Helping Ca²⁺ into mitochondria

The mitochondrial calcium uniporter (MCU) was recently identified as the ion-conducting pore through which mitochondria are likely to take up Ca²⁺. Mallilankaraman et al. now identify CCDC90A, which they name mitochondrial calcium uniporter regulator 1 (MCUR1), as “an integral membrane protein required for MCU-dependent mitochondrial Ca²⁺ uptake.” In an RNAi screen of mitochondrial membrane proteins, the authors found that MCUR1 depletion inhibited mitochondrial Ca²⁺ uptake. Further characterization of this protein revealed that it interacts with the MCU, and that this interaction is necessary for MCU-mediated mitochondrial Ca²⁺ uptake. Finally, the authors found that cells depleted of MCUR1 had abnormal bioenergetic properties similar to those observed in cells in which Ca²⁺ uptake is blocked by established mechanisms. Thus, MCUR1 is necessary for the MCU to efficiently promote mitochondrial Ca²⁺ uptake and to ensure normal mitochondrial bioenergetics.