Muscle denervation reduces mitochondrial biogenesis and mitochondrial translation factor expression in mice

The mitochondrial translation process, in which mitochondrial DNA (mtDNA)-encoded genes are translated into their corresponding proteins, is crucial for mitochondrial function, biogenesis, and integrity. This process is divided into four phases-initiation, elongation, termination, and mitoribosome recycling-which are regulated by specific translation factors, including mitochondrial initiation factor 2 and 3 (mtIF2 and mtIF3), mitochondrial elongation factor Tu, Ts, and G1 (mtEFTu, mtEFTs, and mtEFG1), mitochondrial translational release factor 1-like (mtRF1L), and mitochondrial recycling factor 1 and 2 (mtRRF1 and mtRRF2). Muscle denervation downregulates mitochondrial biomass and induces skeletal muscle atrophy. However, it is unknown whether denervation affects the expression of mitochondrial translation factors in skeletal muscle. In this study, we hypothesized that denervation decreases the expression of mitochondrial translation factors. Therefore, we investigated the effect of muscle denervation on mitochondrial protein and mitochondrial translation factor expression in soleus muscle after surgery. Denervation induced muscle atrophy and activated the ubiquitin-proteasome pathway in soleus muscle. Additionally, muscle denervation decreased the expression of mitochondrial translation factors as well as nuclear DNA and mtDNA-encoded mitochondrial proteins in soleus muscle. Further, a correlation was found between the expression of mitochondrial translation factors and mtDNA-encoded proteins three and seven days after denervation. Taken together, these results demonstrated that the denervation-induced decrease in mitochondrial biogenesis corresponded with changes in mitochondrial translation factors in murine skeletal muscle, providing novel molecular-level insight into the effects of muscle denervation on the mitochondrial translation process.