Department of Kinesiology, College of Health Professions and Social Work, Temple University, Philadelphia, Pennsylvania;
Am J Physiol Regul Integr Comp Physiol. 2013 Oct 15;305(8):R927-38. doi: 10.1152/ajpregu.00502.2012. Epub 2013 Jul 31.
Mitochondria are dynamic organelles forming a tubular network that is continuously fusing and dividing to control their morphology and functions. Recent literature has shed new light on a potential link between the dynamic behavior of mitochondria and muscle development. In this study, we investigate the role of mitochondrial fission factor dynamin-related protein 1 (Drp1) in myogenic differentiation. We found that differentiation of C2C12 myoblasts induced by serum starvation was accompanied by a gradual increase in Drp1 protein expression (to ∼350% up to 3 days) and a fast reduction of Drp1 phosphorylation at Ser-637 (to ∼30%) resulting in translocation of Drp1 protein from the cytosol to mitochondria. During differentiation, treatment of myoblasts with mitochondrial division inhibitor (mdivi-1), a specific inhibitor of Drp1 GTPase activity, caused extensive formation of elongated mitochondria, which coincided with increased apoptosis evidenced by both enhanced caspase-3 activity and increased number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells. Furthermore, the mdivi-1-treated myotubes (day 3 in differentiation media) showed a reduction in mitochondrial DNA content, mitochondrial mass, and membrane potential in a dose-dependent manner indicating defects in mitochondrial biogenesis during myogenic differentiation. Most interestingly, mdivi-1 treatment significantly suppressed myotube formation in both C2C12 cells and primary myoblasts. Likewise, stable overexpression of a dominant negative mutant Drp1 (K38A) dramatically reduced myogenic differentiation. These data suggest that Drp-1-dependent mitochondrial division is a necessary step for successful myogenic differentiation, and perturbation of mitochondrial dynamics hinders normal mitochondrial adaptations during muscle development. Therefore, in the present study, we report a novel physiological role of mitochondrial dynamics in myogenic differentiation.
线粒体是形成管状网络的动态细胞器，通过不断融合和分裂来控制其形态和功能。最近的文献揭示了线粒体动态行为与肌肉发育之间的潜在联系。在这项研究中，我们研究了线粒体裂变因子 dynamin-related protein 1（Drp1）在成肌分化中的作用。我们发现，血清饥饿诱导的 C2C12 成肌细胞分化伴随着 Drp1 蛋白表达的逐渐增加（最多增加 350%，直至 3 天）和 Drp1 蛋白在 Ser-637 位点的磷酸化快速减少（减少到约 30%），导致 Drp1 蛋白从细胞质易位到线粒体。在分化过程中，用线粒体分裂抑制剂（mdivi-1）处理成肌细胞，mdivi-1 是 Drp1 GTP 酶活性的特异性抑制剂，导致长形线粒体的广泛形成，同时伴随着 caspase-3 活性的增强和末端脱氧核苷酸转移酶介导的 dUTP 缺口末端标记（TUNEL）阳性细胞数量的增加，从而导致细胞凋亡增加。此外，mdivi-1 处理的肌管（分化培养基中第 3 天）表现出线粒体 DNA 含量、线粒体质量和膜电位的剂量依赖性降低，表明在成肌分化过程中线粒体生物发生存在缺陷。最有趣的是，mdivi-1 处理显著抑制了 C2C12 细胞和成肌原细胞的肌管形成。同样，显性负突变体 Drp1（K38A）的稳定过表达也显著降低了成肌分化。这些数据表明，Drp1 依赖性线粒体分裂是成肌分化成功的必要步骤，线粒体动力学的扰动阻碍了肌肉发育过程中线粒体的正常适应。因此，在本研究中，我们报告了线粒体动力学在成肌分化中的新的生理作用。
