NF-κB mediates the protein loss induced by TNF-α in differentiated skeletal muscle myotubes
NF-κB mediates the protein loss induced by TNF-α in differentiated skeletal muscle myotubes
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DOI：
10.1152/ajpregu.2000.279.4.r1165
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发表时间：
2000-10-01
影响因子：
2.8
通讯作者：
Reid, MB
中科院分区：
文献类型：
--
作者：
Li, YP;Reid, MB
核因子-κ B（NF κ B）调节参与免疫应答、细胞生长和细胞死亡的多种基因的转录。然而，NF-κ B B在肌肉生物学中的作用知之甚少。我们最近报道，肿瘤坏死因子-α（TNF-α）迅速激活分化的骨骼肌肌管中的NF-κ B B，TNF-α直接作用于肌细胞，诱导蛋白质降解。在目前的研究中，我们问是否NF-κ B B介导的蛋白质损失诱导的TNF-α。我们通过创建稳定的反式显性负肌细胞系来解决这个问题。C2 C12成肌细胞转染病毒质粒构建体，诱导突变I-κ B α蛋白的过表达，该蛋白对通过泛素-蛋白酶体途径的降解不敏感。这些突变蛋白选择性抑制NF-κ B活化。我们发现，分化的肌管转染的空病毒载体（对照）经历了总蛋白含量和快速型肌球蛋白重链含量下降，在72小时的暴露于TNF-α。相反，总蛋白和快型肌球蛋白重链水平在反式显性阴性细胞系中未被TNF-α改变。TNF-α在任何细胞系中均不诱导凋亡，如DNA梯状条带和膜联蛋白V测定所评估。这些数据表明，NF-κ B B是分化的肌细胞中TNF-α诱导的catalysis的重要介质。
Nuclear factor-kappa B (NF kappa B) regulates the transcription of a variety of genes involved in immune responses, cell growth, and cell death. However, the role of NF-kappa B in muscle biology is poorly understood. We recently reported that tumor necrosis factor-alpha (TNF-alpha) rapidly activates NF-kappa B in differentiated skeletal muscle myotubes and that TNF-alpha acts directly on the muscle cell to induce protein degradation. In the present study, we ask whether NF-kappa B mediates the protein loss induced by TNF-alpha. We addressed this problem by creating stable, transdominant negative muscle cell lines. C2C12 myoblasts were transfected with viral plasmid constructs that induce overexpression of mutant I-kappa B alpha proteins that are insensitive to degradation via the ubiquitin-proteasome pathway. These mutant proteins selectively inhibit NF-kappa B activation. We found that differentiated myotubes transfected with the empty viral vector (controls) underwent a drop in total protein content and in fast-type myosin heavy-chain content during 72 h of exposure to TNF-alpha. In contrast, total protein and fast-type myosin heavy-chain levels were unaltered by TNF-alpha in the transdominant negative cell lines. TNF-alpha did not induce apoptosis in any cell line, as assessed by DNA ladder and annexin V assays. These data indicate that NF-kappa B is an essential mediator of TNF-alpha-induced catabolism in differentiated muscle cells.