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MICU1 encodes a mitochondrial EF hand protein required for Ca2+ uptake

Abstract

Mitochondrial calcium uptake has a central role in cell physiology by stimulating ATP production, shaping cytosolic calcium transients and regulating cell death. The biophysical properties of mitochondrial calcium uptake have been studied in detail, but the underlying proteins remain elusive. Here we use an integrative strategy to predict human genes involved in mitochondrial calcium entry based on clues from comparative physiology, evolutionary genomics and organelle proteomics. RNA interference against 13 top candidates highlighted one gene, CBARA1, that we call hereafter mitochondrial calcium uptake 1 (MICU1). Silencing MICU1 does not disrupt mitochondrial respiration or membrane potential but abolishes mitochondrial calcium entry in intact and permeabilized cells, and attenuates the metabolic coupling between cytosolic calcium transients and activation of matrix dehydrogenases. MICU1 is associated with the mitochondrial inner membrane and has two canonical EF hands that are essential for its activity, indicating a role in calcium sensing. MICU1 represents the founding member of a set of proteins required for high-capacity mitochondrial calcium uptake. Its discovery may lead to the complete molecular characterization of mitochondrial calcium uptake pathways, and offers genetic strategies for understanding their contribution to normal physiology and disease.

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Figure 1: Targeted RNAi screen for mitochondrial Ca 2+ uptake.
Figure 2: Mitochondrial membrane potential, respiration and mtDNA copy number in MICU1 -silenced cells.
Figure 3: Measurement of mitochondrial Ca 2+ uptake kinetics in populations of cells, individual cells and permeabilized cells.
Figure 4: MICU1 is an EF-hand protein localized to mitochondria.
Figure 5: Contribution of MICU1 to cytosolic Ca 2+ dynamics and metabolic coupling.

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Acknowledgements

We thank Z. Grabarek, S. Silver and D. Root for advice; S. Calvo and A. Wolf for assistance with bioinformatics; P. Federico for technical assistance; and members of the Mootha Laboratory for valuable feedback. This work was supported by grants from the National Institutes of Health (GM084027) to A.E.P, TR2 GM08759 to J.E.M. and GM0077465, DK080261 awarded to V.K.M., and by an HHMI Early Career Physician Scientist Award to V.K.M.

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F.P. and V.K.M conceived of the project and its design. F.P., V.M.G., H.S.G., X.R.B., J.E.M. and A.E.P. performed experiments and data analysis. F.P. and V.K.M. 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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Perocchi, F., Gohil, V., Girgis, H. et al. MICU1 encodes a mitochondrial EF hand protein required for Ca2+ uptake. Nature 467, 291–296 (2010). https://doi.org/10.1038/nature09358

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