Department of Incretin Biology, Novo Nordisk, DK-2820 Gentofte, Denmark; Department of Chemistry, MEMPHYS - Center for Biomembrane Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
Peptides. 2013 Nov;49:100-8. doi: 10.1016/j.peptides.2013.09.001. Epub 2013 Sep 14.
The glucagon-like peptide-1 receptor (GLP-1R) belongs to family B of the G-protein coupled receptors (GPCRs), and has become a promising target for the treatment of type 2 diabetes. Here we describe the development and characterization of a fully functional cysteine-deprived and C-terminally truncated GLP-1R. Single cysteines were initially substituted with alanine, and functionally redundant cysteines were subsequently changed simultaneously. Our results indicate that Cys(174), Cys(226), Cys(296) and Cys(403) are important for the GLP-1-mediated response, whereas Cys(236), Cys(329), Cys(341), Cys(347), Cys(438), Cys(458) and Cys(462) are not. Extensive deletions were made in the C-terminal tail of GLP-1R in order to determine the limit for truncation. As for other family B GPCRs, we observed a direct correlation between the length of the C-terminal tail and specific binding of (125)I-GLP-1, indicating that the membrane proximal part of the C-terminal is involved in receptor expression at the cell surface. The results show that seven cysteines and more than half of the C-terminal tail can be removed from GLP-1R without compromising GLP-1 binding or function.
胰高血糖素样肽-1 受体（GLP-1R）属于 G 蛋白偶联受体（GPCR）家族 B，已成为治疗 2 型糖尿病的有前途的靶点。在这里，我们描述了一种完全功能性的半胱氨酸缺乏和 C 末端截断的 GLP-1R 的开发和特性。最初用丙氨酸替代单个半胱氨酸，然后同时改变功能冗余的半胱氨酸。我们的结果表明，Cys(174)、Cys(226)、Cys(296)和 Cys(403)对 GLP-1 介导的反应很重要，而 Cys(236)、Cys(329)、Cys(341)、Cys(347)、Cys(438)、Cys(458)和 Cys(462)则不是。为了确定截断的极限，我们在 GLP-1R 的 C 末端尾部进行了广泛的缺失。与其他家族 B GPCR 一样，我们观察到 C 末端尾部的长度与（125）I-GLP-1 的特异性结合之间存在直接相关性，这表明 C 末端的膜近端部分参与了细胞表面受体的表达。结果表明，GLP-1R 可以去除七个半胱氨酸和 C 末端尾部的一半以上而不影响 GLP-1 结合或功能。
