Comparative pharmacological characterization of D-1-like dopamine receptors from Anopheles gambiae, Aedes aegypti and Culex quinquefasciatus suggests pleiotropic signaling in mosquito vector lineages

Small molecule antagonists of mosquito dopamine receptors (DARs) are under investigation as a new class of vector-selective insecticides. Antagonists that inhibit the D-1-like DARs AaDOP2 and CqDOP2 from the mosquitoes Aedes aegypti L. and Culex quinquefasciatus Say, respectively, also cause larval mortality in bioassays. Here, we report on the orthologous DAR, AgDOP2, from the malaria mosquito Anopheles gambiae Giles that was cloned and pharmacologically characterized in HEK293 cells. Larval bioassays were then conducted to examine the potential of DAR antagonist insecticides against Anopheles vectors. Findings: Previous in vitro cAMP accumulation assays demonstrated Gas coupling for AaDOP2 and CqDOP2 and dose-dependent inhibition by DAR antagonists. We observed a negligible response of AgDOP2 in the cAMP assay, which prompted an investigation of alternative coupling for mosquito DARs. In an in vitro IP-One Ga-q second messenger assay of calcium signaling, dopamine stimulation increased IP1 accumulation in AaDOP2-, CqDOP2- and AgDOP2-expressing cells, and DAR antagonists inhibited IP1 signaling in a dose-dependent manner. In larval bioassays, DAR antagonists caused considerable mortality of An. gambiae larvae within 24 h post-exposure. Conclusions: In vitro data reveal pleiotropic coupling of AaDOP2 and CqDOP2 to Ga-q and Ga-s. In contrast, AgDOP2 appeared to selectively couple to Gaq signaling. In vitro antagonist studies revealed general conservation in pharmacology between mosquito DARs. In vivo data suggest potential for DAR antagonist insecticides against An. gambiae. Sequence conservation among the DOP2 receptors from 15 Anopheles species indicates utility of antagonists to control residual malaria transmission. AgDOP2 Ga-q-dependent signaling could be exploited for An. gambiae control via pathway specific antagonists