AMP-activated protein kinase agonists increase mRNA content of the muscle-specific ubiquitin ligases MAFbx and MuRF1 in C2C12 cells
AMP-activated protein kinase agonists increase mRNA content of the muscle-specific ubiquitin ligases MAFbx and MuRF1 in C2C12 cells
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DOI：
10.1152/ajpendo.00622.2006
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发表时间：
2007-06-01
影响因子：
5.1
通讯作者：
Lang, Charles H.
中科院分区：
文献类型：
--
作者：
Krawiec, Brian J.;Nystrom, Gerald J.;Lang, Charles H.
本研究的假设是，将分化的肌肉细胞暴露于amp活化蛋白激酶（AMPK）的激动剂会增加肌肉特异性泛素连接酶肌萎缩F-box （MAFbx）和肌肉环指1 （MuRF1）的mRNA含量。C2C12细胞用递增剂量的5-氨基咪唑- 4-碳酰亚胺核糖核苷（AICAR）或二甲双胍孵卵24小时。MAFbx和MuRF1 mRNA对这些AMPK激活剂均呈剂量依赖性增加。AICAR、二甲双胍和2-脱氧- D-葡萄糖产生泛素连接酶表达的时间依赖性改变，其典型表现为双期表达模式，标志着急性抑制随后持续诱导。AMPK-激活治疗联合地塞米松对连接酶mRNA在后期的表达产生了明显的协同作用。这种协同反应发生在没有地塞米松依赖性AMPK表达或活性增加的情况下，通过免疫印迹检测AMPK α及其下游靶标乙酰辅酶a羧化酶（ACC）的磷酸化和表达。AMPK单独激活或与地塞米松联合激活引起的这些反应没有扩展到UBR盒子家族E3s UBR1/E3 α I和UBR2/E3 α II的mRNA表达。用AMPK抑制剂化合物C治疗可阻止血清剥夺以及AICAR和地塞米松单独或联合治疗时MAFbx和MuRF1 mRNA的升高。通过AICAR注射刺激AMPK活性可以增加小鼠骨骼肌中MAFbx和MuRF1 mRNA的表达。这些数据表明，骨骼肌中AMPK的激活会导致MAFbx和MuRF1的特异性上调，这些反应让人想起在各种骨骼肌萎缩条件下执行的萎缩转录程序。因此，AMPK可能是控制骨骼肌萎缩的信号通路插入网络的关键组成部分，其输入作用是修改抗和促萎缩信号，以影响分解代谢扰动反应中的基因表达。
The hypothesis of the present study was that exposure of differentiated muscle cells to agonists of the AMP-activated protein kinase ( AMPK) would increase the mRNA content of the muscle-specific ubiquitin ligases muscle atrophy F-box ( MAFbx) and muscle RING finger 1 ( MuRF1). C2C12 cells were incubated with incremental doses of 5- aminoimidazol- 4- carboximide ribonucleoside ( AICAR) or metformin for 24 h. Both MAFbx and MuRF1 mRNA increased dose dependently in response to these AMPK activators. AICAR, metformin, and 2- deoxy- D- glucose produced time-dependent alterations in ubiquitin ligase expression, typified by a biphasic pattern of expression marked by an acute repression followed by a sustained induction. AMPK- activating treatments in conjunction with dexamethasone produced a pronounced synergistic effect on ligase mRNA expression at later time points. This cooperative response occurred in the absence of a dexamethasone- dependent increase in AMPK expression or activity, as determined by immunoblotting for phosphorylation and expression of AMPK alpha and its downstream target acetyl- CoA carboxylase ( ACC). These responses elicited by AMPK activation singly or in combination with dexamethasone did not extend to the mRNA expression of the UBR box family E3s UBR1/E3 alpha I and UBR2/E3 alpha II. Treatment with the AMPK inhibitor compound C prevented increases in MAFbx and MuRF1 mRNA in response to serum deprivation, as well as AICAR and dexamethasone treatment individually or jointly. Stimulation of AMPK activity in vivo via AICAR injection increased both MAFbx and MuRF1 mRNA in murine skeletal muscle. These data suggest that activation of AMPK in skeletal muscle results in a specific upregulation of MAFbx and MuRF1, responses that are reminiscent of the proposed atrophic transcriptional program executed under various conditions of skeletal muscle wasting. Therefore, AMPK may be a critical component of the intercalated network of signaling pathways governing skeletal muscle atrophy, where its input acts to modify anti- and proatrophic signals to influence gene expression in reaction to catabolic perturbations.