Abstract
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.
Highlights
Mitochondria provide the main source of energy in eukaryotic cells, oxidizing sugars, fats and amino acids to generate ATP by oxidative phosphorylation (OXPHOS)
We have previously shown that transmitochondrial cybrid cells carrying a homoplasmic m.13565C>T mitochondrial DNA (mtDNA) mutation, which results in a p.Ser410Phe amino acid change in the complex I subunit ND5, have defects in mitochondrial respiration and a reduced Δψm [9]
The relationship between mitochondrial metabolism and calcium signaling was first recognized in the early 1960’s, when it was discovered that isolated mitochondria could take up calcium [14]
Summary
Mitochondria provide the main source of energy in eukaryotic cells, oxidizing sugars, fats and amino acids to generate ATP by oxidative phosphorylation (OXPHOS). This series of enzymatic reactions is performed by five protein complexes (I-V) within the mitochondrial inner membrane. Complex I (NADH: ubiquinone oxidoreductase) and II (succinate-ubiquinone oxidoreductase) accept electrons from the TCA cycle, which are passed to molecular oxygen. Mitochondrial DNA Mutations and Calcium Handling Defects medical-research-institutes/) to MMCK. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
