MICU1 is a Ca2+-binding protein that regulates the mitochondrial Ca2+ uniporter channel (mtCU ) and mitochondrial Ca2+ (mCa2+) uptake. MICU1 knockout mice display perinatal lethality and disorganized mitochondrial architecture. These phenotypes are distinct from other mtCU loss-of-function models and thus are not explained by changes in mCa2+ content. Utilizing multiple proteomic approaches, we found that MICU1 localized to mitochondrial complexes lacking MCU, suggesting that MICU1 has cellular functions independent of mCa2+ uptake. The overall aim of the current project is to identify the global and mtCU independent MICU1 interactome to characterize the MCU independent functions of the MICU1.