Identification of human GnIH homologs, RFRP-1 and RFRP-3, and the cognate receptor, GPR147 in the human hypothalamic pituitary axis.
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.
Ubuka
Takayoshi
T
Department of Integrative Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA. ubukat@berkeley.edu
Morgan
Kevin
K
Pawson
Adam J
AJ
Osugi
Tomohiro
T
Chowdhury
Vishwajit S
VS
Minakata
Hiroyuki
H
Tsutsui
Kazuyoshi
K
Millar
Robert P
RP
Bentley
George E
GE
D000328:Adult; D000595:Amino Acid Sequence; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000737:chemistry*; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000166:cytology / Q000378:metabolism*; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009479:Neuropeptides / Q000737:chemistry / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018013:Receptors, Neuropeptide / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D006023:Glycoproteins; D009479:Neuropeptides; C416987:RFamide peptide; D012333:RNA, Messenger; D018013:Receptors, Neuropeptide; C014995:gonadotropin inhibitor; C083929:neuropeptide FF receptor