title: Adipokinetic hormone signaling through the gonadotropin-releasing hormone receptor modulates egg-laying in Caenorhabditis elegans.
abstract: In mammals, hypothalamic gonadotropin-releasing hormone (GnRH) is a neuropeptide that stimulates the release of gonadotropins from the anterior pituitary. The existence of a putative functional equivalent of this reproduction axis in protostomian invertebrates has been a matter of debate. In this study, the ligand for the GnRH receptor in the nematode Caenorhabditis elegans (Ce-GnRHR) was found using a bioinformatics approach. The peptide and its precursor are reminiscent of both insect adipokinetic hormones and GnRH-preprohormone precursors from tunicates and higher vertebrates. We cloned the AKH-GnRH-like preprohormone and the Ce-GnRHR and expressed the GPCR in HEK293T cells. The GnRHR was activated by the C. elegans AKH-GnRH-like peptide (EC(50) = 150 nM) and by Drosophila AKH and other nematode AKH-GnRHs that we found in EST databases. Analogous to both insect AKH receptor and vertebrate GnRH receptor signaling, Ce-AKH-GnRH activated its receptor through a Galpha(q) protein with Ca(2+) as a second messenger. Gene silencing of Ce-GnRHR, Ce-AKH-GnRH, or both resulted in a delay in the egg-laying process, comparable to a delay in puberty in mammals lacking a normal dose of GnRH peptide or with a mutated GnRH precursor or receptor gene. The present data support the view that the AKH-GnRH signaling system probably arose very early in metazoan evolution and that its role in reproduction might have been developed before the divergence of protostomians and deuterostomians.
authors.affiliation: Functional Genomics and Proteomics Research Unit, Katholieke Universiteit Leuven, Naamsestraat 59, B-3000 Leuven, Belgium.
authors.forename: Marleen
authors.initials: M
authors.lastname: Lindemans
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Tom
authors.initials: T
authors.lastname: Janssen
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Husson
authors.forename: Inge
authors.initials: I
authors.lastname: Mertens
authors.forename: Gerd
authors.initials: G
authors.lastname: Gäde
authors.forename: Liliane
authors.initials: L
authors.lastname: Schoofs
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000378:metabolism / Q000502:physiology*; D050260:Carbohydrate Metabolism; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D006801:Humans; D007301:Insect Hormones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010063:Ovum; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D011966:Receptors, LHRH / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D017931:DNA Primers; D007301:Insect Hormones; D009842:Oligopeptides; D011966:Receptors, LHRH; C044833:adipokinetic hormone; D011761:Pyrrolidonecarboxylic Acid