IRS-2 mediates the antiapoptotic effect of insulin in neonatal hepatocytes
IRS-2 mediates the antiapoptotic effect of insulin in neonatal hepatocytes
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DOI：
10.1002/hep.20485
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发表时间：
2004-12-01
期刊：
影响因子：
13.5
通讯作者：
Benito, M
中科院分区：
文献类型：
--
作者：
Valverde, AM;Fabregat, I;Benito, M
为了评估胰岛素在肝脏中的作用和不作用，从胰岛素受体底物（IRS）-2（-/-）和野生型小鼠中产生了永生化肝细胞系。使用这个模型，我们最近已经证明，IRS-2在新生儿肝细胞中的缺乏导致胰岛素抵抗。在目前的研究中，我们发现永生化新生肝细胞在血清戒断时发生凋亡，在IRS-2不存在的情况下，caspase-3活化和DNA梯状化发生得更早。胰岛素以剂量依赖性方式从血清戒断诱导的caspase-3活化和DNA片段化中拯救野生型肝细胞，但未能拯救缺乏IRS-2的肝细胞。在IRS-2（-/-）细胞中，胰岛素不能磷酸化Bad。此外，在这些细胞中，胰岛素不能将Foxo 1从细胞核转运到细胞质。腺病毒感染野生型细胞组成型活性Foxo 1（ADA）诱导caspase-8和caspase-3的活动，促凋亡基因的表达，DNA梯状和凋亡。显性负性Foxo 1以相反的方式调节整个通路。延长胰岛素治疗（24小时）增加抗凋亡基因（Bcl-x（L））的表达，下调。促凋亡基因（Bim和核Foxo 1），并降低了野生型肝细胞中的caspase-3活性，但在IRS-2（-/-）细胞中没有。用编码IRS-2的腺病毒感染IRS-2（-/-）肝细胞重建磷脂酰肌醇3-激酶（PI 3-kinase）/Akt/Foxo 1信号传导，恢复促凋亡和抗凋亡基因表达，并降低响应胰岛素的caspase-3活性，从而阻断凋亡。总之，IRS-2信号传导是PIP 3产生介导胰岛素存活效应所必需的。表皮生长因子，通过PIP 3/Akt/Foxo 1磷酸化，能够拯救IRS-2（-/-）肝细胞从血清撤药诱导的细胞凋亡，调节促凋亡和抗凋亡基因的表达和下调caspase-3活性。
To assess the role of insulin action and inaction in the liver, immortalized hepatocyte cell lines have been generated from insulin receptor substrate (IRS)-2(-/-) and wild-type mice. Using this model, we have recently demonstrated that the lack of IRS-2 in neonatal hepatocytes resulted in insulin resistance. In the current study, we show that immortalized neonatal hepatocytes undergo apoptosis on serum withdrawal, with caspase-3 activation and DNA laddering occurring earlier in the absence of IRS-2. Insulin rescued wild-type hepatocytes from serum withdrawal-induced caspase-3 activation and DNA fragmentation in a dose-dependent manner, but it failed to rescue hepatocytes lacking IRS-2. In IRS-2(-/-) cells, insulin failed to phosphorylate Bad. Furthermore in these cells, insulin was unable to translocate Foxo1 from the nucleus to the cytosol. Adenoviral infection of wild-type cells with constitutively active Foxo1 (ADA) induced caspase-8 and caspase-3 activities, proapoptotic gene expression, DNA laddering and apoptosis. Dominant negative Foxo1 regulated the whole pathway in an opposite manner. Prolonged insulin treatment (24 hours) increased expression of antiapoptotic genes (Bcl-x(L)), downregulated. proapoptotic genes (Bim and nuclear Foxo1), and decreased caspase-3 activity in wild-type hepatocytes but not in IRS-2(-/-) cells. Infection of IRS-2(-/-) hepatocytes with adenovirus encoding IRS-2 reconstituted phosphatidylinositol 3-kinase (PI 3-kinase)/Akt/Foxo1 signaling, restored pro- and antiapoptotic gene expression, and decreased caspase-3 activity in response to insulin, thereby blocking apoptosis. In conclusion, IRS-2 signaling is specifically required through PIP3 generation to mediate the survival effects of insulin. Epidermal growth factor, via PIP3/Akt/Foxo1 phosphorylation, was able to rescue IRS-2(-/-) hepatocytes from serum withdrawal-induced apoptosis, modulating pro- and anti-apoptotic gene expression and downregulating caspase-3 activity.