CC chemokine receptor 5 coordinates the glycolysis-to-oxidative phosphorylation transition during myogenic differentiation

Skeletal muscle regeneration requires coordination between myogenic transcription programs and metabolic reprogramming from glycolysis to oxidative phosphorylation. CC chemokine receptor 5 (CCR5), a G protein-coupled receptor associated with immune cell trafficking, has recently been implicated in skeletal muscle energy metabolism. We previously showed that Ccr5 −/− mice exhibit reduced mitochondrial content and impaired exercise performance. However, whether CCR5 directly regulates myogenic differentiation and the accompanying bioenergetic transition remains unknown. Myogenic differentiation was induced in C2C12 and primary mouse myoblasts. CCR5 was pharmacologically inhibited with maraviroc or genetically via stable short-hairpin RNA knockdown. Myogenic progression was assessed by quantitative RT-PCR, Western blotting, and measurement of myotube width. Hindlimb muscles from Ccr5 −/− mice were analyzed for myofiber cross-sectional area. Cellular bioenergetics were characterized using Seahorse extracellular flux analysis. Exercise capacity was evaluated by treadmill exhaustion, grip strength, and rotarod tests. Acute skeletal muscle injury was induced by BaCl₂ injection in WT and Ccr5 deficient mice, followed by histological, immunohistochemical, and transcriptional analyses of the regenerative response. Recombinant CCL3, CCL4, and CCL5 were used to identify pro-myogenic ligands. Data were analyzed using Student’s t -test, one-way or two-way ANOVA with Tukey’s post hoc test, nested t -test, and log-rank test as appropriate. CCR5 inhibition significantly impaired myogenic differentiation in both C2C12 and primary myoblasts, with reduced myotube width and suppressed expression of myogenic regulatory factors. Ccr5 −/− mice exhibited decreased myofiber cross-sectional area in tibialis anterior and soleus muscles and impaired exercise endurance, grip strength, and motor coordination. Following BaCl₂-induced injury, Ccr5 deficient muscle exhibited attenuated induction of myogenic regulatory genes and reduced expression of mitochondrial/metabolic regulators compared with injured WT muscle. Notably, CCR5 exerted differentiation-stage-dependent effects on bioenergetics: in myoblasts, Ccr5 knockdown paradoxically enhanced mitochondrial respiration, whereas in myotubes, it impaired oxidative phosphorylation and augmented glycolytic flux. CCL4 and CCL5, but not CCL3, promoted myogenic differentiation, while Ccl5 deficiency selectively impaired treadmill endurance. These findings identify CCR5 as an important metabolic regulator that coordinates the transition from glycolysis to oxidative phosphorylation during myogenesis.