Mini-review: the evolution of neuropeptide signaling.

Neuropeptides and their G protein-coupled receptors (GPCRs) have an early evolutionary origin and are already abundant in basal animals with primitive nervous systems such as cnidarians (Hydra, jellyfishes, corals, and sea anemones). Most animals emerging after the Cnidaria belong to two evolutionary lineages, the Protostomia (to which the majority of invertebrates belong) and Deuterostomia (to which some minor groups of invertebrates, and all vertebrates belong). These two lineages split about 700 million years (Myr) ago. Many mammalian neuropeptide GPCRs have orthologues in the Protostomia and this is also true for some of the mammalian neuropeptides. Examples are oxytocin/vasopressin, GnRH, gastrin/CCK, and neuropeptide Y and their GPCRs. These results implicate that protostomes (for example insects and nematodes) can be used as models to study the biology of neuropeptide signaling.

Grimmelikhuijzen CJ ，Hauser F 《-》

Evolution of the AKH/corazonin/ACP/GnRH receptor superfamily and their ligands in the Protostomia.

In this review we trace the evolutionary connections between GnRH receptors from vertebrates and the receptors for adipokinetic hormone (AKH), AKH/corazonin-related peptide (ACP), and corazonin from arthropods. We conclude that these G protein-coupled receptors (GPCRs) are closely related and have a common evolutionary origin, which dates back to the split of Proto- and Deuterostomia, about 700 million years ago. We propose that in the protostomian lineage, the ancestral GnRH-like receptor gene duplicated as did its GnRH-like ligand gene, followed by diversification, leading to (i) a corazonin receptor gene and a corazonin-like ligand gene, and (ii) an AKH receptor gene and an AKH-like ligand gene in the Mollusca and Annelida. Subsequently, the AKH receptor and ligand genes duplicated once more, yielding the situation that we know from arthropods today, where three independent hormonal systems exist, signalling with AKH, ACP, and corazonin. Our model for the evolution of GnRH signaling in the Protostomia is a striking example of receptor-ligand co-evolution. This model has been developed using several bioinformatics tools (TBLASTN searches, phylogenetic tree analyses), which also helped us to annotate six novel AKH preprohormones and their corresponding AKH sequences from the following molluscs: the sea hare Aplysia californica (AKH sequence: pQIHFSPDWGTamide), the sea slug Tritonia diomedea (pQIHFSPGWEPamide), the fresh water snail Bithynia siamensis goniomphalos (pQIHFTPGWGSamide), the owl limpet Lottia gigantea (pQIHFSPTWGSamide), the oyster Crassostrea gigas (pQVSFSTNWGSamide), and the freshwater pearl mussel Hyriopsis cumingii (pQISFSTNWGSamide). We also found AKHs in the tardigrade Hysibius dujardini (pQLSFTGWGHamide), the rotifer Brachionus calycifloros (pQLTFSSDWSGamide), and the penis worm Priapulus caudatus (pQIFFSKGWRGamide). This is the first report, showing that AKH signaling is widespread in molluscs.

Hauser F ，Grimmelikhuijzen CJ 《-》

Adipokinetic hormones and their G protein-coupled receptors emerged in Lophotrochozoa.

Li S ，Hauser F ，Skadborg SK ，Nielsen SV ，Kirketerp-Møller N ，Grimmelikhuijzen CJ ... -  《Scientific Reports》

Urbilaterian origin of paralogous GnRH and corazonin neuropeptide signalling pathways.

Tian S ，Zandawala M ，Beets I ，Baytemur E ，Slade SE ，Scrivens JH ，Elphick MR ... -  《Scientific Reports》

Cloning and characterization of the adipokinetic hormone receptor from the cockroach Periplaneta americana.

Hansen KK ，Hauser F ，Cazzamali G ，Williamson M ，Grimmelikhuijzen CJ ... -  《BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS》