Electrical recordings of the mitochondrial calcium uniporter in Xenopus oocytes

J Gen Physiol. 2018 Jul 2;150(7):1035-1043. doi: 10.1085/jgp.201812015. Epub 2018 Jun 11.


The mitochondrial calcium uniporter is a multisubunit Ca2+ channel that mediates mitochondrial Ca2+ uptake, a cellular process crucial for the regulation of oxidative phosphorylation, intracellular Ca2+ signaling, and apoptosis. In the last few years, genes encoding uniporter proteins have been identified, but a lack of efficient tools for electrophysiological recordings has hindered quantitative analysis required to determine functional mechanisms of this channel complex. Here, we redirected Ca2+-conducting subunits (MCU and EMRE) of the human uniporter to the plasma membrane of Xenopus oocytes. Two-electrode voltage clamp reveals inwardly rectifying Ca2+ currents blocked by a potent inhibitor, Ru360 (half maximal inhibitory concentration, ~4 nM), with a divalent cation conductivity of Ca2+ > Sr2+ > Ba2+, Mn2+, and Mg2+ Patch clamp recordings further reveal macroscopic and single-channel Ca2+ currents sensitive to Ru360. These electrical phenomena were abolished by mutations that perturb MCU-EMRE interactions or disrupt a Ca2+-binding site in the pore. Altogether, this work establishes a robust method that enables deep mechanistic scrutiny of the uniporter using classical strategies in ion channel electrophysiology.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Action Potentials*
  • Animals
  • Barium / metabolism
  • Binding Sites
  • Calcium / metabolism
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / chemistry
  • Calcium Channels / metabolism*
  • Cell Membrane / drug effects
  • Cell Membrane / physiology
  • Humans
  • Magnesium / metabolism
  • Ruthenium Compounds / pharmacology
  • Strontium / metabolism
  • Xenopus


  • Calcium Channel Blockers
  • Calcium Channels
  • Ru 360
  • Ruthenium Compounds
  • SMDT1 protein, human
  • mitochondrial calcium uniporter
  • Barium
  • Magnesium
  • Calcium
  • Strontium