1998 Fiscal Year Final Research Report Summary
Regulation of gene expression of a novel G-protein coupled receptor involved in growth hormone secretion
| Project/Area Number |
09671076
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
内分泌・代謝学
|
|---|
| Research Institution | Tokyo Women's Medical University |
|---|
Principal Investigator |
MIKI Nobuhiro Tokyo Women's Med.Univ.Department of Medicine Assistant professor, 医学部, 講師 (40157467)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
MURATA Yoji Tokyo Women's Med.Univ.Department of Medicine Assistant professor, 医学部, 助手 (50277117)
ONO Masami Tokyo Women's Med.Univ.Department of Medicine Assistant professor, 医学部, 助手 (90152537)
|
|---|
| Project Period (FY) |
1997 – 1998
|
| Keywords | Growth hormone / GH secretagogue / Pituitary / Hypothalamus / Gene expression |
|---|
| Research Abstract |
In 1996, Merck research laboratory reported molecular cloning of a novel G-protein coupled receptor, termed growth hormone (GH) secretagogue receptor (GHS-R), from porcine and human pituitaries, that binds synthetic GH-releasing peptides and nonpeptidyl GH secretagogues (GHSs). This receptor functions in stimulating and amplifying pulsatile GH secretion although its endogenous ligand remains unknown. The discovery of GHS-R indicates that secretion of GH is regulated by three factors, a putative natural GHS and the two hypothalamic peptides, GH-releasing hormone (GRH) and GH release-inhibiting hormone (somatostatin). Using RT-PCR and a RACE protocol, we cloned a rat homolog of pituitary GHS-R in 1997, which belonged to a family of 7-transmembrane G-protein coupled receptors and showed 94-95 % homology to porcine and human GHS-Rs at amino acid level. In situ hybridization with digoxigenin-labeled cRNA probe revealed that both arcuate and ventromedial nuclei in the hypothalamus expressed
… More
GHS-R mRNA abundantly. GHRP has been shown to stimulate GRH release in animals. This finding provides a morphological support to the views that GHS and GHRP act on the hypothalamic arcuate nucleus to stimulate GRH release thereby amplifying GH pulsatile secretion. We then tried to set up an assay system capable of quantifying GHS-R mRNA levels in1998. Probably because of being a extremely rare transcript, GHS-R mRNA was not detected with Northern blotting, which lead us to develop a more sensitive and specific assay, i.e. RNase protection assay. With this assay we succeeded in detecting and quantitating rat GHS-R mRNA in both the hypothalamus and the pituitary and found that GHS-R mRNA levels per unit total RNA was approximately 2.5 times greater in the medial basal hypothalamus than in the anterior pituitary. Administration of human recombinant GH for 5 days caused a significant decrease on GHS-R mRNA levels in the pituitary but not in the hypothalamus. This finding suggests that GHS-R expression in the pituitaryis negatively regulated by GH and its regulation might be different from that in the hypothalamus. Less
|
