Systematic mapping of mitochondrial calcium uniporter channel (MCUC)-mediated calcium signaling networks

The mitochondrial calcium uniporter channel (MCUC) mediatesmitochondrial calcium entry, regulating energy metabolism and celldeath. Although several MCUC components have been identified,the molecular basis of mitochondrial calcium signaling networksand their remodeling upon changes in uniporter activity have notbeen assessed. Here, we map the MCUC interactome under restingconditions and upon chronic loss or gain of mitochondrial calciumuptake. We identify 89 high-confidence interactors that link MCUCto several mitochondrial complexes and pathways, half of which areassociated with human disease. As a proof-of-concept, we validatethe mitochondrial intermembrane space protein EFHD1 as a bindingpartner of the MCUC subunits MCU, EMRE, and MCUB. We furthershow a MICU1-dependent inhibitory effect of EFHD1 on calciumuptake. Next, we systematically survey compensatory mechanismsand functional consequences of mitochondrial calcium dysho-meostasis by analyzing the MCU interactome upon EMRE, MCUB,MICU1, or MICU2 knockdown. While silencing EMRE reduces MCUinterconnectivity, MCUB loss-of-function leads to a wider interac-tion network. Our study provides a comprehensive and high-confidence resource to gain insights into players and mechanismsregulating mitochondrial calcium signaling and their relevance inhuman diseases.