A Selective and Cell-Permeable Mitochondrial Calcium Uniporter (MCU) Inhibitor Preserves Mitochondrial Bioenergetics after Hypoxia/Reoxygenation Injury

Mitochondrial Ca2+ (mCa2+) uptake
mediated by the mitochondrial calcium uniporter (MCU) plays a critical
role in signal transduction, bioenergetics, and cell death, and its
dysregulation is linked to several human diseases. In this study,
we report a new ruthenium complex Ru265 that is cell-permeable, minimally
toxic, and highly potent with respect to MCU inhibition. Cells treated
with Ru265 show inhibited MCU activity without any effect on cytosolic
Ca2+ dynamics and mitochondrial membrane potential (ΔΨm). Dose-dependent studies reveal that Ru265 is more potent
than the currently employed MCU inhibitor Ru360. Site-directed mutagenesis
of Cys97 in the N-terminal domain of human MCU ablates the inhibitory
activity of Ru265, suggesting that this matrix-residing domain is
its target site. Additionally, Ru265 prevented hypoxia/reoxygenation
injury and subsequent mitochondrial dysfunction, demonstrating that
this new inhibitor is a valuable tool for studying the functional
role of the MCU in intact biological models.