Activation of AMP-activated protein kinase leads to the phosphorylation of elongation factor 2 and an inhibition of protein synthesis
Activation of AMP-activated protein kinase leads to the phosphorylation of elongation factor 2 and an inhibition of protein synthesis
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DOI：
10.1016/s0960-9822(02)01077-1
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发表时间：
2002-08-20
期刊：
影响因子：
9.2
通讯作者：
Rider, MH
中科院分区：
文献类型：
--
作者：
Horman, S;Browne, GJ;Rider, MH
蛋白质合成，特别是肽链延长，会消耗细胞能量。缺氧会激活 AMP 激活蛋白激酶（AMPK，参见 [1]），从而抑制生物合成途径以保存 ATP。在缺氧的大鼠肝细胞或用 5-氨基咪唑-4-甲酰胺 (AICA) 核苷处理的肝细胞中，AMPK 被激活，蛋白质合成受到抑制。蛋白质合成的抑制不能用起始因子 4E 结合蛋白-1 (4E-BP1) 或真核起始因子 2α (eIF2α) 磷酸化状态的变化来解释。然而，在缺氧和 AICA 核苷处理的肝细胞以及 AICA 核苷处理的 CHO-K1 细胞中，真核延伸因子 2 (eEF2) 的磷酸化状态增加，并且已知 eEF2 磷酸化会抑制其活性。将 CHO-K1 细胞与浓度不断增加的 2-脱氧葡萄糖一起孵育表明，雷帕霉素 (mTOR) 信号通路的哺乳动物靶标在响应轻度 ATP 耗竭而控制 eEF2 磷酸化水平方面并未发挥主要作用。在 HEK293 细胞中，显性失活 AMPK 构建体的转染消除了寡霉素诱导的蛋白质合成和 eEF2 磷酸化抑制。最后，eEF2 激酶（磷酸化 eEF2 的激酶）在缺氧或 AICA 核苷处理的肝细胞中被激活。因此，AMPK激活eEF2激酶，导致eEF2磷酸化和失活，为抑制蛋白质合成提供了新的机制。
Protein synthesis, in particular peptide-chain elongation, consumes cellular energy. Anoxia activates AMP-activated protein kinase (AMPK, see [1]), resulting in the inhibition of biosynthetic pathways to conserve ATP. In anoxic rat hepatocytes or in hepatocytes treated with 5-aminoimidazole-4-carboxamide (AICA) riboside, AMPK was activated and protein synthesis was inhibited. The inhibition of protein synthesis could not be explained by changes in the phosphorylation states of initiation factor 4E binding protein-1 (4E-BP1) or eukaryotic initiation factor 2alpha (eIF2alpha). However, the phosphorylation state of eukaryotic elongation factor 2 (eEF2) was increased in anoxic and AICA riboside-treated hepatocytes and in AICA riboside-treated CHO-K1 cells, and eEF2 phosphorylation is known to inhibit its activity. Incubation of CHO-K1 cells with increasing concentrations of 2-deoxyglucose suggested that the mammalian target of the rapamycin (mTOR) signaling pathway did not play a major role in controlling the level of eEF2 phosphorylation in response to mild ATP depletion. In HEK293 cells, transfection of a dominant-negative AMPK construct abolished the oligomycin-induced inhibition of protein synthesis and eEF2 phosphorylation. Lastly, eEF2 kinase, the kinase that phosphorylates eEF2, was activated in anoxic or AICA riboside-treated hepatocytes. Therefore, the activation of eEF2 kinase by AMPK, resulting in the phosphorylation and inactivation of eEF2, provides a novel mechanism for the inhibition of protein synthesis.