Molecular Genetics, Institute of Life Science, Kurume University, Kurume, Fukuoka 839-0864, Japan.
J Biochem. 2009 Nov;146(5):675-82. doi: 10.1093/jb/mvp112. Epub 2009 Jul 23.
Ghrelin was originally isolated from rat stomach as an endogenous ligand for the GH secretagogue receptor. The major active form of ghrelin is a 28-amino acid peptide modified by an n-octanoic acid on the serine 3 residue, and this lipid modification is essential for the biological activity of ghrelin. However, it is not clear whether prohormone convertase (PC) and ghrelin O-acyltransferase (GOAT) are the minimal requirements for synthesis of acyl-modified ghrelin in cultured cells. By using three cultured cell lines, TT, AtT20 and COS-7, in which the expression levels of processing proteases and GOAT vary, we examined the processing patterns of ghrelin precursor. We found that not only PC1/3 but also both PC2 and furin could process proghrelin to the 28-amino acid ghrelin. Moreover, the presence of PC and GOAT in the cells, as well as n-octanoic acid in the culture medium, was necessary to produce n-octanoyl ghrelin.
胃饥饿素最初从大鼠胃中分离出来，是生长激素促分泌素受体的内源性配体。胃饥饿素的主要活性形式是一种 28 个氨基酸的肽，在丝氨酸 3 残基上修饰有一个 n-辛酰基，这种脂质修饰对于胃饥饿素的生物学活性是必不可少的。然而，目前尚不清楚前激素转化酶（PC）和胃饥饿素 O-酰基转移酶（GOAT）是否是培养细胞中合成酰化修饰胃饥饿素的最小要求。通过使用三种培养细胞系 TT、AtT20 和 COS-7，其中表达水平的加工蛋白酶和 GOAT 不同，我们研究了胃饥饿素前体的加工模式。我们发现，不仅 PC1/3，而且 PC2 和弗林蛋白酶都可以将前胃饥饿素加工成 28 个氨基酸的胃饥饿素。此外，细胞中存在 PC 和 GOAT 以及培养基中的 n-辛酸对于产生 n-辛酰基胃饥饿素是必要的。
