Bennett JL et al. (1988) Parasitol Today "Pharmacology of ivermectin."

Williams JF, Bennett JL, Dave V

[Parasitol Today, 1988]

Ivermectin is a semi-synthetic macrocyclic lactone (Fig. I) active in single low doses against many parasites - particularly nematodes and arthropods. It has been registered for animal health use since early 1985, and was earlier this year approved for human use by the French Directorate o f Pharmacy and Drugs. Of particular interest is ivermectin's potential as a micro filaricide for treatment o f onchocerciasis. Clinical trials leave little doubt about the potential o f ivermectin as a therapeutic tool for symptomatic relief from the effects o f infection with Onchocerca volvulus, and the drug is also recognized to have potential in reducing transmission o f the parasite. The manufacturers (Merck, Sharp and Dohme) recently arranged to provide the drug free o f charge to the WHO for mass trials against onchocerciasis in 12 African and Central American countries. In this article we focus on the pharmacological properties o f ivermectin, with a brief consideration of its absorption, fate, excretion and side-effects, and a discussion o f its micro filaricidal action.

Delgado SE et al. (2023) eNeuro "Microbiota and diapause-induced neuroprotection share a dependency on calcium but differ in their effects on mitochondrial morphology."

Chiu CQ, Delgado SE, Calixto A, Urrutia A, Gutzwiller F

[eNeuro, 2023]

The balance between the degeneration and regeneration of damaged neurons depends on intrinsic and environmental variables. In nematodes, neuronal degeneration can be reversed by intestinal GABA and lactate-producing bacteria, or by hibernation driven by food deprivation. However, it is not known whether these neuroprotective interventions share common pathways to drive regenerative outcomes. Using a well-established neuronal degeneration model in the touch circuit of the bacterivore nematode <i>Caenorhabditis elegans,</i> we investigate the mechanistic commonalities between neuroprotection offered by the gut microbiota and hunger-induced diapause. Using transcriptomics approaches coupled to reverse genetics, we identify genes that are necessary for neuroprotection conferred by the microbiota. Some of these genes establish links between the microbiota and calcium homeostasis, diapause entry, and neuronal function and development. We find that extracellular calcium as well as mitochondrial MCU-1 and reticular SCA-1 calcium transporters are needed for neuroprotection by bacteria and by diapause entry. While the benefits exerted by neuroprotective bacteria requires mitochondrial function, the diet itself does not affect mitochondrial size. In contrast, diapause increases both the number and length of mitochondria. These results suggest that metabolically-induced neuronal protection may occur via multiple mechanisms.<b>Significance statement</b>Calcium signaling and mitochondrial function have recently been suggested to promote axonal growth following neuronal damage, but the underlying mechanisms and physiological significance are unclear. Combining transcriptomics, genetics and cell biological approaches in a simple animal model of axonal degeneration and regeneration, we demonstrate that neuronal repair conferred by two different metabolic processes occurs in diverse ways, requiring differential changes in mitochondrial function and calcium homeostasis. Furthermore, this work shows that neuroprotection can be additive, providing a new conceptual framework for developing therapeutic interventions in neurodegenerative conditions that leverage the intersection of metabolism, microbiota and mitochondrial function.

Kwiatkowski AV et al. (2010) Proc Natl Acad Sci U S A "In vitro and in vivo reconstitution of the cadherin-catenin-actin complex from Caenorhabditis elegans."

Hardin J, Weis WI, Nelson WJ, Choi HJ, Lynch AM, Kwiatkowski AV, Benjamin JM, Pokutta S, Maiden SL

[Proc Natl Acad Sci U S A, 2010]

The ternary complex of cadherin, beta-catenin, and alpha-catenin regulates actin-dependent cell-cell adhesion. alpha-Catenin can bind beta-catenin and F-actin, but in mammals alpha-catenin either binds beta-catenin as a monomer or F-actin as a homodimer. It is not known if this conformational regulation of alpha-catenin is evolutionarily conserved. The Caenorhabditis elegans alpha-catenin homolog HMP-1 is essential for actin-dependent epidermal enclosure and embryo elongation. Here we show that HMP-1 is a monomer with a functional C-terminal F-actin binding domain. However, neither full-length HMP-1 nor a ternary complex of HMP-1-HMP-2(beta-catenin)-HMR-1(cadherin) bind F-actin in vitro, suggesting that HMP-1 is auto-inhibited. Truncation of either the F-actin or HMP-2 binding domain of HMP-1 disrupts C. elegans development, indicating that HMP-1 must be able to bind F-actin and HMP-2 to function in vivo. Our study defines evolutionarily conserved properties of alpha-catenin and suggests that multiple mechanisms regulate alpha-catenin binding to F-actin.

Wang A et al. (2021) BMC Genomics "Genome-wide characterization, evolution, structure, and expression analysis of the F-box genes in Caenorhabditis."

Chen W, Tao S, Wang A

[BMC Genomics, 2021]

Background: F-box proteins represent a diverse class of adaptor proteins of the ubiquitin-proteasome system (UPS) that play critical roles in the cell cycle, signal transduction, and immune response by removing or modifying cellular regulators. Among closely related organisms of the Caenorhabditis genus, remarkable divergence in F-box gene copy numbers was caused by sizeable species-specific expansion and contraction. Although F-box gene number expansion plays a vital role in shaping genomic diversity, little is known about molecular evolutionary mechanisms responsible for substantial differences in gene number of F-box genes and their functional diversification in Caenorhabditis. Here, we performed a comprehensive evolution and underlying mechanism analysis of F-box genes in five species of Caenorhabditis genus, including C. brenneri, C. briggsae, C. elegans, C. japonica, and C. remanei.Results: Herein, we identified and characterized 594, 192, 377, 39, 1426 F-box homologs encoding putative F-box proteins in the genome of C. brenneri, C. briggsae, C. elegans, C. japonica, and C. remanei, respectively. Our work suggested that extensive species-specific tandem duplication followed by a small amount of gene loss was the primary mechanism responsible for F-box gene number divergence in Caenorhabditis genus. After F-box gene duplication events occurred, multiple mechanisms have contributed to gene structure divergence, including exon/intron gain/loss, exonization/pseudoexonization, exon/intron boundaries alteration, exon splits, and intron elongation by tandem repeats. Based on high-throughput RNA sequencing data analysis, we proposed that F-box gene functions have diversified by sub-functionalization through highly divergent stage-specific expression patterns in Caenorhabditis species.Conclusions: Massive species-specific tandem duplications and occasional gene loss drove the rapid evolution of the F-box gene family in Caenorhabditis, leading to complex gene structural variation and diversified functions affecting growth and development within and among Caenorhabditis species. In summary, our findings outline the evolution of F-box genes in the Caenorhabditis genome and lay the foundation for future functional studies.

Ono S et al. (2001) J Biol Chem "The C-terminal tail of UNC-60B (actin depolymerizing factor/cofilin) is critical for maintaining its stable association with F-actin and is implicated in the second actin-binding site."

Gernert KM, Weeds AG, McGough A, Bui A, Pope BJ, Benian GM, Ono S, Tolbert VT, Pohl J

[J Biol Chem, 2001]

Actin depolymerizing factor (ADF)/cofilin changes the twist of actin filaments by binding two longitudinally associated actin subunits, In the absence of an atomic model of the ADF/cofilin-F-actin complex, we have identified residues in ADF/cofilin that are essential for filament binding. Here, we have characterized the C-terminal tail of UNC-60B (a nematode ADF/cofilin isoform) as a novel determinant for its association with F-actin, Removal of the C-terminal isoleucine (Ile(152)) by carboxypeptidase A or truncation by mutagenesis eliminated F-actin binding activity but strongly enhanced actin depolymerizing activity, Replacement of Ile(152) by Ala had a similar but less marked effect; F-actin binding was weakened and depolymerizing activity slightly enhanced. Truncation of both Arg(151) and Ile(152) or replacement of Arg(151) with Ala also abolished F-actin binding and enhanced depolymerizing activity. Loss of F-actin binding in these mutants was accompanied by loss or greatly decreased severing activity. All of the variants of UNC-60B interacted with G-actin in an indistinguishable manner from wild type. Cryoelectron microscopy showed that UNC-60B changed the twist of F-actin to a similar extent to vertebrate ADF/cofilins. Helical reconstruction and structural modeling of UNC-60B-F-actin complex reveal how the C terminus of UNC-60B might be involved in one of the two actin-binding sites.

Gabaldon C et al. (2020) mBio "Intergenerational Pathogen-Induced Diapause in Caenorhabditis elegans Is Modulated by mir-243."

Gabaldon C, Gutzwiller F, Calixto A, Palominos MF, Legue M, Verdugo L

[mBio, 2020]

The interaction and communication between bacteria and their hosts modulate many aspects of animal physiology and behavior. Dauer entry as a response to chronic exposure to pathogenic bacteria in <i>Caenorhabditis elegans</i> is an example of a dramatic survival response. This response is dependent on the RNA interference (RNAi) machinery, suggesting the involvement of small RNAs (sRNAs) as effectors. Interestingly, dauer formation occurs after two generations of interaction with two unrelated moderately pathogenic bacteria. Therefore, we sought to discover the identity of <i>C. elegans</i> RNAs involved in pathogen-induced diapause. Using transcriptomics and differential expression analysis of coding and long and small noncoding RNAs, we found that <i>mir-243-3p</i> (the mature form of <i>mir-243</i>) is the only transcript continuously upregulated in animals exposed to both <i>Pseudomonas aeruginosa</i> and <i>Salmonella enterica</i> for two generations. Phenotypic analysis of mutants showed that <i>mir-243</i> is required for dauer formation under pathogenesis but not under starvation. Moreover, DAF-16, a master regulator of defensive responses in the animal and required for dauer formation was found to be necessary for <i>mir-243</i> expression. This work highlights the role of a small noncoding RNA in the intergenerational defensive response against pathogenic bacteria and interkingdom communication.<b>IMPORTANCE</b> Persistent infection of the bacterivore nematode <i>C. elegans</i> with bacteria such as <i>P. aeruginosa</i> and <i>S. enterica</i> makes the worm diapause or hibernate. By doing this, the worm closes its mouth, avoiding infection. This response takes two generations to be implemented. In this work, we looked for genes expressed upon infection that could mediate the worm diapause triggered by pathogens. We identify <i>mir-243-3p</i> as the only transcript commonly upregulated when animals feed on <i>P. aeruginosa</i> and <i>S. enterica</i> for two consecutive generations. Moreover, we demonstrate that <i>mir-243-3p</i> is required for pathogen-induced dauer formation, a new function that has not been previously described for this microRNA (miRNA). We also find that the transcriptional activators DAF-16, PQM-1, and CRH-2 are necessary for the expression of <i>mir-243</i> under pathogenesis. Here we establish a relationship between a small RNA and a developmental change that ensures the survival of a percentage of the progeny.

Jayamani E et al. (2017) Antimicrob Agents Chemother "Characterization of a Francisella tularensis-Caenorhabditis elegans pathosystem for the evaluation of therapeutic compounds."

Ausubel FM, Nau GJ, Kim W, Mylonakis E, Coleman JJ, Okoli I, Lee K, RajaMuthiah R, Tharmalingam N, Hernandez AM, Jayamani E

[Antimicrob Agents Chemother, 2017]

Francisella tularensis is a highly infectious Gram-negative intracellular pathogen that causes tularemia. Because of its potential as a bioterrorism agent, there is a need for new therapeutic agents. We therefore developed a whole animal Caenorhabditis elegans-F. tularensis pathosystem for high throughput screening to identify and characterize potential therapeutic compounds. We found that the C. elegans p38 MAP kinase cascade is involved in the immune response to F. tularensis and we developed a robust F. tularensis-mediated C. elegans killing assay with a Z'-factor consistently &gt;0.5, which was then utilized to screen a library of FDA approved compounds that included 1,760 small molecules. In addition to clinically used antibiotics, 5 FDA-approved drugs were also identified as potential hits, including the anti-inflammatory drug diflunisal that showed anti-F. tularensis activity in vitro Moreover, the NSAID diflunisal, at 4X MIC, blocked the replication of a F. tularensis live vaccine strain (LVS) in primary human macrophages and non-phagocytic cells. Diflunisal was non-toxic to human erythrocytes and HepG2 human liver cells at concentrations 32-g/ml. Finally, diflunisal exhibited synergetic activity with the antibiotic ciprofloxacin in both a checkerboard assay and a macrophage infection assay. In conclusion, the liquid C. elegans - F. tularensis LVS assay described here allows screening for anti-F. tularensis compounds and suggests that diflunisal could potentially be repurposed for the management of tularemia.

Chisholm AD et al. (1989) Genes Dev "The mab-9 gene controls the fate of B, the major male-specific blast cell in the tail region of Caenorhabditis elegans."

Chisholm AD, Hodgkin JA

[Genes Dev, 1989]

The internal structures of the tail of male Caenorhabditis elegans nematodes are made by the descendants of four cells (B, Y, F, and U) which divide only in males. These cells are also present in hermaphrodites, where they have minor structural roles in the rectum. Here we show that the gene mab-9 is required for the correct development of two of these male-specific blast cells, B and F. In mutant males, the lineages of B and F resemble those of Y and U, respectively. These abnormal lineages lead to grossly defective male tails. We suggest that in mab-9 males the identities of B and F are transformed into Y and U, their respective anterior neighbors. The case for the F-to-U transformation is less strong than for the B-to-Y transformation because the wild-type lineages of F and U are very similar. Some mab-9 hermaphrodites are constipated as a result of abnormal rectal structure. This may be the result of an analogous fate transformation. mab-9 worms of both sexes are slightly uncoordinated. We propose that the fates of the four rectal cells are initially specified as two pairs (B and Y, F and U) and that the function of mab-9 in both sexes is to differentiate the posterior member of each pair from its anterior neighbor.

Shukla VK et al. (2015) Biochem J "Solution structures and dynamics of ADF/cofilins UNC-60A and UNC-60B from Caenorhabditis elegans."

Ono S, Shukla VK, Jain A, Maheshwari D, Kabra A, Kumar D, Tripathi S, Arora A, Yadav R

[Biochem J, 2015]

The nematode Caenorhabditis elegans has two ADF (actin-depolymerizing factor)/cofilin isoforms, UNC-60A and UNC-60B, which are expressed by the unc60 gene by alternative splicing. UNC-60A has higher activity to cause net depolymerization, and to inhibit polymerization, than UNC-60B. UNC-60B, on the other hand, shows much stronger severing activity than UNC-60A. To understand the structural basis of their functional differences, we have determined the solution structures of UNC-60A and UNC-60B proteins and characterized their backbone dynamics. Both UNC-60A and UNC-60B show a conserved ADF/cofilin fold. The G-actin (globular actin)-binding regions of the two proteins are structurally and dynamically conserved. Accordingly, UNC-60A and UNC-60B individually bind to rabbit muscle ADP-G-actin with high affinities, with Kd values of 32.25 nM and 8.62 nM respectively. The primary differences between these strong and weak severing proteins were observed in the orientation and dynamics of the F-actin (filamentous actin)-binding loop (F-loop). In the strong severing activity isoform UNC-60B, the orientation of the F-loop was towards the recently identified F-loop-binding region on F-actin, and the F-loop was relatively more flexible with 14 residues showing motions on a nanosecond-picosecond timescale. In contrast, in the weak severing protein isoform UNC-60A, the orientation of the F-loop was away from the F-loop-binding region and inclined towards its own C-terminal and strand 6. It was also relatively less flexible with only five residues showing motions on a nanosecond-picosecond timescale. These differences in structure and dynamics seem to directly correlate with the differential F-actin site-binding and severing properties of UNC-60A and UNC-60B, and other related ADF/cofilin proteins.

Hoang HD et al. (2013) PLoS Genet "A heterogeneous mixture of F-series prostaglandins promotes sperm guidance in the Caenorhabditis elegans reproductive tract."

Dorand D, Prasain JK, Miller MA, Hoang HD

[PLoS Genet, 2013]

The mechanisms that guide motile sperm through the female reproductive tract to oocytes are not well understood. We have shown that Caenorhabditis elegans oocytes synthesize sperm guiding F-series prostaglandins from polyunsaturated fatty acid (PUFA) precursors provided in yolk lipoprotein complexes. Here we use genetics and electrospray ionization tandem mass spectrometry to partially delineate F-series prostaglandin metabolism pathways. We show that omega-6 and omega-3 PUFAs, including arachidonic and eicosapentaenoic acids, are converted into more than 10 structurally related F-series prostaglandins, which function collectively and largely redundantly to promote sperm guidance. Disruption of omega-3 PUFA synthesis triggers compensatory up-regulation of prostaglandins derived from omega-6 PUFAs. C. elegans F-series prostaglandin synthesis involves biochemical mechanisms distinct from those in mammalian cyclooxygenase-dependent pathways, yet PGF(2) stereoisomers are still synthesized. A comparison of F-series prostaglandins in C. elegans and mouse tissues reveals shared features. Finally, we show that a conserved cytochrome P450 enzyme, whose human homolog is implicated in Bietti's Crystalline Dystrophy, negatively regulates prostaglandin synthesis. These results support the model that multiple cyclooxygenase-independent prostaglandins function together to promote sperm motility important for fertilization. This cyclooxygenase-independent pathway for F-series synthesis may be conserved.