目的:肠激素葡萄糖依赖性促胰岛素多肽(GIP)通过GIP受体(GIPR)发出信号,导致餐后增强葡萄糖刺激的胰岛素分泌。从啮齿动物研究到人类研究的结果的翻译已经受到GIPR靶向化合物的意外效果的挑战。我们,因此,研究了物种之间的变异,重点是GIPR脱敏和受体C末端的作用。
方法:来自人类的GIPR,老鼠,老鼠,猪,在体外研究了狗和猫的同源配体亲和力,G蛋白激活(cAMP积累),β-抑制素的招募和内化。鼠标的变体,平行研究了具有交换的C末端尾巴的大鼠和人类GIPR。
结果:人类GIPR比啮齿动物GIPR更容易内化。尽管激动剂对Gαs激活具有相似的亲和力和效力,尤其是,小鼠GIPR显示受体脱敏降低,内在化和β-排除素招募。使用酶稳定,长效GIP类似物,物种差异更加明显。\'换尾\'人类,大鼠和小鼠的GIPR在其Gαs偶联中均具有完全功能,和小鼠GIPR恢复内化和β-抑制素2招募特性与人的尾巴。当人GIPR自身的C末端被大鼠或小鼠尾巴取代时,其丧失募集β-抑制蛋白2的能力。
结论:人GIPR的脱敏作用依赖于C末端尾部。C端尾部的物种依赖性功能和不同的物种依赖性内化模式,特别是在人类和小鼠的GIPR之间,是影响GIPR靶向治疗化合物临床前评价的重要因素。
OBJECTIVE: The gut hormone glucose-dependent insulinotropic polypeptide (GIP) signals via the GIP receptor (GIPR), resulting in postprandial potentiation of glucose-stimulated insulin secretion. The translation of results from rodent studies to
human studies has been challenged by the unexpected effects of GIPR-targeting compounds. We, therefore, investigated the variation between species, focusing on GIPR desensitization and the role of the receptor C-terminus.
METHODS: The GIPR from humans, mice, rats, pigs, dogs and cats was studied in vitro for cognate ligand affinity, G protein activation (cAMP accumulation), recruitment of beta-arrestin and internalization. Variants of the mouse, rat and
human GIPRs with swapped C-terminal tails were studied in parallel.
RESULTS: The
human GIPR is more prone to internalization than rodent GIPRs. Despite similar agonist affinities and potencies for Gαs activation, especially, the mouse GIPR shows reduced receptor desensitization, internalization and beta-arrestin recruitment. Using an enzyme-stabilized, long-acting GIP analogue, the species differences were even more pronounced. \'Tail-swapped\' human, rat and mouse GIPRs were all fully functional in their Gαs coupling, and the mouse GIPR regained internalization and beta-arrestin 2 recruitment properties with the
human tail. The human GIPR lost the ability to recruit beta-arrestin 2 when its own C-terminus was replaced by the rat or mouse tail.
CONCLUSIONS: Desensitization of the
human GIPR is dependent on the C-terminal tail. The species-dependent functionality of the C-terminal tail and the different species-dependent internalization patterns, especially between human and mouse GIPRs, are important factors influencing the preclinical evaluation of GIPR-targeting therapeutic compounds.