Hamilton, JamesBrustovetsky, TatianaRysted, Jacob E.Lin, ZhihongUsachev, Yuriy M.Brustovetsky, Nickolay2020-01-232020-01-232018-10-05Hamilton, J., Brustovetsky, T., Rysted, J. E., Lin, Z., Usachev, Y. M., & Brustovetsky, N. (2018). Deletion of mitochondrial calcium uniporter incompletely inhibits calcium uptake and induction of the permeability transition pore in brain mitochondria. The Journal of biological chemistry, 293(40), 15652–15663. doi:10.1074/jbc.RA118.002926https://hdl.handle.net/1805/21890Ca2+ influx into mitochondria is mediated by the mitochondrial calcium uniporter (MCU), whose identity was recently revealed as a 40-kDa protein that along with other proteins forms the mitochondrial Ca2+ uptake machinery. The MCU is a Ca2+-conducting channel spanning the inner mitochondrial membrane. Here, deletion of the MCU completely inhibited Ca2+ uptake in liver, heart, and skeletal muscle mitochondria. However, in brain nonsynaptic and synaptic mitochondria from neuronal somata/glial cells and nerve terminals, respectively, the MCU deletion slowed, but did not completely block, Ca2+ uptake. Under resting conditions, brain MCU-KO mitochondria remained polarized, and in brain MCU-KO mitochondria, the electrophoretic Ca2+ ionophore ETH129 significantly accelerated Ca2+ uptake. The residual Ca2+ uptake in brain MCU-KO mitochondria was insensitive to inhibitors of mitochondrial Na+/Ca2+ exchanger and ryanodine receptor (CGP37157 and dantrolene, respectively), but was blocked by the MCU inhibitor Ru360. Respiration of WT and MCU-KO brain mitochondria was similar except that for mitochondria that oxidized pyruvate and malate, Ca2+ more strongly inhibited respiration in WT than in MCU-KO mitochondria. Of note, the MCU deletion significantly attenuated but did not completely prevent induction of the permeability transition pore (PTP) in brain mitochondria. Expression level of cyclophilin D and ATP content in mitochondria, two factors that modulate PTP induction, were unaffected by MCU-KO, whereas ADP was lower in MCU-KO than in WT brain mitochondria. Our results suggest the presence of an MCU-independent Ca2+ uptake pathway in brain mitochondria that mediates residual Ca2+ influx and induction of PTP in a fraction of the mitochondrial population.en-USPublisher PolicyCalciumCyclophilin DEnergy metabolismIon channelMitochondriaMitochondrial membrane potentialMitochondrial permeability transition (MPT)RespirationArticle