A Forty-Kilodalton Protein of the Inner Membrane Is the Mitochondrial Calcium Uniporter

Nature. 2011 Jun 19;476(7360):336-40. doi: 10.1038/nature10230.

Abstract

Mitochondrial Ca(2+) homeostasis has a key role in the regulation of aerobic metabolism and cell survival, but the molecular identity of the Ca(2+) channel, the mitochondrial calcium uniporter, is still unknown. Here we have identified in silico a protein (named MCU) that shares tissue distribution with MICU1 (also known as CBARA1), a recently characterized uniporter regulator, is present in organisms in which mitochondrial Ca(2+) uptake was demonstrated and whose sequence includes two transmembrane domains. Short interfering RNA (siRNA) silencing of MCU in HeLa cells markedly reduced mitochondrial Ca(2+) uptake. MCU overexpression doubled the matrix Ca(2+) concentration increase evoked by inositol 1,4,5-trisphosphate-generating agonists, thus significantly buffering the cytosolic elevation. The purified MCU protein showed channel activity in planar lipid bilayers, with electrophysiological properties and inhibitor sensitivity of the uniporter. A mutant MCU, in which two negatively charged residues of the putative pore-forming region were replaced, had no channel activity and reduced agonist-dependent matrix Ca(2+) concentration transients when overexpressed in HeLa cells. Overall, these data demonstrate that the 40-kDa protein identified is the channel responsible for ruthenium-red-sensitive mitochondrial Ca(2+) uptake, thus providing a molecular basis for this process of utmost physiological and pathological relevance.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apoptosis
  • Calcium / metabolism
  • Calcium Channels / chemistry*
  • Calcium Channels / deficiency
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Cell Membrane Permeability
  • Conserved Sequence
  • Gene Silencing
  • HeLa Cells
  • Humans
  • Inositol 1,4,5-Trisphosphate / metabolism
  • Ion Transport
  • Lipid Bilayers / metabolism
  • Membrane Potential, Mitochondrial / physiology
  • Mice
  • Mitochondria / metabolism*
  • Mitochondrial Membranes / metabolism*
  • Molecular Sequence Data
  • Molecular Weight
  • Protein Structure, Tertiary
  • Protein Transport

Substances

  • Calcium Channels
  • Lipid Bilayers
  • mitochondrial calcium uniporter
  • Inositol 1,4,5-Trisphosphate
  • Calcium