Calcium Flux (IMAGE) University of Pennsylvania School of Medicine Caption Ca2+ flux across the inner mitochondrial membrane regulates cell bioenergetics, cytoplasmic Ca2+ signals and activation of cell death pathways. Ca2+ uptake from the cytoplasm is driven by the electrochemical gradient generated during ATP production, mediated by a Ca2+ ion channel called the mitochondrial Ca2+ uniporter. Molecular components of the uniporter include MCU, the Ca2+ conducting pore, and MICU1, a MCU regulator that limits Ca2+ permeation through MCU at rest. MCUR1 is as an essential third component of the uniporter complex. In the absence of MCUR1, mitochondrial Ca2+ uptake is markedly reduced, with adverse cellular consequences, including compromised cellular bioenergetics, diminished oxidative phosphorylation and activation of autophagy. The cover shows mitochondria (green) stained with the mitochondrial membrane potential indicator, rhodamine 123 in living primary mouse embryonic fibroblasts. Nuclei are stained with DAPI (blue). Credit Lili Guo, Perelman School of Medicine, University of Pennsylvania Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.