The Neglected Tropical Diseases (NTDs) include the soil-transmitted helminthiases (STHs) which are caused by diverse groups of intestinal nematodes. The parasites include Ascaris, Trichuris and hookworms. These infections are common. Ascariasis for example, affects 1.4 billion people worldwide and is most common in children between the ages of 3 and 8. Control of these nematode parasites relies on an effective supply of anthelmintics. Taking veterinary medicine as an example, we know that continued use of anthelmintic compounds for mass chemotherapy will lead to drug resistance. There is a need to identify novel target sites for anthelmintic development. Once such site is the nicotinic acetylcholine receptor on the nematode pharynx. We have discovered this receptor does not respond to currently used anrthelmintic drugs. Approach:
The specific aims of this application are: 1. Characterize nAChR responses in A. suum pharynx: using current-, voltage- &patch- clamp techniques. We will test the hypothesis that the A. suum pharynx nAChRs are pharmacologically distinct from the muscle nAChRs activated by cholinergic anthelmintics. 2. Identify &clone pharyngeal specific nicotinic acetylcholine receptor subunits. We will identify the nAChR subunit genes present in the pharynx required to produce functional receptors. 3. Characterize the pharyngeal cholinergic receptors in Xenopus laevis oocytes using voltage- &patch-clamp techniques. We will test the hypothesis that expression of pharyngeal nAChR subunits results in functioning receptors that are pharmacologically similar to those found in vivo. On completion of this project we will have characterized the pharmacology of an important new potential drug target in a parasitic nematode. We will have identified the genes that encode these receptors. Finally, we will have reconstituted the receptors in an accessible platform suitable for screening potential new anthelmintics. The longer term goal of this research is provide ion- channel drug targets from a range of important parasite species in a platform (Xenopus oocytes) suitable for drug discovery screening.
The Neglected Tropical Diseases (NTDs) include soil transmitted nematode parasites like ascariasis, trichuriasis and hookworm. Ascariasis, for example, is one of the most common human parasitic infections. 1.5 billion people worldwide have ascariasis, and the disease is most common in children between the ages of 3 and 8. Treatment of helminthiasis includes use of nicotinic anthelmintics like pyrantel and oxantel which selectively paralyze nematodes by activating cholinergic ion-channels (nAChRs) on their muscle. However, resistance to anthelmintics drugs is a real concern. We have identified a novel potential target site for new anthelmintics, the nAChR on the nematode pharynx, which is not sensitive to currently used drugs. We propose to characterize the pharmacological properties of this receptor, clone the component subunit genes and express the functional receptor in Xenopus oocytes. On completion of the project we will have characterized a potential new drug target (the pharynx nAChR) and reconstituted it in a platform (Xenopus laevis oocytes) suitable for screening compound libraries to identify new anthelmintic compounds.
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