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Characterization and pharmacological analysis of two adipokinetic hormone receptor variants of the tsetse fly, Glossina morsitans morsitans

Caers, Jelle, Janssen, Tom, Van Rompay, Liesbeth, Broeckx, Valérie, Van Den Abbeele, Jan, Gäde, Gerd, Schoofs, Liliane, Beets, Isabel
Insect biochemistry and molecular biology 2016 v.70 pp. 73-84
G-protein coupled receptors, Glossina morsitans morsitans, adipokinetic hormone receptors, calcium, cell membranes, corpora cardiaca, energy metabolism, fat body, gene expression, genes, germplasm conservation, hormones, insects, neuropeptides, open reading frames, pharmacology
Adipokinetic hormones (AKH) are well known regulators of energy metabolism in insects. These neuropeptides are produced in the corpora cardiaca and perform their hormonal function by interacting with specific G protein-coupled receptors (GPCRs) at the cell membranes of target tissues, mainly the fat body. Here, we investigated the sequences, spatial and temporal distributions, and pharmacology of AKH neuropeptides and receptors in the tsetse fly, Glossina morsitans morsitans. The open reading frames of two splice variants of the Glomo-akh receptor (Glomo-akhr) gene and of the AKH neuropeptide encoding genes, gmmhrth and gmmakh, were cloned. Both tsetse AKHR isoforms show strong sequence conservation when compared to other insect AKHRs. Glomo-AKH prepropeptides also have the typical architecture of AKH precursors. In an in vitro Ca2+ mobilization assay, Glomo-AKH neuropeptides activated each receptor isoform up to nanomolar concentrations. We identified structural features of tsetse AKH neuropeptides essential for receptor activation in vitro. Gene expression profiles suggest a function for AKH signaling in regulating Glossina energy metabolism, where AKH peptides are released from the corpora cardiaca and activate receptors mainly expressed in the fat body. This analysis of the ligand-receptor coupling, expression, and pharmacology of the two Glomo-AKHR variants facilitates further elucidation of the function of AKH in G. m. morsitans.