Elucidating a Role for UCP3 in the Control of Mitochondrial Superoxide Flashes

Abstract

Mitochondria are a major site of reactive oxygen species (ROS) production in cells. While ROS can cause oxidative damage, they are vital in many signaling processes. Recently, mitochondrial superoxide flashes (mSOF) were defined through sensitive measurements of temporal and spatial differences in superoxide production. mSOF are stochastic events of quantal bursts in superoxide production, which are temporally linked to transient mitochondrial inner membrane depolarizations. The aims of the present study were to characterize a hydrogen peroxide sensitive biosensor to monitor these events and elucidate a role for uncoupling protein 3 (UCP3) and the mechanistic details of mSOF. While pHyPer- dmito was sensitive enough to monitor these dynamic changes its kinetics were insufficient to detect these ~20s long flashes. Additionally, analyses showed a prolonged duration of flashes in the absence of UCP3. Furthermore, we unearthed a novel relationship between flash amplitude and mitochondrial depolarization. Finally, investigations of mSOF in muscles of various fiber type compositions showed no differences, though additional investigations are warranted.