Insulin-like growth factor-induced transcriptional activity of the skeletal alpha-actin gene is regulated by signaling mechanisms linked to voltage-gated calcium channels during myoblast differentiation.
Insulin-like growth factor-induced transcriptional activity of the skeletal alpha-actin gene is regulated by signaling mechanisms linked to voltage-gated calcium channels during myoblast differentiation.
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DOI：
10.1210/en.2003-1476
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发表时间：
2004-04
期刊：
影响因子：
4.8
通讯作者：
E. Spangenburg;D. Bowles;F. Booth
中科院分区：
文献类型：
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作者：
E. Spangenburg;D. Bowles;F. Booth
IGF-I激活信号通路，增加分化成肌细胞中肌肉特异基因的表达。在分化过程中，通过未知的机制诱导骨骼α-肌动蛋白的表达。本研究的目的是研究IGF-I在C2C12成肌细胞中诱导骨骼肌α-肌动蛋白基因表达的机制。与对照条件相比，IGF-I使骨骼α-肌动蛋白启动子活性增加107%。Ni(+)[T型电压门控钙通道(VGCC)抑制剂]使基础诱导的骨骼α-肌动蛋白启动子的激活减少约84%，而硝苯地平(L型VGCC抑制剂)可抑制IGF-I诱导的骨骼α-肌动蛋白启动子的激活约29%-48%。在分化成肌细胞时，IGF-I不能增加骨骼肌α-肌动蛋白启动子的活性；30 mM K(+)和30 mM K(+)+IGF-I使骨骼α-肌动蛋白启动子活性分别比非IGF-I或单纯IGF-I条件下增加162%和76%。IGF-I可增加钙调神经磷酸酶的活性，该活性可被环孢素A抑制。此外，环孢素A可抑制K(+)+IGF-I诱导的骨骼肌α-肌动蛋白启动子的激活。结构性活性钙调神经磷酸酶可使骨骼肌α-肌动蛋白启动子活性增加154%，并可挽救硝苯地平对L型VGCC的抑制作用，但不能挽救Ni(+)对T型VGCC的抑制作用。硝苯地平和镍(+)不抑制IGF-I诱导的T细胞转录活性。IGF-I不能增加血清反应因子的转录活性；然而，在镍(+)的存在下，血清反应因子的活性降低。这些数据表明，IGF-I诱导的骨骼α-肌动蛋白启动子的激活受L类型的VGCC和钙调神经磷酸酶调节，但不依赖于C2C12成肌细胞分化为肌管时激活的T细胞转录活性的核因素。
IGF-I activates signaling pathways that increase the expression of muscle-specific genes in differentiating myoblasts. Induction of skeletal alpha-actin expression occurs during differentiation through unknown mechanisms. The purpose of this investigation was to examine the mechanisms that IGF-I uses to induce skeletal alpha-actin gene expression in C2C12 myoblasts. IGF-I increased skeletal alpha-actin promoter activity by 107% compared with the control condition. Ni(+) [T-type voltage-gated Ca(2+) channel (VGCC) inhibitor] reduced basal-induced activation of the skeletal alpha-actin promoter by approximately 84%, and nifedipine (L-type VGCC inhibitor) inhibited IGF-I-induced activation of the skeletal alpha-actin promoter by 29-48%. IGF-I failed to increase skeletal alpha-actin promoter activity in differentiating dysgenic (lack functional L-type VGCC) myoblasts; 30 mm K(+) and 30 mm K(+)+IGF-I increased skeletal alpha-actin promoter activity by 162% and 76% compared with non-IGF-I or IGF-I-only conditions, respectively. IGF-I increased calcineurin activity, which was inhibited by cyclosporine A. Further, cyclosporine A inhibited K(+)+IGF-I-induced activation of the skeletal alpha-actin promoter. Constitutively active calcineurin increased skeletal alpha-actin promoter activity by 154% and rescued the nifedipine-induced inhibition of L-type VGCC but failed to rescue the Ni(+)-inhibition of T-type VGCC. IGF-I-induced nuclear factor of activated T-cells transcriptional activity was not inhibited by nifedipine or Ni(+). IGF-I failed to increase serum response factor transcriptional activity; however, serum response factor activity was reduced in the presence of Ni(+). These data suggest that IGF-I-induced activation of the skeletal alpha-actin promoter is regulated by the L-type VGCC and calcineurin but independent of nuclear factor of activated T-cell transcriptional activity as C2C12 myoblasts differentiate into myotubes.