Critical role of mitochondrial aconitase in skeletal muscle maturation.

Skeletal muscle dynamically regulates protein synthesis and degradation through metabolic responses to external stimuli. In the absence of mechanical load, this normal metabolic response is impaired, leading to muscle atrophy. Previous studies have suggested that mitochondrial dysfunction occurs under unloaded conditions. In this study, we focused on aconitase 2 (Aco2), a mitochondrial protein known to contain an iron-sulfur cluster and function as a metabolic sensor. We generated skeletal muscle-specific Aco2 knockout (cKO) mice to investigate its role in muscle function. Although these mice appeared grossly normal, they died shortly after birth. Analysis of the diaphragm muscle revealed signs of muscle fiber atrophy and impaired muscle maturation. Besides these signs of immaturity, abnormal muscle cells exhibiting disrupted sarcomere structures were frequently observed. Furthermore, these cells showed a marked increase in the apoptotic marker Active Caspase-3, indicating that Aco2 deficiency induces muscle cell death. These findings suggest that Aco2 plays a critical role in skeletal muscle maturation and maintenance of muscle homeostasis. Moreover, these findings highlighted the potential involvement of Aco2 in disuse muscle atrophy and its utility as a therapeutic target.