In Vivo Regulation of Oxidative Phosphorylation in Cells Harboring a Stop-codon Mutation in Mitochondrial DNA-encoded Cytochrome c Oxidase Subunit I

Marilena D'Aurelio, Francesco Pallotti, Antoni Barrientos, Carl D. Gajewski, Jennifer Q. Kwong, Claudio Bruno, M. Flint Beal, Giovanni Manfredi

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

The mechanisms that regulate oxidative phosphorylation in mammalian cells are largely unknown. To address this issue, cybrids were generated by fusing osteosarcoma cells devoid of mitochondrial DNA (mtDNA) with platelets from a patient with a stop-codon mutation in cytochrome c oxidase subunit I (COX I). The molecular and biochemical characteristics of cybrids harboring varying levels of mutated mitochondrial DNA were studied. We found a direct correlation between the levels of mutated COX I DNA and mutated COX I mRNA, whereas the levels of COX I total mRNA were unchanged. COX I polypeptide synthesis and steady-state levels were inversely proportional to mutation levels. Cytochrome c oxidase subunit II was reduced proportionally to COX I, indicating impairment in complex assembly. COX enzymatic activity was inversely proportional to the levels of mutated mtDNA. However, both cell respiration and ATP synthesis were preserved in cells with lower proportions of mutated genomes, with a threshold at ∼40%, and decreased linearly with increasing mutated mtDNA. These results indicate that COX levels in mutated cells were not regulated at the transcriptional, translational, and post-translational levels. Because of a small excess of COX capacity, the levels of expression of COX subunits exerted a relatively tight control on oxidative phosphorylation.

Original languageEnglish (US)
Pages (from-to)46925-46932
Number of pages8
JournalJournal of Biological Chemistry
Volume276
Issue number50
DOIs
StatePublished - Dec 14 2001
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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