Functional analysis of a newly identified ligand and search for novel bioactive peptides associated with regulation of feeding behavior.

肥胖是世界范围内最严重的问题之一，因为它与生活方式相关的疾病有关，如高血压，心血管疾病和2型糖尿病。2005年，我们在大鼠脑中发现了一种新的生物活性肽--神经介肽S（neuromedin S，NMS），它是G蛋白偶联受体（GPCRs）FM-3/GPR 66和FM-4/TGR-1的内源性配体。NMS具有与致氧化神经肽神经介肽U（NMU）相同的受体结合所必需的核心结构。侧脑室（ICV）注射NMS比NMU诱导更强的摄食抑制作用。弓状核的α-MSH和室旁核的CRH参与NMS的摄食作用。Ghrelin是一种从胃中纯化的新肽，是生长激素促分泌素受体（GHS-R）的内源性配体，具有刺激摄食的作用。我们发现母体ghrelin在妊娠后期调节胎儿发育，ICV给予大鼠去酰基ghrelin通过与不同于GHS-R的受体相互作用刺激进食，ghrelin和去酰基ghrelin都参与胎儿脊髓的神经发生。我们建立了20个稳定表达孤儿GPCR的细胞系，并开发了使用BRET（生物发光共振能量转移）和受体内化的新方法。

Obesity is one of the most serious problems worldwide, because it is associated with lifestyle-related disease such as hypertension, cardiovascular disease and type 2 diabetes. The aims of this study are to identify novel bioactive peptides associated with regulation of energy balance and feeding behavior, and to clarify the biochemical and pathophysiological significance of the peptides.In 2005, we identified a novel bioactive peptide, neuromedin S (NMS), in rat brain as an endogenous ligand for the G protein-coupled receptors (GPCRs) FM-3/GPR66 and FM-4/TGR-1. NMS has same core structure essential for receptor binding as anorexigenic neuropeptide, neuromedin U (NMU). Intracerebroventricular (ICV) administration of NMS in rats induced more potent suppression of feeding than that of NMU. α-MSH in the arcuate nucleus and CRH in the paraventricular nucleus were involved in NMS action on feeding. Furthermore we isolated NMS of Eurasian bombinid toads, indicating that NMS and NMU genes had already diverged at the level of the Amphibia.Ghrelin, a novel peptide purified from stomach as an endogenous ligand for the growth hormone secretagogue receptor (GHS-R), is an acylated peptide that stimulates food intake. We showed that maternal ghrelin regulates fetal development during the late stages of pregnancy, ICV administration of des-acyl ghrelin to rats stimulates feeding through interactions with a receptor distinct from the GHS-R, and both ghrelin and des-acyl ghrelin are involved in neurogenesis of the fetal spinal cord.In order to search for novel peptides associated with regulation of feeding behavior, we established twenty cell lines stably expressing orphan GPCRs, and developed new methods using BRET (Bioluminescence Resonance Energy Transfer) and receptor internalization.