Regulation of protein kinase B and 4E-BP1 by oxidative stress in cardiac myocytes
Regulation of protein kinase B and 4E-BP1 by oxidative stress in cardiac myocytes
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DOI：
10.1161/01.res.86.12.1252
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发表时间：
2000-06-23
影响因子：
20.1
通讯作者：
Clerk, A
中科院分区：
文献类型：
--
作者：
Pham, FH;Sugden, PH;Clerk, A
磷脂酰肌醇3’-激酶（PI3K）和蛋白激酶B （PKB）的刺激与多种细胞中蛋白质合成的调节有关。其中一种机制涉及PI3K/ pkb依赖性的4E-BP1磷酸化，该磷酸化与eIF4E分离，允许从mrna的7-甲基gtp帽开始翻译。我们研究了胰岛素和H2O2对新生儿心肌细胞中这一途径的影响。胰岛素增加心肌细胞蛋白合成，H2O2抑制心肌细胞蛋白合成。PI3K抑制剂降低了蛋白质合成的基础水平，并抑制了胰岛素诱导的蛋白质合成的增加。胰岛素或H2O2通过PI3K增加了PKB的磷酸化（激活），但是，胰岛素诱导了持续的反应，H2O2的反应是短暂的，4E-BP1在未受刺激的细胞中被磷酸化，胰岛素增加了4E-BP1的磷酸化，H2O2通过增加蛋白磷酸酶（PP1/PP2A）活性刺激了4E-BP1的去磷酸化。这增加了4E-BP1与eIF4E的关联，与H2O2抑制蛋白质合成一致。H2O2的作用足以覆盖胰岛素诱导的蛋白合成和4E-BP1磷酸化的刺激。这些结果表明，PI3K和PKB是心肌细胞蛋白合成的重要调节因子，但其他因素，包括磷酸酶活性，调节整体反应。
Stimulation of phosphatidylinositol 3'-kinase (PI3K) and protein kinase B (PKB) is implicated in the regulation of protein synthesis in various cells. One mechanism involves PI3K/PKB-dependent phosphorylation of 4E-BP1, which dissociates from eIF4E, allowing initiation of translation from the 7-methylGTP cap of mRNAs, We examined the effects of insulin and H2O2 on this pathway in neonatal cardiac myocytes. Cardiac myocyte protein synthesis was increased by insulin, but was inhibited by H2O2. PI3K inhibitors attenuated basal levels of protein synthesis and inhibited the insulin-induced increase in protein synthesis. Insulin or H2O2 increased the phosphorylation (activation) of PKB through PI3K, but, whereas insulin induced a sustained response, the response to H2O2 was transient, 4E-BP1 was phosphorylated in unstimulated cells, and 4E-BP1 phosphorylation was increased by insulin, H2O2 stimulated dephosphorylation of 4E-BP1 by increasing protein phosphatase (PP1/PP2A) activity. This increased the association of 4E-BP1 with eIF4E, consistent with H2O2 inhibition of protein synthesis. The effects of H2O2 were sufficient to override the stimulation of protein synthesis and 4E-BP1 phosphorylation induced by insulin. These results indicate that PI3K and PKB are important regulators of protein synthesis in cardiac myocytes, but other factors, including phosphatase activity, modulate the overall response.