Autoregulation of the Mechanistic Target of Rapamycin (mTOR) Complex 2 Integrity Is Controlled by an ATP-dependent Mechanism
Autoregulation of the Mechanistic Target of Rapamycin (mTOR) Complex 2 Integrity Is Controlled by an ATP-dependent Mechanism
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DOI：
10.1074/jbc.m113.498055
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发表时间：
2013-09-20
影响因子：
4.8
通讯作者：
Sarbassov, Dos D.
中科院分区：
文献类型：
--
作者：
Chen, Chien-Hung;Kiyan, Vladimir;Sarbassov, Dos D.
营养物质对生物体是必不可少的，因为它们为细胞中的生物过程提供燃料。细胞监测营养丰度，协调合成代谢和分解代谢反应的比例。雷帕霉素（mTOR）信号传导机制是控制细胞合成代谢过程的重要营养感应途径。该通路的核心成分是mTOR，这是一种高度保守和必需的蛋白激酶，存在于两种不同的功能复合物中。营养敏感的mTOR复合体1 （mTORC1）通过磷酸化蛋白质合成调节因子S6K1和4EBP1来控制细胞生长和细胞大小，而其第二个复合体mTORC2通过作为Akt和其他AGC激酶家族成员的调节激酶来调节细胞增殖。mTORC2的调控仍然不清楚。我们的研究表明，细胞ATP平衡控制mTORC2的基础激酶活性，维持mTORC2的完整性和Akt在turn motif Thr-450位点的磷酸化。我们发现mTOR通过磷酸化其疏水性和保守的Ser-260位点来稳定SIN1，以维持mTORC2的完整性。mTORC2的最佳激酶活性需要高于1.2 mM的ATP浓度，这使得该激酶复合物对ATP耗尽高度敏感。我们发现，不是氨基酸而是细胞的葡萄糖剥夺或急性ATP耗尽阻止了Ser-260上SIN1的mtor依赖性磷酸化和Thr-450上Akt的mtor依赖性磷酸化。在低糖培养基中，携带SIN1及其拟磷突变体替代的细胞显示出与mTORC2丰度较高和Akt磷酸化相关的细胞增殖率增加。因此，稳态ATP传感器mTOR控制mTORC2的完整性和Akt在turn基序位点的磷酸化。
Nutrients are essential for living organisms because they fuel biological processes in cells. Cells monitor nutrient abundance and coordinate a ratio of anabolic and catabolic reactions. Mechanistic target of rapamycin (mTOR) signaling is the essential nutrient-sensing pathway that controls anabolic processes in cells. The central component of this pathway is mTOR, a highly conserved and essential protein kinase that exists in two distinct functional complexes. The nutrient-sensitive mTOR complex 1 (mTORC1) controls cell growth and cell size by phosphorylation of the regulators of protein synthesis S6K1 and 4EBP1, whereas its second complex, mTORC2, regulates cell proliferation by functioning as the regulatory kinase of Akt and other members of the AGC kinase family. The regulation of mTORC2 remains poorly characterized. Our study shows that the cellular ATP balance controls a basal kinase activity of mTORC2 that maintains the integrity of mTORC2 and phosphorylation of Akt on the turn motif Thr-450 site. We found that mTOR stabilizes SIN1 by phosphorylation of its hydrophobic and conserved Ser-260 site to maintain the integrity of mTORC2. The optimal kinase activity of mTORC2 requires a concentration of ATP above 1.2 mM and makes this kinase complex highly sensitive to ATP depletion. We found that not amino acid but glucose deprivation of cells or acute ATP depletion prevented the mTOR-dependent phosphorylation of SIN1 on Ser-260 and Akt on Thr-450. In a low glucose medium, the cells carrying a substitution of SIN1 with its phosphomimetic mutant show an increased rate of cell proliferation related to a higher abundance of mTORC2 and phosphorylation of Akt. Thus, the homeostatic ATP sensor mTOR controls the integrity of mTORC2 and phosphorylation of Akt on the turn motif site.