More than two decades of research on insect neuropeptide GPCRs: an overview

Abstract

This review focuses on the state of the art on neuropeptide receptors in insects. Most of these receptors are G protein-coupled receptors (GPCRs) and are involved in the regulation of virtually all physiological processes during an insect's life. More than 20 years ago a milestone in invertebrate endocrinology was achieved with the characterization of the first insect neuropeptide receptor, i.e., the Drosophila tachykinin-like receptor. However, it took until the release of the Drosophila genome in 2000 that research on neuropeptide receptors boosted. In the last decade a plethora of genomic information of other insect species also became available, leading to a better insight in the functions and evolution of the neuropeptide signaling systems and their intracellular pathways. It became clear that some of these systems are conserved among all insect species, indicating that they fulfill crucial roles in their physiological processes. Meanwhile, other signaling systems seem to be lost in several insect orders or species, suggesting that their actions were superfluous in those insects, or that other neuropeptides have taken over their functions. It is striking that the deorphanization of neuropeptide GPCRs gets much attention, but the subsequent unraveling of the intracellular pathways they elicit, or their physiological functions are often hardly examined. Especially in insects besides Drosophila this information is scarce if not absent. And although great progress made in characterizing neuropeptide signaling systems, even in Drosophila several predicted neuropeptide receptors remain orphan, awaiting for their endogenous ligand to be determined. The present review gives a précis of the insect neuropeptide receptor research of the last two decades. But it has to be emphasized that the work done so far is only the tip of the iceberg and our comprehensive understanding of these important signaling systems will still increase substantially in the coming years.

Tailless and Atrophin control Drosophila aggression by regulating neuropeptide signalling in the pars intercerebralis

“…The identity of the specific neuropeptide(s) that regulate aggression through this transcriptional module is currently not known. There are at least 40 different neuropeptide-encoding genes with corresponding receptors in the Drosophila genome 69 , and it will be interesting not only to identify the causative peptide but to show whether it is conserved in mammals and whether it is directly regulated by the Tll/Atro transcriptional repressor complex. The well-established role of Tll as a transcription factor 20,21,26,70 makes it likely that the behavioural effects that we observe are caused by changes in transcription, although we have not identified direct targets of Tll in this novel adult process.…”

Natalisin, a tachykinin-like signaling system, regulates sexual activity and fecundity in insects

“…Furthermore, the tools available in biotechnology that are readily applicable in suitable insect model species have advanced our understanding of the functions of neuropeptides. Drosophila melanogaster has been the best model system, allowing functional studies of neuropeptides and their receptors by the use of highly advanced molecular genetic tools and various publicly available resources (6). A number of other insect species, especially those with sequenced genomes, such as Bombyx mori and Tribolium castaneum, also have been used for investigations into the functions of neuropeptide signals, using piggyBac transformation (7) and RNAi (8,9).…”

Identification and Characterization of Receptors for Ion Transport Peptide (ITP) and ITP-like (ITPL) in the Silkworm Bombyx mori

“…Most neuropeptide receptors, with few exceptions, belong to the G protein-coupled receptor (GPCR) superfamily (25). Indeed, the estimated molecular weight of receptors for CHH family peptides in crustacean species coincides with those of class A and B GPCRs (26,27).…”