Mitophagy is required for mitochondrial biogenesis and myogenic differentiation of C2C12 myoblasts

Abstract

Myogenesis is a crucial process governing skeletal muscle development and homeostasis. Differentiation of primitive myoblasts into mature myotubes requires a metabolic switch to support the increased energetic demand of contractile muscle. Skeletal myoblasts specifically shift from a highly glycolytic state to relying predominantly on oxidative phosphorylation (OXPHOS) upon differentiation. We have found that this phenomenon requires dramatic remodeling of the mitochondrial network involving both mitochondrial clearance and biogenesis. During early myogenic differentiation, autophagy is robustly upregulated and this coincides with DNM1L/DRP1 (dynamin 1-like)-mediated fragmentation and subsequent removal of mitochondria via SQSTM1 (sequestosome 1)-mediated mitophagy. Mitochondria are then repopulated via PPARGC1A/PGC-1α (peroxisome proliferator-activated receptor gamma, coactivator 1 alpha)-mediated biogenesis. Mitochondrial fusion protein OPA1 (optic atrophy 1 [autosomal dominant]) is then briskly upregulated, resulting in the reformation of mitochondrial networks. The final product is a myotube replete with new mitochondria. Respirometry reveals that the constituents of these newly established mitochondrial networks are better primed for OXPHOS and are more tightly coupled than those in myoblasts. Additionally, we have found that suppressing autophagy with various inhibitors during differentiation interferes with myogenic differentiation. Together these data highlight the integral role of autophagy and mitophagy in myogenic differentiation.

Downregulation of p53 drives autophagy during human trophoblast differentiation

“…This assumption is based on observations in myotube formation, showing dynamic remodeling of the mitochondrial network, including mitochondrial clearance and biogenesis [15]. Importantly, this mitochondrial remodeling is impaired when autophagy is inhibited [45]. In the human placenta, mitochondria of the syncytiotrophoblast show a different appearance, compared to cytotrophoblasts [4].…”

Roles of mitophagy in cellular physiology and development

“…In addition to the direct role of mitophagy in erythrocyte maturation, mitophagy has been implicated in developmental transitions in muscle tissue. It was recently shown that, upon differentiation of mouse myoblasts, mitophagy is induced and is necessary for differentiation (Sin et al 2016). Furthermore, essential metabolic transitions that occur during differentiation of cardiomyocytes have been shown to be mitophagydependent (Gong et al 2015).…”

Expanding perspectives on the significance of mitophagy in cancer

“…While mitophagy can be induced artificially with respiratory chain inhibitors and uncoupling agents, such as carbonyl cyanide 3-chlorophenylhydrazone (CCCP) that depolarize mitochondria, it is also part of the response to key physiological stresses, such as hypoxia and nutrient deprivation [3]. In addition, mitophagy is a programmed component of developmental and differentiation processes, including elimination of paternal mitochondria from the fertilized egg [4–6] and removal of mitochondria during red blood cell production [7,8] and muscle differentiation [9]. By promoting elimination of dysfunctional, supernumery and/or aged mitochondria, mitophagy plays a central role in maintaining mitochondrial and cellular integrity.…”