胰岛素和佛波酯在蛋白质合成中经不同途径激活p70 S6激酶

为研究佛波酯 (PMA)和胰岛素在蛋白质合成中的信号传递 ,应用激酶活性测定和Western印迹等方法 ,分别检测mTOR(mammaliantargetofrapamycin)特异性抑制剂rapamycin或磷脂酰肌醇 3激酶 (PI3K)的特异性抑制剂LY2 94 0 0 2预处理、PMA或胰岛素处理的血清饥饿的中国仓鼠肺成纤维细胞 (CHL)中p70S6激酶 (p70S6K)和蛋白激酶B(PKB)的活性及表达 .结果显示 ,PMA或胰岛素刺激促进p70S6K的活化和表达 .而rapamycin预处理可阻断PMA和胰岛素对p70S6K的激活作用 ,表明PMA和胰岛素可能是通过mTOR 依赖性途径激活p70S6K .结果还显示 ,胰岛素刺激促进PKB的活化和表达 ,而PMA对PKB的活性和表达无影响 .LY2 94 0 0 2预处理可阻断胰岛素对p70S6K和PKB的激活作用 ,但不能抑制PMA刺激引起的p70S6K的活化 .表明胰岛素和PMA介导p70S6K活化的信号途径有所不同 ,胰岛素介导p70S6K的活化可能依赖于PI3K途径 ,而PMA介导p70S6K的活化不通过PI3K途径

P70 S6 Kinase Activated by Insulin and PMA Through Distinct Pathways in Protein Synthesis

Stimulation of serum-starved Chinese hamster lung (CHL) cells with either phorbol 12-myristate 13-acetate (PMA) or insulin resulted in the activation of p70 S6 kinase. All these effects were blocked by rapamycin, a specific inhibitor of mTOR(mammalian target of rapamycin), confirming that mTOR activation played an essential role in the activation of p70 S6 kinase stimulated by insulin and PMA. Protein kinase B (PKB) was activated by insulin but not by PMA. LY294002, a specific inhibitor of phosphatidylinositol-3 kinase (PI3K), could block the activation of p70 S6 kinase and PKB stimulated by insulin. The activation of p70 S6 kinase stimulated by PMA was unaffected by LY294002.These data suggested that p70 S6 kinase was activated by insulin and PMA through different pathways. PMA could induce the activation of p70 S6 kinase independently without PI3K and PKB, whereas insulin stimulated the activation of p70 S6 kinase through a mechanism that required PI3K and might involve PKB.