVK interneurons acts on AVA and other neurons through DMSR-4, DMSR7, and DMSR-8 GPCR receptors to maintain baseline speed and to promote locomotory response to hypoxia.We also found that hypoxia could induce food leaving behavior in C. elegans. Animals quickly escaped from the bacterial lawn when exposed to 1% O2. The known O2 response mechanisms cannot explain this phenotype, instead, neuropeptidergic signalling seems to be required for this behaviour.It's known that pro-inflammatory cytokine ILC-17.1, the homologue of mammalian IL-17s, act as a neuromodulator involved in hyperoxia sensing in C. elegans. We found that it was not involved in acute hypoxia response. Instead, ILC-17.1 could modulate lifespan and damage defense mechanisms against stress in C. elegans by triggering an inhibitory network to constrain the activity of the nuclear hormone receptor, NHR-49.In summary, our research can provide molecular and neurological understanding of how O2 is sensed by animals. Additionally, it further emphasis C. elegans as a good model to understand oxygen sensing
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| 50. |
- Zhao, Yani, 1983-
(författare)
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Systemic RNAi Relies on the Endomembrane System in Caenorhabditis elegans
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The membrane system of a eukaryotic cell is a large and complex system handling the transport, exchange and degradation of many kinds of material. Recent research shows that double-stranded RNA (dsRNA) mediated gene silencing (RNA interference) is a membrane related process. After long dsRNA is processed to small interfering RNA (siRNA) by Dicer, the guide strand and passenger strand are separated in the RNA induced silencing complex (RISC) by Argonaute. The process of loading siRNA into RISC has been suggested to occur at the rough Endoplasmic Reticulum (rER).The components of RISC also associate with late endosomes/multivesicular bodies (MVBs). Furthermore, disturbing the balance between late endosomes/MVBs and lysosomes has been shown to affect the efficiency of silencing.We use the nematode Caenorhabditis elegans as our model organism to study two questions: how does membrane transport affect RNAi and spreading of RNAi from the recipient cells to other tissues (systemic RNAi); and how does RNA transport contribute to the multigenerational silencing induced by dsRNA (RNAi inheritance)? Using SID-5, a protein required for efficient systemic RNAi, as bait in a yeast two-hybrid (Y2H) screen, we got 32 SID-5 interacting candidate proteins. Two of these are the SNARE protein SEC-22 and the putative RNA binding protein C12D8.1. In two additional Y2H screens, we found that SID-5 interacts with multiple syntaxin SNAREs, including SYX-6, whereas SEC-22 only interacts with SYX-6. SNAREs usually function in vesicle fusion processes. We found the two SNARE proteins SEC-22 and SYX-6 to be negative regulators of RNAi and to localize to late endosomes/MVBs. In addition, loss of sid-5 leads to an endosome maturation defect. Finally, we found that the putative RNA binding protein C12D8.1 negatively regulates RNAi inheritance and that C12D8.1 mutant animals show impaired RNAi upon targeting a new gene. Taken together, the results presented in this thesis provide us with more evidence for the connection of the membrane transport system and RNAi. The identification of a putative negative regulator of RNAi inheritance further enriches this research field.
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