Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA.
Science. 2011 Jun 10;332(6035):1317-22. doi: 10.1126/science.1199498.
The mammalian target of rapamycin (mTOR) protein kinase is a master growth promoter that nucleates two complexes, mTORC1 and mTORC2. Despite the diverse processes controlled by mTOR, few substrates are known. We defined the mTOR-regulated phosphoproteome by quantitative mass spectrometry and characterized the primary sequence motif specificity of mTOR using positional scanning peptide libraries. We found that the phosphorylation response to insulin is largely mTOR dependent and that mTOR exhibits a unique preference for proline, hydrophobic, and aromatic residues at the +1 position. The adaptor protein Grb10 was identified as an mTORC1 substrate that mediates the inhibition of phosphoinositide 3-kinase typical of cells lacking tuberous sclerosis complex 2 (TSC2), a tumor suppressor and negative regulator of mTORC1. Our work clarifies how mTORC1 inhibits growth factor signaling and opens new areas of investigation in mTOR biology.
哺乳动物雷帕霉素靶蛋白（mTOR）激酶是一种主要的生长促进剂，它可以形成两个复合物，mTORC1 和 mTORC2。尽管 mTOR 控制着多种过程，但已知的底物却很少。我们通过定量质谱法定义了 mTOR 调节的磷酸化蛋白质组，并使用位置扫描肽文库表征了 mTOR 的主要序列基序特异性。我们发现，胰岛素的磷酸化反应在很大程度上依赖于 mTOR，并且 mTOR 对 +1 位的脯氨酸、疏水性和芳香族残基表现出独特的偏好。衔接蛋白 Grb10 被鉴定为 mTORC1 的底物，它介导了缺乏结节性硬化复合物 2（TSC2）的细胞中典型的磷酸肌醇 3-激酶的抑制作用，TSC2 是一种肿瘤抑制因子，也是 mTORC1 的负调节剂。我们的工作阐明了 mTORC1 如何抑制生长因子信号，并为 mTOR 生物学的新研究领域开辟了道路。
