Naturally-occurring missense mutations in the human growth hormone-releasing hormone receptor alter ligand binding.
Naturally-occurring missense mutations in the human growth hormone-releasing hormone receptor alter ligand binding.
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DOI：
10.1677/joe.1.06213
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发表时间：
2005-09
期刊：
影响因子：
--
通讯作者：
M. Alba;R. Salvatori
中科院分区：
文献类型：
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作者：
M. Alba;R. Salvatori
生长激素（GH）释放激素（GHRH）是刺激GH分泌的下丘脑因子。它通过激活由垂体促生长细胞表达的423个氨基酸的七个跨膜结构域G蛋白偶联受体（GHRH受体，GHRH-R）起作用。家族性孤立性生长激素缺乏症（IGHD）可由人类和小鼠GHRH-R基因突变引起。我们已经描述了IGHD患者中该基因的六个致病错义突变（H137 L，L144 H，A176 V，A222 E，F242 C，K329 E）。这些突变作为常染色体隐性遗传性状遗传，并导致受体传递GHRH信号的受损。本研究的目的是研究这些突变导致受体功能障碍的机制。为此，我们将每种突变的受体瞬时表达到中国仓鼠卵巢细胞中。表达每种突变受体的细胞没有显示出响应于GHRH的细胞内环AMP的增加。免疫沉淀和免疫荧光研究表明，氨基酸的变化不会导致蛋白质降解，也不会改变受体正确插入细胞膜。与人125 I-GHRH的结合研究表明，缺乏对GHRH的反应是由于所有突变的受体都不能结合配体。这些研究表明，异常配体结合是天然发生的错义突变改变GHRH-R功能的常见机制。
Growth hormone (GH) releasing hormone (GHRH) is a hypothalamic factor that stimulates GH secretion. It acts by activating a seven transmembrane domain G protein-coupled receptor of 423 amino acids expressed by the somatotroph cells of the pituitary gland (GHRH receptor, GHRH-R). Familial isolated growth hormone deficiency (IGHD) can be caused by mutations in the GHRH-R gene both in humans and mice. We have described six disease-causing missense mutations in this gene in IGHD patients (H137L, L144H, A176V, A222E, F242C, K329E). These mutations are inherited as autosomal recessive traits, and cause impairment of the receptor to transmit GHRH signalling. The aim of this study is to investigate the mechanisms through which these mutations cause receptor malfunction. To this end, we transiently expressed each mutated receptor into Chinese hamster ovary cells. Cells expressing each of the mutated receptors did not show an increase in intracellular cyclic AMP in response to GHRH. Immunoprecipitation and immunofluorescence studies indicated that the amino acid changes do not cause protein degradation, and do not alter the proper insertion of the receptor into the cell membrane. Binding studies with human 125I-GHRH showed that the lack of response to GHRH is due to inability of all the mutated receptors to bind the ligand. These studies demonstrate that abnormal ligand binding is a common mechanism by which naturally occurring missense mutation alter GHRH-R function.