Novel growth hormone releasing peptide, ghrelin: analyses of its structure and function

生长激素促分泌素（GH Ss）是一种人工合成的小分子物质，通过孤儿蛋白偶联受体GHS-R刺激垂体释放生长激素（GH）。为了寻找GHS-R的天然配体，我们构建了稳定表达大鼠GHS-R的CHO细胞系，用于监测大鼠组织提取物诱导的细胞内钙离子浓度（[Ca^2+] i）变化。使用该细胞系，我们从胃中纯化了一种有效激活GHS-R的肽。纯化的多肽由28个氨基酸组成，其中Ser-3残基被正辛酰化。令人惊讶的是，Ser-3的正辛酰基修饰对于活性是必需的，因为去酰基肽不能诱导（[Ca^<2+>]_i）变化。我们克隆了哺乳动物（人、大鼠、小鼠、犬、猪、羊和牛）的gbrelin cDNA并确定了它们的结构。Manimalian ghrelin的前体结构高度h ...更多信息 omomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomomom Ghrelin的N-末端10个氨基酸完全相同，证明了Ghrelin的辛酰基修饰对Ghrelin活性的重要性。Ghrelin在体内外均能诱导GH的释放，并呈剂量依赖性。ICV注射ghrelin也刺激GH释放。胃内Ghrein免疫反应阳性细胞为胃内分泌细胞X/A样细胞。Ghrelin存在于X/A样细胞的分泌颗粒中，其激素产物和生理功能尚未阐明。在大鼠脑中，发现ghrelin免疫反应神经元位于下丘脑弓状核，该区域调节食物摄入。事实上，ICV注射ghrelin强烈刺激大鼠进食并增加体重增加。另一方面，抗生长素释放肽IgG强烈抑制进食。最近我们从鸡、青蛙（牛蛙）和鱼（鳗鱼和鳟鱼）中分离纯化了ghrein肽。生长激素释放肽的氨基酸序列在所有脊椎动物中是非常保守的。此外，ghrelin肽均被辛酸修饰。这些结果表明ghrelin在脊椎动物中起着非常重要的作用。少

Small synthetic molecules termed growth hormone secretagogues (GHSs) act through an orphan 0protein coupled receptor, GHS-R, to stimulate growth hormone (GH) release from pituitary. To search for the natural ligand for GHS-R, we constructed a stable CHO cell line expressing rat GHS-R for monitoring intracellular calcium concentration ([Ca^<2+>]_i) changes induced by rat tissue extracts. Using this cell line, we purified a peptide from stomach that potently activated GHS-R. The purified peptide was consisted of 28 amino acids, in which the Ser-3 residue was n-octanoylated. Surprisingly, this n-octanoyl modification at Ser-3 was essential to the activity, since des-acyl-peptide could not induce ([Ca^<2+>]_i) changes. We named the GH-releasing peptide ghrelin (ghre is the Proto-Indo-European root of the word grow).We cloned mammalian gbrelin cDNAs (human, rat, mouse, canine, porcine, ovine and bovine) and determined their structures. Precursor structures of manimalian ghrelin are highly h … More omologous. In particular, N-terminal 10 amino-acids are identical, which supports the importance of octanoyl modification for ghrelin s activity.Ghrelin induced GH release in a dose-dependent manner both in vitro and in vivo. ICV injection of ghrelin also stimulated GH release. Ghrein immunoreactive cells in the stomach were found in X/A-like cells, an endocrine cell in stomach. Ghrelin is found in the secretary granules of X/A-like cells whose hormonal product and physiological functions have not been previously clarified. In rat brain, ghrelin immunoreactive neurons were found to be localized in the hypothalamic arcuate nucleus, a region where regulates food intake. In fact, ICV injection of ghrelin strongly stimulated feeding in rats and increased body weight gain. On the other hand, anti-ghrelin IgG robustly suppressed feeding. These facts suggest that ghrelin is a new physiological regulator of nutritional homeostasis.Recently we purified ghrein peptides from chicken, frog (bullfrog) and fish (eel and trout). Aminoacid sequences of ghrelin peptides in all vertebrates are well conserved. Moreover, the ghrelin peptides are all modified by octanoic acid. These results suggest that ghrelin plays a fundamentally important role in vertebrates. Less