Decreased emodepside sensitivity in unc-49 γ-aminobutyric acid (GABA)-receptor-deficient Caenorhabditis elegans.
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 GABA(A)-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.
Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Königsweg 67, 14163 Berlin, Germany.
Sandra M
SM
Miltsch
Jürgen
J
Krücken
Janina
J
Demeler
I Jana I
IJ
Janssen
Nina
N
Krüger
Achim
A
Harder
Georg
G
von Samson-Himmelstjerna
D000595:Amino Acid Sequence; D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology*; D017173:Caenorhabditis elegans / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics*; D047630:Depsipeptides / Q000494:pharmacology*; D005260:Female; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D021261:Parasitic Sensitivity Tests; D010802:Phylogeny; D011963:Receptors, GABA-A / Q000737:chemistry / Q000172:deficiency* / Q000235:genetics*; D016415:Sequence Alignment
D000871:Anthelmintics; D029742:Caenorhabditis elegans Proteins; D047630:Depsipeptides; D011963:Receptors, GABA-A; C524882:Unc-49 protein, C elegans; C468987:emodepside