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Uncoupling proteins 2 and 3 are fundamental for mitochondrial Ca2+ uniport

A Corrigendum to this article was published on 01 November 2008

This article has been updated

Abstract

Mitochondrial Ca2+ uptake is crucial for the regulation of the rate of oxidative phosphorylation1, the modulation of spatio-temporal cytosolic Ca2+ signals2,3,4 and apoptosis5. Although the phenomenon of mitochondrial Ca2+ sequestration, its characteristics and physiological consequences have been convincingly reported6,7, the actual protein(s) involved in this process are unknown. Here, we show that the uncoupling proteins 2 and 3 (UCP2 and UCP3) are essential for mitochondrial Ca2+ uptake. Using overexpression, knockdown (small interfering RNA) and mutagenesis experiments, we demonstrate that UCP2 and UCP3 are elementary for mitochondrial Ca2+ sequestration in response to cell stimulation under physiological conditions — observations supported by isolated liver mitochondria of Ucp2−/− mice lacking ruthenium red-sensitive Ca2+ uptake. Our results reveal a novel molecular function for UCP2 and UCP3, and may provide the molecular mechanism for their reported effects8,9,10. Moreover, the identification of proteins fundemental for mitochondrial Ca2+ uptake expands our knowledge of the physiological role for mitochondrial Ca2+ sequestration.

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Figure 1: Expression of UCP orthologues and functional tests on Ca2+ carrier function of UCP2 or UCP3 in human endothelial cells.
Figure 2: UCP2 or UCP3 knockdown by siRNAs resulted in diminution and/or elimination of mitochondrial Ca2+ uptake.
Figure 3: In isolated liver mitochondria from Ucp2−/− mice, no ruthenium red (RR)-sensitive Ca2+ uniporter exists.
Figure 4: Mutagenesis of UCP2 and UCP3 resulted in loss of Ca2+ function of the proteins and provided dominant-negative UCP homologues.

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Change history

  • 16 October 2008

    In the version of this article initially published, the third and fifth histogram columns in the right panel of Fig. 2a were incorrectly labelled. The third column should have been siUCP3 and the fifth should have been siUPC2. These errors have been corrected in the HTML and PDF versions of the article.

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Acknowledgements

We thank: B. B. Lowell (Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA) for providing the Ucp2−/− and Ucp3−/− mice; M. D. Brand (MRC Dunn Human Nutrition Unit, Cambridge, UK) for the yeast strains expressing UCP2 and UCP3; A. Miyawaki (Riken,Wako, Saitama, Japan) for mitochondria-targeted ratiometric pericam; C. J. S. Edgell (University of North Carolina, Chapel Hill, NC) for the EA.hy926 cells; T. Pozzan (University Padova, Padova, Italy) for mitochondria-targeted DsRed; R. Tsien (University of California/San Diego, CA) for D1ER and YC4er; and R. Rizzuto (University Ferrara, Ferrara, Italy) for the luciferase construct. The excellent technical assistance of B. Petschar and A. Schreilechner, and the help of K. Osibow in designing cloning strategies are highly appreciated by the authors. We thank N. Demaurex and M. Frieden (University of Geneva, Geneva, Switzerland) for critical review of the manuscript. This work was supported by the Austrian Science Funds (P16860-B9; F3010-B05) and the Franz-Lanyar-Stiftung. The Institute of Molecular Biology and Biochemistry was supported by the infrastructure program of the Austrian ministry of education, science and culture.

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All authors designed this work. M.T. cloned all constructs, designed siRNAs and performed western blots, tissue isolation and Ca2+ measurements. I.F. isolated single mitochondria. S.L.-F. was responsible for breeding the knockout mice. R.M. performed the image analyses and ATP measurements and, together with W.F.G., who wrote the paper, initiated and guided this study. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Wolfgang F. Graier.

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The authors declare no competing financial interests.

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Supplementary Figures S1, S2, S3, S4, Supplementary Table and Methods (PDF 1867 kb)

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Trenker, M., Malli, R., Fertschai, I. et al. Uncoupling proteins 2 and 3 are fundamental for mitochondrial Ca2+ uniport. Nat Cell Biol 9, 445–452 (2007). https://doi.org/10.1038/ncb1556

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