Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Oncogene. 2012 Apr 19;31(16):2115-20. doi: 10.1038/onc.2011.404. Epub 2011 Sep 12.
Growth factor signaling coupled to activation of the phosphatidylinositol-3-OH kinase (PI3K)/Akt pathway plays a crucial role in the regulation of cell proliferation and survival. The key regulatory kinase of Akt has been identified as mammalian target of rapamycin complex 2 (mTORC2), which functions as the PI3K-dependent Ser-473 kinase of Akt. This kinase complex is assembled by mTOR and its essential components rictor, Sin1 and mLST8. The recent genetic screening study in Caenorhabditis elegans has linked a specific point mutation of rictor to an elevated storage of fatty acids that resembles the rictor deficiency phenotype. In our study, we show that in mammalian cells the analogous single rictor point mutation (G934E) prevents the binding of rictor to Sin1 and the assembly of mTORC2, but this mutation does not interfere with the binding of the rictor-interacting protein Protor. A substitution of the rictor Gly-934 residue to a charged amino acid prevents formation of the rictor/Sin1 heterodimer. The cells expressing the rictor G934E mutant remain deficient in the mTORC2 signaling, as detected by the reduced phosphorylation of Akt on Ser-473 and a low cell proliferation rate. Thus, although a full length of rictor is required to interact with its binding partner Sin1, a single amino acid of rictor Gly-934 controls its interaction with Sin1 and assembly of mTORC2.
生长因子信号与磷酸肌醇-3-羟基激酶（PI3K）/Akt 途径的激活偶联，在调节细胞增殖和存活方面起着至关重要的作用。Akt 的关键调节激酶已被确定为雷帕霉素靶蛋白复合物 2（mTORC2），它作为 Akt 的 PI3K 依赖性 Ser-473 激酶发挥作用。该激酶复合物由 mTOR 及其必需成分rictor、Sin1 和 mLST8 组装而成。最近在秀丽隐杆线虫中的遗传筛选研究将 rictor 的特定点突变与脂肪酸的升高储存联系起来，这种储存类似于 rictor 缺乏表型。在我们的研究中，我们表明在哺乳动物细胞中，类似的 rictor 单点突变（G934E）可阻止 rictor 与 Sin1 的结合以及 mTORC2 的组装，但该突变不干扰 rictor 相互作用蛋白 Protor 的结合。 rictor Gly-934 残基取代带电荷的氨基酸可防止 rictor/Sin1 异二聚体的形成。表达 rictor G934E 突变体的细胞仍然缺乏 mTORC2 信号，如 Akt 在 Ser-473 上的磷酸化减少和细胞增殖率低所检测到的。因此，尽管全长 rictor 是与其结合伴侣 Sin1 相互作用所必需的，但 rictor Gly-934 的单个氨基酸控制其与 Sin1 的相互作用和 mTORC2 的组装。
