Impaired Cellular Bioenergetics Causes Mitochondrial Calcium Handling Defects in MT-ND5 Mutant Cybrids.
Mutations in mitochondrial DNA (mtDNA) can cause mitochondrial disease, a group of metabolic disorders that affect both children and adults. Interestingly, individual mtDNA mutations can cause very different clinical symptoms, however the factors that determine these phenotypes remain obscure. Defects in mitochondrial oxidative phosphorylation can disrupt cell signaling pathways, which may shape these disease phenotypes. In particular, mitochondria participate closely in cellular calcium signaling, with profound impact on cell function. Here, we examined the effects of a homoplasmic m.13565C>T mutation in MT-ND5 on cellular calcium handling using transmitochondrial cybrids (ND5 mutant cybrids). We found that the oxidation of NADH and mitochondrial membrane potential (Δψm) were significantly reduced in ND5 mutant cybrids. These metabolic defects were associated with a significant decrease in calcium uptake by ND5 mutant mitochondria in response to a calcium transient. Inhibition of glycolysis with 2-deoxy-D-glucose did not affect cytosolic calcium levels in control cybrids, but caused an increase in cytosolic calcium in ND5 mutant cybrids. This suggests that glycolytically-generated ATP is required not only to maintain Δψm in ND5 mutant mitochondria but is also critical for regulating cellular calcium homeostasis. We conclude that the m.13565C>T mutation in MT-ND5 causes defects in both mitochondrial oxidative metabolism and mitochondrial calcium sequestration. This disruption of mitochondrial calcium handling, which leads to defects in cellular calcium homeostasis, may be an important contributor to mitochondrial disease pathogenesis.
Centre for Genetic Diseases, Hudson Institute of Medical Research, Clayton, Melbourne, Victoria 3168, Australia.|The Department of Molecular and Translational Science, Monash University, Clayton, Melbourne, Victoria 3168, Australia.
Matthew
0000-0001-7508-1800
M
McKenzie
Department of Physiology, University College London, Gower St, London, UK WC1E6BT.
Michael R
MR
Duchen
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D003847:Deoxyglucose / Q000494:pharmacology; D042967:Electron Transport Complex I / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D006019:Glycolysis / Q000187:drug effects / Q000235:genetics; D006801:Humans; D006822:Hybrid Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D017241:MELAS Syndrome / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009243:NAD / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010085:Oxidative Phosphorylation / Q000187:drug effects; D061251:Primary Cell Culture; D015398:Signal Transduction
D024101:Mitochondrial Proteins; D009243:NAD; D000255:Adenosine Triphosphate; D003847:Deoxyglucose; C481838:MT-ND5 protein, human; D042967:Electron Transport Complex I; D002118:Calcium