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Integrative genomics identifies MCU as an essential component of the mitochondrial calcium uniporter

Abstract

Mitochondria from diverse organisms are capable of transporting large amounts of Ca2+ via a ruthenium-red-sensitive, membrane-potential-dependent mechanism called the uniporter1,2,3,4. Although the uniporter’s biophysical properties have been studied extensively, its molecular composition remains elusive. We recently used comparative proteomics to identify MICU1 (also known as CBARA1), an EF-hand-containing protein that serves as a putative regulator of the uniporter5. Here, we use whole-genome phylogenetic profiling, genome-wide RNA co-expression analysis and organelle-wide protein coexpression analysis to predict proteins functionally related to MICU1. All three methods converge on a novel predicted transmembrane protein, CCDC109A, that we now call ‘mitochondrial calcium uniporter’ (MCU). MCU forms oligomers in the mitochondrial inner membrane, physically interacts with MICU1, and resides within a large molecular weight complex. Silencing MCU in cultured cells or in vivo in mouse liver severely abrogates mitochondrial Ca2+ uptake, whereas mitochondrial respiration and membrane potential remain fully intact. MCU has two predicted transmembrane helices, which are separated by a highly conserved linker facing the intermembrane space. Acidic residues in this linker are required for its full activity. However, an S259A point mutation retains function but confers resistance to Ru360, the most potent inhibitor of the uniporter. Our genomic, physiological, biochemical and pharmacological data firmly establish MCU as an essential component of the mitochondrial Ca2+ uniporter.

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Figure 1: Integrative genomics predicts MCU to be functionally related to MICU1
Figure 2: MCU is required for mitochondrial Ca 2+ uptake in cultured cells and in purified mouse liver mitochondria.
Figure 3: MCU is oligomeric and resides in the mitochondrial inner membrane as a larger complex.
Figure 4: Impact of point mutations on MCU activity and its sensitivity to Ru360.

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Acknowledgements

We thank R. Nilsson, J. Engreitz and S. Calvo for bioinformatics assistance; D. Root and S. Silver for assistance in lentiviral RNAi; B. R. Bettencourt, K. Charisse, S. Kuchimanchi and L. Speciner for siRNA design, synthesis and formulation; M. Blower, J. Avruch and R. Ward for advice; and members of the Mootha laboratory for valuable feedback. J.M.B. and L.S. were supported by graduate student fellowships from the National Science Foundation. This work was supported by grants from the National Institutes of Health (GM0077465, DK080261) awarded to V.K.M.

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J.M.B., F.P. and V.K.M. conceived of the project and its design. J.M.B., F.P., H.S.G., M.P., O.G., L.S., C.A.B.-T., X.R.B., Y.S. and R.L.B. performed experiments and data analysis. V.K. aided in experimental design. V.K.M., J.M.B., F.P. and M.P. wrote the manuscript.

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Correspondence to Vamsi K. Mootha.

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The authors declare no competing financial interests.

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Baughman, J., Perocchi, F., Girgis, H. et al. Integrative genomics identifies MCU as an essential component of the mitochondrial calcium uniporter. Nature 476, 341–345 (2011). https://doi.org/10.1038/nature10234

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