| Abstract No.: | A-B1055 |
| Country: | Canada |
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| Title: | DEVELOPING A CLASS OF NEMATOCIDES THAT TARGET NEMATODE-SPECIFIC ACETYLCHOLINE-GATED CHLORIDE CHANNELS |
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| Authors/Affiliations: | 1 Claudia Wever*; 1 Joseph Dent;
1 McGill University, Montreal, QC, Canada
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| Content: | Nematodes cause disease in both humans and animals in the forms of river-blindness and heartworm respectively. Although there are successful antiparasitic drugs, resistance is beginning to reduce their effectiveness. Many of these successful antiparasitic drugs, including Ivermectin, target ion channels. The success of these drugs depends on their specificity to the target organism and their capacity to slow the onset of resistance. We have identified a novel class of acetylcholine-gated chloride (ACC) ion channels in Caenorhabditis elegans (C. elegans). These channels are specific to worms and are not targets of previously known pesticides. The class of ACCs comprises 8 subunits which is beneficial because a gene family that represents multiple targets of a single drug would cause the development of resistance to slow. A drug that targets these channels is therefore predicted to be effective and safe, and consequently, we think the ACCs are promising drug target candidates.
Objectives: The goal of the project is to test the validity of these ACC subunits as targets for antiparasitic drugs. One part of the project is to determine the pattern of expression of all 8 ACC subunits. A second part of the project is to determine the outcome of over-exciting the ACC channels. Since these are anion (chloride) channels, permanent over-excitation of the ACC channels would cause the cells to remain in a permanently unexcitable state. A third part of the project is to perform high-throughput drug screens to determine what chemicals function as agonists of these channels.
Materials and Methods: The expression pattern of the ACC subunits will be determined via microinjection of promoter-GFP gene fusions. To test what occurs when ACCs are overexcited, we will exploit an already well-known system; Ivermectin is known to overexcite glutamate gated chloride channels (GluCl). In order to simulate over-excitation of ACCs, we will express GluCls in tissues that normally express ACCs. We will do this by microinjecting GluCl coding DNA with ACC promoters into worms that lack all four endogenous GluCl subunits. We will then expose these worms to Ivermectin and observe any effects on the worm. To perform the drug screen, we will express the ACC subunits in cultured cells and in oocytes. We will conduct both electrophysiological experiments and optical screens using ion-sensitive dyes to determine what compounds are agonists of the ACC channels.
Results: We have determined the expression pattern for 6 of the 8 subunits. Some subunits show promising expression patterns; two subunits, Y71 and F47, are expressed in approximately 20 neurons in C. elegans. The second and third parts of the project are ongoing.
Conclusions: Due to the expression of ACCs in a significant fraction of the nervous system, a drug that targets these channels by over-activating them promises to have highly deleterious effects on nematode physiology. Therefore, we conclude that ACCs merit further investigation as antiparasitic drug targets.
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