Liu Xin-Hua, Bauman William A, Cardozo Christopher
National Center of Excellence for the Medical Consequences of Spinal Cord Injury, James J. Peter VA Medical Center, Bronx, NY 10468, USA; Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
National Center of Excellence for the Medical Consequences of Spinal Cord Injury, James J. Peter VA Medical Center, Bronx, NY 10468, USA; Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; Department of Rehabilitation Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
Biochem Biophys Res Commun. 2015 Aug 14;464(1):208-13. doi: 10.1016/j.bbrc.2015.06.118. Epub 2015 Jun 20.
Transcription factors of the nuclear factor-kappa B (NF-κB) family play a pivotal role in inflammation, immunity and cell survival responses. Recent studies revealed that NF-κB also regulates the processes of muscle atrophy. NF-κB activity is regulated by various factors, including ankyrin repeat domain 2 (AnkrD2), which belongs to the muscle ankyrin repeat protein family. Another member of this family, AnkrD1 is also a transcriptional effector. The expression levels of AnkrD1 are highly upregulated in denervated skeletal muscle, suggesting an involvement of AnkrD1 in NF-κB mediated cellular responses to paralysis. However, the molecular mechanism underlying the interactive role of AnkrD1 in NF-κB mediated cellular responses is not well understood. In the current study, we examined the effect of AnkrD1 on NF-κB activity and determined the interactions between AnkrD1 expression and NF-κB signaling induced by TNFα in differentiating C2C12 myoblasts. TNFα upregulated AnkrD1 mRNA and protein levels. AnkrD1-siRNA significantly increased TNFα-induced transcriptional activation of NF-κB, whereas overexpression of AnkrD1 inhibited TNFα-induced NF-κB activity. Co-immunoprecipitation studies demonstrated that AnkrD1 was able to bind p50 subunit of NF-κB and vice versa. Finally, CHIP assays revealed that AnkrD1 bound chromatin at a NF-κB binding site in the AnrkD2 promoter and required NF-κB to do so. These results provide evidence of signaling integration between AnkrD1 and NF-κB pathways, and suggest a novel anti-inflammatory role of AnkrD1 through feedback inhibition of NF-κB transcriptional activity by which AnkrD1 modulates the balance between physiological and pathological inflammatory responses in skeletal muscle.
核因子-κB（NF-κB）家族的转录因子在炎症、免疫和细胞存活反应中起关键作用。最近的研究表明，NF-κB还调节肌肉萎缩过程。NF-κB的活性受多种因素调节，包括锚蛋白重复结构域2（AnkrD2），它属于肌肉锚蛋白重复蛋白家族。该家族的另一个成员AnkrD1也是一种转录效应物。AnkrD1的表达水平在失神经支配的骨骼肌中高度上调，表明AnkrD1参与了NF-κB介导的细胞对麻痹的反应。然而，AnkrD1在NF-κB介导的细胞反应中的相互作用分子机制尚不清楚。在本研究中，我们研究了AnkrD1对NF-κB活性的影响，并确定了在分化的C2C12成肌细胞中AnkrD1表达与TNFα诱导的NF-κB信号传导之间的相互作用。TNFα上调了AnkrD1的mRNA和蛋白水平。AnkrD1-siRNA显著增加了TNFα诱导的NF-κB转录激活，而AnkrD1的过表达抑制了TNFα诱导的NF-κB活性。免疫共沉淀研究表明，AnkrD1能够结合NF-κB的p50亚基，反之亦然。最后，染色质免疫沉淀分析显示，AnkrD1在AnrkD2启动子的NF-κB结合位点结合染色质，并且需要NF-κB才能这样做。这些结果提供了AnkrD1和NF-κB信号通路之间信号整合的证据，并表明AnkrD1通过对NF-κB转录活性的反馈抑制具有新的抗炎作用，通过这种作用AnkrD1调节骨骼肌中生理和病理炎症反应之间的平衡。
