PLD1 regulates mTOR signaling and mediates Cdc42 activation of S6K1
PLD1 regulates mTOR signaling and mediates Cdc42 activation of S6K1
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DOI：
10.1016/j.cub.2003.11.021
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发表时间：
2003-12-02
期刊：
影响因子：
9.2
通讯作者：
Chen, J
中科院分区：
文献类型：
--
作者：
Fang, YM;Park, IH;Chen, J
背景：哺乳动物靶标雷帕霉素(MTOR)通过下游靶标核糖体S6蛋白1(S6K1)和真核细胞翻译起始因子4E结合蛋白1(4E-BP1)调节细胞生长和增殖。我们已经确定磷脂酸(PA)是mTOR信号有丝分裂激活的媒介。在本研究中，我们验证了磷脂酶D_1(PLD_1)是mTOR上游调节因子的假设，以及先前报道的CDC42激活S6K1是由PLD_1介导的假说。结果：在血清刺激的细胞中，野生型PLD_1的过表达增加了S6K1的活性，而催化失活的PLD_1对S6K1起显性-负性作用。更重要的是，通过RNAi消除内源性PLD1后，HEK293和COS-7细胞中S6K1的激活和4E-BP1的过度磷酸化都受到强烈的抑制。PLD1基因的敲除也导致细胞尺寸减小，这表明PLD1在细胞生长控制中起着关键作用。利用雷帕霉素抗性突变体S6K1，Cdc42‘S被证明是通过mTOR途径发挥作用的。当CDC42在PLD1激活所需的特定区域发生突变时，其在血清存在的情况下激活S6K1的能力受到阻碍。然而，当外源PA作为刺激物时，PLD1失活的CDC42突变体的行为与野生型蛋白相似。结论：我们的观察揭示了PLD1参与mTOR信号转导和细胞大小控制，并为CDC42激活S6K1提供了分子机制。提出了一种新的级联机制，通过CDC42、PLD1和PA将有丝分裂信号连接到mTOR。
Background: The mammalian target of rapamycin (mTOR) regulates cell growth and proliferation via the downstream targets ribosomal S6 kinase 1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1). We have identified phosphatidic acid (PA) as a mediator of mitogenic activation of mTOR signaling. In this study, we set out to test the hypotheses that phospholipase D 1 (PLD1) is an upstream regulator of mTOR and that the previously reported S6K1 activation by Cdc42 is mediated by PLD1.Results: Overexpression of wild-type PLD1 increased S6K1 activity in serum-stimulated cells, whereas a catalytically inactive PLD1 exerted a dominant-negative effect on S6K1. More importantly, eliminating endogenous PLD1 by RNAi led to drastic inhibition of serum-stimulated S6K1 activation and 4E-BP1 hyperphosphorylation in both HEK293 and COS-7 cells. Knockdown of PLD1 also resulted in reduced cell size, suggesting a critical role for PLD1 in cell growth control. Using a rapamycin-resistant S6K1 mutant, Cdc42's action was demonstrated to be through the mTOR pathway. When Cdc42 was mutated in a region specifically required for PLD1 activation, its ability to activate S6K1 in the presence of serum was hindered. However, when exogenous PA was used as a stimulus, the PLD1-inactive Cdc42 mutant behaved similarly to the wild-type protein.Conclusions: Our observations reveal the involvement of PLD1 in mTOR signaling and cell size control, and provide a molecular mechanism for Cdc42 activation of S6K1. A new cascade is proposed to connect mitogenic signals to mTOR through Cdc42, PLD1, and PA.