Cationic Amphiphilic Drugs (CADs) severely disrupt lysosomal function, which leads to a cellular pathology characterized by excess phospholipids called phospholipidosis. Through a forward genetic screen and mining of published datasets, we discovered that CADs induce the expression of the CYP-35B family of cytochrome P450s and the PGP-13 p-glycoprotein pump via the nuclear receptors NHR-70 and NHR-107 in the nematode C. elegans. A pgp-13 fluorescent reporter revealed hundreds of human drugs that upregulate the CAD defense system in vivo. Chemoinformatic analyses indicate that the pgp-13 reporter may be useful in identifying CADs that have pathogenic potential in humans. Mutant analyses coupled to metabolomics and structural modeling show that the CYP-35Bs are necessary and sufficient for CAD metabolism, and that CYP-35B2 D311 is key in mediating electrostatic interactions with the positively charged CADs. We also show that CAD metabolites are effluxed via PGP-13 acting partially redundantly with PGP-14 and that an intact defense system is necessary to resist CAD-induced pathology. Finally, we demonstrate that bacteria that likely cohabitate with C. elegans in nature trigger the CAD defense system, providing a plausible explanation for why a pathway that protects against anthropogenic small molecules exists in nematodes.

Parasitic nematodes are a significant concern in human and veterinary medicine as well as agriculture. In this study, we prepared twenty-seven 5-phenyl-1H-indole derivatives bearing various substituents on the phenyl ring and assessed their efficacy against nematodes. Using Caenorhabditis elegans, we selected the most potent compounds and evaluated their toxicity on selected animal and plant-parasitic nematode species. Compounds featuring 4-chloro, 4-fluoro, and 4-trifluoromethoxy groups on the phenyl ring inhibited the motility of exsheathed L3 larvae of Hemonchus contortus while exhibiting limited cytotoxicity in mammalian cell cultures. These compounds showed similar effects against the plant-parasitic nematodes Heterodera schachtii and Ditylenchus destructor, albeit with reduced potency. We propose that the compounds might act as inhibitors of mitochondrial complex II as inferred from molecular modeling, decreased mitochondrial membrane potential, and reduced activity in C. elegans complex II mutants.

Phenotypic screens of living organisms often require real-time, high spatial resolution imaging. We report here on the design and application of a line-scan imaging platform that enables bright-field imaging of live nematodes using a 96-well plate configuration. The system optics are such that each individual well is projected across the full field of view of a 4 K line scanning camera. To minimize motional artifacts, the camera system is translated, while the sample is kept stationary. We discuss the challenges in establishing flat field illumination, image registration and stitching, and the opportunities that this platform has enabled for phenotypic screens of living systems.

Since its inception as a model system, Caenorhabditis elegans has provided insight about the mechanism of action of drugs through genetic analyses. With the arrival of diverse drug-like small molecule libraries sometime later, the worm also became a platform for drug discovery that was previously inaccessible to academics. Here, the history of larger-scale drug screens using C. elegans is reviewed. The current approaches used to identify the targets and targeted pathways of the novel hits from these screens are also discussed. We focus on the development of small molecule tools for biological investigation, the discovery of novel candidate nematicides and anthelmintics, and touch on screens related to other areas of biology, including neurodegeneration. Finally, we draw attention to the fundamental aspects of C. elegans biology that lends itself to chemical genetic research. When combined with diverse small molecule libraries, the worm's tractability and genetic power make it an unparalleled whole-animal model system for early-stage drug discovery.

Widespread anthelmintic resistance has complicated the management of parasitic nematodes. Resistance to the benzimidazole (BZ) drug class is nearly ubiquitous in many species and is associated with mutations in beta-tubulin genes. However, mutations in beta-tubulin alone do not fully explain all BZ resistance. We performed a genome-wide association study using a genetically diverse panel of Caenorhabditis elegans strains to identify loci that contribute to resistance to the BZ drug thiabendazole (TBZ). We identified a quantitative trait locus (QTL) on chromosome V independent of all beta-tubulin genes and overlapping with two promising candidate genes, the cytochrome P450 gene cyp-35D1 and the nuclear hormone receptor nhr-176. Both genes were previously demonstrated to play a role in TBZ metabolism. NHR-176 binds TBZ and induces the expression of CYP-35D1, which metabolizes TBZ. We generated single gene deletions of cyp-35D1 and nhr-176 and found that both genes play a role in TBZ response. A predicted high-impact lysine-to-glutamate substitution at position 267 (K267E) in CYP-35D1 was identified in a sensitive strain, and reciprocal allele replacement strains in different genetic backgrounds were used to show that the lysine allele conferred increased TBZ resistance. Using competitive fitness assays, we found that neither allele was deleterious, but the lysine allele was selected in the presence of TBZ. Additionally, we found that the lysine allele significantly increased the rate of TBZ metabolism compared to the glutamate allele. Moreover, yeast expression assays showed that the lysine version of CYP-35D1 had twice the enzymatic activity of the glutamate allele. To connect our results to parasitic nematodes, we analyzed four Haemonchus contortus cytochrome P450 orthologs but did not find variation at the 267 position in fenbendazole-resistant populations. Overall, we confirmed that variation in this cytochrome P450 gene is the first locus independent of beta-tubulin to play a role in BZ resistance.

Left unchecked, plant-parasitic nematodes have the potential to devastate crops globally. Highly effective but non-selective nematicides are justifiably being phased-out, leaving farmers with limited options for managing nematode infestation. Here, we report our discovery of a 1,3,4-oxadiazole thioether scaffold called Cyprocide that selectively kills nematodes including diverse species of plant-parasitic nematodes. Cyprocide is bioactivated into a lethal reactive electrophilic metabolite by specific nematode cytochrome P450 enzymes. Cyprocide fails to kill organisms beyond nematodes, suggesting that the targeted lethality of this pro-nematicide derives from P450 substrate selectivity. Our findings demonstrate that Cyprocide is a selective nematicidal scaffold with broad-spectrum activity that holds the potential to help safeguard our global food supply.

Amyloids are associated with over 50 human diseases and have inspired significant effort to identify small molecule remedies. Here, we present an in vivo platform that efficiently yields small molecule inhibitors of amyloid formation. We previously identified small molecules that kill the nematode C. elegans by forming membrane-piercing crystals in the pharynx cuticle, which is rich in amyloid-like material. We show here that many of these molecules are known amyloid-binders whose crystal-formation in the pharynx can be blocked by amyloid-binding dyes. We asked whether this phenomenon could be exploited to identify molecules that interfere with the ability of amyloids to seed higher-order structures. We therefore screened 2560 compounds and found 85 crystal suppressors, 47% of which inhibit amyloid formation. This hit rate far exceeds other screening methodologies. Hence, in vivo screens for suppressors of crystal formation in C. elegans can efficiently reveal small molecules with amyloid-inhibiting potential.

ABSTRACT Left unchecked, plant-parasitic nematodes have the potential to devastate crops globally. Highly effective but non-selective nematicides are justifiably being phased-out, leaving farmers with limited options for managing nematode infestation. Here, we report our discovery of a 1,3,4-oxadiazole thioether scaffold called Cyprocide that selectively kills diverse plant-parasitic nematodes. Cyprocide is bioactivated into a lethal reactive electrophilic metabolite by specific nematode cytochrome P450 enzymes. Because Cyprocide fails to kill non-target organisms, we infer that the targeted lethality of this pro-nematicide derives from P450 substrate selectivity. Our findings demonstrate that Cyprocide is a selective nematicidal scaffold with broad-spectrum activity that holds the potential to help safeguard our global food supply.

Parasitic nematodes are a major threat to global food security, particularly as the world amasses 10 billion people amid limited arable land(1-4). Most traditional nematicides have been banned owing to poor nematode selectivity, leaving farmers with inadequate means of pest control(4-12). Here we use the model nematode Caenorhabditis elegans to identify a family of selective imidazothiazole nematicides, called selectivins, that undergo cytochrome-p450-mediated bioactivation in nematodes. At low parts-per-million concentrations, selectivins perform comparably well with commercial nematicides to control root infection by Meloidogyne incognita, a highly destructive plant-parasitic nematode. Tests against numerous phylogenetically diverse non-target systems demonstrate that selectivins are more nematode-selective than most marketed nematicides. Selectivins are first-in-class bioactivated nematode controls that provide efficacy and nematode selectivity.

Nematode worms that parasitize plants ravage food crops and threaten global food security. Conventional nematode control relies on agrochemicals that are broadly toxic, so less-risky strategies are needed. Benign precursor chemicals that are metabolically converted to lethal products selectively in worm tissue could be the solution.

The cuticles of ecdysozoan animals are barriers to material loss and xenobiotic insult. Key to this barrier is lipid content, the establishment of which is poorly understood. Here, we show that the p-glycoprotein PGP-14 functions coincidently with the sphingomyelin synthase SMS-5 to establish a polar lipid barrier within the pharyngeal cuticle of the nematode C. elegans. We show that PGP-14 and SMS-5 are coincidentally expressed in the epithelium that surrounds the anterior pharyngeal cuticle where PGP-14 localizes to the apical membrane. pgp-14 and sms-5 also peak in expression at the time of new cuticle synthesis. Loss of PGP-14 and SMS-5 dramatically reduces pharyngeal cuticle staining by Nile Red, a key marker of polar lipids, and coincidently alters the nematode's response to a wide-range of xenobiotics. We infer that PGP-14 exports polar lipids into the developing pharyngeal cuticle in an SMS-5-dependent manner to safeguard the nematode from environmental insult.

Nematode parasites of humans and livestock pose a significant burden to human health, economic development, and food security. Anthelmintic drug resistance is widespread among parasites of livestock and many nematode parasites of humans lack effective treatments. Here, we present a nitrophenyl-piperazine scaffold that induces motor defects rapidly in the model nematode Caenorhabditis elegans . We call this scaffold Nemacol and show that it inhibits the vesicular acetylcholine transporter (VAChT), a target recognized by commercial animal and crop health groups as a viable anthelmintic target. We demonstrate that it is possible to create Nemacol analogs that maintain potent in vivo activity whilst lowering their affinity to the mammalian VAChT 10-fold. We also show that Nemacol enhances the ability of the anthelmintic Ivermectin to paralyze C. elegans and the ruminant nematode parasite Haemonchus contortus . Hence, Nemacol represents a promising new anthelmintic scaffold that acts through a validated anthelmintic target.

Nematode parasites of humans, livestock and crops pose a significant burden on human health and welfare. Alarmingly, parasitic nematodes of animals have rapidly evolved resistance to anthelmintic drugs, and traditional nematicides that protect crops are facing increasing restrictions because of poor phylogenetic selectivity. Here, we present a pipeline that exploits multiple motor outputs of the model nematode C. elegans for nematicide discovery. This pipeline yielded a compound, which we call Nementin, that selectively immobilizes diverse nematode parasites. We find that Nementin induces convulsions by agonizing neuronal dense core vesicle release, which in turn agonizes cholinergic signaling. Consequently, Nementin synergistically enhances the potency of acetylcholinesterase inhibitors that are restricted agrochemicals. Nementin therefore represents a novel candidate nematicide that may improve the selectivity of broad-acting pesticides. One-Sentence Summary A C. elegans-based screening pipeline identifies a selective nematicide that potentiates acetylcholinesterase inhibitors.

Over the 70 years since the introduction of plastic into everyday items, plastic waste has become an increasing problem. With over 360 million tonnes of plastics produced every year, solutions for plastic recycling and plastic waste reduction are sorely needed. Recently, multiple enzymes capable of degrading PET (polyethylene terephthalate) plastic have been identified and engineered. In particular, the enzymes PETase and MHETase from Ideonella sakaiensis depolymerize PET into the two building blocks used for its synthesis, ethylene glycol (EG) and terephthalic acid (TPA). Importantly, EG and TPA can be re-used for PET synthesis allowing complete and sustainable PET recycling. In this study we used Saccharomyces cerevisiae, a species utilized widely in bioindustrial fermentation processes, as a platform to develop a whole-cell catalyst expressing the MHETase enzyme, which converts monohydroxyethyl terephthalate (MHET) into TPA and EG. We assessed six expression architectures and identified those resulting in efficient MHETase expression on the yeast cell surface. We show that the MHETase whole-cell catalyst has activity comparable to recombinant MHETase purified from Escherichia coli. Finally, we demonstrate that surface displayed MHETase is active across a range of pHs, temperatures, and for at least 12 days at room temperature. We demonstrate the feasibility of using S. cerevisiae as a platform for the expression and surface display of PET degrading enzymes and predict that the whole-cell catalyst will be a viable alternative to protein purification-based approaches for plastic degradation.

Microsporidia are a diverse group of fungal-related obligate intracellular parasites that infect most animal phyla. Despite the emerging threat that microsporidia represent to humans and agricultural animals, few reliable treatment options exist. Here, we develop a high-throughput screening method for the identification of chemical inhibitors of microsporidia infection, using liquid cultures of Caenorhabditis elegans infected with the microsporidia species Nematocida parisii . We screen a collection of 2560 FDA-approved compounds and natural products, and identify 11 candidate microsporidia inhibitors. Five compounds prevent microsporidia infection by inhibiting spore firing, whereas one compound, dexrazoxane, slows infection progression. The compounds have in vitro activity against several other microsporidia species, including those known to infect humans. Together, our results highlight the effectiveness of C. elegans as a model host for drug discovery against intracellular pathogens, and provide a scalable high-throughput system for the identification and characterization of microsporidia inhibitors.

Understanding how to pharmacologically manipulate amyloids is an essential step towards managing dozens of amyloid-based human diseases. Here, we present a pipeline that yields small molecule antagonists of amyloidogenesis. Screens for small molecules that perturb the development of the nematode C. elegans revealed 24 distinct small molecule scaffolds that crystalize on the non-luminal face of the pharyngeal cuticle. Consistent with the amyloid-like nature of the pharyngeal cuticle, 25% of these scaffolds are known to bind human amyloids with nanomolar affinity. The growing crystals preferentially disrupt the amyloid-like material within the cuticle but leave its chitin-based matrix relatively intact. We screened a collection of drugs and natural products for those that suppress crystal formation and found 45 distinct scaffolds, 33% of which are known amyloid busters. Screening for pharmacological suppressors of crystal formation therefore represents an inexpensive high-throughput in vivo approach that enriches for small molecules with amyloid-busting potential.

Unsupervised Uniform Manifold Approximation and Projection (UMAP) plots of single cell sequencing data from synchronized Caenorhabditis elegans larvae yield tissue-specific data clusters, some of which are plotted as elongated archipelagos. These archipelagos likely represent a single cell type. I show that the pharyngeal archipelagos express a myriad of asynchronous temporally regulated genes, which likely accounts for their elongated topology. With one archipelago, I show that there is a high correlation between a) the base pair distance between the binding sites of an archipelago-specific transcription factor (HLH-6) and the transcriptional start site of the targeted genes and b) the timing of peak gene expression of those genes that are expressed in an archipelago-specific manner. Despite the correlation being made with only four genes, it prompts the hypothesis that the physical distance between a transcription factor and the relevant transcription start site may be an important factor in determining the temporal onset of transcription and transcript abundance.

Nematode parasites of humans, livestock and crops dramatically impact human health and welfare. Alarmingly, parasitic nematodes of animals have rapidly evolved resistance to anthelmintic drugs, and traditional nematicides that protect crops are facing increasing restrictions because of poor phylogenetic selectivity. Here, we exploit multiple motor outputs of the model nematode C. elegans towards nematicide discovery. This work yielded multiple compounds that selectively kill and/or immobilize diverse nematode parasites. We focus on one compound that induces violent convulsions and paralysis that we call nementin. We find that nementin stimulates neuronal dense core vesicle release, which in turn enhances cholinergic signaling. Consequently, nementin synergistically enhances the potency of widely-used non-selective acetylcholinesterase (AChE) inhibitors, but in a nematode-selective manner. Nementin therefore has the potential to reduce the environmental impact of toxic AChE inhibitors that are used to control nematode infections and infestations.

Nematode parasites of humans, livestock and crops pose a significant burden on human health and welfare. Alarmingly, parasitic nematodes of animals have rapidly evolved resistance to anthelmintic drugs, and traditional nematicides that protect crops are facing increasing restrictions because of poor phylogenetic selectivity. Here, we present a pipeline that exploits multiple motor outputs of the model nematode C. elegans for nematicide discovery. This pipeline yielded multiple compounds that selectively kill and/or immobilize diverse nematode parasites. We focus on one compound that induces violent convulsions and paralysis that we call Nementin. We find that Nementin agonizes neuronal dense core vesicle release, which in turn agonizes cholinergic signaling. Consequently, Nementin synergistically enhances the potency of widely-used non-selective acetylcholinesterase inhibitors (AChEIs), but in a nematode-selective manner. Nementin therefore has the potential to reduce the environmental impact of toxic AChEI pesticides used to control nematode infections and infestations. Significance Statement Parasitic nematodes pose a considerable burden to human health and food security. Small molecules that have traditionally been used to control these parasites have either been banned because of toxicity concerns or are being rendered ineffective because of the evolution of resistance. Significant gaps in our nematicidal toolkit are therefore becoming an alarming problem. Here, we describe our discovery of Nementin, a small molecule that disrupts the nematode nervous system but is ineffective against non-targeted organisms. We find that Nementin also enhances the activity of non-selective pesticides but does so in a nematode-selective manner. Hence, Nementin is an innovative solution to combat parasitic nematodes in a safe and phylum-selective manner. One-Sentence Summary A C. elegans -based screening pipeline identifies a selective nematicide that also potentiates acetylcholinesterase inhibitors.

Plant-parasitic nematodes (PPNs) destroy over 12% of global food crops every year, which equates to roughly 157 billion dollars (USD) lost annually. With a growing global population and limited arable land, controlling PPN infestation is critical for food production. Compounding the challenge of maximizing crop yields are the mounting restrictions on effective pesticides because of a lack of nematode selectivity. Hence, developing new and safe chemical nematicides is vital to food security. In this protocol, the culture and collection of the PPN species Ditylenchus dipsaci are demonstrated. D. dipsaci is both economically damaging and relatively resistant to most modern nematicides. The current work also explains how to use these nematodes in screens for novel small molecule nematicides and reports on data collection and analysis methodologies. The demonstrated pipeline affords a throughput of thousands of compounds per week and can be easily adapted for use with other PPN species such as Pratylenchus penetrans. The techniques described herein can be used to discover new nematicides, which may, in turn, be further developed into highly selective commercial products that safely combat PPNs to help feed an increasingly hungry world.