12th Annual Meeting of the LARC-Neuroscience Network edition:12 location:Rouen date:17 october 2008
In mammals, key hormones of the hypothalamic-pituitary-gonadal axis control reproduction. The hypothalamus is capable of sensing the environmental cues and regulates the production of gonadotropin-releasing hormone (GnRH), which can be considered as the first essential signaling component for the regulation of reproduction. In invertebrates, however, GnRH was so far unable to demonstrate robust gonadotropin-releasing activities. Using an in vitro reverse pharmacologic approach, the ligand of the GnRH receptor in the fruit fly Drosophila melanogaster and the silkworm Bombyx mori have been identified as adipokinetic hormone (AKH), which is involved in energy mobilization. In the nematode C. elegans, a GnRH receptor has recently been identified1. In this study, this C. elegans receptor has been deorphanized and functionally characterized. Its activating peptide ligand, found by a bioinformatic approach, resembles strongly AKH from invertrebrates as well as GnRH from tunicates and higher vertebrates, both on peptide and entire precursor level. This is the first report of an AKH/GnRH-like peptide in nematodes. Analogous to the situation of insect AKH receptors and vertebrate GnRH receptors, the C. elegans GnRH receptor signals through a Gαq protein with Ca2+ as second messenger. Its function however is related to GnRH and reproduction since gene sinlencing of receptor and/or ligand precursor results in a delay in the egg laying process. We suggest the existence of an ancestral neuropeptidergic system for the regulation of reproduction. In this view, a potential role of AKH in insects may be overlooked and remains to be investigated in the future.