Helmholtz Junior Research Group Posttranscriptional Control of Gene Expression, Center for Organismal Studies, Heidelberg, Germany.
Mol Biol Cell. 2012 Oct;23(19):3786-800. doi: 10.1091/mbc.E12-04-0296. Epub 2012 Aug 8.
Cells respond to different types of stress by inhibition of protein synthesis and subsequent assembly of stress granules (SGs), cytoplasmic aggregates that contain stalled translation preinitiation complexes. Global translation is regulated through the translation initiation factor eukaryotic initiation factor 2α (eIF2α) and the mTOR pathway. Here we identify cold shock as a novel trigger of SG assembly in yeast and mammals. Whereas cold shock-induced SGs take hours to form, they dissolve within minutes when cells are returned to optimal growth temperatures. Cold shock causes eIF2α phosphorylation through the kinase PERK in mammalian cells, yet this pathway is not alone responsible for translation arrest and SG formation. In addition, cold shock leads to reduced mitochondrial function, energy depletion, concomitant activation of AMP-activated protein kinase (AMPK), and inhibition of mTOR signaling. Compound C, a pharmacological inhibitor of AMPK, prevents the formation of SGs and strongly reduces cellular survival in a translation-dependent manner. Our results demonstrate that cells actively suppress protein synthesis by parallel pathways, which induce SG formation and ensure cellular survival during hypothermia.
细胞通过抑制蛋白质合成和随后组装应激颗粒 (SGs) 来应对不同类型的应激,SGs 是细胞质中的聚集体,其中包含停滞的翻译起始复合物。全球翻译通过翻译起始因子真核起始因子 2α (eIF2α) 和 mTOR 途径进行调节。在这里,我们发现冷休克是酵母和哺乳动物中 SG 组装的新触发因素。虽然冷休克诱导的 SG 需要数小时才能形成,但当细胞恢复到最佳生长温度时,它们会在几分钟内溶解。冷休克通过哺乳动物细胞中的激酶 PERK 引起 eIF2α 的磷酸化,但该途径并不是导致翻译抑制和 SG 形成的唯一因素。此外,冷休克会导致线粒体功能降低、能量耗竭,同时激活 AMP 激活的蛋白激酶 (AMPK) 并抑制 mTOR 信号通路。化合物 C,一种 AMPK 的药理学抑制剂,可防止 SG 的形成,并以依赖翻译的方式强烈降低细胞存活率。我们的结果表明,细胞通过平行途径积极抑制蛋白质合成,这些途径诱导 SG 形成并确保细胞在体温过低时的存活。