内质网应激期间控制蛋白质翻译的负反馈调节环的描绘。

Delineation of a negative feedback regulatory loop that controls protein translation during endoplasmic reticulum stress.

作者信息

Ma Yanjun, Hendershot Linda M

机构信息

Department of Genetics and Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

出版信息

J Biol Chem. 2003 Sep 12;278(37):34864-73. doi: 10.1074/jbc.M301107200. Epub 2003 Jul 1.

Abstract

Transient protein synthesis inhibition is an important protective mechanism used by cells during various stress conditions including endoplasmic reticulum (ER) stress. This response centers on the phosphorylation state of eukaryotic initiation factor (eIF)-2 alpha, which is induced by kinases like protein kinase R-like ER kinase (PERK) and GCN2 to suppress translation and is later reversed so translation resumes. GADD34 was recently identified as the factor that activates the type 1 protein serine/threonine phosphatase (PP1), which dephosphorylates eIF-2 alpha during cellular stresses. Our study delineates a negative feedback regulatory loop in which the eIF-2 alpha-controlled inhibition of protein translation leads to GADD34 induction, which promotes translational recovery. We show that activating transcription factor-4 (ATF4), which is paradoxically translated during the eIF-2 alpha-mediated translational block, is required for the transactivation of the GADD34 promoter in response to ER stress and amino acid deprivation. ATF4 directly binds to and trans-activates a conserved ATF site in the GADD34 promoter during ER stress. Examination of ATF4-/- MEFs revealed an absence of GADD34 induction, prolonged eIF-2 alpha phosphorylation, delayed protein synthesis recovery, and diminished translational up-regulation of BiP during ER stress. These studies demonstrate the essential role of GADD34 in the resumption of protein synthesis, define the pathway for its induction, and reveal that cytoprotective unfolded protein response targets like BiP are sensitive to the eIF-2 alpha-mediated block in translation.

摘要

瞬时蛋白质合成抑制是细胞在包括内质网(ER)应激在内的各种应激条件下所采用的一种重要保护机制。这种反应以真核起始因子(eIF)-2α的磷酸化状态为中心,该状态由蛋白激酶R样内质网激酶(PERK)和GCN2等激酶诱导,以抑制翻译,随后逆转,使翻译恢复。GADD34最近被确定为激活1型蛋白丝氨酸/苏氨酸磷酸酶(PP1)的因子,PP1在细胞应激期间使eIF-2α去磷酸化。我们的研究描绘了一个负反馈调节环,其中eIF-2α控制的蛋白质翻译抑制导致GADD34的诱导,从而促进翻译恢复。我们表明,激活转录因子-4(ATF4)在eIF-2α介导的翻译阻滞期间反常地被翻译,它是ER应激和氨基酸剥夺时GADD34启动子反式激活所必需的。在ER应激期间,ATF4直接结合并反式激活GADD34启动子中一个保守的ATF位点。对ATF4-/-小鼠胚胎成纤维细胞(MEF)的检测显示,在ER应激期间,不存在GADD34的诱导,eIF-2α磷酸化延长,蛋白质合成恢复延迟,并且BiP的翻译上调减弱。这些研究证明了GADD34在蛋白质合成恢复中的重要作用,确定了其诱导途径,并揭示了像BiP这样的细胞保护性未折叠蛋白反应靶点对eIF-2α介导的翻译阻滞敏感。

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