ROS-Drp1-mitophagy feedback loop regulates myogenic differentiation via actin cytoskeleton remodeling-mediated MRTF-A/SRF axis

Mitochondrial division is one of the main characteristics for the initiation of myogenic differentiation. However, the role and mechanism of Dynamin-related protein 1 (Drp1), the most important protein that regulates mitochondrial fission in mammals, in regulating myogenic differentiation are not well understood. Drp1 siRNAs were transfected to C2C12 cells, or AAV9-shDrp1 were injected to C57BL/6J mice to knockdown Drp1 expression. Then, mitochondrial damage, ROS level, myogenic differentiation, mitophagy and actin/MRTF-A/SRF pathway was detected by quantitative real-time PCR, western blotting, immunofluorescence staining and flow cytometry. The results showed that Drp1 was upregulated after C2C12 differentiation; Drp1 knockdown by siRNA transfection impaired myotube formation. ROS are the upstream activators for Drp1 expression, and Drp1 inversely reduces ROS by facilitating mitophagy to form a ROS-Drp1-mitophagy feedback loop during myogenic differentiation. Knockdown of Drp1 disrupted the ROS-Drp1-mitophagy feedback loop-mediated ROS homeostasis, thereby accelerating F-action depolymerization and blocking MRTF-A nuclear translocation by reducing the phosphorylation of cofilin. A decrease in MRTF-A nuclear translocation impaired SRF activity and hindered myogenic differentiation. In summary, this study revealed the functional mechanism of Drp1 and clarified the interactions among ROS, Drp1-mediated mitophagy and actin cytoskeleton remodeling during myogenic differentiation.