SK2 channels regulate mitochondrial respiration and mitochondrial Ca 2+ uptake

Cell Death Differ. 2017 May;24(5):761-773. doi: 10.1038/cdd.2017.2. Epub 2017 Mar 10.

Abstract

Mitochondrial calcium ([Ca2+]m) overload and changes in mitochondrial metabolism are key players in neuronal death. Small conductance calcium-activated potassium (SK) channels provide protection in different paradigms of neuronal cell death. Recently, SK channels were identified at the inner mitochondrial membrane, however, their particular role in the observed neuroprotection remains unclear. Here, we show a potential neuroprotective mechanism that involves attenuation of [Ca2+]m uptake upon SK channel activation as detected by time lapse mitochondrial Ca2+ measurements with the Ca2+-binding mitochondria-targeted aequorin and FRET-based [Ca2+]m probes. High-resolution respirometry revealed a reduction in mitochondrial respiration and complex I activity upon pharmacological activation and overexpression of mitochondrial SK2 channels resulting in reduced mitochondrial ROS formation. Overexpression of mitochondria-targeted SK2 channels enhanced mitochondrial resilience against neuronal death, and this effect was inhibited by overexpression of a mitochondria-targeted dominant-negative SK2 channel. These findings suggest that SK channels provide neuroprotection by reducing [Ca2+]m uptake and mitochondrial respiration in conditions, where sustained mitochondrial damage determines progressive neuronal death.

MeSH terms

  • Aequorin / genetics
  • Aequorin / metabolism
  • Animals
  • Apamin / pharmacology
  • Calcium / metabolism*
  • Cell Death / drug effects
  • Cell Line
  • Cell Survival / drug effects
  • Electron Transport Complex I / genetics*
  • Electron Transport Complex I / metabolism
  • Fluorescence Resonance Energy Transfer
  • Gene Expression Regulation
  • Genes, Reporter
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Indoles / pharmacology
  • Membrane Potential, Mitochondrial / drug effects
  • Mice
  • Mitochondria / drug effects
  • Mitochondria / metabolism*
  • Neurons / cytology
  • Neurons / drug effects
  • Neurons / metabolism*
  • Oxidative Phosphorylation / drug effects
  • Oximes / pharmacology
  • Patch-Clamp Techniques
  • Primary Cell Culture
  • Pyrazoles / pharmacology
  • Pyrimidines / pharmacology
  • Rats
  • Signal Transduction
  • Small-Conductance Calcium-Activated Potassium Channels / agonists
  • Small-Conductance Calcium-Activated Potassium Channels / antagonists & inhibitors
  • Small-Conductance Calcium-Activated Potassium Channels / genetics*
  • Small-Conductance Calcium-Activated Potassium Channels / metabolism

Substances

  • 6,7-dichloro-1H-indole-2,3-dione 3-oxime
  • Indoles
  • Kcnn2 protein, mouse
  • Oximes
  • Pyrazoles
  • Pyrimidines
  • Small-Conductance Calcium-Activated Potassium Channels
  • cyclohexyl-(2-(3,5-dimethylpyrazol-1-yl)-6-methylpyrimidin-4-yl)amine
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • Apamin
  • Aequorin
  • Electron Transport Complex I
  • Calcium