Radisavljevic Ziv Manasija, González-Flecha Beatriz
Harvard University, School of Public Health, Physiology Program, Boston, Massachusetts 02115, USA.
J Cell Biochem. 2004 Apr 15;91(6):1293-300. doi: 10.1002/jcb.20037.
Hydrogen peroxide (H2O2) activates signaling cascades essential for cell proliferation via phosphatidylinositol-3-kinase (PI3K) and Akt. Here we show that induction of mitogenic signaling by H2O2 activates sequentially PI3K, Akt, mammalian target of rapamycin (mTOR), and Ran protein. Akt activation is followed by signaling through the mTOR kinase and upregulation of Ran in primary type II pneumocytes, a cell type implicated in the development of lung adenocarcinoma. Pretreatment of the cells with wortmannin, a specific inhibitor of PI3K, or rapamycin, a specific inhibitor of mTOR kinase, prevented H2O2-increased mitosis. H2O2-induced Akt ser-473 phosphorylation and upregulation of Ran protein were prevented by wortmannin but not by rapamycin, indicating that PI3K is upstream of Akt and mTOR is downstream from Akt. Overexpression of myr-Akt or Ran-wt in type II pneumocytes increased Akt ser-473 phosphorylation and mitosis in a catalase-dependent manner, indicating that H2O2 is essential for Akt and Ran signaling. These results indicate that H2O2-induced mitogenic signaling in primary type II pneumocytes is mediated by PI3K, Akt, mTOR-kinase, and Ran protein.
过氧化氢（H2O2）通过磷脂酰肌醇-3-激酶（PI3K）和Akt激活细胞增殖所必需的信号级联反应。在此我们表明，H2O2诱导的促有丝分裂信号依次激活PI3K、Akt、雷帕霉素哺乳动物靶蛋白（mTOR）和Ran蛋白。在原代II型肺细胞（一种与肺腺癌发生有关的细胞类型）中，Akt激活后接着通过mTOR激酶发出信号并使Ran上调。用PI3K的特异性抑制剂渥曼青霉素或mTOR激酶的特异性抑制剂雷帕霉素预处理细胞，可防止H2O2增加的有丝分裂。渥曼青霉素可阻止H2O2诱导的Akt丝氨酸473磷酸化和Ran蛋白上调，但雷帕霉素不能，这表明PI3K在Akt上游，而mTOR在Akt下游。在II型肺细胞中过表达myr-Akt或Ran-wt以过氧化氢酶依赖性方式增加了Akt丝氨酸473磷酸化和有丝分裂，表明H2O2对Akt和Ran信号传导至关重要。这些结果表明，原代II型肺细胞中H2O2诱导的促有丝分裂信号由PI3K、Akt、mTOR激酶和Ran蛋白介导。
