Dasgupta N et al. (2007) Curr Biol "Hypoxic preconditioning requires the apoptosis protein CED-4 in C. elegans."

Crowder CM, Patel AM, Scott BA, Dasgupta N

[Curr Biol, 2007]

Hypoxic preconditioning (HP) is a rapid and reversible proadaptive response to mild hypoxic exposure with such a response protecting cells from subsequent hypoxic or ischemic insult [1, 2]. HP mechanisms are of great interest because of their therapeutic potential and insight into metabolic adaptation and cell death. HP has been widely demonstrated in the vertebrate subphylum but not in invertebrates [2]. Here, we report that the nematode Caenorhabditis elegans has a potent HP mechanism that protects the organism as well as its neurons and myocytes from hypoxic injury. The time course of C. elegans HP was consistent with vertebrate-delayed HP, appearing 16 hr after preconditioning and lasting at least 36 hr. The apoptosis pathway has been proposed as either a trigger or target of HP. Testing of mutations in the canonical C. elegans apoptosis pathway showed that in general, genes in this pathway are not required for HP. However, loss-of-function mutations in ced-4, which encodes an Apaf-1 homolog, completely blocked HP. RNAi silencing of ced-4 in adult animals immediately preceding preconditioning blocked HP, indicating that CED-4 is required in adults during or after preconditioning. CED-4/Apaf-1 is essential for HP in C. elegans and acts through a mechanism independent of the classical apoptosis pathway.

Zhou J et al. (2022) Nat Cell Biol "A feedback loop engaging propionate catabolism intermediates controls mitochondrial morphology."

Ma T, Duan M, Wang G, Yin Q, Zhou J, Tian F, Yang C, Zhou H, Wang X, Zhang F, Zhang J

[Nat Cell Biol, 2022]

D-2-Hydroxyglutarate (D-2HG) is an -ketoglutarate-derived mitochondrial metabolite that causes D-2-hydroxyglutaric aciduria, a devastating developmental disorder. How D-2HG adversely affects mitochondria is largely unknown. Here, we report that in Caenorhabditis elegans, loss of the D-2HG dehydrogenase DHGD-1 causes D-2HG accumulation and mitochondrial damage. The excess D-2HG leads to a build-up of 3-hydroxypropionate (3-HP), a toxic metabolite in mitochondrial propionate oxidation, by inhibiting the 3-HP dehydrogenase HPHD-1. We demonstrate that 3-HP binds the MICOS subunit MIC60 (encoded by immt-1) and inhibits its membrane-binding and membrane-shaping activities. We further reveal that dietary and gut bacteria affect mitochondrial health by modulating the host production of 3-HP. These findings identify a feedback loop that links the toxic effects of D-2HG and 3-HP on mitochondria, thus providing important mechanistic insights into human diseases related to D-2HG and 3-HP.

Horn M et al. (2020) iScience "Hexosamine Pathway Activation Improves Protein Homeostasis through the Integrated Stress Response."

Allmeroth K, Denzel SI, Breuer P, Horn M, Miethe S, Antebi A, Srinivasan B, Schiffer I, Karthikaisamy V, Denzel MS

[iScience, 2020]

Activation of the hexosamine pathway (HP) through gain-of-function mutations in its rate-limiting enzyme glutamine fructose-6-phosphate amidotransferase (GFAT-1) ameliorates proteotoxicity and increases lifespan in Caenorhabditis elegans. Here, we investigate the role of the HP in mammalian protein quality control. In mouse neuronal cells, elevation of HP activity led to phosphorylation of both PERK and eIF2 as well as downstream ATF4 activation, identifying the HP as a modulator of the integrated stress response (ISR). Increasing uridine 5'-diphospho-N-acetyl-D-glucosamine (UDP-GlcNAc) levels through GFAT1 gain-of-function mutations or supplementation with the precursor GlcNAc reduces aggregation of the polyglutamine (polyQ) protein Ataxin-3. Blocking PERK signaling or autophagy suppresses this effect. In C.elegans, overexpression of gfat-1 likewise activates the ISR. Consistently, co-overexpression of gfat-1 and proteotoxic polyQ peptides in muscles reveals a strong protective cell-autonomous role of the HP. Thus, the HP has a conserved role in improving protein quality control through modulation of the ISR.

Rohela M et al. (2006) Southeast Asian J Trop Med Public Health "Eye lesion caused by adult Brugia malayi: a first case reported in a child from Malaysia."

Jamaiah I, Rohela M, Yaw CC

[Southeast Asian J Trop Med Public Health, 2006]

We are reporting a case of an eye lesion caused by an adult Brugia malayi. The patient was a 3-year-old Chinese boy from Kemaman District, Terengganu, Peninsular Malaysia. He presented with a one week history of redness and palpebral swelling of his right eye. He claimed that he could see a worm in his right eye beneath the conjunctiva. He had no history of traveling overseas and the family kept dogs at home. He was referred from Kemaman Hospital to the eye clinic of Hospital Tengku Ampuan Afzan, Kuantan, Pahang, Malaysia. On examination by the ophthalmologist, he was found to have a subconjunctival worm in his right eye. Full blood count revealed eosinophilia (10%). Four worm fragments, each about 1 cm long were removed from his right eye under general anesthesia. A thick blood smear stained with Giemsa was positive for microfilariae of Brugia malayi. A Brugia Rapid test done was positive. He was treated with diethylcarbamazine.

Asif, Muhammad Zaka et al. (2021) MicroPubl Biol

Van der Gaag, Victoria L., Edison, Arthur S., Muzio, Cole J., Asif, Muhammad Zaka, Nocilla, Kelsey A., Guo, Jane

[MicroPubl Biol, 2021]

1-Hydroxyphenazine (1-HP) is a small molecule produced by Pseudomonas aeruginosa, a bacterium that is used for pathogenesis models in C. elegans (Cezairliyan et al., 2013; Mahajan-Miklos, Tan, Rahme, & Ausubel, 1999). 1-HP is an especially interesting toxin to study as it has been shown to interact with human cells causing ciliary-slowing associated with dyskinesia and ciliostasis (Wilson et al., 1987). Prior research in our lab has shown that this molecule is toxic to C. elegans, with an LD50 between 150 and 200 M, but C. elegans can glycosylate 1-HP, which detoxifies the molecule (Stupp et al., 2013).

Mao XR et al. (2010) Mol Cell Biol "Protein misfolding induces hypoxic preconditioning via a subset of the unfolded protein response machinery."

Crowder CM, Mao XR

[Mol Cell Biol, 2010]

Prolonged cellular hypoxia results in energy failure and ultimately cell death. However, less-severe hypoxia can induce a cytoprotective response termed hypoxic preconditioning (HP). The unfolded protein response pathway (UPR) has been known for some time to respond to hypoxia and regulate hypoxic sensitivity; however, the role of the UPR, if any, in HP essentially has been unexplored. We have shown previously that a sublethal hypoxic exposure of the nematode Caenorhabditis elegans induces a protein chaperone component of the UPR (L. L. Anderson, X. Mao, B. A. Scott, and C. M. Crowder, Science 323:630-633, 2009). Here, we show that HP induces the UPR and that the pharmacological induction of misfolded proteins is itself sufficient to stimulate a delayed protective response to hypoxic injury that requires the UPR pathway proteins IRE-1, XBP-1, and ATF-6. HP also required IRE-1 but not XBP-1 or ATF-6; instead, GCN-2, which is known to suppress translation and induce an adaptive transcriptional response under conditions of UPR activation or amino acid deprivation, was required for HP. The phosphorylation of the translation factor eIF2, an established mechanism of GCN-2-mediated translational suppression, was not necessary for HP. These data suggest a model where hypoxia-induced misfolded proteins trigger the activation of IRE-1, which along with GCN-2 controls an adaptive response that is essential to HP.

Jang SH et al. (2004) Biotechnol Lett "Antinematodal activity and the mechanism of the antimicrobial peptide, HP (2-20), against Caenorhabditis elegans."

Lee DG, Hahm KS, Park SC, Park Y, Kim PI, Jang SH

[Biotechnol Lett, 2004]

The peptide HP (2-20), derived from the N-terminal sequence of Helicobacter pylori ribosomal protein L1 (RPL1), has a nematicidal activity against eggs and worms of Caenorhabditis elegans. Eggs treated with HP (2-20) (69%) has a higher fluorescence intensity with propidium iodide staining, which was similar to that of melittin (82%) but higher than untreated cells (5.7%). Confocal microscopy showed that the peptides were located in the shell of the eggs and the inner and outer surfaces of the worms. HP (2-20) therefore may exert its antinematodal activity by disrupting the structure of the egg's shell and the cell membrane via pore formation or by direct interaction with the lipid bilayers in a detergent-like manner.

Ruegenberg S et al. (2021) Nat Commun "Protein kinase A controls the hexosamine pathway by tuning the feedback inhibition of GFAT-1."

Baumann U, Denzel MS, Ruegenberg S, Atanassov I, Mayr FAMC

[Nat Commun, 2021]

The hexosamine pathway (HP) is a key anabolic pathway whose product uridine 5'-diphospho-N-acetyl-D-glucosamine (UDP-GlcNAc) is an essential precursor for glycosylation processes in mammals. It modulates the ER stress response and HP activation extends lifespan in Caenorhabditis elegans. The highly conserved glutamine fructose-6-phosphate amidotransferase 1 (GFAT-1) is the rate-limiting HP enzyme. GFAT-1 activity is modulated by UDP-GlcNAc feedback inhibition and via phosphorylation by protein kinase A (PKA). Molecular consequences of GFAT-1 phosphorylation, however, remain poorly understood. Here, we identify the GFAT-1 R203H substitution that elevates UDP-GlcNAc levels in C. elegans. In human GFAT-1, the R203H substitution interferes with UDP-GlcNAc inhibition and with PKA-mediated Ser205 phosphorylation. Our data indicate that phosphorylation affects the interactions of the two GFAT-1 domains to control catalytic activity. Notably, Ser205 phosphorylation has two discernible effects: it lowers baseline GFAT-1 activity and abolishes UDP-GlcNAc feedback inhibition. PKA controls the HP by uncoupling the metabolic feedback loop of GFAT-1.

Wojtovich AP et al. (2012) FEBS Lett "Mitochondrial ATP-sensitive potassium channel activity and hypoxic preconditioning are independent of an inwardly rectifying potassium channel subunit in Caenorhabditis elegans."

Wojtovich AP, Nehrke K, DiStefano P, Sherman T, Brookes PS

[FEBS Lett, 2012]

Hypoxic preconditioning (HP) is an evolutionarily-conserved mechanism that protects an organism against stress. The mitochondrial ATP-sensitive K(+) channel (mK(ATP)) plays an essential role in the protective signaling, but remains molecularly undefined. Several lines of evidence suggest that mK(ATP) may arise from an inward rectifying K(+) channel (Kir). The genetic model organism Caenorhabditis elegans exhibits HP and displays mK(ATP) activity. Here, we investigate the tissue expression profile of the three C. elegans Kir genes and demonstrate that mutant strains where the irk genes have been deleted either individually or in combination can be protected by HP and exhibit robust mK(ATP) channel activity in purified mitochondria. These data suggest that the mK(ATP) in C. elegans does not arise from a Kir derived channel.

Asif MZ et al. (2024) Chem Res Toxicol "Role of UDP-Glycosyltransferase (ugt) Genes in Detoxification and Glycosylation of 1-Hydroxyphenazine (1-HP) in Caenorhabditis elegans."

Smadi Y, Shah M, Asif MZ, Parnes M, Leach FE, Hafeez Z, Glushka JN, Manson A, Edison AS, Nocilla KA, Ngo L

[Chem Res Toxicol, 2024]

<i>Caenorhabditis elegans</i> is a useful model organism to study the xenobiotic detoxification pathways of various natural and synthetic toxins, but the mechanisms of phase II detoxification are understudied. 1-Hydroxyphenazine (1-HP), a toxin produced by the bacterium <i>Pseudomonas aeruginosa</i>, kills <i>C. elegans</i>. We previously showed that <i>C. elegans</i> detoxifies 1-HP by adding one, two, or three glucose molecules in N2 worms. Our current study evaluates the roles that some UDP-glycosyltransferase (<i>ugt</i>) genes play in 1-HP detoxification. We show that <i>ugt-23</i> and <i>ugt-49</i> knockout mutants are more sensitive to 1-HP than reference strains N2 or PD1074. Our data also show that <i>ugt-23</i> knockout mutants produce reduced amounts of the trisaccharide sugars, while the <i>ugt-49</i> knockout mutants produce reduced amounts of all 1-HP derivatives except for the glucopyranosyl product compared to the reference strains. We characterized the structure of the trisaccharide sugar phenazines made by <i>C. elegans</i> and showed that one of the sugar modifications contains an <i>N</i>-acetylglucosamine (GlcNAc) in place of glucose. This implies broad specificity regarding UGT function and the role of genes other than <i>ogt-1</i> in adding GlcNAc, at least in small-molecule detoxification.