Chicken RFamide-related Peptide (GnIH) and Two Distinct Receptor Subtypes: Identification, Molecular Characterization, and Evolutionary Considerations

Abstract

Abstract. RFamide-related peptides (RFRPs) regulate the release of various pituitary hormones in vertebrates. It is completely unknown how the functions of RFRPs vary among animal classes and whether vertebrate RFRPs are orthologous to each other and belong to the same peptide family. This report concerns identification of avian RFRP (gonadotropin-inhibitory hormone, GnIH) from the chicken. Chromosome-wide synteny conservation demonstrated the orthologous relationships among vertebrate RFRPs. The consensus motif for RFRP was modified to Pro-Xaa-Arg-Phe-NH2. We also describe the first identification of two distinct types of receptors for non-mammalian RFRP (RFRPR and NPFFR) from the chicken. Amino acid comparison revealed substantial differences in both termini of receptors among classes of vertebrates. The 5'-flanking regions of chicken RFRPR and NPFFR suggested their expressions in the pituitary gland, and this was confirmed by the RT-PCR analysis. Localizations of both chicken RFRP and its receptors were distinct from those of mammals. These results indicated that avian RFRP, unlike the mammalian one, directly acts on the pituitary gland via receptors to regulate gonadotropin release. It was also suggested that functional differences, especially between avian and mammalian RFRPs, are substantially due to divergences in the structures and expression sites of their receptors.

Gonadotropin-inhibitory hormone (GnIH) receptor gene is expressed in the chicken ovary: potential role of GnIH in follicular maturation

“…The membrane fraction of COS-7 cells wherein putative quail GnIHR was overexpressed showed a dose-dependent high-affinity binding to GnIH (Yin et al 2005). Furthermore, GnIH treatment of COS-7 cells overexpressing chicken GnIHR resulted in a dose-dependent decrease in the accumulation of G ai2 mRNA (Ikemoto & Park 2005). At the tissue level, GnIHR cDNA was found to be expressed in the diencephalon and anterior pituitary gland in chickens and Japanese quail (Ikemoto & Park 2005, Yin et al 2005.…”

“…GnIH is a dodecapeptide belonging to a family of RFamide peptides with a C-terminal Pro-Xaa-Arg-Phe-NH 2 motif. The gene encoding a precursor protein for GnIH in Japanese quail, chickens, and white-crowned sparrows has been cloned and found to share a high degree of homology (Satake et al 2001, Osugi et al 2004, Ikemoto & Park 2005. GnIH-immunoreactive (ir) neurons are exclusively found in the hypothalamic paraventricular nucleus while GnIH-ir fibers are found throughout the brain including the median eminence in Japanese quail and sparrows (Bentley et al 2003).…”

“…Recently, the chicken and Japanese quail GnIH receptor (GnIHR) cDNAs were cloned and found to be 97% similar to each other (Ikemoto & Park 2005, Yin et al 2005. The deduced protein sequence of Japanese quail GnIHR appears to be a seven-transmembrane receptor belonging to a family of G-protein-coupled receptors (Yin et al 2005).…”

“…Furthermore, GnIH treatment of COS-7 cells overexpressing chicken GnIHR resulted in a dose-dependent decrease in the accumulation of G ai2 mRNA (Ikemoto & Park 2005). At the tissue level, GnIHR cDNA was found to be expressed in the diencephalon and anterior pituitary gland in chickens and Japanese quail (Ikemoto & Park 2005, Yin et al 2005. However, regulation of GnIHR gene expression or its possible expression in the gonads has not been investigated in any species.…”

Controle sobre GnRH durante o anestro pós-parto em bovinos

“…O GnIH foi inicialmente isolado do hipotálamo de codornas, tendo sido demonstrado que ele inibe a secreção do LH da hipófise anterior in vivo e in vitro (TSUTSUI et al, 2000). O gene que codifica o precursor da proteína para GnIH já foi clonado em várias espécies de aves e possui um alto grau de homologia entre espécies (SATAKE et al, 2001;IKEMOTO & PARK, 2005). Nesses animais, neurônios imunoreativos (ir) para o GnIH são exclusivamente encontrados no núcleo hipotalâmico paraventricular, enquanto fibras GnIH são encontradas em outras regiões do cérebro, incluindo a eminência média (UKENA et al, 2003).…”