Glucokinase expression is regulated by glucose through O-GlcNAc glycosylation
Glucokinase expression is regulated by glucose through O-GlcNAc glycosylation
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DOI：
10.1016/j.bbrc.2016.08.056
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发表时间：
2016-09-16
影响因子：
3.1
通讯作者：
Guinez, Celine
中科院分区：
文献类型：
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作者：
Baldini, Steffi F.;Steenackers, Agata;Guinez, Celine
血糖随着禁食周期而波动。肝脏的功能之一是将血糖浓度维持在生理范围内。葡萄糖激酶（GCK）或己糖激酶IV，是调节肝脏中葡萄糖流量和使用的主要酶，导致高血糖症的补偿。在肝细胞中，GCK催化葡萄糖磷酸化为葡萄糖-6-磷酸。这种关键的酶促反应是肝脏中葡萄糖代谢的决定因素，包括糖原合成、糖酵解、脂肪生成和脂肪异生。在肝脏中，葡萄糖和胰岛素的同时增加增强GCK活性和基因表达，改变其亚细胞位置和与调节蛋白的相互作用。翻译后O-连接的β-N-乙酰葡糖胺化（O-G1 cNAc化）作为葡萄糖敏感性修饰，被认为通过修饰关键调控蛋白参与肝脏葡萄糖传感。因此，我们的目的是确定GCK是否被小鼠肝脏中的O-GlcNAc化修饰，并研究这种修饰在调节GCK蛋白表达中的作用。我们证明了内源性GCK表达与病理生理模型ob/ob小鼠中的O-GlcNAc水平相关。更具体地，响应于O-G1 cNAcase（OGA）的药理学抑制，GCK的含量增加。使用GlcNAc特异性凝集素琥珀酰化-WGA和点击化学标记方法，我们证明GCK通过O-GlcNAc酰化修饰。此外，我们证明了siRNA介导的Ogt敲除不仅降低O-GlcNAc含量，而且降低GCK蛋白水平。总之，我们在体内和体外的结果表明，GCK的表达是由营养感应O-GlcNAc在肝脏中的循环调节。(C)2016 Elsevier Inc. All rights reserved.
Blood glucose fluctuates with the fasting-feeding cycle. One of the liver's functions is to maintain blood glucose concentrations within a physiological range. Glucokinase (GCK) or hexokinase IV, is the main enzyme that regulates the flux and the use of glucose in the liver leading to a compensation of hyperglycemia. In hepatocytes, GCK catalyzes the phosphorylation of glucose into glucose-6-phosphate. This critical enzymatic reaction is determinant for the metabolism of glucose in the liver which includes glycogen synthesis, glycolysis, lipogenesis and gluconeogenesis. In liver, simultaneous increase of glucose and insulin enhances GCK activity and gene expression, changes its subcellular location and interaction with regulatory proteins. The post-translational O-linked beta-N-acetylglucosaminylation (O-G1cNAcylation) acts as a glucose-sensitive modification and is believed to take part in hepatic glucose sensing by modifying key regulatory proteins. Therefore, we aimed to determine whether GCK is modified by O-GlcNAcylation in the liver of mice and investigated the role that this modification plays in regulating GCK protein expression. We demonstrated that endogenous GCK expression correlated with O-GIcNAc levels in the pathophysiological model ob/ob mice. More specifically, in response to the pharmacological inhibition of O-G1cNAcase (OGA) contents of GCK increased. Using the GlcNAc specific lectin succinylated-WGA and click chemistry labeling approaches, we demonstrated that GCK is modified by O-GIcNAcylation. Further, we demonstrated that siRNA-mediated Ogt knock-down not only decreases O-GlcNAc content but also GCK protein level. Altogether, our in vivo and in vitro results demonstrate that GCK expression is regulated by nutrient-sensing O-GlcNAc cycling in liver. (C) 2016 Elsevier Inc. All rights reserved.