Hydrogen peroxide impairs insulin-stimulated assembly of mTORC1.
Hydrogen peroxide impairs insulin-stimulated assembly of mTORC1.
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DOI：
10.1016/j.freeradbiomed.2009.03.001
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发表时间：
2009-06-01
影响因子：
7.4
通讯作者：
Shenberger, Jeffrey S.
中科院分区：
文献类型：
--
作者：
Zhang, Lianqin;Kimball, Scot R.;Jefferson, Leonard S.;Shenberger, Jeffrey S.
关键词：
众所周知，氧化剂能够降低哺乳动物雷帕霉素靶蛋白（mTOR）底物、真核起始因子4 E结合蛋白1（4 E-BP 1）和p70 S6激酶1（S6 K1）的磷酸化，从而在起始水平上阻碍mRNA翻译。mTOR通过形成信号复合物mTORC 1（mTOR，raptor，GβL）来调节mRNA的翻译。胰岛素信号传导至mTORC 1依赖于Akt/PKB的磷酸化和结节性硬化症复合体（TSC 1/2）的抑制，从而增强4 E-BP 1和S6 K1的磷酸化。在这项研究中，我们报告了过氧化氢对胰岛素刺激的mTORC 1活性和组装A549和牛主动脉平滑肌细胞的影响。我们发现胰岛素刺激TSC 2的磷酸化，导致raptor-mTOR结合减少和富含脯氨酸的Akt底物40（PRAS 40）与mTOR沉淀的量减少。胰岛素还增加4 E-BP 1与mTOR的共沉淀以及mTORC 1底物4 E-BP 1和S6 K1的磷酸化。另一方面，H2 O2通过增加两种细胞类型中raptor-mTOR结合和来自mTOR免疫沉淀物的PRAS 40/raptor的比率来对抗胰岛素的作用。这些作用与4 E-BP 1磷酸化和4 E-BP 1/raptor比率的降低一起发生。siRNA介导的A549细胞中PRAS 40的敲低部分逆转了H2 O2对4 E-BP 1磷酸化的影响，但对S6 K1没有影响。这些发现与PRAS 40在氧化应激期间作为胰岛素刺激的mTORC 1活性的负调节剂起作用一致。
Oxidants are well-recognized for their capacity to reduce the phosphorylation of the mammalian target of rapamycin (mTOR) substrates, eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) and p70 S6 kinase 1 (S6K1), thereby hindering mRNA translation at the level of initiation. mTOR functions to regulate mRNA translation by forming the signaling complex mTORC1 (mTOR, raptor, GβL). Insulin signaling to mTORC1 is dependent upon phosphorylation of Akt/PKB and the inhibition of the tuberous sclerosis complex (TSC1/2), thereby enhancing the phosphorylation of 4E-BP1 and S6K1. In this study we report the effect of H2O2 on insulin-stimulated mTORC1 activity and assembly using A549 and bovine aortic smooth muscle cells. We show that insulin stimulated the phosphorylation of TSC2 leading to a reduction in raptor-mTOR binding and in the quantity of proline-rich Akt substrate 40 (PRAS40) precipitating with mTOR. Insulin also increased 4E-BP1 co-precipitating with mTOR and the phosphorylation of the mTORC1 substrates, 4E-BP1 and S6K1. H2O2, on the other hand, opposed the effects of insulin by increasing raptor-mTOR binding and the ratio of PRAS40/raptor derived from the mTOR immunoprecipitates in both cell types. These effects occurred in conjunction with a reduction in 4E-BP1 phosphorylation and the 4E-BP1/raptor ratio. siRNA-mediated knockdown of PRAS40 in A549 cells partially reversed the effect of H2O2 on 4E-BP1 phosphorylation but not on S6K1. These findings are consistent with PRAS40 functioning as a negative regulator of insulin-stimulated mTORC1 activity during oxidant stress.
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