Amino acid-dependent control of p70s6k -: Involvement of tRNA aminoacylation in the regulation
Amino acid-dependent control of p70s6k -: Involvement of tRNA aminoacylation in the regulation
复制标题
DOI：
10.1074/jbc.274.2.1092
复制
发表时间：
1999-01-08
影响因子：
4.8
通讯作者：
Terada, N
中科院分区：
文献类型：
--
作者：
Iiboshi, Y;Papst, PJ;Terada, N
在人 T 类淋巴母细胞中，哺乳动物雷帕霉素靶点 (mTOR) 的下游信号转导事件，包括 p70(s6k) 的活性和真核起始因子 4E 结合蛋白 1 的磷酸化，依赖于培养基中的氨基酸浓度，而其他生长相关蛋白激酶则不然。氨基酸诱导的 p70(s6k) 激活被雷帕霉素完全抑制，但仅被渥曼青霉素部分抑制。此外，氨基酸浓度同样影响p70(s6k)活性，这依赖于mTOR的雷帕霉素抗性突变体(S2035I)。这些数据表明 mTOR 是 p70(s6k) 氨基酸依赖性激活所必需的。进一步探讨了氨基酸调节p70(s6k)活性的机制：1)氨基酸醇通过与tRNA合成酶竞争性结合抑制tRNA氨酰化，从而抑制p70(s6k)活性； 2) 放线菌酮或嘌呤霉素可阻断氨基酸消耗对 p70(s6k) 的抑制，从而抑制细胞中氨酰化 tRNA 的利用； 3) 在具有组氨酰 tRNA 合成酶温度敏感突变体的细胞中，p70(s6k) 通过细胞转变至不允许的温度而受到抑制，通过添加高浓度的组氨酸可部分恢复。这些结果表明，抑制 tRNA 氨酰化能够抑制 p70(s6k) 活性。脱酰化 tRNA 可能是 p70(s6k) 的负调节因子。
In human T-lymphoblastoid cells, downstream signaling events of mammalian target of rapamycin (mTOR), including the activity of p70(s6k) and phosphorylation of eukaryotic initiation factor 4E-binding protein 1, were dependent on amino acid concentration in the culture media, whereas other growth-related protein kinases were not. Amino acid-induced p70(s6k) activation was completely inhibited by rapamycin but only partially inhibited by wortmannin. Moreover, amino acid concentration similarly affected the p70(s6k) activity, which was dependent on a rapamycin-resistant mutant (S2035I) of mTOR. These data indicate that mTOR is required for amino acid-dependent activation of p70(s6k). The mechanism by which amino acids regulate p70(s6k) activity was further explored: 1) amino acid alcohols, which inhibit aminoacylation of tRNA by their competitive binding to tRNA synthetases, suppressed p70(s6k) activity; 2) suppression of p70(s6k) by amino acid depletion was blocked by cycloheximide or puromycin, which inhibit utilization of aminoacylated tRNA in cells; and 3) in cells having a temperature-sensitive mutant of histidyl tRNA synthetase, p70(s6k) was suppressed by a transition of cells to a nonpermissible temperature, which was partially restored by addition of high concentrations of histidine. These results indicate that suppression of tRNA aminoacylation is able to inhibit p70(s6k) activity. Deacylated tRNA may be a factor negatively regulating p70(s6k).