Department of Genetics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Center for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, UK.
Int J Mol Sci. 2024 Sep 18;25(18):10042. doi: 10.3390/ijms251810042.
mTOR plays a crucial role in cell growth by controlling ribosome biogenesis, metabolism, autophagy, mRNA translation, and cytoskeleton organization. It is a serine/threonine kinase that is part of two distinct extensively described protein complexes, mTORC1 and mTORC2. We have identified a rapamycin-resistant mTOR complex, called mTORC3, which is different from the canonical mTORC1 and mTORC2 complexes in that it does not contain the Raptor, Rictor, or mLST8 mTORC1/2 components. mTORC3 phosphorylates mTORC1 and mTORC2 targets and contains the ETS transcription factor ETV7, which binds to mTOR and is essential for mTORC3 assembly in the cytoplasm. Tumor cells that assemble mTORC3 have a proliferative advantage and become resistant to rapamycin, indicating that inhibiting mTORC3 may have a therapeutic impact on cancer. Here, we investigate which domains or amino acid residues of ETV7 and mTOR are involved in their mutual binding. We found that the mTOR FRB and LBE sequences in the kinase domain interact with the pointed (PNT) and ETS domains of ETV7, respectively. We also found that forced expression of the mTOR FRB domain in the mTORC3-expressing, rapamycin-resistant cell line Karpas-299 out-competes mTOR for ETV7 binding and renders these cells rapamycin-sensitive in vivo. Our data provide useful information for the development of molecules that prevent the assembly of mTORC3, which may have therapeutic value in the treatment of mTORC3-positive cancer.
mTOR 通过控制核糖体生物发生、代谢、自噬、mRNA 翻译和细胞骨架组织在细胞生长中发挥关键作用。它是一种丝氨酸/苏氨酸激酶，是两种不同的广泛描述的蛋白质复合物 mTORC1 和 mTORC2 的一部分。我们已经鉴定出一种雷帕霉素抗性 mTOR 复合物，称为 mTORC3，它与经典的 mTORC1 和 mTORC2 复合物不同，因为它不包含 Raptor、Rictor 或 mLST8 mTORC1/2 成分。mTORC3 磷酸化 mTORC1 和 mTORC2 靶标，并包含 ETS 转录因子 ETV7，它与 mTOR 结合，对于 mTORC3 在细胞质中的组装是必需的。组装 mTORC3 的肿瘤细胞具有增殖优势，并对雷帕霉素产生抗性，这表明抑制 mTORC3可能对癌症具有治疗作用。在这里，我们研究了 ETV7 和 mTOR 的哪些结构域或氨基酸残基参与它们的相互结合。我们发现激酶结构域中的 mTOR FRB 和 LBE 序列分别与 ETV7 的指向（PNT）和 ETS 结构域相互作用。我们还发现，在表达 mTORC3 的雷帕霉素抗性细胞系 Karpas-299 中强制表达 mTOR FRB 结构域会与 ETV7 竞争结合 mTOR，并使这些细胞在体内对雷帕霉素敏感。我们的数据为开发防止 mTORC3 组装的分子提供了有用的信息，这些分子在治疗 mTORC3 阳性癌症方面可能具有治疗价值。
