Molecular Cell Manuscript_Zhiwei et al., 2017

Ca2+ dynamics and oxidative signaling are fundamental mechanisms for mitochondrial bioenergetics and cell function. The Mitochondrial Calcium Uniporter (MCU) complex is the major pathway by which these signals are integrated in the mitochondria. Whether and how these coactive elements interact with MCU has not been established. As an approach towards understanding the regulation of MCU channel activity by oxidative milieu, we adapted inflammatory and hypoxia model systems. Our studies identified the conserved cysteine at position 97 to be the only reactive thiol in human MCU that undergoes S-glutathionylation. Furthermore, biochemical, structural and superresolution imaging analysis revealed that MCU oxidation promotes MCU higher-order oligomer formation in the inner mitochondrial membrane. Both oxidation and mutation of MCU Cys-97 exhibited persistent activation of the MCU channel with higher [Ca2+]m uptake rate, increased IMCU, elevated mitochondrial ROS and enhanced [Ca2+]m overload-induced cell death. In contrast, these effects were largely independent of MCU interaction with its regulatory components. These findings reveal a distinct functional role for Cys-97 in ROS sensing and regulation of MCU activity.