The conserved aspartate ring of MCU mediates MICU1 binding and regulation in the mitochondrial calcium uniporter complex

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Abstract

The mitochondrial calcium uniporter is a Ca²⁺ channel that regulates intracellular Ca²⁺ signaling, oxidative phosphorylation, and apoptosis. It contains the pore-forming MCU protein, which possesses a DIME sequence thought to form a Ca²⁺ selectivity filter, and also regulatory EMRE, MICU1, and MICU2 subunits. To properly carry out physiological functions, the uniporter must stay closed in resting conditions, becoming open only when stimulated by intracellular Ca²⁺ signals. This Ca²⁺-dependent activation, known to be mediated by MICU subunits, is not well understood. Here, we demonstrate that the DIME-aspartate mediates a Ca²⁺-modulated electrostatic interaction with MICU1, forming an MICU1 contact interface with a nearby Ser residue at the cytoplasmic entrance of the MCU pore. A mutagenesis screen of MICU1 identifies two highly-conserved Arg residues that might contact the DIME-Asp. Perturbing MCU-MICU1 interactions elicits unregulated, constitutive Ca²⁺ flux into mitochondria. These results indicate that MICU1 confers Ca²⁺-dependent gating of the uniporter by blocking/unblocking MCU.

Data availability

All data generated or analyzed during this study are included in the manuscript and supporting files. Source data for calcium-45 flux experiments are available via Dryad.

The following data sets were generated

1. Phillips C
2. Tsai
3. C
4. Tsai M
(2019) Date from: The conserved aspartate ring of MCU mediates MICU1 binding and regulation in the mitochondrial calcium uniporter complex
Dryad Digital Repository, 10.5061/dryad.1976kg3.

https://doi.org/10.5061/dryad.1976kg3

Article and author information

Author details

Charles B Phillips

Department of Biochemistry, Brandeis University, Waltham, United States

Competing interests
The authors declare that no competing interests exist.
Chen-Wei Tsai

Department of Biochemistry, Brandeis University, Waltham, United States

Competing interests
The authors declare that no competing interests exist.
Ming-Feng Tsai

Department of Biochemistry, Brandeis University, Waltham, United States

For correspondence
mftsai@brandeis.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-4277-1885

Funding

Howard Hughes Medical Institute

Ming-Feng Tsai

National Institute of General Medical Sciences (R01-GM129345)

Chen-Wei Tsai
Ming-Feng Tsai

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication. The funders pay for the authors' salary and other research expenses.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.