作者:David J. Lloyd、David J. St Jean、Robert J. M. Kurzeja、Robert C. Wahl、Klaus Michelsen、Rod Cupples、Michelle Chen、John Wu、Glenn Sivits、Joan Helmering、Renée Komorowski、Kate S. Ashton、Lewis D. Pennington、Christopher Fotsch、Mukta Vazir、Kui Chen、Samer Chmait、Jiandong Zhang、Longbin Liu、Mark H. Norman、Kristin L. Andrews、Michael D. Bartberger、Gwyneth Van、Elizabeth J. Galbreath、Steven L. Vonderfecht、Minghan Wang、Steven R. Jordan、Murielle M. Véniant、Clarence Hale
DOI:10.1038/nature12724
日期:2013.12
Two small-molecule disruptors of the glucokinaseâglucokinase-regulatory-protein complex, AMG-1694 and AMG-3969, are identified that decrease blood glucose levels in various models of hyperglycaemic rodents. Glucokinase (GK) is involved in the regulation of glucose homeostasis and is an important target for drug discovery against diabetes, but some current GK activators are associated with an increased risk for hypoglycaemia in the clinic. This paper presents an alternative therapeutic point of intervention, focused on the liver-specific GK regulatory protein (GKRP) that binds and inhibits GK in the nucleus. David Lloyd et al. report on a small molecule, AMG-1694, that specifically disrupts the GKâGKRP complex and reduces blood glucose in hyperglycaemic rodent models. Importantly AMG-1694 has no effect in normoglycaemic animals. Disruption of the GKâGKRP complex offers a liver-specific approach of upregulating GK activity in type II diabetes while reducing the risk of hypoglycaemia. Glucose homeostasis is a vital and complex process, and its disruption can cause hyperglycaemia and type II diabetes mellitus1. Glucokinase (GK), a key enzyme that regulates glucose homeostasis, converts glucose to glucose-6-phosphate2,3 in pancreatic β-cells, liver hepatocytes, specific hypothalamic neurons, and gut enterocytes4. In hepatocytes, GK regulates glucose uptake and glycogen synthesis, suppresses glucose production3,5, and is subject to the endogenous inhibitor GK regulatory protein (GKRP)6,7,8. During fasting, GKRP binds, inactivates and sequesters GK in the nucleus, which removes GK from the gluconeogenic process and prevents a futile cycle of glucose phosphorylation. Compounds that directly hyperactivate GK (GK activators) lower blood glucose levels and are being evaluated clinically as potential therapeutics for the treatment of type II diabetes mellitus1,9,10. However, initial reports indicate that an increased risk of hypoglycaemia is associated with some GK activators11. To mitigate the risk of hypoglycaemia, we sought to increase GK activity by blocking GKRP. Here we describe the identification of two potent small-molecule GKâGKRP disruptors (AMG-1694 and AMG-3969) that normalized blood glucose levels in several rodent models of diabetes. These compounds potently reversed the inhibitory effect of GKRP on GK activity and promoted GK translocation both in vitro (isolated hepatocytes) and in vivo (liver). A co-crystal structure of full-length human GKRP in complex with AMG-1694 revealed a previously unknown binding pocket in GKRP distinct from that of the phosphofructose-binding site. Furthermore, with AMG-1694 and AMG-3969 (but not GK activators), blood glucose lowering was restricted to diabetic and not normoglycaemic animals. These findings exploit a new cellular mechanism for lowering blood glucose levels with reduced potential for hypoglycaemic risk in patients with type II diabetes mellitus.
两种小分子破坏剂AMG-1694和AMG-3969能够破坏葡糖激酶-葡糖激酶调节蛋白复合体,降低高血糖啮齿动物模型的血糖水平。葡糖激酶(GK)参与调节血糖内平衡,是针对糖尿病发现药物的重要靶点,但是一些现有的GK活化剂会导致临床患者发生低血糖的风险上升。在这篇文章中我们介绍了一个新的治疗干预点,专注于与GK在细胞核中结合并抑制GK、具有肝脏特异性的葡糖激酶调节蛋白(GKRP)。大卫·劳埃德等人报告了一个可特异性破坏GK-GKRP复合体,在啮齿类高血糖模型中降低血糖的小分子AMG-1694。重要的是,AMG-1694对血糖正常的动物没有作用。破坏GK-GKRP复合体提供了只针对肝脏上调II型糖尿病患者的GK活性的方法,同时降低了低血糖的风险。血糖内平衡是一个非常重要的、复杂的过程,其受到破坏会导致高血糖和II型糖尿病。葡糖激酶是调节血糖内平衡的一个关键酶,在胰腺β-细胞、肝脏肝细胞、特定下丘脑神经元和肠道上皮细胞中将葡萄糖转化成6-磷酸葡糖。在肝脏肝细胞中,GK调节葡萄糖摄取和糖原合成,抑制葡萄糖生成,受到内源性抑制剂GK调节蛋白的抑制。空腹期间,GK调节蛋白结合GK、使GK失活并将GK裹入细胞核,GK因此不参与糖异生过程,不会出现葡萄糖磷酸化的无效循环。直接超活化GK(GK活化剂)的化合物可降低血糖水平,作为可能的治疗I型糖尿病的药物正在接受临床评估。但是最初的报告表明,一些GK活化剂在使用时会增加低血糖的风险。为了降低低血糖发生的风险,我们试图通过抑制GK调节蛋白增加GK活性。本文介绍了两种破坏GK-GKRP复合体的小分子AMG-1694和AMG-3969,它们使糖尿病啮齿类动物模型的血糖水平恢复正常。这两种化合物都能逆转GK调节蛋白对GK活性的抑制效应,促进GK定位转移,不论是在体外分离出的肝细胞中还是在体内的肝脏组织中。AMG-1694与全长人类GK调节蛋白形成的复合体的共晶体结构显示,GK调节蛋白存在一个不同于磷酸果糖结合位点的未知结合口袋。此外,使用AMG-1694和AMG-3969(而非GK活化剂)降低血糖仅对糖尿病模型动物有效,而不会影响正常动物的血糖水平。本研究利用一种新的细胞机制降低II型糖尿病患者的血糖水平,发生低血糖的风险较低。