title: Gonadotropin-inhibitory hormone inhibits GnRH-induced gonadotropin subunit gene transcriptions by inhibiting AC/cAMP/PKA-dependent ERK pathway in LβT2 cells.
abstract: A neuropeptide that directly inhibits gonadotropin secretion from the pituitary was discovered in quail and named gonadotropin-inhibitory hormone (GnIH). The presence and functional roles of GnIH orthologs, RF-amide-related peptides (RFRP), that possess a common C-terminal LPXRF-amide (X = L or Q) motif have also been demonstrated in mammals. GnIH orthologs inhibit gonadotropin synthesis and release by acting on pituitary gonadotropes and GnRH neurons in the hypothalamus via its receptor (GnIH receptor). It is becoming increasingly clear that GnIH is an important hypothalamic neuropeptide controlling reproduction, but the detailed signaling pathway mediating the inhibitory effect of GnIH on target cells is still unknown. In the present study, we investigated the pathway of GnIH cell signaling and its possible interaction with GnRH signaling using a mouse gonadotrope cell line, LβT2. First, we demonstrated the expression of GnIH receptor mRNA in LβT2 cells by RT-PCR. We then examined the inhibitory effects of mouse GnIH orthologs [mouse RFRP (mRFRP)] on GnRH-induced cell signaling events. We showed that mRFRP effectively inhibited GnRH-induced cAMP signaling by using a cAMP-sensitive reporter system and measuring cAMP levels, indicating that mRFRP function as an inhibitor of adenylate cyclase. We further showed that mRFRP inhibited GnRH-stimulated ERK phosphorylation, and this effect was mediated by the inhibition of the protein kinase A pathway. Finally, we demonstrated that mRFRP inhibited GnRH-stimulated gonadotropin subunit gene transcriptions and also LH release. Taken together, the results indicate that mRFRP function as GnIH to inhibit GnRH-induced gonadotropin subunit gene transcriptions by inhibiting adenylate cyclase/cAMP/protein kinase A-dependent ERK activation in LβT2 cells.
authors.affiliation: Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, Center for Medical Life Science of Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
authors.forename: You Lee
authors.initials: YL
authors.lastname: Son
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Ubuka
authors.forename: Robert P
authors.initials: RP
authors.lastname: Millar
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Kanasaki
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Tsutsui
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D052681:Gonadotrophs / Q000187:drug effects / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000494:pharmacology; D006065:Gonadotropins, Pituitary / Q000096:biosynthesis* / Q000235:genetics; D007028:Hypothalamic Hormones / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009479:Neuropeptides / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D006065:Gonadotropins, Pituitary; D007028:Hypothalamic Hormones; D009479:Neuropeptides; C416987:RFamide peptide; D007987:Gonadotropin-Releasing Hormone; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D000262:Adenylyl Cyclases