Iron depletion suppresses mTORC1-directed signalling in intestinal Caco-2 cells via induction of REDD1.
Iron depletion suppresses mTORC1-directed signalling in intestinal Caco-2 cells via induction of REDD1.
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DOI：
10.1016/j.cellsig.2016.01.014
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发表时间：
2016-05
影响因子：
4.8
通讯作者：
Hundal HS
中科院分区：
文献类型：
--
作者：
Watson A;Lipina C;McArdle HJ;Taylor PM;Hundal HS
铁是一种不可或缺的微量营养素，它调节细胞功能的许多方面，包括生长和增殖。这些过程严重依赖于通过哺乳动物或雷帕霉素复合体1的机械靶点(MTORC1)进行的信号传递。在这里，我们测试了细胞与铁螯合剂去铁胺(DFO)孵育引起的铁耗竭是否通过mTORC1指导的信号和蛋白质合成来调节其对细胞生长的影响。我们使用了Caco-2细胞，这是一个成熟的人类肠道上皮细胞的体外模型。铁缺乏增加了铁调节蛋白(转铁蛋白受体和二价金属转运蛋白DMT1)的表达，但也明显抑制了Caco-2细胞的生长和增殖。这与mTORC1信号的抑制密切相关，通过mTOR底物、S6K1和4E-BP1的磷酸化减少和蛋白质合成减少来判断。MTORC1信号的减少与Redd1(在DNA损伤和发育中调节)的表达和积累增加以及Akt和TSC2的磷酸化减少密切相关。当细胞缺铁时，Redd1丰度的增加被迅速逆转，但也被基因转录抑制剂、蛋白磷酸酶2A(PP2A)和Redd1 siRNA所减弱-这两种策略也可以对抗与缺铁相关的mTORC1信号的丢失。我们的发现表明，在缺铁细胞中，Redd1和PP2A是mTORC1活性的关键调节因子，并表明它们的调节可能有助于缓解因缺铁而可能发生的肠粘膜萎缩。细胞铁(Fe)的耗竭显著减少了肠道Caco-2细胞的生长。在铁缺乏的细胞中，mTORC1引导的信号和蛋白质合成减少。铁缺乏以PP2A依赖的方式诱导Redd1的表达和获得。在铁缺乏的细胞中，抑制PP2A可阻断Redd1的获得并恢复mTORC1的活性。
Iron is an indispensable micronutrient that regulates many aspects of cell function, including growth and proliferation. These processes are critically dependent upon signalling via the mammalian or mechanistic target of rapamycin complex 1 (mTORC1). Herein, we test whether iron depletion induced by cell incubation with the iron chelator, deferoxamine (DFO), mediates its effects on cell growth through mTORC1-directed signalling and protein synthesis. We have used Caco-2 cells, a well-established in vitro model of human intestinal epithelia. Iron depletion increased expression of iron-regulated proteins (TfR, transferrin receptor and DMT1, divalent metal transporter, as predicted, but it also promoted a marked reduction in growth and proliferation of Caco-2 cells. This was strongly associated with suppressed mTORC1 signalling, as judged by reduced phosphorylation of mTOR substrates, S6K1 and 4E-BP1, and diminished protein synthesis. The reduction in mTORC1 signalling was tightly coupled with increased expression and accumulation of REDD1 (regulated in DNA damage and development 1) and reduced phosphorylation of Akt and TSC2. The increase in REDD1 abundance was rapidly reversed upon iron repletion of cells but was also attenuated by inhibitors of gene transcription, protein phosphatase 2A (PP2A) and by REDD1 siRNA — strategies that also antagonised the loss in mTORC1 signalling associated with iron depletion. Our findings implicate REDD1 and PP2A as crucial regulators of mTORC1 activity in iron-depleted cells and indicate that their modulation may help mitigate atrophy of the intestinal mucosa that may occur in response to iron deficiency. Cellular iron (Fe) depletion dramatically reduces growth of intestinal Caco-2 cells. mTORC1-directed signalling and protein synthesis are reduced in Fe-depleted cells. Fe deficiency induces expression and gain of REDD1 in a PP2A-dependent manner. PP2A inhibition blocks REDD1 gain and restores mTORC1 activity in Fe-depleted cells.