Functional Characterization of Odorant Receptors in Disease Vector Mosquitoes

This dissertation is concerned with the expression patterns, functionality and mechanisms of disease vector mosquito odorant receptors. The principal afrotropical vector for malaria, Anopheles gambiae, discriminates human host cues through the use of a highly divergent family of odorant receptors (AgORs). In vivo, ORs form a functional complex consisting of a conserved and broadly expressed non-conventional OR co-receptor (ORco) and a conventional odor-binding OR, which provides coding specificity to each complex. I have used next-generation RNA sequencing to discriminate OR expression patterns, and identified novel candidate genes involved in chemosensory signal transduction. In addition, I have functionally characterized and identified conserved ORs between multiple disease vector mosquitoes. In an effort to identify novel modulators of AgORs for insect control, we have performed high-throughput, cell-based calcium imaging screens, and as a result, I have identified the first ORco family agonist. Through the heterologous expression of AgORco, we demonstrated the novel activity of this agonist, its effects upon the signaling properties of ORco, and elucidated a molecular mechanism of OR signaling. In addition, single unit electrophysiology studies demonstrate the ability of this ligand to activate AgORco-expressing cells in vivo. As such, ligand-mediated modulation serves as a proof-of-concept demonstration that ORco is a viable target for the development of behaviorally disruptive olfactory compounds (BDOCs) that could foster malaria reduction programs. These studies have established a new model for OR-signaling and identified a new class of molecules with the future potential to reduce global burdens of malaria and other vector borne diseases.