Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA.
J Biol Chem. 2011 Sep 16;286(37):32651-60. doi: 10.1074/jbc.M111.238014. Epub 2011 Jul 22.
Mammalian target of rapamycin (mTOR) is a kinase that plays a key role in a wide array of cellular processes and exists in two distinct functional complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Although mTORC2 is primarily activated by growth factors, mTORC1 is regulated by numerous extracellular and intracellular signals such as nutrients, growth factors, and cellular redox. Previous study has shown that cysteine oxidants sufficiently activate mTORC1 activity under amino acid-depleted conditions and that a reducing agent effectively suppresses amino acid-induced mTORC1 activity, thereby raising the possibility that redox-sensitive mechanisms underlie amino acid-dependent mTORC1 regulation. However, the molecular mechanism by which redox regulates mTORC1 activity is not well understood. In this study, we show that the redox-sensitive regulation of mTORC1 occurs via Rheb but not the Rag small GTPase. Enhancing cellular redox potential with cysteine oxidants significantly increases Rheb GTP levels. Importantly, modulation of the cellular redox potential with a cysteine oxidant or reducing agent failed to alter mTORC1 activity in TSC1(-/-) or TSC2(-/-) mouse embryonic fibroblast cells. Furthermore, a cysteine oxidant has little effect on mTOR localization but sufficiently activates mTORC1 activity in both p18(-/-) and control mouse embryonic fibroblast cells, suggesting that the redox-sensitive regulation of mTORC1 occurs independent of the Ragulator·Rag complex. Taken together, our results suggest that the TSC complex plays an important role in redox-sensitive mTORC1 regulation and argues for the activation of mTORC1 in places other than the lysosome upon inhibition of the TSC complex.
哺乳动物雷帕霉素靶蛋白（mTOR）是一种激酶，在广泛的细胞过程中发挥关键作用，存在于两个不同的功能复合物中，即 mTOR 复合物 1（mTORC1）和 mTOR 复合物 2（mTORC2）。虽然 mTORC2 主要由生长因子激活，但 mTORC1 受到许多细胞外和细胞内信号的调节，如营养素、生长因子和细胞氧化还原。先前的研究表明，半胱氨酸氧化剂在氨基酸缺乏条件下充分激活 mTORC1 活性，还原剂有效抑制氨基酸诱导的 mTORC1 活性，从而提出氧化还原敏感机制可能是氨基酸依赖性 mTORC1 调节的基础。然而，氧化还原调节 mTORC1 活性的分子机制尚不清楚。在这项研究中，我们表明，mTORC1 的氧化还原敏感调节是通过 Rheb 而不是 Rag 小 GTPase 发生的。用半胱氨酸氧化剂增强细胞氧化还原电势会显著增加 Rheb GTP 水平。重要的是，用半胱氨酸氧化剂或还原剂调节细胞氧化还原电势未能改变 TSC1(-/-)或 TSC2(-/-)小鼠胚胎成纤维细胞中的 mTORC1 活性。此外，半胱氨酸氧化剂对 mTOR 定位几乎没有影响，但在 p18(-/-)和对照小鼠胚胎成纤维细胞中充分激活 mTORC1 活性，这表明 mTORC1 的氧化还原敏感调节独立于 Ragulator·Rag 复合物发生。总之，我们的结果表明，TSC 复合物在氧化还原敏感的 mTORC1 调节中发挥重要作用，并表明在 TSC 复合物抑制后，mTORC1 在溶酶体以外的地方被激活。
