title: Intrinsic mitochondrial dysfunction in ATM-deficient lymphoblastoid cells.
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.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA 90095-1732, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Ambrose
authors.forename: Jimena V
authors.initials: JV
authors.lastname: Goldstine
authors.forename: Richard A
authors.initials: RA
authors.lastname: Gatti
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D001260:Ataxia Telangiectasia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000235:genetics; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D028361:Mitochondrial Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D024101:Mitochondrial Proteins / Q000096:biosynthesis / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D010101:Oxygen Consumption; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D008063:Thioctic Acid / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D025521:Tumor Suppressor Proteins; D008063:Thioctic Acid; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases