Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Tokyo, 187-8502, Japan.
Cell Death Dis. 2023 Oct 19;14(10):689. doi: 10.1038/s41419-023-06192-2.
Skeletal muscle comprises different muscle fibers, including slow- and fast-type muscles, and satellite cells (SCs), which exist in individual muscle fibers and possess different myogenic properties. Previously, we reported that myoblasts (MBs) from slow-type enriched soleus (SOL) had a high potential to self-renew compared with cells derived from fast-type enriched tibialis anterior (TA). However, whether the functionality of myogenic cells in adult muscles is attributed to the muscle fiber in which they reside and whether the characteristics of myogenic cells derived from slow- and fast-type fibers can be distinguished at the genetic level remain unknown. Global gene expression analysis revealed that the myogenic potential of MBs was independent of the muscle fiber type they reside in but dependent on the region of muscles they are derived from. Thus, in this study, proteomic analysis was conducted to clarify the molecular differences between MBs derived from TA and SOL. NADH dehydrogenase (ubiquinone) iron-sulfur protein 8 (Ndufs8), a subunit of NADH dehydrogenase in mitochondrial complex I, significantly increased in SOL-derived MBs compared with that in TA-derived cells. Moreover, the expression level of Ndufs8 in MBs significantly decreased with age. Gain- and loss-of-function experiments revealed that Ndufs8 expression in MBs promoted differentiation, self-renewal, and apoptosis resistance. In particular, Ndufs8 suppression in MBs increased p53 acetylation, followed by a decline in NAD/NADH ratio. Nicotinamide mononucleotide treatment, which restores the intracellular NAD level, could decrease p53 acetylation and increase myogenic cell self-renewal ability in vivo. These results suggested that the functional differences in MBs derived from SOL and TA governed by the mitochondrial complex I-encoding gene reflect the magnitude of the decline in SC number observed with aging, indicating that the replenishment of NAD is a possible approach for improving impaired cellular functions caused by aging or diseases.
骨骼肌由不同的肌纤维组成，包括慢肌和快肌，以及卫星细胞（SCs），它们存在于单个肌纤维中，具有不同的成肌特性。此前，我们报道过，与来源于快肌丰富的比目鱼肌（TA）的细胞相比，来源于慢肌丰富的比目鱼肌（SOL）的成肌细胞（MBs）具有更高的自我更新能力。然而，成肌细胞在成年肌肉中的功能是否归因于它们所在的肌纤维，以及是否可以在遗传水平上区分来源于慢肌和快肌纤维的成肌细胞的特征，目前尚不清楚。全基因组表达分析显示，MBs 的成肌能力与其所在的肌纤维类型无关，但取决于其来源的肌肉区域。因此，在这项研究中，进行了蛋白质组学分析，以阐明来源于 TA 和 SOL 的 MBs 之间的分子差异。NADH 脱氢酶（泛醌）铁硫蛋白 8（Ndufs8）是线粒体复合物 I 中 NADH 脱氢酶的一个亚基，在 SOL 衍生的 MBs 中显著高于 TA 衍生的细胞。此外，MBs 中的 Ndufs8 表达水平随年龄的增长而显著降低。获得和丧失功能实验表明，MBs 中的 Ndufs8 表达促进分化、自我更新和抗凋亡。特别是，MBs 中 Ndufs8 的抑制增加了 p53 乙酰化，随后 NAD/NADH 比值下降。烟酰胺单核苷酸处理可恢复细胞内 NAD 水平，可降低 p53 乙酰化，增加体内成肌细胞自我更新能力。这些结果表明，来源于 SOL 和 TA 的 MBs 的功能差异受线粒体复合物 I 编码基因的调控，反映了随着年龄增长 SC 数量下降的幅度，表明补充 NAD 可能是改善因衰老或疾病导致的细胞功能障碍的一种方法。
