Insulin induction of SOCS-2 and SOCS-3 mRNA expression in C2C12 skeletal muscle cells is mediated by Stat5
Insulin induction of SOCS-2 and SOCS-3 mRNA expression in C2C12 skeletal muscle cells is mediated by Stat5
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DOI：
10.1074/jbc.m101014200
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发表时间：
2001-06-08
影响因子：
4.8
通讯作者：
Sadowski, HB
中科院分区：
文献类型：
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作者：
Sadowski, CL;Choi, TS;Sadowski, HB
此前，通过酵母 2 杂交筛选，我们鉴定出信号转导子和转录激活子 5b (Stat5b) 作为胰岛素受体 (IR) 的底物。我们证明，禁食小鼠的重新喂养会导致肝脏、骨骼肌和脂肪中 Stat5 蛋白的快速激活，这表明 Stat5b 是胰岛素的生理靶标。在这里，我们证明向禁食的小鼠注射葡萄糖或胰岛素会导致骨骼肌中 Stat5a 和 Stat5b 的强烈激活。在 C2C12 肌管中，我们发现胰岛素刺激 Stat5a 和 Stat5b 的酪氨酸磷酸化 3-5 倍。 Stat5 体外激活程度显着低于我们在体内观察到的水平，并且与 IRS-1/2 水平呈负相关。我们可以通过人 IR (hIR) 的稳定过表达来概括 C2C12 细胞中 Stat5 的胰岛素强烈激活。为了鉴定作为 Stat5 靶标的胰岛素激活基因，我们还过度表达了 IR 突变体 (LA-hIR)，该突变体通常为丝裂原激活蛋白激酶和磷脂酰肌醇 3 激酶依赖性途径发出信号，但在响应胰岛素的 Stat5 信号传导中缺乏。我们证明胰岛素在野生型 hIR 中诱导 SOCS-2 mRNA 的表达，但在 LA-hIR 过表达细胞中不诱导 SOCS-2 mRNA 的表达。 LA-hIR 细胞中胰岛素对 SOCS-3 的诱导减少但并未消失。因此，我们的结果表明，SOCS-2 的胰岛素诱导以及部分 SOCS-3 mRNA 表达是由 Stat5 介导的，并且可以独立于丝裂原激活蛋白激酶和磷脂酰肌醇 3-激酶信号通路。
Previously, by a yeast 2-hybrid screen, we identified signal transducer and activator of transcription 5b (Stat5b) as a substrate of the insulin receptor (IR). We demonstrated that refeeding of fasted mice leads to rapid activation of Stat5 proteins in liver, skeletal muscle, and fat, suggesting that Stat5b is a physiological target of insulin. Here, we show that injection of glucose or insulin into fasted mice leads to robust activation of both Stat5a and Stat5b in skeletal muscle. In C2C12 myotubes, we find that insulin stimulates tyrosine phosphorylation of Stat5a and Stat5b by 3-5-fold. This degree of Stat5 activation in vitro is significantly lower than what we observe in vivo and inversely correlates with IRS-1/2 levels. We can recapitulate robust insulin activation of Stat5 in C2C12 cells by stable overexpression of the human IR (hIR). To identify insulin-activated genes that are Stat5 targets, we also overexpressed an IR mutant (LA-hIR) that signals normally for mitogen-activated protein kinase- and phosphatidylinositol 3-kinase-dependent pathways but is deficient in Stat5 signaling in response to insulin. We demonstrate that insulin induces the expression of SOCS-2 mRNA in the wild type hIR but not in the LA-hIR-overexpressing cells. The induction of SOCS-3 by insulin is reduced but not lost in the LA-hIR cells. Therefore, our results suggest that insulin induction of SOCS-2, and in part SOCS-3 mRNA expression, is mediated by Stat5 and can be independent of mitogen activated protein kinase and phosphatidylinositol 3-kinase-signaling pathways.