Decreased emodepside sensitivity in unc-49 γ-aminobutyric acid (GABA)-receptor-deficient Caenorhabditis elegans

• Published in: International journal for parasitology Vol. 42; no. 8; pp. 761 - 770
• Main Authors: Miltsch, Sandra M., Krücken, Jürgen, Demeler, Janina, Janssen, I. Jana I., Krüger, Nina, Harder, Achim, von Samson-Himmelstjerna, Georg
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.07.2012; Elsevier
• Subjects: Amino Acid Sequence; Animals; anthelmintics; Anthelmintics - pharmacology; Biological and medical sciences; Caenorhabditis elegans; Caenorhabditis elegans - classification; Caenorhabditis elegans - drug effects; Caenorhabditis elegans - genetics; Caenorhabditis elegans - metabolism; Caenorhabditis elegans Proteins - chemistry; Caenorhabditis elegans Proteins - genetics; complementary DNA; Depsipeptides - pharmacology; Emodepside; Female; Fundamental and applied biological sciences. Psychology; GABA-receptor; gamma-aminobutyric acid; genes; Life cycle. Host-agent relationship. Pathogenesis; Male; mechanism of action; Molecular Sequence Data; mutants; Mutation; nucleotide sequences; Parasitic Sensitivity Tests; phenotype; Phylogeny; Protozoa; receptors; Receptors, GABA-A - chemistry; Receptors, GABA-A - deficiency; Receptors, GABA-A - genetics; Rescue; Sequence Alignment; Toxocara canis; unc-49; Rescue; Toxocara canis; Caenorhabditis elegans; unc-49; GABA-receptor; Emodepside; Helmintha; GABA; Parasite; Nemathelminthia; Invertebrata; Nematoda
• ISSN: 0020-7519; 1879-0135
• DOI: 10.1016/j.ijpara.2012.05.009

[Display omitted] ► Caenorhabditis elegans GABA-receptor UNC-49 loss of function strains showed decreased susceptibility on emodepside. ► C. elegans emodepside susceptible phenotype was restored with the unc-49B cDNA from the parasite Toxocara canis. ► First known complete specific rescue reported in C. elegans with a gene from a clade III parasitic nematode. Emodepside, a semi-synthetic derivative of PF1022A, belongs to a new class of anthelmintic drugs, the cyclooctadepsipeptides, and shows good efficacy against macrocyclic lactone-, levamisole- or benzimidazole-resistant nematode populations. Although putative receptors for emodepside have already been discovered, its mode of action is still not fully understood. The involvement of the γ-aminobutyric acid (GABA)-receptor on the PF1022A mode of action has previously been postulated. Therefore, a possible role of the GABA-receptor, unc-49, in the mode of action of emodepside was investigated using two different Caenorhabditis elegans in vitro assays, a motility assay and a development assay. It was found that there is a clearly reduced sensitivity against emodepside of strains carrying a GABA-receptor, unc-49, loss of function mutation compared with N2 wild type C. elegans. To transfer these results from the model system to parasitic nematodes, the Toxocara canis unc-49B cDNA sequence was identified and used in a rescue experiment. The emodepside-susceptible phenotype could be fully rescued by injection of the T. canis unc-49B cDNA sequence. We believe that this is the first functional rescue of a C. elegans mutant strain with a gene from a clade III parasitic nematode. These findings, together with the earlier data on GABA-receptor binding of PF1022A, suggest that the GABAA-receptor UNC-49 is associated with the emodepside mode of action. However, the only partially resistant phenotype of the loss of function mutants indicates that other pathways play a more significant role.