Discovery of peptide probes to modulate oxytocin-type receptors of insects

Abstract

The oxytocin/vasopressin signalling system is conserved across the animal kingdom. In insects, the role of oxytocin-type (inotocin) neuropeptides has only been studied in locusts, beetles and ants, but their physiology continues to be poorly understood. One reason for this knowledge deficit is the lack of available research tools to complement functional genomics efforts. Consequently, ligands to probe insect inotocin receptors are essential. In this study, we sought to identify novel agonists and antagonists of the inotocin receptor from the representative model species Tribolium castaneum and Lasius niger. Drawing upon known ligands of the human receptors, we examined the pharmacology of the plant-derived cyclotide kalata B7 and the synthetic oxytocin analogue atosiban. Kalata B7 is a weak partial agonist of both inotocin receptors. This is the first reported direct interaction of cyclotides with an insect receptor, an observation that may explain their presumed role in herbivore defence. Furthermore, we discovered atosiban is an antagonist of the Tribolium receptor, which may provide a useful probe to investigate the functionality of inotocin signalling in beetles and related insect species. Our findings will enable further examination of insect inotocin receptor pharmacology and physiology, and may trigger studies to comprehend the interaction of plant cyclotides and insects.

Nature-Derived Peptides: A Growing Niche for GPCR Ligand Discovery

“…Cyclotides exhibit manifold bioactivities, such as uterotonic [17] and immunomodulatory properties [14]. Their endogenous function appears to be as plant defense molecules: they modulate insect GPCRs [18] and exhibit antiherbivore effects towards plant pests [19]. Intriguingly, a single species can express over 150 distinct cyclotides and the number of cyclotides to be discovered in plants has been predicted to exceed 150 000 [16].…”

Fresh-blood-free diet for rearing malaria mosquito vectors

“…The insect and human GPCR systems have recently been characterised using comparative genomics approaches 16,17 . The mosquito genome contains orphan receptor genes that have a similar sequence and may be functional homologues of some vertebrate GPCRs.…”

I8-arachnotocin–an arthropod-derived G protein-biased ligand of the human vasopressin V2 receptor

“…All cell culture work was performed with human embryonic kidney cells 293 (HEK293) 24 . Unless otherwise stated, cells were incubated at 37 °C and 5% CO 2 and grown in Dulbecco’s Modified Eagle’s Medium (DMEM; Thermo Fisher Scientific, Australia and Fisher Scientific, Austria) containing 10% fetal bovine serum (GE Life Sciences, Australia and Sigma-Aldrich, Germany), 50 U/mL penicillin and 50 U/mL streptomycin (Thermo Fisher Scientific, Australia and Sigma-Aldrich, Germany).…”