Identification and functional characterization of FGLamide-related allatostatin receptor in Rhodnius prolixus

FGLamide-related ASTs (FGLa/ASTs) are a family of brain/gut peptides with numerous physiological roles, including inhibition of juvenile hormone (JH) biosynthesis by the corpora allata and inhibition of visceral muscle contraction. FGLa/ASTs mediate their effects by binding to a rhodopsin-like G-protein coupled receptor that is evolutionarily related to the vertebrate galanin receptor. Here we determine the cDNA sequence encoding FGLa/AST receptor (FGLa/AST-R) from the Chagas disease vector, Rhodnius prolixus (Rhopr-FGLa/AST-R), determine its spatial expression pattern using quantitative PCR and functionally characterize the receptor using a heterologous assay. Our expression analysis indicates that Rhopr-FGLa/AST-R is highly expressed in the central nervous system. The receptor is also expressed in various peripheral tissues including the dorsal vessel, midgut, hindgut and reproductive tissues of both males and females, suggesting a role in processes associated with feeding and reproduction. The possible involvement of Rhopr-FGLa/ASTs in the inhibition of JH biosynthesis is also implicated due to presence of the receptor transcript in the R. prolixus corpora cardiaca/corpora allata complex. The functional assay showed that various Rhopr-FGLa/ASTs activate the receptor, with EC50 values for the response in the nanomolar range. Moreover, Rhopr-FGLa/AST-R can couple with Gq alpha subunits and cause an increase in intracellular calcium concentration. Lastly, we tested various FGLa/AST analogs in our heterologous assay. These compounds also activated the receptor and thus have the potential to serve as insect growth regulators and aid in pest control.