Dopamine receptors as targets in a "Genome-to-Lead" insecticide discovery pipeline

Resistance to commercial insecticides among arthropod vectors of infectious disease necessitates the development of new mode-of-action chemistries for vector control.  Biogenic amine-binding G protein-coupled receptors (GPCRs) are promising targets for insecticide discovery because of their critical role in the neurological processes of arthropods.  The Purdue Invertebrate Receptor Group (PIRG) was created to pursue target-based insecticide discovery around these receptors. The research group has mined multiple arthropod vector genomes to identify candidate GPCR targets. In proof of concept studies, D₁-like dopamine receptors (DARs) from the Lyme disease tick, Ixodes scapularis, the yellow fever mosquito, Aedes aegypti, the malaria mosquito, Anopheles gambiae and the northern house mosquito, Culex quinquefasciatus, were expressed in reporter cell lines and pharmacological profiles in response to biogenic amines and a panel of DAR antagonists and agonists were evaluated.  The arthropod D₁-like DAR, DOP2, from these four vectors exhibits pharmacological properties distinct from human D₁-like DARs. On the basis of strong signal-to-noise ratio, the Ae. aegypti AaDOP2 and I. scapularis IsDOP2 targets were selected for high-throughput chemical library screening to identify small molecule antagonists.  The most potent antagonist “hits” were validated via in vitro confirmation assays, and molecules with >10-fold selectivity for the invertebrate target versus the human DAR, hD1, were identified that caused significant mortality of Ae. aegypti and C. quinquefasciatus larvae and Ae. aegypti adults in vivo. Our results demonstrate the utility of the PIRG strategy for identification of novel, vector-specific insecticidal leads that are broadly effective against key vector species.