Rapamycin inhibits F-actin reorganization and phosphorylation of focal adhesion proteins
Rapamycin inhibits F-actin reorganization and phosphorylation of focal adhesion proteins
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DOI：
10.1038/onc.2008.137
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发表时间：
2008-08-28
期刊：
影响因子：
8
通讯作者：
Huang, S.
中科院分区：
文献类型：
--
作者：
Liu, L.;Chen, L.;Huang, S.
细胞迁移的早期事件的特征是肌动蛋白细胞骨架的快速重组。最近，我们已经证明，雷帕霉素抑制肿瘤细胞的运动。为了了解潜在的机制，本研究旨在确定雷帕霉素对细胞运动的抑制是否与其阻止F-肌动蛋白重组有关。我们发现，雷帕霉素阻止I型胰岛素样生长因子（IGF-I）刺激的人横纹肌肉瘤（Rh 30），尤文肉瘤（Rh 1），胶质母细胞瘤（U-373）和前列腺癌（PC-3）细胞中的F-肌动蛋白重组，并同时抑制细胞中的粘着斑蛋白，包括粘着斑激酶（FAK），桩蛋白和p130（Cas）的磷酸化。雷帕霉素的作用被雷帕霉素抗性mTOR突变体（mTORrr）的表达阻断，但不是激酶死亡的mTORrr。raptor的下调模拟了雷帕霉素的作用。用表达组成型活性和雷帕霉素抗性突变体p70 S6激酶1（S6 K1）的重组腺病毒感染的细胞赋予雷帕霉素抗性。此外，IGF-I未能刺激F-actin重组和S6 K1下调细胞中黏着斑蛋白的磷酸化。组成性低磷酸化的真核起始因子4 E（eIF 4 E）结合蛋白1（4 E-BP 1 -5A）的表达抑制IGF-I刺激的F-肌动蛋白重组，但不改变细胞蛋白或黏着斑蛋白的磷酸化水平。结果表明，雷帕霉素通过破坏mTOR-raptor复合物抑制IGF-I诱导的F-肌动蛋白重组和粘着斑蛋白的磷酸化。由mTOR-raptor复合物介导的S6 K1和4 E-BP 1通路均参与IGF-I刺激的F-肌动蛋白重组的调节，但只有前者控制IGF-I刺激的粘着斑蛋白的磷酸化。
An early event of cell migration is characterized as the rapid reorganization of the actin cytoskeleton. Recently, we have demonstrated that rapamycin inhibits tumor cell motility. To understand the underlying mechanism, this study was set to determine whether rapamycin inhibition of cell motility is related to its prevention of F-actin reorganization. We found that rapamycin prevented type I insulin-like growth factor (IGF-I)-stimulated F-actin reorganization in human rhabdomyosarcoma (Rh30), Ewing sarcoma (Rh1), glioblastoma (U-373) and prostate carcinoma (PC-3) cells, and concurrently inhibited phosphorylation of focal adhesion proteins, including focal adhesion kinase (FAK), paxillin and p130(Cas) in the cells. The effect of rapamycin was blocked by expression of a rapamycin-resistant mutant of mTOR (mTORrr), but not a kinase-dead mTORrr. Downregulation of raptor mimicked the effect of rapamycin. Cells infected with a recombinant adenovirus expressing constitutively active and rapamycin-resistant mutant of p70 S6 kinase 1 (S6K1) conferred to resistance to rapamycin. Further, IGF-I failed to stimulate F-actin reorganization and phosphorylation of the focal adhesion proteins in the S6K1-downregulated cells. Expression of constitutively hypophosphorylated eukaryotic initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1-5A) inhibited IGF-I-stimulated F-actin reorganization, but did not alter the cellular protein or phosphorylation levels of the focal adhesion proteins. The results suggest that rapamycin inhibits IGF-I-induced F-actin reorganization and phosphorylation of the focal adhesion proteins by disruption of mTOR-raptor complex. Both S6K1 and 4E-BP1 pathways, mediated by the mTOR-raptor complex, are involved in the regulation of IGF-I-stimulated F-actin reorganization, but only the former controls IGF-I-stimulated phosphorylation of the focal adhesion proteins.