Molecular cloning and pharmacological characterization of two novel GnRH receptors in the lamprey (Petromyzon marinus).
ABSTRACT This paper reports the identification, expression, binding kinetics, and functional studies of two novel type III lamprey GnRH receptors (lGnRH-R-2 and lGnRH-R-3) in the sea lamprey, a basal vertebrate. These novel GnRH receptors share the structural features and amino acid motifs common to other known gnathostome GnRH receptors. The ligand specificity and activation of intracellular signaling studies showed ligands lGnRH-II and -III induced an inositol phosphate (IP) response at lGnRH-R-2 and lGnRH-R-3, whereas the ligand lGnRH-I did not stimulate an IP response. lGnRH-II was a more potent activator of lGnRH-R-3 than lGnRH-III. Stimulation of lGnRH-R-2 and lGnRH-R-3 testing all three lGnRH ligands did not elicit a cAMP response. lGnRH-R-2 has a higher binding affinity in response to lGnRH-III than lGnRH-II, whereas lGnRH-R-3 has a higher binding affinity in response to lGnRH-II than IGnRH-III. lGnRH-R-2 precursor transcript was detected in a wide variety of tissues including the pituitary whereas lGnRH-R-3 precursor transcript was not as widely expressed and primarily expressed in the brain and eye of male and female lampreys. From our phylogenetic analysis, we propose that lGnRH-R-1 evolved from a common ancestor of all vertebrate GnRH receptors and lGnRH-R-2 and lGnRH-R-3 likely occurred due to a gene duplication within the lamprey lineage. In summary, we propose from our findings of receptor subtypes in the sea lamprey that the evolutionary recruitment of specific pituitary GnRH receptor subtypes for particular physiological functions seen in later evolved vertebrates was an ancestral character that first arose in a basal vertebrate.
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ABSTRACT: The gonadotropin-releasing hormone (GnRH) system is well known as the main regulator of reproductive physiology in vertebrates. It is also part of a network of brain structures and pathways that integrate information from the internal and external milieu and coordinate the adaptive behavioral and physiological responses to social and reproductive survival needs. In this paper we review the state of knowledge of the GnRH system in relation to the behavior, external, and internal factors that control reproduction in one of the oldest lineage of vertebrates, the lampreys.Frontiers in Endocrinology 01/2013; 4:151.
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ABSTRACT: Gonadotropin-releasing hormone (GnRH) and its receptor are essential for reproduction in vertebrates. Although there are three major types of GnRH peptides and two major types of receptors in vertebrates, the pattern of distribution is unusual. Evidence is presented from genome mining that type I GnRHRs are not restricted to mammals, but can be found in the lobe-finned and cartilaginous fishes. This implies that this tail-less GnRH receptor emerged early in vertebrate evolution, followed by several independent losses in different lineages. Also, we have identified representatives from the three major GnRH peptide types (mammalian GnRH1, vertebrate GnRH2 and dogfish GnRH3) in a single cartilaginous fish, the little skate. Skate and coelacanth are the only examples of animals with both type I and II GnRH receptors and all three peptide types, suggesting this was the ancestral condition in vertebrates. Our analysis of receptor synteny in combination with phylogeny suggests that there were three GnRHR receptor types present before the two rounds of whole genome duplication in early vertebrates. To further understand the origin of the GnRH peptide-receptor system, the relationship of vertebrate and invertebrate homologs was examined. Our evidence supports the hypothesis of a GnRH superfamily with a common ancestor for the vertebrate GnRHs, invertebrate (inv)GnRHs, corazonins and adipokinetic hormones. The invertebrate deuterostomes (echinoderms, hemichordates and amphioxus) have derived GnRH-like peptides, although one amphioxus GnRH with a syntenic relationship to human GnRHs has been shown to be functional. Phylogenetic analysis suggests that gene duplications in the ancestral bilaterian produced two receptor types, one of which became adipokinetic hormone receptor/GnRHR and the other corazonin receptor/invGnRHR. It appears that the ancestral deuterostome had both a GnRHR and invGnRHR, and this is still the case in amphioxus. During the transition to vertebrates both the invertebrate-type peptide and receptor were lost, leaving only the vertebrate-type system that presently exists.General and Comparative Endocrinology 08/2014; · 2.82 Impact Factor
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ABSTRACT: Gonadotropin-releasing hormone (GnRH) and the GnRH receptor (GnRHR) play an important role in vertebrate reproduction. Although many GnRHR genes have been identified in a large variety of vertebrate species, the evolutionary history of GnRHR in vertebrates is unclear. To trace the evolutionary origin of GnRHR we examined the conserved synteny of chromosomes harboring GnRHR genes and matched the genes to linkage groups of reconstructed vertebrate ancestor chromosomes. Consistent with the phylogenetic tree, three pairs of GnRHR subtypes were identified in three paralogous linkage groups, indicating that an ancestral pair emerged through local duplication before two rounds of whole genome duplication (2R). The 2R then led to the generation of six subtypes of GnRHR. Some subtypes were lost during vertebrate evolution after the divergence of teleosts and tetrapods. One subtype includes mammalian GnRHR and a coelacanth GnRHR that showed the greatest response to GnRH1 among the three types of GnRH. This study provides new insight into the evolutionary relationship of vertebrate GnRHRs.PLoS ONE 01/2014; 9(2):e87901. · 3.53 Impact Factor