The Mitochondrial Calcium Uniporter Is a Multimer That Can Include a Dominant-Negative Pore-Forming Subunit

EMBO J. 2013 Aug 28;32(17):2362-76. doi: 10.1038/emboj.2013.157. Epub 2013 Jul 30.

Abstract

Mitochondrial calcium uniporter (MCU) channel is responsible for Ruthenium Red-sensitive mitochondrial calcium uptake. Here, we demonstrate MCU oligomerization by immunoprecipitation and Förster resonance energy transfer (FRET) and characterize a novel protein (MCUb) with two predicted transmembrane domains, 50% sequence similarity and a different expression profile from MCU. Based on computational modelling, MCUb includes critical amino-acid substitutions in the pore region and indeed MCUb does not form a calcium-permeable channel in planar lipid bilayers. In HeLa cells, MCUb is inserted into the oligomer and exerts a dominant-negative effect, reducing the [Ca(2+)]mt increases evoked by agonist stimulation. Accordingly, in vitro co-expression of MCUb with MCU drastically reduces the probability of observing channel activity in planar lipid bilayer experiments. These data unveil the structural complexity of MCU and demonstrate a novel regulatory mechanism, based on the inclusion of dominant-negative subunits in a multimeric channel, that underlies the fine control of the physiologically and pathologically relevant process of mitochondrial calcium homeostasis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Calcium / metabolism*
  • Calcium Channels / chemistry*
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Fluorescence Resonance Energy Transfer
  • HeLa Cells
  • Homeostasis
  • Humans
  • Lipid Bilayers
  • Membrane Potential, Mitochondrial
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Conformation
  • Protein Structure, Tertiary
  • Protein Subunits

Substances

  • Calcium Channels
  • Lipid Bilayers
  • Protein Subunits
  • mitochondrial calcium uniporter
  • Calcium