Regulation of protein synthesis by hypoxia via activation of the endoplasmic reticulum kinase PERK and phosphorylation of the translation initiation factor eIF2α
Regulation of protein synthesis by hypoxia via activation of the endoplasmic reticulum kinase PERK and phosphorylation of the translation initiation factor eIF2α
复制标题
DOI：
10.1128/mcb.22.21.7405-7416.2002
复制
发表时间：
2002-11-01
影响因子：
5.3
通讯作者：
Wouters, BG
中科院分区：
文献类型：
--
作者：
Koumenis, C;Naczki, C;Wouters, BG
缺氧深刻影响肿瘤的发展和对治疗的反应。虽然在识别缺氧下其合成发生改变的单个基因产物方面已经取得了进展，但人们对缺氧诱导蛋白质合成整体下调的机制知之甚少。响应应激调节蛋白质合成的一个关键步骤是翻译起始因子 eIF2α 在 Ser51 上的磷酸化，这会导致新蛋白质合成的抑制。在这里，我们报道，人类二倍体成纤维细胞和转化细胞暴露于缺氧会导致 eIF2α 磷酸化，这种修饰在重新充氧后很容易逆转。 eIF2α 的反式显性非磷酸化突变等位基因的表达减弱了缺氧条件下蛋白质合成的抑制。内质网 (ER) 驻留的 eIF2a 激酶 PERK 在缺氧应激下过度磷酸化，野生型 PERK 的过度表达增加了缺氧诱导的 eIF2α 磷酸化水平。稳定表达显性失活 PERK 等位基因的细胞和具有 PERK 纯合缺失的小鼠胚胎成纤维细胞表现出 eIF2α 磷酸化减弱，并减少对缺氧反应的蛋白质合成抑制。 PERK-/-小鼠胚胎成纤维细胞未能磷酸化 eIF2α，并且在长期暴露于缺氧后表现出比野生型成纤维细胞更低的存活率。这些结果表明细胞对缺氧应激的适应需要 PERK 的激活和 eIF2α 的磷酸化，并表明缺氧诱导的翻译减弱的机制可能与 ER 应激和未折叠蛋白反应有关。
Hypoxia profoundly influences tumor development and response to therapy. While progress has been made in identifying individual gene products whose synthesis is altered under hypoxia, little is known about the mechanism by which hypoxia induces a global downregulation of protein synthesis. A critical step in the regulation of protein synthesis in response to stress is the phosphorylation of translation initiation factor eIF2alpha on Ser51, which leads to inhibition of new protein synthesis. Here we report that exposure of human diploid fibroblasts and transformed cells to hypoxia led to phosphorylation of eIF2alpha, a modification that was readily reversed upon reoxygenation. Expression of a transdominant, nonphosphorylatable mutant allele of eIF2alpha attenuated the repression of protein synthesis under hypoxia. The endoplasmic reticulum (ER)-resident eIF2a kinase PERK was hyperphosphorylated upon hypoxic stress, and overexpression of wild-type PERK increased the levels of hypoxia-induced phosphorylation of eIF2alpha. Cells stably expressing a dominant-negative PERK allele and mouse embryonic fibroblasts with a homozygous deletion of PERK exhibited attenuated phosphorylation of eIF2alpha and reduced inhibition of protein synthesis in response to hypoxia. PERK-/- mouse embryo fibroblasts failed to phosphorylate eIF2alpha and exhibited lower survival after prolonged exposure to hypoxia than did wild-type fibroblasts. These results indicate that adaptation of cells to hypoxic stress requires activation of PERK and phosphorylation of eIF2alpha and suggest that the mechanism of hypoxia-induced translational attenuation may be linked to ER stress and the unfolded-protein response.