An allosteric activator of glucokinase impairs the interaction of glucokinase and glucokinase regulatory protein and regulates glucose metabolism
An allosteric activator of glucokinase impairs the interaction of glucokinase and glucokinase regulatory protein and regulates glucose metabolism
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DOI：
10.1074/jbc.m605186200
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发表时间：
2006-12-08
影响因子：
4.8
通讯作者：
Nagata, Yasufumi
中科院分区：
文献类型：
--
作者：
Futamura, Mayumi;Hosaka, Hideka;Nagata, Yasufumi
葡萄糖激酶（GK）在控制血糖稳态中起关键作用。我们鉴定了一种小分子GK激活剂，化合物A，其增加葡萄糖亲和力和GK的最大速度（V-max）。化合物A增强了分离的大鼠胰岛的胰岛素分泌，并增强了原代培养的大鼠肝细胞中的葡萄糖利用。在大鼠口服葡萄糖耐量试验中，口服给药化合物A降低血浆葡萄糖升高，同时血浆胰岛素和肝糖原增加。在肝脏中，GK活性受其与葡萄糖激酶调节蛋白（GKRP）的结合的急性控制。为了解释GK激活剂如何影响GK在细胞核和细胞质之间穿梭的分子方面，进一步研究了化合物A对GK-GKRP相互作用的影响。化合物A增加了分离的大鼠原代肝细胞和大鼠肝组织中细胞质GK的水平。在无细胞系统中的实验揭示了化合物A与葡萄糖结合的游离GK相互作用，从而损害GK和GKRP的缔合。另一方面，化合物A不与葡萄糖未结合的GK或GKRP相关的GK结合。此外，我们发现葡萄糖依赖性GK-GKRP相互作用也需要ATP。鉴于GK对胰岛素分泌和肝脏葡萄糖代谢的联合显著作用，其中涉及GK-GKRP机制，GK的活化在2型糖尿病的治疗中具有新的治疗潜力。
Glucokinase (GK) plays a key role in the control of blood glucose homeostasis. We identified a small molecule GK activator, compound A, that increased the glucose affinity and maximal velocity (V-max) of GK. Compound A augmented insulin secretion from isolated rat islets and enhanced glucose utilization in primary cultured rat hepatocytes. In rat oral glucose tolerance tests, orally administrated compound A lowered plasma glucose elevation with a concomitant increase in plasma insulin and hepatic glycogen. In liver, GK activity is acutely controlled by its association to the glucokinase regulatory protein (GKRP). In order to decipher the molecular aspects of how GK activator affects the shuttling of GK between nucleus and cytoplasm, the effect of compound A on GK-GKRP interaction was further investigated. Compound A increased the level of cytoplasmic GK in both isolated rat primary hepatocytes and the liver tissues from rats. Experiments in a cell-free system revealed that compound A interacted with glucose-bound free GK, thereby impairing the association of GK and GKRP. On the other hand, compound A did not bind to glucose-unbound GK or GKRP-associated GK. Furthermore, we found that glucose- dependent GK-GKRP interaction also required ATP. Given the combined prominent role of GK on insulin secretion and hepatic glucose metabolism where the GK-GKRP mechanism is involved, activation of GK has a new therapeutic potential in the treatment of type 2 diabetes.