Petriv OI et al. (2004) J Mol Biol "A new definition for the consensus sequence of the peroxisome targeting signal type 2."

Rachubinski RA, Titorenko VI, Tang L, Petriv OI

[J Mol Biol, 2004]

All organisms except the nematode Caenorhabditis elegans have been shown to possess an import system for peroxisomal proteins containing a peroxisome targeting signal type 2 (PTS2). The currently accepted consensus sequence for this amino-terminal nonapeptide is -(R/K)(L/V/I)X-5(H/Q)(L/A)-. Some C. elegans proteins contain putative PTS2 motifs, including the ortholog (CeMeK) of human mevalonate kinase, an enzyme known to be targeted by PTS2 to mammalian peroxisomes. We cloned the gene for CeMeK (open reading frame Y42G9A.4) and examined the subcellular localization of CeMeK and of two other proteins with putative PTS2s at their amino termini encoded by the open reading frames D1053.2 and W10G11.11. All three proteins localized to the cytosol, confirming and extending the finding that C. elegans lacks PTS2-dependent peroxisomal protein import. The putative PTS2s of the proteins encoded by D1053.2 and W10G11.11 did not function in targeting to peroxisomes in yeast or mammalian cells, suggesting that the current PTS2 consensus sequence is too broad. Analysis of available experimental data on both functional and nonfunctional PTS2s led to two re-evaluated PTS2 consensus sequences: -R(L/V/I/Q)XX(L/V/I/H)(L/S/G/A)X(H/Q)(L/A)-, describes the most common variants of PTS2, while -(R/K)(L/V/I/Q)XX(L/V/I/H/ Q)(L/S/G/A/K)X(H/Q)(L/A/F)-, describes essentially all variants of PTS2. These redefined PTS2 consensus sequences will facilitate the identification of proteins of unknown cellular localization as possible peroxisomal proteins.

Ellwood RA et al. (2022) Commun Biol "Sulfur amino acid supplementation displays therapeutic potential in a C. elegans model of Duchenne muscular dystrophy."

Ellwood RA, Slade L, Piasecki M, Whiteman M, Torregrossa R, Lewis J, Etheridge T, Sudevan S, Szewczyk NJ

[Commun Biol, 2022]

Mutations in the dystrophin gene cause Duchenne muscular dystrophy (DMD), a common muscle disease that manifests with muscle weakness, wasting, and degeneration. An emerging theme in DMD pathophysiology is an intramuscular deficit in the gasotransmitter hydrogen sulfide (H₂S). Here we show that the C. elegans DMD model displays reduced levels of H₂S and expression of genes required for sulfur metabolism. These reductions can be offset by increasing bioavailability of sulfur containing amino acids (L-methionine, L-homocysteine, L-cysteine, L-glutathione, and L-taurine), augmenting healthspan primarily via improved calcium regulation, mitochondrial structure and delayed muscle cell death. Additionally, we show distinct differences in preservation mechanisms between sulfur amino acid vs H₂S administration, despite similarities in required health-preserving pathways. Our results suggest that the H₂S deficit in DMD is likely caused by altered sulfur metabolism and that modulation of this pathway may improve DMD muscle health via multiple evolutionarily conserved mechanisms.

Oleh I Petriv et al. (2003) International Worm Meeting "Redefining the consensus sequence of the peroxisomal targeting signal type 2"

Richard A Rachubinski, Oleh I Petriv, Vladimir I Titorenko

[International Worm Meeting, 2003]

All organisms studied so far, except for the nematode Caenorhabditis elegans, have been shown to have developed an import system for peroxisomal proteins containing a peroxisomal targeting signal type 2 (PTS2). The currently accepted consensus sequence of this amino-terminal nonapeptide is (R/K)(L/V/I)X5(H/Q)(L/A). Some C. elegans proteins contain putative PTS2 motifs, including the ortholog (CeMeK) of human mevalonate kinase, an enzyme known to be targeted by a PTS2 to mammalian peroxisomes. We cloned the gene for CeMeK (Y42G9A.4) and examined the subcellular localization of CeMeK and of two other proteins with putative PTS2s at their amino termini encoded by the ORFs D1053.2 and W10G11.11. Two proteins (CeMeK and the product of ORF W10G11.11) localized to the cytosol, while the protein encoded by D1053.2 was found in nucleoli. The three putative PTS2s did not function in targeting to peroxisomes in yeast or mammalian cells, suggesting that the current PTS2 consensus sequence is too broad. After extensive analysis of available experimental data on both functional and nonfunctional PTS2s, we propose two re-evaluated PTS2 consensus sequences. The first, R(L/V/I)XX(L/V/I)(S/A/L/K)X(H/Q)(L/A), describes the most common PTS2 variants, while the second (R/K)(L/V/I/Q)XX(L/V/I/H/Q)(S/A/L/K/G)X(H/Q)(L/A/F) includes all rare variants of PTS2. Our study also confirms the finding that C. elegans apparently lacks any PTS2-dependant peroxisomal protein import.

Sese BT et al. (2009) J Toxicol Environ Health A "Toxicity of polycyclic aromatic hydrocarbons to the nematode Caenorhabditis elegans."

Grant A, Sese BT, Reid BJ

[J Toxicol Environ Health A, 2009]

The presence of polycyclic aromatic hydrocarbons (PAHs) in the environment has attracted much concern owing to their mutagenic and carcinogenic properties. Regulatory authorities have favored the use of biological indicators as an essential means of assessing potential toxicity of environmental pollutants. This study aimed to assess the toxicity of acenaphthene, phenanthrene, anthracene, fluoranthene, pyrene, and benzo[a]pyrene to Caenorhabditis elegans by measuring LC50 and EC50 values for growth and reproduction. The exposure to all chemicals was carried out in aqueous medium. All PAHs showed a low acute toxicity to C. elegans. There was no significant mortality in C. elegans after 24 h of exposure at PAH concentrations within (and indeed above) their respective solubility limits. Prolonged exposure (72 h) at high concentrations for acenaphthene (70,573 microg/L), phenanthrene (3758 microg/L), anthracene (1600 microg/L), fluoranthene (1955 microg/L), pyrene (1653 microg/L), and benzo[a]pyrene (80 microg/L) produced mortality. Results also showed that reproduction and growth were much more sensitive parameters of adverse response than lethality, and consequently may be more useful in assessing PAH toxicity using C. elegans. In comparison with previous studies, C. elegans was found to be approximately 2-fold less sensitive to acenaphthene, 5-fold less sensitive to phenanthrene, and 20-fold less sensitive to fluoranthene than Daphnia magna. However, the 48-h LC50 for benzo[a]pyrene (174 microg/L) reported in the present study with C. elegans was similar to that reported elsewhere for Daphnia magna (200 microg/L). Although C. elegans indicated greater sensitivity to benzo[a]pyrene than Artemia salina (174 microg/L vs. 10000 microg/L), the organism showed less sensitivity to pyrene (8 microg/L vs. 2418 microg/L), fluoranthene (40 microg/L vs. 2719 microg/L), and phenanthrene (677 microg/L vs. 4772 microg/L) than Artemia salina. Caenorhabditis elegans, while not the most sensitive of species for PAH toxicity assessment, may still hold applicability in screening of contaminated soils and sediments.

Flydal MI et al. (2010) Amino Acids "Superstoichiometric binding of L-Phe to phenylalanine hydroxylase from Caenorhabditis elegans: evolutionary implications."

Siltberg-Liberles J, Mohn TC, Teigen K, Pey AL, Martinez A, Flydal MI

[Amino Acids, 2010]

Phenylalanine hydroxylase (PAH) catalyzes the hydroxylation of L-Phe to L-Tyr. Dysfunctional PAH results in phenylketonuria and mammalian PAH is therefore highly regulated and displays positive cooperativity for L-Phe (Hill coefficient (h)=2). L-Phe does not bind to the regulatory ACT domain in full-length tetrameric human PAH and cooperativity is elicited by homotropic binding to the catalytic site (Thorolfsson et al. in Biochemistry 41:7573-7585, 2002). PAH from Caenorhabditis elegans (cePAH) is devoid of cooperativity for L-Phe (h=0.9), and, as shown in this work, structural analysis reveal an additional L-Phe binding site at the regulatory domain of full-length cePAH. This site involves the GA(S)L/ISRP motifs, which are also found in ACT domains of other L-Phe binding proteins, such as prephenate dehydratase. Isothermal titration calorimetry further demonstrated 2 binding sites per subunit for cePAH versus ~1 for hPAH. Steric occlusion of the regulatory site, notably by residues Lys215/Tyr216 from the adjacent catalytic domain, appears to hinder regulatory binding in full-length hPAH. Accordingly, the humanized mutant Q215K/N216Y of cePAH binds ~1.4 L-Phe/subunit. This mutant also displays high catalytic activity and certain positive cooperativity for L-Phe (h=1.4). Our results support that the acquisition of positive cooperativity in mammalian forms of PAH is accompanied by a closure of the regulatory L: -Phe binding site. Concomitantly, the function of the regulatory ACT domain appears to be adapted from amino acid binding to serving the communication of conformational changes among catalytic subunits.

Rui Q et al. (2013) Chemosphere "Biosafety assessment of titanium dioxide nanoparticles in acutely exposed nematode Caenorhabditis elegans with mutations of genes required for oxidative stress or stress response."

Rui Q, Wang D, Wu Q, Tang M, Zhao Y

[Chemosphere, 2013]

We used Caenorhabditis elegans to investigate whether acute exposure to TiO2-NPs at the concentration of 20 g L(-1) reflecting predicted environmental relevant concentration and 25 mg L(-1) reflecting concentration in food can cause toxicity on nematodes with mutations of susceptible genes. Among examined mutants associated with oxidative stress and stress response, we found that genes of sod-2, sod-3, mtl-2, and hsp-16.48 might be susceptible for TiO2-NPs toxicity. Mutations of these genes altered functions of both possible primary and secondary targeted organs in nematodes exposed to 25 mg L(-1) of TiO2-NPs for 24-h. Mutations of these genes caused similar expression patterns of genes required for oxidative stress in TiO2-NPs exposed mutant nematodes, implying their similar mechanisms to form the susceptible property. Nevertheless, acute exposure to 20 g L(-1) of TiO2-NPs for 24-h and 25 mg L(-1) of TiO2-NPs for 0.48-h or 5.71-h did not influence functions of both possible primary and secondary targeted organs in sod-2, sod-3, mtl-2, and hsp-16.48 mutants. Therefore, our results suggest the relatively safe property of acute exposure to TiO2-NPs with certain durations at predicted environmental relevant concentrations or concentrations comparable to those in food in nematodes with mutations of some susceptible genes.

Hoss S et al. (2002) Environ Pollut "Enhanced growth and reproduction of Caenorhabditis elegans (Nematoda) in the presence of 4-nonylphenol."

Pfister G, Juttner I, Schramm KW, Steinberg CEW, Traunspurger W, Hoss S

[Environ Pollut, 2002]

The nematode Caenorhabditis elegans was exposed over a whole life-cycle (72 h) to several concentrations of 4-nonylphenol (NP; nominal concentrations: 0-350 mug/l). Growth and reproduction of C. elegans were enhanced at NP concentrations of 66 and 40 mug/l, respectively, with effects showing dose-response relationships. These stimulatory effects might be of ecological relevance in benthic habitats, where organisms can be exposed to high concentrations of NP.

Huang YE et al. (2015) Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi "[Biological toxicity of heavy metals to Caenorhabditis elegans]."

Guo W, Li CP, Zhang N, Jiang YX, Huang YE

[Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi, 2015]

OBJECTIVE: To evaluate the biological toxicity of heavy metals by using Caenorhabditis elegans. METHODS: The C. elegans at L4 stage were exposed to CdCl, CrCl3, As2O3, PbCh2, HgCl2 with low concentrations and M9 buffer (the control group) for 72 h, respectively, and the effects of heavy metals with different concentrations on the survival time and reproduction of C. elegans were evaluated. RESULTS: After exposure to 2.5, 10 mol/L HgCl2 and PbCl2, 10 mol/L CdCl2, and 50 mol/L CrCl3 for 72 h, respectively, the life spans and survival curves of the C. elegans were different from those in the control group, the differences were statistically significant (all P < 0.05). After exposure to CdCl2, CrCl3, As2O3, PbCl2 and HgCl2 with the con- centrations of 2.5, 50, 100 mol/L for 72 h, respectively, the generational time and brood size of C. elegans were all different from those in the control group (all P < 0.01). Among the 5 heavy metals at low concentrations, the reproduction toxicity of Hg was bigger than Pb, Cd, Cr, and the toxicity of As was the weakest. CONCLUSION: Heavy metal exposure can affect the life span and reproductive toxicity of C. elegans.

Xiao J et al. (2009) J Environ Sci (China) "Prolonged manganese exposure induces severe deficits in lifespan, development and reproduction possibly by altering oxidative stress response in Caenorhabditis elegans."

Wang D, Chang X, Guo Y, Rui Q, Xiao J

[J Environ Sci (China), 2009]

We examined the possible multiple defects induced by acute and prolonged exposure to high levels of manganese (Mn) solution by monitoring the endpoints of lifespan, development, reproduction, and stress response. Our data suggest that acute exposure (6 h) to Mn did not cause severe defects of life span, development, and reproduction, similarly, no significant defect could be found in animals exposed to a low concentration of Mn (2.5 micromol/L) for 48 h. In contrast, prolonged exposure (48 h) to high Mn concentrations (75 and 200 micromol/L) resulted in significant defects of life span, development, and reproduction, as well as the increase of the percentage of population with hsp-16.2::gfp expression indicating the obvious induction of stress responses in exposed animals. Moreover, prolonged exposure (48 h) to high concentrations (75 and 200 micromol/L) of Mn decreased the expression levels of antioxidant genes of sod-1, sod-2, sod-3, and sod-4 compared to control. Therefore, prolonged exposure to high concentrations of Mn will induce the severe defects of life span, development, and reproduction in nematodes possibly by affecting the stress response and expression of antioxidant genes in Caenorhabditis elegans.

Khanna N et al. (1997) Arch Environ Contam Toxicol "Tolerance of the nematode Caenorhabditis elegans to pH, salinity, and hardness in aquatic media."

Tatara CP, Cressman CP, Khanna N, Williams PL

[Arch Environ Contam Toxicol, 1997]

The toxicity of many chemicals depends on the physical conditions of the test environment, and any change or adjustment made to the tests can alter the results. Therefore it is important to establish the sensitivity of the test organism over a range of test conditions to determine when it is necessary to make adjustment and to what extent. In this study, we established the tolerance range of the nematode Caenorhabditis elegans for pH, salinity and hardness using 24- (without food source) and 96-h (with food source) aquatic toxicity tests. The tests were performed in two media: K-medium and moderately hard reconstituted water (MHRW). C.elegans has high tolerance under these test conditions. In K-medium worms survived a pH range of 3.1 to 11.9 for 24 h and 3.2 to 11.8 for 96 h without significant (p > 0.05) lethality. In MHRW the pH range was 3. 4 to 11.9 for 24 h and 3.4 to 11.7 for 96 h. Salinity tolerance tests were approximated with NaCl and KCl individually. Up to 15.46 g/L NaCl and 11.51 g/L KCl were tolerated by C. elegans in K-medium without significant lethality (p> 0.05). In MHRW higher salt concentrations were tolerated; about 20.5 g/L NaCl and 18.85 g/L KCl did not show any adverse effect compared to control. Hardness tolerance was tested by adding NaHCO3. The nematode could tolerate 0. 236 to 0.246 g/L of NaHCO3. The high tolerance of C. elegans to these test conditions (pH, salinity, and hardness) allows more versatility than other organisms commonly used in aquatic toxicity tests. It also allows the monitoring of effluents and receiving waters from freshwater or estuarine sources without dilution or adjustment.