A direct linkage between the phosphoinositide 3-kinase-AKT signaling pathway and the mammalian target of rapamycin in mitogen-stimulated and transformed cells.
A direct linkage between the phosphoinositide 3-kinase-AKT signaling pathway and the mammalian target of rapamycin in mitogen-stimulated and transformed cells.
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发表时间：
2000-07
期刊：
影响因子：
11.2
通讯作者：
A. Sekulic;Christine C. Hudson;James L. Homme;Peng Yin;D. Otterness;L. Karnitz;R. Abraham
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文献类型：
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作者：
A. Sekulic;Christine C. Hudson;James L. Homme;Peng Yin;D. Otterness;L. Karnitz;R. Abraham
微生物来源的抗增殖剂雷帕霉素通过干扰哺乳动物雷帕霉素靶标（mTOR）的信号传导功能来抑制细胞生长。在这项研究中，我们证明了白细胞介素-3刺激诱导骨髓祖细胞系中mTOR激酶活性的渥曼青霉素敏感性增加。磷酸肌醇3 '-激酶（PI 3 K）参与调节mTOR活性的研究结果进一步表明，mTOR在体外和体内被PI 3 K调节的蛋白激酶AKT/PKB磷酸化。尽管AKT在体外磷酸化mTOR的两个COOH末端位点（Thr 2446和Ser 2448），但Ser 2448是胰岛素刺激或激活的表达AKT的人胚肾细胞中的主要磷酸化位点。在Ser 2448和/或Thr 2446处具有Ala取代的mTOR突变体的瞬时转染试验表明，AKT依赖性mTOR磷酸化对于HEK细胞中PHAS-I磷酸化或p70 S6 K活化不是必需的。然而，mTOR中氨基酸2430-2450的缺失（包括潜在的AKT磷酸化位点）显著增加了mTOR的基础蛋白激酶活性和体内信号传导功能。这些结果表明，mTOR是有丝分裂原刺激的细胞中PI 3 K-AKT信号传导途径的直接靶标，并且鉴定的AKT磷酸化位点嵌套在负调节mTOR的催化活性的“阻遏物结构域”内。此外，癌细胞中PI 3 K-AKT通路的活化状态可能是细胞对雷帕霉素的细胞抑制作用的敏感性的重要决定因素。
The microbially derived antiproliferative agent rapamycin inhibits cell growth by interfering with the signaling functions of the mammalian target of rapamycin (mTOR). In this study, we demonstrate that interleukin-3 stimulation induces a wortmannin-sensitive increase in mTOR kinase activity in a myeloid progenitor cell line. The involvement of phosphoinositide 3'-kinase (PI3K) in the regulation of mTOR activity was further suggested by findings that mTOR was phosphorylated in vitro and in vivo by the PI3K-regulated protein kinase, AKT/PKB. Although AKT phosphorylated mTOR at two COOH-terminal sites (Thr2446 and Ser2448) in vitro, Ser2448 was the major phosphorylation site in insulin-stimulated or -activated AKT-expressing human embryonic kidney cells. Transient transfection assays with mTOR mutants bearing Ala substitutions at Ser2448 and/or Thr2446 indicated that AKT-dependent mTOR phosphorylation was not essential for either PHAS-I phosphorylation or p70S6K activation in HEK cells. However, a deletion of amino acids 2430-2450 in mTOR, which includes the potential AKT phosphorylation sites, significantly increased both the basal protein kinase activity and in vivo signaling functions of mTOR. These results demonstrate that mTOR is a direct target of the PI3K-AKT signaling pathway in mitogen-stimulated cells, and that the identified AKT phosphorylation sites are nested within a "repressor domain" that negatively regulates the catalytic activity of mTOR. Furthermore, the activation status of the PI3K-AKT pathway in cancer cells may be an important determinant of cellular sensitivity to the cytostatic effect of rapamycin.