Intrinsic mitochondrial dysfunction in ATM-deficient lymphoblastoid cells

Hum Mol Genet. 2007 Sep 15;16(18):2154-64. doi: 10.1093/hmg/ddm166. Epub 2007 Jul 2.

Abstract

One of the characteristic features of cells from patients with ataxia telangiectasia (A-T) is that they are in a state of continuous oxidative stress and exhibit constitutive activation of pathways that normally respond to oxidative damage. In this report, we investigated whether the oxidative stress phenotype of A-T cells might be a reflection of an intrinsic mitochondrial dysfunction. Mitotracker Red staining showed that the structural organization of mitochondria in A-T cells was abnormal compared to wild-type. Moreover, A-T cells harbored a much larger population of mitochondria with decreased membrane potential (DeltaPsi) than control cells. In addition, the basal expression levels of several nuclear DNA-encoded oxidative damage responsive genes whose proteins are targeted to the mitochondria--polymerase gamma, mitochondrial topoisomerase I, peroxiredoxin 3 and manganese superoxide dismutase--are elevated in A-T cells. Consistent with these results, we found that overall mitochondrial respiratory activity was diminished in A-T compared to wild-type cells. Treating A-T cells with the antioxidant, alpha lipoic acid (ALA), restored mitochondrial respiration rates to levels approaching those of wild-type. When wild-type cells were transfected with ATM-targeted siRNA, we observed a small but significant reduction in the respiration rates of mitochondria. Moreover, mitochondria in A-T cells induced to stably express full-length ATM, exhibited respiration rates approaching those of wild-type cells. Taken together, our results provide evidence for an intrinsic mitochondrial dysfunction in A-T cells, and implicate a requirement for ATM in the regulation of mitochondrial function.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antioxidants / pharmacology
  • Ataxia Telangiectasia / genetics
  • Ataxia Telangiectasia / metabolism*
  • Ataxia Telangiectasia / pathology
  • Ataxia Telangiectasia Mutated Proteins
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Line
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Humans
  • Membrane Potential, Mitochondrial / genetics
  • Mitochondria / genetics
  • Mitochondria / metabolism*
  • Mitochondria / pathology
  • Mitochondrial Diseases / genetics
  • Mitochondrial Diseases / metabolism*
  • Mitochondrial Diseases / pathology
  • Mitochondrial Proteins / biosynthesis
  • Mitochondrial Proteins / genetics
  • Oxidative Stress* / drug effects
  • Oxidative Stress* / genetics
  • Oxygen Consumption
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Thioctic Acid / pharmacology
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*

Substances

  • Antioxidants
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Mitochondrial Proteins
  • Tumor Suppressor Proteins
  • Thioctic Acid
  • ATM protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Protein-Serine-Threonine Kinases