Intracellular signaling pathways regulating net protein balance following diaphragm muscle denervation
Intracellular signaling pathways regulating net protein balance following diaphragm muscle denervation
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DOI：
10.1152/ajpcell.00172.2010
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发表时间：
2011-02-01
影响因子：
5.5
通讯作者：
Sieck, Gary C.
中科院分区：
文献类型：
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作者：
Argadine, Heather M.;Mantilla, Carlos B.;Sieck, Gary C.
阿加丁HM，Mantilla CB，詹文志，Sieck GC。横隔肌失神经后调节净蛋白平衡的细胞内信号通路。Am J Physiol Cell Physiol 300：C318-C327,2011。2010年11月17日首次出版；DOI：10.1152/ajpcell.00172.2010。-大鼠单侧去神经支配(DNV)后3天(DNV-3D)增加蛋白质合成，并在DNV-5D降解，因此DNV-5D明显的净蛋白质分解。在现有蛋白质平衡模型的基础上，我们研究了DNV诱导的Akt、AMP激活的蛋白激酶(AMPK)和ERK1/2激活的变化，这些变化可以通过哺乳动物靶标雷帕霉素(MTOR)/p70S6激酶(P70S6K)、糖原合成酶激酶-3β(GSK3β)或真核细胞起始因子4E(EIF4E)导致蛋白质合成增加，并通过叉头盒蛋白O(FoxO)增加蛋白质降解。通过DNV-5D用Western分析检测蛋白质的磷酸化。与假手术组相比，DNV后1h和6h，AKT的磷酸化水平降低，而AMPK的磷酸化水平降低。经DNV-1D处理后，Akt和AMPK的磷酸化均恢复到假手术水平。其下游效应子mTOR(Ser2481)的磷酸化在DNV后的任何时间点都没有变化，而磷酸化的p70S6K和eIF4E结合蛋白1(4EBP1)仅在DNV-5D作用下增加。相比之下，ERK1/2磷酸化及其下游效应因子eIF4E在DNV-1D时增加1.7倍，磷酸化GSK3β在DNV-3D时增加1.5倍(两种比较P<；0.05)。因此，DNV对蛋白质合成途径有不同的影响，优先激活GSK3β和eIF4E而不是p70S6K。DNV-1D引起Foxo1核易位，与DNV-5D证实的增加泛素-蛋白酶体激活所必需的阿托品表达的作用一致。根据我们的结果，DNV后蛋白质合成增加与ERK1/2依赖的通路的改变有关，但蛋白质降解是Akt下调和FoxO1核转位的结果。没有单一的触发因素负责DNV之后的蛋白质平衡。骨骼肌中的蛋白质平衡依赖于多种合成/降解途径，应对这些途径进行联合研究。
Argadine HM, Mantilla CB, Zhan WZ, Sieck GC. Intracellular signaling pathways regulating net protein balance following diaphragm muscle denervation. Am J Physiol Cell Physiol 300: C318-C327, 2011. First published November 17, 2010; doi: 10.1152/ajpcell.00172.2010.-Unilateral denervation (DNV) of rat diaphragm muscle increases protein synthesis at 3 days after DNV (DNV-3D) and degradation at DNV-5D, such that net protein breakdown is evident by DNV-5D. On the basis of existing models of protein balance, we examined DNV-induced changes in Akt, AMP-activated protein kinase (AMPK), and ERK1/2 activation, which can lead to increased protein synthesis via mammalian target of rapamycin (mTOR)/p70S6 kinase (p70S6K), glycogen synthase kinase-3 beta (GSK3 beta), or eukaryotic initiation factor 4E (eIF4E), and increased protein degradation via forkhead box protein O (FoxO). Protein phosphorylation was measured using Western analyses through DNV-5D. Akt phosphorylation decreased at 1 h and 6 h after DNV compared with sham despite decreased AMPK phosphorylation. Both Akt and AMPK phosphorylation returned to sham levels by DNV-1D. Phosphorylation of their downstream effector mTOR (Ser2481) did not change at any time point after DNV, and phosphorylated p70S6K and eIF4E-binding protein 1 (4EBP1) increased only by DNV-5D. In contrast, ERK1/2 phosphorylation and its downstream effector eIF4E increased 1.7-fold at DNV-1D and phosphorylated GSK3 beta increased 1.5-fold at DNV-3D (P < 0.05 for both comparisons). Thus, following DNV there are differential effects on protein synthetic pathways with preferential activation of GSK3 beta and eIF4E over p70S6K. FoxO1 nuclear translocation occurred by DNV-1D, consistent with its role in increasing expression of atrogenes necessary for subsequent ubiquitin-proteasome activation evident by DNV-5D. On the basis of our results, increased protein synthesis following DNV is associated with changes in ERK1/2-dependent pathways, but protein degradation results from downregulation of Akt and nuclear translocation of FoxO1. No single trigger is responsible for protein balance following DNV. Protein balance in skeletal muscle depends on multiple synthetic/degradation pathways that should be studied in concert.