Insect GPCRs and TRP Channels: Putative Targets for Insect Repellents

Many insects such as mosquitoes cause life-threatening diseases such as malaria, yellow fever and West Nile virus. Malaria alone infects 500 million people annually and causes 1-3 million death per year. Volatile insect repellents, which are detected through the sense of smell, have long been used to protect humans against insect pests. Antifeed-ants are non-volatile aversive compounds that are detected through the sense of taste and prevent insects from feeding on plants. The molecular targets and signaling path-ways required for sensing insect repellents and antifeedants are poorly understood. Transient Receptor Potential (TRP) Ca2+-permeable cation channels exist in organisms ranging from C. elegans to D. melanogaster and Homo sapiens. Drosophila has 13 family members, which mainly function in sensory physiology such as vision, thermotaxis and chemotaxis. G protein-coupled receptors (GPCRs) initiate olfactory signaling cascades in mammals and in nematodes C.elegans. However, the mechanisms of G protein signaling cascades in insect chemosensation are controversial. In this review, I will discuss the putative roles of G protein-coupled receptors (GPCRs) and Transient Receptor Potential (TRP) channels as targets for insect repellents.