Dysregulation of Mitochondrial Ca(2+) Uptake and Sarcolemma Repair Underlie Muscle Weakness and Wasting in Patients and Mice Lacking MICU1

Muscle function is regulated by Ca(2+), which mediates excitation-contraction coupling, energy metabolism, adaptation to exercise, and sarcolemmal repair. Several of these actions rely on Ca(2+) delivery to the mitochondrial matrix via the mitochondrial Ca(2+) uniporter, the pore of which is formed by mitochondrial calcium uniporter (MCU). MCU’s gatekeeping and cooperative activation are controlled by MICU1. Loss-of-protein mutation in MICU1 causes a neuromuscular disease. To determine the mechanisms underlying the muscle impairments, we used MICU1 patient cells and skeletal muscle-specific MICU1 knockout mice. Both these models show a lower threshold for MCU-mediated Ca(2+) uptake. Lack of MICU1 is associated with impaired mitochondrial Ca(2+) uptake during excitation-contraction, aerobic metabolism impairment, muscle weakness, fatigue, and myofiber damage during physical activity. MICU1 deficit compromises mitochondrial Ca(2+) uptake during sarcolemmal injury, which causes ineffective repair of the damaged myofibers. Thus, dysregulation of mitochondrial Ca(2+) uptake hampers myofiber contractile function, likely through energy metabolism and membrane repair.