Biophysical Society Conference | Tahoe 2024

Molecular Biophysics of Membranes

Poster Abstracts

15-POS Board 4 INVESTIGATING THE ROLE OF THE MCUR1 PROTEIN IN THE MITOCHONDRIAL CALCIUM UNIPORTER COMPLEX I-Chi Lee 1 ; Ming-Feng Tsai 1 ;

1 University of Virginia, Molecular Physiology and Biological Physics, Charlottesville, VA, USA The Mitochondrial Calcium Uniporter, which is a calcium channel complex that mediates mitochondrial calcium uptake, plays critical roles in maintaining mitochondrial calcium homeostasis, regulating energy production, cell survival, and metabolic balance. MCUR1 was identified as a subunit of the uniporter complex, but its function is currently under debate — whether it is a uniporter regulator, a regulator of the mitochondrial permeability transition pore, or an assembly factor of the cytochrome c oxidase. To investigate MCUR1 function, we generated an MCUR1 knockout (KO) cell line using CRISPR-Cas9. Measuring mitochondrial calcium uptake shows that MCUR1 KO only reduces uniporter function by 15%. Moreover, we did not observe changes in the mitochondrial permeability transition in these cells. While MCUR1 KO causes a modest 15% reduction in the expression of COX1, a protein in the cytochrome c oxidase complex, we found the effect is indirectly caused by altered mitochondrial calcium homeostasis. We have now conducted extensive studies to elucidate MCUR1’s molecular properties and interactions within the uniporter complex. Our data show that MCUR1 binds to MCU, MCU paralogue MCUb, and MCUR1, but not EMRE, MICU1, or MICU2. Furthermore, the interaction between MCUR1 and MCU occurs through the transmembrane helix and is highly conserved. Based on our findings, we propose that MCUR1 functions to connect MCU together to enhance the uniporter’s ability to generate larger calcium microdomains. These results shed light on the regulatory mechanisms governing mitochondrial calcium transport and underscore the importance of MCUR1 in modulating MCU complex activity.

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