Sensitivity of global translation to mTOR inhibition in REN cells depends on the equilibrium between eIF4E and 4E-BP1.
Sensitivity of global translation to mTOR inhibition in REN cells depends on the equilibrium between eIF4E and 4E-BP1.
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DOI：
10.1371/journal.pone.0029136
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发表时间：
2011
期刊：
影响因子：
3.7
通讯作者：
Biffo S
中科院分区：
文献类型：
--
作者：
Grosso S;Pesce E;Brina D;Beugnet A;Loreni F;Biffo S
起始是蛋白质合成的限速阶段，由调节翻译因子磷酸化的信号通路控制。引发有三个步骤，43 S、48 S和80 S的形成。43 S的形成受到eIF 2 α磷酸化的抑制。随后的步骤，48 S和80 S的形成是通过生长因子实现的。48 S依赖于eIF 4 E介导的eIF 4F复合物的组装; 4 E-BP竞争性地从eIF 4F置换eIF 4 E。两种途径控制eIF 4F：1）mTORc 1磷酸化并灭活4 E-BP，导致eIF 4F形成; 2）Ras-Mnk级联磷酸化eIF 4 E。我们发现，REN和NCI-H28间皮瘤细胞具有组成性激活的两个途径和最大的翻译速率，在没有外源性生长因子。翻译被eIF 2 α的磷酸化迅速消除。令人惊讶的是，药理学抑制mTORc 1导致下游靶点的完全去磷酸化，而甲硫氨酸掺入没有变化。此外，mTORc 1和MAPK/Mnk抑制剂的联合给药没有累加效应。mTORc 1和mTORc 2的抑制不影响代谢率。尽管如此，mTORc 1抑制减少eIF 4F复合物的形成，并抑制TOP mRNA在多核糖体上的易位。eIF 4 E的下调和4 E-BP 1的过表达诱导雷帕霉素敏感性，表明由于eIF 4 E调节，eIF 4F复合物的破坏与其向核糖体的再循环竞争。这些数据表明存在动态平衡，其中eIF 4F不是所有mRNA所必需的，并且在再循环到下一个之前不会从翻译的mRNA中被置换。
Initiation is the rate-limiting phase of protein synthesis, controlled by signaling pathways regulating the phosphorylation of translation factors. Initiation has three steps, 43S, 48S and 80S formation. 43S formation is repressed by eIF2α phosphorylation. The subsequent steps, 48S and 80S formation are enabled by growth factors. 48S relies on eIF4E-mediated assembly of eIF4F complex; 4E-BPs competitively displace eIF4E from eIF4F. Two pathways control eIF4F: 1) mTORc1 phosphorylates and inactivates 4E-BPs, leading to eIF4F formation; 2) the Ras-Mnk cascade phosphorylates eIF4E. We show that REN and NCI-H28 mesothelioma cells have constitutive activation of both pathways and maximal translation rate, in the absence of exogenous growth factors. Translation is rapidly abrogated by phosphorylation of eIF2α. Surprisingly, pharmacological inhibition of mTORc1 leads to the complete dephosphorylation of downstream targets, without changes in methionine incorporation. In addition, the combined administration of mTORc1 and MAPK/Mnk inhibitors has no additive effect. The inhibition of both mTORc1 and mTORc2 does not affect the metabolic rate. In spite of this, mTORc1 inhibition reduces eIF4F complex formation, and depresses translocation of TOP mRNAs on polysomes. Downregulation of eIF4E and overexpression of 4E-BP1 induce rapamycin sensitivity, suggesting that disruption of eIF4F complex, due to eIF4E modulation, competes with its recycling to ribosomes. These data suggest the existence of a dynamic equilibrium in which eIF4F is not essential for all mRNAs and is not displaced from translated mRNAs, before recycling to the next.
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影响因子：
64.8
作者：
Gandin, Valentina;Miluzio, Annarita;Barbieri, Anna Maria;Beugnet, Anne;Kiyokawa, Hiroaki;Marchisio, Pier Carlo;Biffo, Stefano
通讯作者：
Biffo, Stefano
DOI：
10.1073/pnas.0409513102
发表时间：
2005-06-28
影响因子：
11.1
作者：
Gorrini, C;Loreni, F;Biffo, S
通讯作者：
Biffo, S
影响因子：
5.3
作者：
Cook, JW;Sterman, DH;Kaiser, LR
通讯作者：
Kaiser, LR
影响因子：
21.3
作者：
Grandori, C;Gomez-Roman, N;White, RJ
通讯作者：
White, RJ
影响因子：
8
作者：
Constantinou, C;Clemens, MJ
通讯作者：
Clemens, MJ