腺苷一磷酸激活蛋白激酶激活剂研究进展

徐亚洲，廖红，张陆勇，李佳，庞涛*

（1. 中国药科大学新药筛选中心，江苏 南京 210009；2. 中国科学院上海药物研究所，国家新药筛选中心，上海 201203）

腺苷一磷酸激活蛋白激酶激活剂研究进展

徐亚洲1，廖红1，张陆勇1，李佳2，庞涛1*

（1. 中国药科大学新药筛选中心，江苏 南京 210009；2. 中国科学院上海药物研究所，国家新药筛选中心，上海 201203）

腺苷一磷酸激活蛋白激酶（AMPK）是调控能量代谢的重要激酶，在代谢障碍、心血管疾病及肿瘤等疾病的病理进程中都有重要的调节作用。对AMPK的结构及其生理调节作用进行介绍，并重点综述AMPK间接激活剂和直接激活剂的研究进展，旨在为AMPK激活剂的深入开发提供参考。

腺苷一磷酸激活蛋白激酶；间接激活剂；直接激活剂

腺苷一磷酸激活蛋白激酶（adenosine 5'-monophosphateactivated protein kinase, AMPK）广泛存在于生物体内，对细胞能量代谢、生长分化等发挥关键作用，是一种极其重要的蛋白激酶，其生物学效应及其激活剂在临床疾病治疗方面的研究日益广泛。目前认为，AMPK作为靶点在治疗心血管疾病、糖尿病[1]、肥胖症[2]、中枢性疾病[3]以及癌症[4]等方面有着很大的应用潜力。

1 AMPK的结构

AMPK属丝氨酸/苏氨酸蛋白激酶，是由α、β和γ3个亚基组成的异源三聚体复合物（见图1）。其中，α亚基为催化亚基，有α1和α2这2种亚型；β、γ亚基为调节亚基，有β1、β2、γ1、γ2和γ3亚型，各种亚型由独立的基因编码，可组成多种可能的复合体形式[5]。这些复合体在机体不同组织中有不同的表达，且有可能发挥不同的作用，其中α2、β2在心脏和骨骼肌中高表达，γ2在心脏、脑等少数组织中表达，γ3只在骨骼肌中表达，而α1、β1、γ1在机体各组织中普遍存在[6]。最新研究表明：人类骨骼肌中AMPK复合体主要为α2β2γ3型[7]，肝脏内的AMPK复合体主要为α1β2γ1型[8]。

AMPK的α亚基N端含1个高度保守的催化结构域，其172位苏氨酸（Thr172）为磷酸化激活位点，另外还包括1个自抑制区（auto-inhibitory domain，AID）以及C端1个与β亚基和γ亚基结合的区域。β亚基包含1个N端豆蔻酰化位点(N-terminal myristoylation site)、中间的糖原结合区域和C端1个与其他2个亚基的结合区。γ亚基4个胱硫醚-β-合成酶（cystathionine-β-synthase，CBS）序列，组成2个Bateman域，每个Bateman域能结合1个腺嘌呤核苷酸如AMP或ATP[6-7]。

图1 腺苷一磷酸激活蛋白激酶结构图Figure 1 Structure of AMPK

2 AMPK的生理调节

目前认为，体内存在多种激酶可激活AMPK（见图2），主要有2种：一是肝激酶B1（liver kinase B1，LKB1），依赖细胞内AMP激活AMPK；二是钙/钙调蛋白依赖蛋白激酶激酶β（calcium/calmodulin-dependent protein kinase kinase beta，CaMKKβ），依赖第2信使钙离子的参与[9]。LKB1存在于除Hela细胞外的大多数组织细胞内，而CaMKKβ在中枢系统中高度表达且发挥着重要作用[6,10]。此外，还存在转化生长因子β激活激酶（transforming growth factor beta-activated kinase-1，Tak1）能激活AMPK。这3种激酶都作用于α亚基上的Thr172位点，使其磷酸化进而激活AMPK[7]。体内的蛋白磷酸酶2C（protein phosphotases 2C，PP2C）可催化AMPK的Thr172位点的去磷酸化[11]，使其变成无活性形式。

生理状态下，单磷酸腺苷（adenosine monophosphate，AMP）结合到γ亚基Bateman域上变构激活AMPK，同时AMP与γ亚基的结合促进α亚基上Thr172的磷酸化并阻碍PP2C的去磷酸化效应，从而大大增强了AMPK的活性[6,11]。研究表明，ATP可拮抗AMP结合到γ亚基上[12]，因此，生理或病理状态下只要能引起细胞内AMP/ATP比值细微变化的因素均能影响AMPK活性，如运动、激素刺激、缺血、缺氧、氧化应激等。激活的AMPK可激活其下游通路，从而发挥一系列重要作用，如调控营养物质代谢[1]、抑制促炎因子的合成释放[13]、影响肿瘤细胞生长[4]等。因此，AMPK已成为广泛关注的多种疾病的治疗新靶点，其激活剂也成为药物研究与开发的热点之一。

图2 腺苷一磷酸激活蛋白激酶的生理调节Figure 2 Physiological regulation of AMPK

3 AMPK激活剂

3.1 间接激活剂

很多药物和激素可在体内激活AMPK，但由于这些激活剂的作用机制尚未完全阐释清楚，且目前的研究证明其并不能与AMPK直接作用，而是通过影响AMP/ATP比值或AMPK上游激酶活性等途径间接激活AMPK，此类激活剂被称为间接激活剂（部分间接激活剂的作用机制见图3）。

图3 腺苷一磷酸激活蛋白激酶间接激活剂的作用机制Figure 3 Activation mechanism of AMPK by indirect activators

3.1.1 5-氨基咪唑-4-甲酰胺核苷 5-氨基咪唑-4-甲酰胺核苷（5-aminoimidazole-4-carboxamide riboside，AICAR，1)，又名阿卡地新（acadesine），是首个被发现的AMPK激活剂，现已作为研究工具广泛用于AMPK的相关实验研究。AICAR在腺苷转运体的作用下进入细胞，而后在腺苷激酶作用下转化为单磷酸衍生物5-aminoimidazole-4-carboxamide-1-β-D-ribofuranosyl-5'-monophosphate（ZMP）。ZMP与AMP类似，可结合到AMPKγ亚基，变构激活AMPK并阻碍AMPK的去磷酸化，但并不影响细胞内AMP/ATP比值[14]。AICAR在2型糖尿病大鼠模型中可降低血浆三酰甘油酯和游离脂肪酸水平、增加机体葡萄糖清除率、减少肝糖原分解、抑制脂肪分解等，从而减轻代谢障碍的诸多症状[15]。AICAR在培养的垂体肿瘤细胞内可降低p70S6激酶活性，抑制细胞生长[16]，且能在应激条件下引起星形细胞癌凋亡并保护正常脑细胞[17]。但有研究表明，AICAR并不是选择性AMPK激活剂，其可作用于其他AMP敏感酶，如抑制果糖-1,6-二磷酸酶的活性[18]、刺激糖原磷酸化酶[19]，故在使用AICAR作为AMPK激活剂进行研究时要考虑其可能影响体内多种酶活性这一性质。

AICAR可抑制核转录因子-κB（nuclear factor κB，NF-κB）和CCAAT增强子结合蛋白（CCAAT/enhancerbinding protein，C/EBP）转录因子进而下调促炎因子、诱

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Advances in Research on AMPK Activators

XU Yazhou1, LIAO Hong1, ZHANG Luyong1, LI Jia2, PANG Tao1*
(1. New Drug Screening Center, China Pharmaceutical University, Nanjing 210009, China; 2. National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China)

Adenosine 5′-monophosphate-activated protein kinase (AMPK) is a key player in regulating energy metabolism. It is placed at the center stage in studies of many pathological conditions including metabolic disorders, cardiovascular disease and cancer. The structure and physiological regulation of AMPK have been introduced in this paper. Moreover,the research progresses in indirect and direct activators of AMPK have been especially reviewed, so as to provide insights for the further development of this kind of drugs.

AMPK; indirect activator; direct activator

R962

A

1001-5094（2014）02-0125-07

接受日期：2013-12-16

*通讯作者：庞涛，副研究员；

研究方向：药物筛选及新药开发；

Tel: 025-83271340；E-mail: tpang2012@gmail.com