Original Article

Subject Category: Cancer Metabolism

Citation: Cell Death and Disease () 4, e670; doi:10.1038/cddis.2013.201
Published online 13 June 2013

Alterations in c-Myc phenotypes resulting from dynamin-related protein 1 (Drp1)-mediated mitochondrial fission
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M Sarin1, Y Wang2, F Zhang1, K Rothermund1, Y Zhang2, J Lu1, S Sims-Lucas3, D Beer-Stolz4, B E Van Houten5,6, J Vockley2, E S Goetzman2, J Anthony Graves1 and E V Prochownik1,5,7

  1. 1Division of Hematology/Oncology, Children’s Hospital of Pittburgh of UPMC, Pittsburgh, PA, USA
  2. 2Division of Medical Genetics, Children’s Hospital of Pittburgh of UPMC, Pittsburgh, PA, USA
  3. 3Division of Nephrology, Children’s Hospital of Pittsburgh of UPMC, Pittsburgh, PA, USA
  4. 4Center for Biological Imaging, The University of Pittsburgh, Pittsburgh, PA, USA
  5. 5The University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA
  6. 6The Department of Pharmacology and Chemical Biology, The University of Pittsburgh Medical Center, Pittsburgh, PA, USA
  7. 7Department of Microbiology and Molecular Genetics, The University of Pittsburgh Medical Center, Pittsburgh, PA, USA

Correspondence: EV Prochownik, Section of Hematology/Oncology, Rangos Research Center, Room 5124, Children’s Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA. Tel: (412) 692-6795; Fax: (412) 692-5228; E-mail: procev@chp.edu

Received 9 April 2013; Revised 7 May 2013; Accepted 10 May 2013

Edited by G Raschellà

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Abstract

The c-Myc (Myc) oncoprotein regulates numerous phenotypes pertaining to cell mass, survival and metabolism. Glycolysis, oxidative phosphorylation (OXPHOS) and mitochondrial biogenesis are positively controlled by Myc, with myc−/ rat fibroblasts displaying atrophic mitochondria, structural and functional defects in electron transport chain (ETC) components, compromised OXPHOS and ATP depletion. However, while Myc influences mitochondrial structure and function, it is not clear to what extent the reverse is true. To test this, we induced a state of mitochondrial hyper-fission in rat fibroblasts by de-regulating Drp1, a dynamin-like GTPase that participates in the terminal fission process. The mitochondria from these cells showed reduced mass and interconnectivity, a paucity of cristae, a marked reduction in OXPHOS and structural and functional defects in ETC Complexes I and V. High rates of abortive mitochondrial fusion were observed, likely reflecting ongoing, but ultimately futile, attempts to normalize mitochondrial mass. Cellular consequences included reduction of cell volume, ATP depletion and activation of AMP-dependent protein kinase. In response to Myc deregulation, apoptosis was significantly impaired both in the absence and presence of serum, although this could be reversed by increasing ATP levels by pharmacologic means. The current work demonstrates that enforced mitochondrial fission closely recapitulates a state of Myc deficiency and that mitochondrial integrity and function can affect Myc-regulated cellular behaviors. The low intracellular ATP levels that are frequently seen in some tumors as a result of inadequate vascular perfusion could favor tumor survival by countering the pro-apoptotic tendencies of Myc overexpression.

Keywords:

apoptosis; glycolysis; mitofusins; OXPHOS; Warburg effect

Abbreviations:

AICAR, 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide; AMPK, AMP-dependent protein kinase; AUC, area under the curve; CM-H2DCFDA, chloromethyl derivative of 2′,7′-dichlorodihydrofluorescein diacetate; BNGE, blue-native gel electrophoresis; CHX, cycloheximide; DMEM, Dulbecco’s modified Eagle’s minimal essential medium; Drp1, dynamin-related protein 1; DsRED-mito, Discosoma sp. red fluorescent protein fused to a mitochondrial signal peptide; 2-DG, 2-deoxyglucose; ECAR, extracellular acidification rate; EGFP-Mito, enhanced green fluorescent protein fused to a mitochondrial localization signal; ETC, electron transport chain; FCCP, cyanide p-trifluoromethoxy-phenylhydrazone; MycER, human Myc protein fused to the estrogen receptor hormone-binding domain; NAO, 10-nonoyl-acridine orange; OXPHOS, oxidative phosphorylation; OCR, oxygen consumption rate; PEG, polyethylene glycol; ROS, reactive oxygen species