Insect vectors of human disease infect hundreds of millions of individuals annually with deadly infectious diseases, including Malaria, Dengue and Yellow Fever, and West Nile Encephalitis. Insects are attracted to human hosts by specific sensory cues, with olfactory cues playing a dominant role. The Broad," Long-Term Objectives of this proposal are to understand the mechanisms by which the olfactory system allows insects to hone in on human hosts. Such knowledge could be translated to a new class of chemical agents that act on the insect olfactory system to interrupt vector insect host-seeking behavior. Responsive to PA-05-154, the overall goal of this specific project is to increase understanding of the molecular structure and function of the odorant receptors (ORs) that mediate odor recognition in insects. In preliminary studies, we have documented a unique chaperoning co-receptor function for OR83b. OR83b is co-expressed and forms OR/ OR83b heterodimers with conventional ORs in most olfactory sensory neurons in vivo and is necessary for the targeting and maintenance of ORs in ciliated dendrites where odor transduction occurs. These preliminary studies have led to the hypothesis that the OR/OR83b complex is essential for insect olfactory function. To test this hypothesis, three Specific Aims are proposed: 1) Identify protein domains that mediate OR83b targeting to olfactory cilia 2) Define protein domains that mediate the formation of heteromeric OR/OR83b complexes 3) Characterize post-translational modifications that modulate the OR/OR83b complex The Research Design involves targeted mutagenesis of OR83b to uncover motifs necessary for trafficking, OR/OR83b heteromerization, and post-translational modifications. The Methods used are phenotypic analysis of Drosophila OR function in vivo and in vitro employing electrophysiological, imaging, cell biological, biochemical, and behavioral techniques. A molecular understanding of insect OR function may aid in the design of novel chemical agents that selectively disrupt insect ORs and thus interrupt host- seeking behaviors of insect disease vectors such as mosquitoes. The Health-Relatedness of this proposal is that such chemical agents may act to reduce infectious disease transmission by vector insects in the future.