RT Journal Article SR Electronic T1 The Mechanism of MICU-Dependent Gating of the Mitochondrial Ca2+ Uniporter JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.04.04.025833 DO 10.1101/2020.04.04.025833 A1 Vivek Garg A1 Ishan Paranjpe A1 Tiffany Unsulangi A1 Junji Suzuki A1 Lorin S. Milescu A1 Yuriy Kirichok YR 2020 UL http://biorxiv.org/content/early/2020/08/29/2020.04.04.025833.abstract AB Mitochondrial Ca2+ uniporter (MCU) mediates mitochondrial Ca2+ uptake, regulating ATP production and cell death. According to the existing paradigm, MCU is occluded at the resting cytosolic [Ca2+] and only opens above an ∼400 nM threshold. This Ca2+-dependent gating is putatively conferred by MICUs, EF hand-containing auxiliary subunits that block/unblock the MCU pore depending on cytosolic [Ca2+]. Here we provide the first direct, patch-clamp based analysis of the Ca2+-dependent MCU gating and the role played by MICUs. Surprisingly, MICUs do not occlude the MCU pore, and MCU is a constitutively active channel without cytosolic [Ca2+] activation threshold. Instead, MICUs potentiate MCU activity when cytosolic Ca2+ binds to their EF hands. MICUs cause this potentiation by increasing the probability of open state of the MCU channel.One Sentence Summary Auxiliary MICU subunits do not occlude the mitochondrial Ca2+ uniporter (MCU) but increase its activity as cytosolic Ca2+ is elevated.Competing Interest StatementThe authors have declared no competing interest.