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. Optimize expression of C. elegans eat-2 and eat 18 and pharmacologically characterize the resulting receptor. We will investigate optimal conditions for receptor expression and characterize the resulting receptor responses using a range of agonists, antagonists and potential allosteric modulators. 2. Clone and express A. suum eat-2 and eat-18. Are other subunits required for the pharyngeal receptor? We will identify orthologs of eat-2 and eat-18 from Ascaris suum, clone, and express them in Xenopus oocytes for characterization. Additionally we will test the hypothesis that other subunit genes are required to form the receptor. 3. Do eat-2 and eat 18 combine to form the mature receptor? We will test the novel hypothesis that eat-2 and eat-18 combine to form a functional nAChR. On completion of this project we will have expressed in a heterologous system an important new potential drug target from a parasitic nematode. We will have characterized an extremely novel nAChR (one that lacks any alpha subunits). We will have identified the genes that encode these receptors in the parasitic nematode Ascaris suum. Finally, we will have determined whether the small (71 a.a.) protein eat-18 is required in the mature ion channel receptor.