Identification of human GnIH homologs, RFRP-1 and RFRP-3, and the cognate receptor, GPR147 in the human hypothalamic pituitary axis

• Published in: PloS one 2009-12, Vol.4 (12), p.e8400-e8400
• Main Authors: Ubuka, Takayoshi, Morgan, Kevin, Pawson, Adam J, Osugi, Tomohiro, Chowdhury, Vishwajit S, Minakata, Hiroyuki, Tsutsui, Kazuyoshi, Millar, Robert P, Bentley, George E
• Format: Article
• Language: English
• Subjects: Adult; Amino Acid Sequence; Analysis; Biological activity; Biology; Brain; Brain research; Calcium mobilization; Chromatography; Councils; Deoxyribonucleic acid; Diabetes and Endocrinology/Endocrinology; Diabetes and Endocrinology/Neuroendocrinology and Pituitary; Diabetes and Endocrinology/Reproductive Endocrinology; DNA; DNA sequencing; Endocrinology; Gene expression; Gene Expression Regulation; Gene sequencing; Glycoproteins; Glycoproteins - chemistry; Gonadotropin-releasing hormone; Gonadotropins; Gynecology; Homology; Hormones; Humans; Hybridization; Hypothalamic-pituitary-gonadal axis; Hypothalamo-Hypophyseal System - cytology; Hypothalamo-Hypophyseal System - metabolism; Hypothalamus; Hypothalamus (dorsomedial); Identification; Immunocytochemistry; Inhibition; Luteinizing hormone; Mammals; Mass spectrometry; Mass spectroscopy; Medical research; Molecular Sequence Data; Neurons; Neurons - cytology; Neurons - metabolism; Neuropeptides; Neuropeptides - chemistry; Neuropeptides - metabolism; Neurosciences; Ovis aries; Pituitary; Pituitary (anterior); Pituitary-Adrenal System - cytology; Pituitary-Adrenal System - metabolism; Pituitary-gonadal axis; Polymerase chain reaction; Polypeptides; Preoptic area; Purification; Receptors, Neuropeptide - genetics; Receptors, Neuropeptide - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA; RNA, Messenger - genetics; RNA, Messenger - metabolism; Rodents; Scientific imaging; Sequence Homology, Amino Acid; Sheep; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Studies
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0008400

The existence of a hypothalamic gonadotropin-inhibiting system has been elusive. A neuropeptide named gonadotropin-inhibitory hormone (GnIH, SIKPSAYLPLRF-NH(2)) which directly inhibits gonadotropin synthesis and release from the pituitary was recently identified in quail hypothalamus. Here we identify GnIH homologs in the human hypothalamus and characterize their distribution and biological activity. GnIH homologs were isolated from the human hypothalamus by immunoaffinity purification, and then identified as MPHSFANLPLRF-NH(2) (human RFRP-1) and VPNLPQRF-NH(2) (human RFRP-3) by mass spectrometry. Immunocytochemistry revealed GnIH-immunoreactive neuronal cell bodies in the dorsomedial region of the hypothalamus with axonal projections to GnRH neurons in the preoptic area as well as to the median eminence. RT-PCR and subsequent DNA sequencing of the PCR products identified human GnIH receptor (GPR147) mRNA expression in the hypothalamus as well as in the pituitary. In situ hybridization further identified the expression of GPR147 mRNA in luteinizing hormone producing cells (gonadotropes). Human RFRP-3 has recently been shown to be a potent inhibitor of gonadotropin secretion in cultured sheep pituitary cells by inhibiting Ca(2+) mobilization. It also directly modulates GnRH neuron firing. The identification of two forms of GnIH (RFRP-1 and RFRP-3) in the human hypothalamus which targets human GnRH neurons and gonadotropes and potently inhibit gonadotropin in sheep models provides a new paradigm for the regulation of hypothalamic-pituitary-gonadal axis in man and a novel means for manipulating reproductive functions.