Relieving Autophagy and 4EBP1 from Rapamycin Resistance
Relieving Autophagy and 4EBP1 from Rapamycin Resistance
复制标题
DOI：
10.1128/mcb.05430-11
复制
发表时间：
2011-07-01
影响因子：
5.3
通讯作者：
Murphy, Leon O.
中科院分区：
文献类型：
--
作者：
Nyfeler, Beat;Bergman, Philip;Murphy, Leon O.
哺乳动物雷帕霉素靶蛋白复合物1 （mTORC1）是一种由癌基因和肿瘤抑制因子调控的多蛋白信号复合物。mTORC1下游的输出包括核糖体蛋白S6激酶1 （S6K1）、真核翻译起始因子4E （eIF4E）和自噬，它们的调节导致细胞生长、增殖和代谢的变化。雷帕霉素，一种变构的mTORC1抑制剂，并不能同样拮抗这些输出，但其原因尚不清楚。在这里，我们证明了雷帕霉素在不同细胞系中激活自噬的能力与mTORC1的稳定性相关。雷帕霉素暴露会破坏mTORC1的稳定性，但在自噬对药物不敏感的细胞系中，检测到的mtor结合的raptor水平高于雷帕霉素刺激自噬的细胞。利用小干扰RNA (siRNA)，我们发现敲低raptor可减轻自噬和eIF4E效应途径对雷帕霉素耐药的影响。重要的是，无效浓度的atp竞争性mTOR抑制剂可以与雷帕霉素联合抑制mTORC1并激活自噬，但保持mTORC2信号完整。这些数据表明，使用联合策略可以克服雷帕霉素对mTORC1的部分抑制，并为实现mTORC1的完全和选择性抑制提供了一种治疗途径。
The mammalian target of rapamycin complex 1 (mTORC1) is a multiprotein signaling complex regulated by oncogenes and tumor suppressors. Outputs downstream of mTORC1 include ribosomal protein S6 kinase 1 (S6K1), eukaryotic translation initiation factor 4E (eIF4E), and autophagy, and their modulation leads to changes in cell growth, proliferation, and metabolism. Rapamycin, an allosteric mTORC1 inhibitor, does not antagonize equally these outputs, but the reason for this is unknown. Here, we show that the ability of rapamycin to activate autophagy in different cell lines correlates with mTORC1 stability. Rapamycin exposure destabilizes mTORC1, but in cell lines where autophagy is drug insensitive, higher levels of mTOR-bound raptor are detected than in cells where rapamycin stimulates autophagy. Using small interfering RNA (siRNA), we find that knockdown of raptor relieves autophagy and the eIF4E effector pathway from rapamycin resistance. Importantly, nonefficacious concentrations of an ATP-competitive mTOR inhibitor can be combined with rapamycin to synergistically inhibit mTORC1 and activate autophagy but leave mTORC2 signaling intact. These data suggest that partial inhibition of mTORC1 by rapamycin can be overcome using combination strategies and offer a therapeutic avenue to achieve complete and selective inhibition of mTORC1.