Volz A, Göke R, Lankat-Buttgereit B, Fehmann H C, Bode H P, Göke B
Department of Internal Medicine, Philipps University of Marburg, Germany.
FEBS Lett. 1995 Oct 2;373(1):23-9. doi: 10.1016/0014-5793(95)01006-z.
Glucose-dependent insulinotropic polypeptide (GIP) plays an important role in the regulation of postprandial insulin secretion and proinsulin gene expression of pancreatic beta-cells. This study demonstrates the molecular cloning of a cDNA for the GIP-receptor from a human insulinoma lambda gt11 cDNA library. The cloned cDNA encoded a seven transmembrane domain protein of 466 amino acids which showed high homology (41%) to the human glucagon-like peptide 1 (GLP-1) receptor. Homology to the GIP receptor from rat or hamster was 79% and 81%, respectively. When transfected stably into fibroblast CHL-cells a high affinity receptor was expressed which coupled to the adenylate cyclase with normal basal cAMP and increasing intracellular cAMP levels under stimulation with human GIP-1-42 (EC50 = 1.29 x 10(-13) M). The receptor accepted only human GIP 1-42 (Kd = 1.93 +/- 0.2 x 10(-8) M) and porcine truncated GIP 1-30 (Kd = 1.13 +/- 0.1 x 10(-8) M) as high affinity ligands. At 1 microM, exendin-4 and (9-39)amide weakly reduced GIP-binding (25%) whereas secretin, glucagon, glucagon-like peptide-1, vasoactive intestinal polypeptide, peptide histidine-isoleucine, and pituitary adenylyl cyclase activating peptide were without effect. In transfected CHL cells, GIP-1-42 did not increase intracellular calcium. Northern analysis revealed one transcript of human GIP receptor mRNA with an apparent size of 5.5 kb. The exact understanding of GIP receptor regulation and signal transduction will aid in the understanding of the incretin hormone's failure to exert its biological action at the pancreatic B-cell in type II diabetes mellitus.
葡萄糖依赖性促胰岛素多肽（GIP）在餐后胰岛素分泌调节及胰岛β细胞胰岛素原基因表达中发挥重要作用。本研究展示了从人胰岛素瘤λgt11 cDNA文库中对GIP受体cDNA的分子克隆。克隆的cDNA编码一个含466个氨基酸的七跨膜结构域蛋白，该蛋白与人胰高血糖素样肽1（GLP-1）受体具有高度同源性（41%）。与大鼠或仓鼠的GIP受体同源性分别为79%和81%。当稳定转染至成纤维细胞CHL细胞时，表达出一种高亲和力受体，该受体在人GIP-1-42刺激下（EC50 = 1.29×10⁻¹³ M）与腺苷酸环化酶偶联，具有正常基础cAMP水平并使细胞内cAMP水平升高。该受体仅接受人GIP 1-42（Kd = 1.93±0.2×10⁻⁸ M）和猪截短型GIP 1-30（Kd = 1.13±0.1×10⁻⁸ M）作为高亲和力配体。在1 microM浓度下，艾塞那肽-4和（9-39）酰胺对GIP结合有微弱降低作用（25%），而促胰液素、胰高血糖素、胰高血糖素样肽-1、血管活性肠多肽、肽组氨酸-异亮氨酸和垂体腺苷酸环化酶激活肽则无作用。在转染的CHL细胞中，GIP-1-42不会增加细胞内钙。Northern分析显示人GIP受体mRNA有一个明显大小为5.5 kb的转录本。对GIP受体调节和信号转导的确切理解将有助于理解在II型糖尿病中肠促胰岛素激素在胰岛B细胞未能发挥其生物学作用的原因。
