Jeong Jae Hoon, Cheol Kang Young, Piao Ying, Kang Sora, Pak Youngmi Kim
Department of Neuroscience, Graduate School, Seoul, Korea.
Department of Physiology, College of Medicine, Kyung Hee University, Seoul, Korea.
Exp Mol Med. 2017 Apr 7;49(4):e313. doi: 10.1038/emm.2016.174.
Mitochondrial deficits or altered expressions of microRNAs are associated with the pathogenesis of various diseases, and microRNA-operated control of mitochondrial activity has been reported. Using a retrovirus-mediated short-hairpin RNA (shRNA) system, we observed that miR-24-mediated H2AX knockdown (H2AX-KD) impaired both mitochondria and the insulin signaling pathway. The overexpression of miR-24 decreased mitochondrial H2AX and disrupted mitochondrial function, as indicated by the ATP content, membrane potential and oxygen consumption. Similar mitochondrial damage was observed in shH2AX-mediated specific H2AX-KD cells. The H2AX-KD reduced the expression levels of mitochondrial transcription factor A (TFAM) and mitochondrial DNA-dependent transcripts. H2AX-KD mitochondria were swollen, and their cristae were destroyed. H2AX-KD also blocked the import of precursor proteins into mitochondria and the insulin-stimulated phosphorylation of IRS-1 (Y632) and Akt (S473 and T308). The rescue of H2AX, but not the nuclear form of ΔC24-H2AX, restored all features of miR-24- or shH2AX-mediated impairment of mitochondria. Hepatic miR-24 levels were significantly increased in db/db and ob/ob mice. A strong feedback loop may be present among miR-24, H2AX, mitochondria and the insulin signaling pathway. Our findings suggest that H2AX-targeting miR-24 may be a novel negative regulator of mitochondrial function and is implicated in the pathogenesis of insulin resistance.
线粒体缺陷或微小RNA的表达改变与多种疾病的发病机制相关，并且已有报道微小RNA对线粒体活性具有调控作用。利用逆转录病毒介导的短发夹RNA（shRNA）系统，我们观察到miR-24介导的H2AX基因敲低（H2AX-KD）损害了线粒体和胰岛素信号通路。miR-24的过表达降低了线粒体H2AX水平并破坏了线粒体功能，这通过ATP含量、膜电位和氧消耗得以体现。在shH2AX介导的特异性H2AX-KD细胞中也观察到了类似的线粒体损伤。H2AX-KD降低了线粒体转录因子A（TFAM）和线粒体DNA依赖性转录本的表达水平。H2AX-KD的线粒体肿胀，其嵴被破坏。H2AX-KD还阻断了前体蛋白向线粒体的导入以及胰岛素刺激的IRS-1（Y632）和Akt（S473和T308）的磷酸化。H2AX的挽救，而非ΔC24-H2AX的核形式，恢复了miR-24或shH2AX介导的线粒体损伤的所有特征。在db/db和ob/ob小鼠中，肝脏miR-24水平显著升高。miR-24、H2AX、线粒体和胰岛素信号通路之间可能存在一个强大的反馈回路。我们的研究结果表明，靶向H2AX的miR-24可能是线粒体功能的一种新型负调节因子，并与胰岛素抵抗的发病机制有关。
