Regulation of translational effectors by amino acid and mammalian target of rapamycin signaling pathways - Possible involvement of autophagy in cultured hepatoma cells
Regulation of translational effectors by amino acid and mammalian target of rapamycin signaling pathways - Possible involvement of autophagy in cultured hepatoma cells
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DOI：
10.1074/jbc.274.2.1058
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发表时间：
1999-01-08
影响因子：
4.8
通讯作者：
Yonezawa, K
中科院分区：
文献类型：
--
作者：
Shigemitsu, K;Tsujishita, Y;Yonezawa, K
氨基酸剥夺过表达人胰岛素受体的中国仓鼠卵巢细胞导致p70 S6激酶（p70）失活和真核起始因子4 E-结合蛋白1（4 E-BP 1）去磷酸化，其对胰岛素无反应，氨基酸的再添加以雷帕霉素敏感的方式恢复这些反应，表明氨基酸和雷帕霉素的哺乳动物靶点通过共同的效应子信号。同样地，从肝癌细胞系H4 IIE中去除培养基氨基酸不会消除胰岛素刺激p70和4 E-BP 1的能力。向缺乏氨基酸的H4 IIE细胞中加入3-甲基腺嘌呤（3 MA），在10 mM时几乎完全抑制了由氨基酸去除引起的蛋白质降解的增加，并且在10 mM时也强烈抑制了胰岛素刺激p70和4 E-BP 1的能力。用3 MA处理H4 IIE细胞没有改变胰岛素激活酪氨酸磷酸化、磷酸肌醇3-激酶、或丝裂原活化蛋白激酶。总之，H4 IIE细胞维持哺乳动物靶的雷帕霉素依赖性信号传导途径的胰岛素响应性的能力在没有外源性氨基酸的情况下冲击p70和4 E-BP 1，反映了通过3 MA敏感过程内源性地产生氨基酸，推测为自噬，这是肝脏中兼性蛋白质降解的主要机制。
Amino acid deprivation of Chinese hamster ovary cells overexpressing human insulin receptors results in deactivation of p70 S6 kinase (p70) and dephosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), which become unresponsive to insulin readdition of amine acids restores these responses in a rapamycin-sensitive manner, suggesting that amino acids and mammalian target of rapamycin signal through common effecters. Contrarily, withdrawal of medium amino acids from the hepatoma cell line H4IIE does not abolish the ability of insulin to stimulate p70 and 4E-BP1. The addition of 3-methyladenine (3MA) to H4IIE cells deprived of amino acids inhibited the increment in protein degradation caused by amino acid withdrawal nearly completely at 10 mM and also strongly inhibited the ability of insulin to stimulate p70 and 4E-BP1 at 10 mM. Treatment of H4IIE cells with 3MA did not alter the ability of insulin to activate tyrosine phosphorylation, phosphoinositide 3-kinase, or mitogen-activated protein kinase. In conclusion, the ability of H4IIE cells to maintain the insulin responsiveness of the mammalian target of rapamycin-dependent signaling pathways impinging on p70 and 4E-BP1 without exogenous amino acids reflects the generation of amino acids endogenously through a 3MA-sensitive process, presumably autophagy, a major mechanism of facultative protein degradation in liver.