Copper deficiency drives OXPHOS impairment and mitochondrial hyperfusion via MTCH2 in skeletal muscle

Copper is an essential trace element for mitochondrial respiration and cellular metabolism, yet its physiological role in skeletal muscle remains incompletely understood. Here, we show that skeletal muscle-specific deletion of the high-affinity copper importer Ctr1 (SMKO) in mice causes local copper deficiency, resulting in exercise intolerance, systemic metabolic dysfunction, and hallmarks of mitochondrial myopathy such as ragged-red fibers, lactic acidosis, and aberrant mitochondrial morphology. Mechanistically, copper starvation disrupted the electron transport chain proteome and drove pathological mitochondrial hyperfusion. We identified mitochondrial carrier homolog 2 (MTCH2), an outer mitochondrial membrane protein, as a copper-binding regulator that coordinates mitochondrial copper distribution and morphology. Restoring copper levels via a copper ionophore or AAV-mediated Ctr1 re-expression rescued mitochondrial function and alleviated myopathic features in SMKO. These findings uncover the functional coupling of CTR1 and MTCH2 as a critical mechanistic link between copper homeostasis and mitochondrial remodeling required for skeletal muscle function.