A novel fission-independent role of dynamin-related protein 1 in cardiac mitochondrial respiration

Cardiovasc Res. 2017 Feb;113(2):160-170. doi: 10.1093/cvr/cvw212. Epub 2016 Oct 29.

Abstract

Aims: Mitochondria in adult cardiomyocytes exhibit static morphology and infrequent dynamic changes, despite the high abundance of fission and fusion regulatory proteins in the heart. Previous reports have indicated that fusion proteins may bear functions beyond morphology regulation. Here, we investigated the role of fission protein, dynamin-related protein 1 (DRP1), on mitochondrial respiration regulation in adult cardiomyocytes.

Methods and results: By using genetic or pharmacological approaches, we manipulated the activity or protein level of fission and fusion proteins and found they mildly influenced mitochondrial morphology in adult rodent cardiomyocytes, which is in contrast to their significant effect in H9C2 cardiac myoblasts. Intriguingly, inhibiting endogenous DRP1 by dominant-negative DRP1 mutation (K38A), shRNA, or Mdivi-1 suppressed maximal respiration and respiratory control ratio in isolated mitochondria from adult mouse heart or in adult cardiomyocytes from rat. Meanwhile, basal respiration was increased due to increased proton leak. Facilitating mitofusin-mediated fusion by S3 compound, however, failed to inhibit mitochondrial respiration in adult cardiomyocytes. Mechanistically, DRP1 inhibition did not affect the maximal activity of individual respiratory chain complexes or the assembly of supercomplexes. Knocking out cyclophilin D, a regulator of mitochondrial permeability transition pore (mPTP), abolished the effect of DRP1 inhibition on respiration. Finally, DRP1 inhibition decreased transient mPTP-mediated mitochondrial flashes, delayed laser-induced mPTP opening and suppressed mitochondrial reactive oxygen species (ROS).

Conclusion: These results uncover a novel non-canonical function of the fission protein, DRP1 in maintaining or positively stimulating mitochondrial respiration, bioenergetics and ROS signalling in adult cardiomyocyte, which is likely independent of morphological changes.

Keywords: Adult cardiomyocyte; Dynamin related protein 1; Mitochondrial morphology; Mitochondrial permeability transition pore; Mitochondrial respiration.

MeSH terms

  • Animals
  • Cell Line
  • Cell Respiration
  • Cyclophilin D
  • Cyclophilins / genetics
  • Cyclophilins / metabolism
  • Dynamins / genetics
  • Dynamins / metabolism*
  • Electron Transport Chain Complex Proteins / metabolism
  • Energy Metabolism* / drug effects
  • Female
  • Genotype
  • Membrane Potential, Mitochondrial
  • Mice
  • Mice, Knockout
  • Mitochondria, Heart / drug effects
  • Mitochondria, Heart / metabolism*
  • Mitochondria, Heart / pathology
  • Mitochondrial Membrane Transport Proteins / metabolism
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / metabolism*
  • Myocytes, Cardiac / pathology
  • Phenotype
  • Quinazolinones / pharmacology
  • RNA Interference
  • Rats
  • Rats, Sprague-Dawley
  • Reactive Oxygen Species / metabolism
  • Signal Transduction
  • Transfection

Substances

  • 3-(2,4-dichloro-5-methoxyphenyl)-2-sulfanyl-4(3H)-quinazolinone
  • Cyclophilin D
  • Electron Transport Chain Complex Proteins
  • Mitochondrial Membrane Transport Proteins
  • PPIF protein, mouse
  • Quinazolinones
  • Reactive Oxygen Species
  • mitochondrial permeability transition pore
  • Dnm1l protein, mouse
  • Dnm1l protein, rat
  • Dynamins
  • Cyclophilins