| 1. |
|
|
| 2. |
- Dongre, Mitesh, et al.
(författare)
-
Flagella-mediated secretion of a novel Vibrio cholerae cytotoxin affecting both vertebrate and invertebrate hosts
- 2018
-
Ingår i: Communications Biology. - : Springer Nature Publishing AG. - 2399-3642. ; 1
-
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.
|
|
| 3. |
- Navarro-Gonzalez, Carmen, et al.
(författare)
-
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
-
Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 13:7
-
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.
|
|
| 4. |
- Rohn, Isabelle, et al.
(författare)
-
Selenium species-dependent toxicity, bioavailability and metabolic transformations in Caenorhabditis elegans
- 2018
-
Ingår i: Metallomics. - : Royal Society of Chemistry. - 1756-5901 .- 1756-591X. ; 10:6, s. 818-827
-
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.
|
|
| 5. |
- Rohn, Isabelle, et al.
(författare)
-
Treatment of Caenorhabditis elegans with Small Selenium Species Enhances Antioxidant Defense Systems
- 2019
-
Ingår i: Molecular Nutrition & Food Research. - : WILEY. - 1613-4125 .- 1613-4133. ; 63:9
-
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.
|
|
| 6. |
- Sheng, Ming, et al.
(författare)
-
Aberrant Fat Metabolism in Caenorhabditis elegans Mutants with Defects in the Defecation Motor Program
- 2015
-
Ingår i: PLOS ONE. - : PLOS one. - 1932-6203. ; 10:4
-
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.
|
|
| 7. |
- Sheng, Ming, et al.
(författare)
-
Fourier transform infrared microspectroscopy for the analysis of the biochemical composition of C. elegans worms
- 2016
-
Ingår i: Worm. - : Taylor & Francis. - 2162-4054. ; 5:1
-
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.
|
|
| 8. |
- Sheng, Ming, 1981-
(författare)
-
Regulation of energy balance in Caenorhabditis elegans
- 2015
-
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.
|
|
| 9. |
- Zhao, Yani, 1983-
(författare)
-
Systemic RNAi Relies on the Endomembrane System in Caenorhabditis elegans
- 2017
-
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.
|
|
