Limostatin was detected in Drosophila in a genetic screen for factors suppressing production and secretion of insulin-like peptides, DILPs (Alfa et al., 2015). This peptide, encoded on the precursor CG8317, consists of 15 residues with the sequence AIVFRPLFVYKQQEIamide. Lst encoding genes were identified in a number of Drosophila species and in the mosquitos Anopheles gambiae and Aedes aegypti (Alfa et al., 2015). The Lst receptor, CG9918, is related to the neuromedin U receptor in vertebrates. This receptor was originally characterized as a pyrokinin (Capability-PK) receptor (PK1-R) in Drosophila (Cazzamali et al., 2005), and now it appears to be shared with Lst.
In Drosophila the Lst gene is expressed in the fat body and in the AKH producing endocrine cells of the corpora cardiaca, and its production is increased during fasting (Alfa et al., 2015). According to FlyAtlas, Lst is highly enriched in fat body, heart, spermatheca and carcass in the adult, and in the larval fat body. The Lst receptor is expressed on the insulin-producing cells (IPCs) in the brain (Alfa et al., 2015).
The expression of Lst is regulated by carbohydrate, but not protein, diet after a period of starvation (Alfa et al., 2015). Application of synthetic Lst attenuated Ca2+ in IPCs and thus depressed release of DILPs. Genetic knockdown of the receptor produced a phenotype similar to Lst mutant flies, or that seen after Lst knockdown in AKH cells (Alfa et al., 2015). Thus, Lst is one of several peptides that regulate production and release of DILPs in Drosophila (Alfa and Kim, 2016; Nässel and Vanden Broeck, 2016). Its function in mosquitos has not yet been studied.
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