Mitochondrial calcium uniporter stabilization preserves energetic homeostasis during Complex I impairment

Mitochondrial complex I deficiency is frequent in congenital, neurologic and cardiovascular disease. Here the authors demonstrate that Complex I stimulates the turnover of a mitochondrial calcium channel, which becomes stabilized during Complex I deficiency, preserving energetic homeostasis. Calcium entering mitochondria potently stimulates ATP synthesis. Increases in calcium preserve energy synthesis in cardiomyopathies caused by mitochondrial dysfunction, and occur due to enhanced activity of the mitochondrial calcium uniporter channel. The signaling mechanism that mediates this compensatory increase remains unknown. Here, we find that increases in the uniporter are due to impairment in Complex I of the electron transport chain. In normal physiology, Complex I promotes uniporter degradation via an interaction with the uniporter pore-forming subunit, a process we term Complex I-induced protein turnover. When Complex I dysfunction ensues, contact with the uniporter is inhibited, preventing degradation, and leading to a build-up in functional channels. Preventing uniporter activity leads to early demise in Complex I-deficient animals. Conversely, enhancing uniporter stability rescues survival and function in Complex I deficiency. Taken together, our data identify a fundamental pathway producing compensatory increases in calcium influx during Complex I impairment.

Automated summary

Mitochondrial complex I deficiency is common in congenital, neurologic, and cardiovascular diseases. This study reveals that Complex I stimulates the turnover of a mitochondrial calcium channel, preserving energetic homeostasis during Complex I deficiency. Calcium influx into mitochondria enhances ATP synthesis and is increased in cardiomyopathies caused by mitochondrial dysfunction. The impairment of Complex I leads to increased activity of the mitochondrial calcium uniporter channel. The authors propose that calcium influx compensates for Complex I dysfunction via an impairment in Complex I-induced protein turnover and Uniporter stabilization.