Characterization of sulfakinin receptor 2 and its role in food intake in the red flour beetle, Tribolium castaneum.

Insects acquire essential nutrients from their food to support a diverse range of biological processes such as development and reproduction. An important role in the food intake regulation is attributed to the neurohormone sulfakinin signaling pathway. Sulfakinins (SKs) elicit satiety together with sulfakinin receptors (SKRs). In this project, the gene coding a second putative SKR, namely skr2, was cloned, characterized and functionally studied in the red flour beetle Tribolium castaneum, with the purpose to understand its role in food intake regulation. The gene skr2 encoded a seven-transmembrane SKR2 protein with 420 amino acids and is evolutionarily close to the two SKRs in Drosophila. A distribution analysis by means of quantitative real-time PCR revealed a tissue- and stage-specific expression pattern with skr2 being dominantly expressed in head, and in the pupal and adult stages. Besides, its expression in gut was notable. With use of dsRNA of skr2, larval food intake was stimulated in an injection RNAi assay. Based on the data obtained, skr2 is considered as an indispensable component in the regulation of food intake in T. castaneum.