AMPK在胰岛素信号转导通路中的作用

单磷酸腺苷活化蛋白激酶(AMP-activated potein kinase,AMPK)作为一种细胞能量调节器,当细胞经历代谢应激反应时,伴随着细胞内AMP水平或AMP与ATP的比例升高,AMPK被AMP激活,其活化的结果导致脂肪酸氧化的增加以产生更多ATP;同时,抑制ATP消耗,综合效应是帮助细胞度过急性损伤,暂时保障细胞的存活。因为一些治疗2型糖尿病的药物通过激活AMPK而发挥作用,故AMPK被认为是各种潜在的和有效的抗糖尿病药物的靶效应器。5-氨基-4-氨甲酰咪唑核苷(5-amino-4-imidazolecarboxamide riboside,AICAR),进入细胞后被磷酸化变成ZMP,后者类似AMP也能够激活AMPK。因此,我们采用AICAR激活AMPK,观察活化的AMPK对脂肪细胞能量代谢及胰岛素信号途径的作用。结果显示,脂肪细胞中的AMPK被激活后,丙酰辅酶A(malonyl-CoA,一种脂肪酸氧化作用的抑制剂及脂肪酸合成的前体中间产物)浓度下降80%;在已分化的3T3-F442a脂肪细胞中,AICAR通过激活AMPK,增强胰岛素对Akt/PKB的激活和GSK3的磷酸化。相反,在AICAR预...     

AMPK在机体骨骼肌运动代谢适应方面的研究进展

腺苷酸活化蛋白激酶(AMP-activated protein kinase,AMPK)作为机体细胞的"能量感受器",可通过激活其下游靶蛋白调节组织细胞糖、脂代谢过程。运动适应涉及机体多个系统和器官,其中骨骼肌在机体对运动产生的代谢适应方面的作用最为明显。运动作为对机体的一个刺激可活化组织细胞AMPK,本文将针对AMPK在机体组织对运动产生代谢适应方面的最新研究进展加以综述,以期为阐明运动防治代谢性疾病的机制提供理论依据。     

瘦蛋白介导的AMPK信号转导途径

瘦蛋白(leptin)介导的腺苷酸激活蛋白激酶(AMP-activated protein kinase,AMPK)信号转导途径在脂肪代谢的调节中起重要作用。瘦蛋白与其受体结合使AMPK信号转导途径激活,最终激活肉碱脂酰转移酶-1,通过促进脂肪酸氧化而参与脂肪代谢的调节。本文主要介绍近年来关于瘦蛋白介导的AMPK信号转导途径的组成、活性调节及其作用机制的最新研究进展。     

腺苷酸活化蛋白激酶：肿瘤治疗新靶点

腺苷酸活化蛋白激酶（AMP—activated proteinkinase,AMPK）是真核细胞内发现的一类与细胞能量代谢有关激酶家族中的一员,被称之为“能量感应器”。当细胞内AMP／ATP值升高时,AMPK被激活。研究发现,在肿瘤细胞中,活化的AMPK可协同相关抑癌因子调节细胞周期、细胞凋亡以及蛋白质合成,最终影响细胞的增殖。因而,AMPK可以通过感应细胞能量水平的变化来调节细胞增殖。这给肿瘤治疗提供了一定的启示,即以肿瘤细胞能量代谢特点而探寻抑制肿瘤细胞增殖的途径。     

AMPK对线粒体功能的调节

5’单磷酸腺苷活化蛋白激酶（AMP—activated protein kinase,AMPK）是细胞的能量感受器,调节细胞能量代谢,在正常细胞和癌细胞中均发挥重要的生物功能,它的激活有助于纠正代谢紊乱,使细胞代谢趋向生理平衡。在细胞应急反应中,细胞感受到能量危机,ATP浓度下降,AMP浓度上升,细胞内AMP／ATP比例上升,AMPK被激活：而在病理状态下,如代谢综合征、肿瘤等,常伴随能量代谢紊乱和AMPK激活抑制,因此,AMPK被视为治疗代谢性疾病与肿瘤的潜在作用靶点。然而,AMPK对能量代谢的调节与线粒体的功能密不可分,线粒体作为细胞的能量工厂,在健康与疾病中也发挥着重要的作用。越来越多的研究表明,线粒体能影响AMPK的活性,同时AMPK也通过多方面对线粒体进行调节,线粒体相关疾病与AMPK的调节有着密切的关系。该文主要针对AMPK是如何对线粒体的合成、线粒体自噬、内源性凋亡及线粒体相关疾病等方面进行综述。     

细胞能量监测器——AMP激活的蛋白激酶

在真核生物中 ,ＡＭＰ激活的蛋白激酶(ＡＭＰＫ)因其活性受ＡＭＰ/ＡＴＰ比值调控 ,被称作细胞的“代谢传感蛋白”或“能量监测器”[1] 。当ＡＭＰ/ＡＴＰ比值升高时ＡＭＰＫ被激活 ,通过对下游靶蛋白的磷酸化 ,关闭消耗ＡＴＰ的合成代谢途径 ,并开启分解代谢途径 ,如 :脂肪酸的氧化等 ,由此来监控细胞中ＡＭＰ和ＡＴＰ的水平[2 ] 。由于其下游靶蛋白的种类、数量众多 ,不同的研究者通过不同的方法曾多次发现了这一类蛋白激酶的调控作用 ,但直到获得了编码这些蛋白激酶的ＤＮＡ序列后 ,才发现它们均为同一蛋白激酶亚家族的成员。1 .早期发现…     

噻唑衍生物WSF-SN-10激活AMPK的机制研究

目的:在噻唑衍生物中筛选新型AMPK激活剂并探究其激活AMPK的分子机制,以期找到副作用少的II型糖尿病治疗药物。方法:用14种噻唑衍生物处理293T细胞,用Western Blot筛选能显著提高AMPK磷酸化水平的化合物;用HPLC和FACS分别检测该化合物对细胞内AMP/ATP比值和Ca~(2+)浓度的影响,探究其激活AMPK的分子机制。结果:WSF-SN-10(2-(2-(6,6-二甲基双环[3,1,1]庚-2-亚基)肼基)-4-(4-氰基苯基)噻唑)为14种噻唑衍生物中活性最强的AMPK激活剂;20μM下WSF-SN-10激活AMPK的活性最强;用20μM WSF-SN-10处理293T细胞后,细胞内的AMP/ATP比值和LKB1的磷酸化水平分别上升至空白对照的1.94和3.04倍,同时Ca~(2+)浓度无明显变化,说明WSF-SN-10通过增加细胞内的AMP/ATP比值来激活AMPK。结论:噻唑衍生物WSF-SN-10能抑制细胞内的ATP合成来间接激活AMPK,是治疗II型糖尿病和肥胖症的潜在药物。     

AMPK与胰岛素抵抗

糖代谢是物质代谢的基础,运动中骨骼肌糖代谢水平直接影响机体运动能力。近年来研究发现,腺苷酸活化蛋白激酶(AMPK)作为能量代谢变化的感受器能够被运动中ATP/AMP的比值变化所激活,并能直接改善骨骼肌胰岛素抵抗,对机体运动能力有重要的影响。同时AMPK的长期激活可能参与了运动训练引起的胰岛素敏感性增加的调节,虽然其机制尚不清楚。本文通过文献检索法对运动中AMPK的激活机制及其在改善胰岛素抵抗过程中的作用及机制进行综述。     

AMPK在机体糖脂代谢中的作用

AMP激活的蛋白激酶(AMPK)是一种广泛参与调节细胞代谢的激酶,被称为"能量感受器".一旦胞浆中AMP/ATP比例升高,或其它因素激活AMPK时,AMPK可增强葡萄糖摄取和利用,以及脂肪酸氧化,产生更多能量;同时抑制葡萄糖异生、脂质合成及糖原合成等通路,减少能量消耗,从而使细胞能量代谢保持平衡.AMPK参与调节包括胰岛β细胞、肝脏、骨骼肌和脂肪在内的多种外周组织的糖脂代谢过程.本文旨在总结并讨论AMPK在机体主要糖脂代谢器官中的作用,并重点分析其在治疗胰岛素抵抗和2型糖尿病中的潜在作用.     

Management of cellular energy by the AMP-activated protein kinase system

The AMP-activated protein kinase is a sensor of cellular energy status that is found in all eukaryotic cells. It is activated by rising AMP and falling ATP by a complex mechanism that results in an ultrasensitive response. The functions of the different domains on the three subunits of the alphabetagamma heterotrimer are slowly being unravelled, and a recent development has been the identification of a glycogen-binding domain on the beta subunit. Along with findings that high cellular glycogen represses kinase activation, this suggests that the system may be a sensor of glycogen content as well as of AMP and ATP. New insights have been obtained into the sequence and structural features by which the kinase recognises its downstream target proteins, and these are discussed. Once activated by depletion of cellular energy reserves, the kinase switches on ATP-producing catabolic pathways and switches off ATP-consuming processes, both via direct phosphorylation of regulatory proteins and via indirect effects on gene expression. A survey of the range of downstream targets for this important signalling pathway is presented.     

Elm1p is one of three upstream kinases for the Saccharomyces cerevisiae SNF1 complex

BACKGROUND: The yeast SNF1 protein kinase and the mammalian AMP-activated protein kinase are highly conserved heterotrimeric complexes that are "metabolic master switches" involved in the switch from fermentative/anaerobic to oxidative metabolism. They are activated by cellular stresses that deplete cellular ATP, and SNF1 is essential in the response to glucose starvation. In both cases, activation requires phosphorylation at a conserved threonine residue within the activation loop of the kinase domain, but identifying the upstream kinase(s) responsible for this has been a challenging, unsolved problem. RESULTS: Using a library of strains that express 119 yeast protein kinases as GST fusions, we identified Elm1p as the sole kinase that could activate the kinase domain of AMP-activated protein kinase in vitro. Elm1p also activated the purified SNF1 complex, and this correlated with phosphorylation of Thr210 in the activation loop. Removal of the C-terminal domain increased the Elm1p kinase activity, indicating that it is auto-inhibitory. Expression of activated, truncated Elm1p from its own promoter gave a constitutive pseudohyphal growth phenotype that was rescued by deletion of SNF1, showing that Snf1p was acting downstream of Elm1p. Deletion of ELM1 does not give an snf- phenotype. However, Elm1p is closely related to Pak1p and Tos3p, and a pak1Delta tos3Delta elm1Delta triple mutant had an snf1- phenotype, i.e., it would not grow on raffinose and did not display hyperphosphorylation of the SNF1 target, Mig1p, in response to glucose starvation. CONCLUSIONS: Elm1p, Pak1p, and Tos3p are upstream kinases for the SNF1 complex that have partially redundant functions.     

Anti-lipolytic action of AMP-activated protein kinase in rodent adipocytes

Despite its importance in terms of energy homeostasis, the role of AMP-activated protein kinase in adipose tissue remains controversial. Initial studies have described an anti-lipolytic role for AMP-activated protein kinase, whereas more recent studies have suggested the converse. Thus we have addressed the role of AMP-activated protein kinase in adipose tissue by modulating AMP-activated protein kinase activity in primary rodent adipocytes using pharmacological activators or by adenoviral expression of dominant negative or constitutively active forms of the kinase. We then studied the effects of AMP-activated protein kinase activity modulation on lipolytic mechanisms. Finally, we analyzed the consequences of a genetic deletion of AMP-activated protein kinase in mouse adipocytes. AMP-activated protein kinase activity in adipocytes is represented mainly by the alpha(1) isoform and is induced by all of the stimuli that increase cAMP in adipocytes, including fasting. When AMP-activated protein kinase activity is increased by 5-aminoimidazole-4-carboxamide-riboside, phenformin, or by the expression of a constitutively active form, isoproterenol-induced lipolysis is strongly reduced. Conversely, when AMP-activated protein kinase activity is decreased either by a dominant negative form or in AMP-activated protein kinase alpha(1) knock-out mice, lipolysis is increased. We present data suggesting that AMP-activated protein kinase acts on hormone-sensitive lipase by blocking its translocation to the lipid droplet. We conclude that, in mature adipocytes, AMP-activated protein kinase activation has a clear anti-lipolytic effect.     

AMP-activated protein kinase--the key role in metabolic regulation

AMP-activated protein kinase (AMPK) is the central component of a protein kinase cascade that acts as an energy sensor maintaining the energy balance at the cellular as well as at the whole body level. Within the healthy cell, metabolic stress leading to an increase in AMP concentration results in AMPK activation. Once activated, AMPK "switches off" many anabolic pathways e.g. fatty acid and protein synthesis while "switches on" catabolic pathways such as fatty acid oxidation or glycolysis which serve to restore intracellular ATP level. Adipocyte derived hormones leptin and adiponectin activate AMPK in peripheral tissues increasing energy expenditure. AMPK also regulates food intake due to response to hormonal and nutrient signals in hypothalamus. Antidiabetic drugs that mimic the action of insulin activate the AMPK signaling pathways. Further studies are needed to clarify the importance of the AMPK activation for therapeutic effects of this drugs.     

Insulin antagonizes ischemia-induced Thr172 phosphorylation of AMP-activated protein kinase alpha-subunits in heart via hierarchical phosphorylation of Ser485/491

Previous studies showed that insulin antagonizes AMP-activated protein kinase activation by ischemia and that protein kinase B might be implicated. Here we investigated whether the direct phosphorylation of AMP-activated protein kinase by protein kinase B might participate in this effect. Protein kinase B phosphorylated recombinant bacterially expressed AMP-activated protein kinase heterotrimers at Ser(485) of the alpha1-subunits. In perfused rat hearts, phosphorylation of the alpha1/alpha2 AMP-activated protein kinase subunits on Ser(485)/Ser(491) was increased by insulin and insulin pretreatment decreased the phosphorylation of the alpha-subunits at Thr(172) in a subsequent ischemic episode. It is proposed that the effect of insulin to antagonize AMP-activated protein kinase activation involves a hierarchical mechanism whereby Ser(485)/Ser(491) phosphorylation by protein kinase B reduces subsequent phosphorylation of Thr(172) by LKB1 and the resulting activation of AMP-activated protein kinase.     

New roles for the LKB1-->AMPK pathway

The AMP-activated protein kinase (AMPK) is a sensor of cellular energy that is conserved throughout eukaryotes. It is activated by rising AMP, signifying falling energy status caused by starvation for a carbon source or other stress. Binding of AMP to the regulatory gamma subunit triggers phosphorylation of the catalytic alpha subunit by the upstream kinase LKB1, and the activated kinase switches on ATP-generating catabolic pathways while switching off ATP-requiring processes. AMPK inhibits the TOR (target of rapamycin) pathway by phosphorylating TSC2, thus inhibiting cell growth during times of stress. AMPK is also a target for adipokines that regulate energy balance at the whole-body level.     

The AMP-activated protein kinase cascade--a unifying system for energy control

AMP-activated protein kinase (AMPK) is the downstream component of a protein kinase cascade that acts as an intracellular energy sensor maintaining the energy balance within the cell. This pivotal role of AMPK places it in an ideal position for regulating whole-body energy metabolism, and AMPK might play a part in protecting the body from metabolic diseases such as type 2 diabetes and obesity. Mutations in AMPK cause cardiac hypertrophy and arrhythmia. Recent findings have identified LKB1--a protein kinase that is mutated in a hereditary form of cancer--as a candidate for the upstream kinase in the AMPK cascade. AMPK could provide a link in human diseases of which the underlying cause is due to defects in energy metabolism.     

AMP-activated/SNF1 protein kinases: conserved guardians of cellular energy

The SNF1/AMP-activated protein kinase (AMPK) family maintains the balance between ATP production and consumption in all eukaryotic cells. The kinases are heterotrimers that comprise a catalytic subunit and regulatory subunits that sense cellular energy levels. When energy status is compromised, the system activates catabolic pathways and switches off protein, carbohydrate and lipid biosynthesis, as well as cell growth and proliferation. Surprisingly, recent results indicate that the AMPK system is also important in functions that go beyond the regulation of energy homeostasis, such as the maintenance of cell polarity in epithelial cells.