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F1FO ATPase Vesicle Preparation and Technique for Performing Patch Clamp Recordings of Submitochondrial Vesicle Membranes
Published on: May 4, 2013
Aprataxin localizes to mitochondria and preserves mitochondrial function.
Peter Sykora1, Deborah L Croteau, Vilhelm A Bohr
1Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
Summary
Aprataxin, a DNA repair protein, localizes to mitochondria and is crucial for mitochondrial DNA maintenance. Its depletion causes mitochondrial dysfunction and increased DNA damage, highlighting its role in preventing ataxia with oculomotor apraxia.
Area of Science:
- Molecular Biology
- Genetics
- Neuroscience
Background:
- Ataxia with oculomotor apraxia 1 is linked to mutations in the APTX gene, encoding the DNA repair protein aprataxin.
- Aprataxin is homologous to histidine triad proteins and removes 5'-adenylate groups from DNA, crucial for DNA repair.
- The precise cellular localization and function of aprataxin, particularly in relation to mitochondrial DNA, remain incompletely understood.
Purpose of the Study:
- To investigate the subcellular localization of aprataxin, focusing on its presence in mitochondria.
- To identify the specific protein sequences responsible for mitochondrial targeting of aprataxin isoforms.
- To elucidate the role of aprataxin in mitochondrial DNA maintenance and its implications for neurodegenerative diseases.
Main Methods:
- Immunofluorescence microscopy to determine aprataxin localization in human cells.
- Bioinformatic analysis to identify mitochondrial targeting sequences.
- Gene silencing (knockdown) of aprataxin in SH-SY5Y neuroblastoma cells and primary myoblasts.
- Assays for mitochondrial function, including citrate synthase activity and mtDNA copy number determination.
- Quantification of DNA damage in both mitochondrial and nuclear DNA post-aprataxin depletion.
Main Results:
- Aprataxin was found to localize to mitochondria in human cells, mediated by a specific N-terminal amino acid sequence.
- Transcripts encoding this mitochondrial-targeting sequence are expressed in the human brain, particularly the cerebellum.
- Aprataxin depletion led to mitochondrial dysfunction, evidenced by reduced citrate synthase activity and mtDNA copy number.
- Knockdown of aprataxin resulted in significantly higher background DNA damage in mtDNA compared to nuclear DNA.
Conclusions:
- Aprataxin plays a direct role in the maintenance and processing of mitochondrial DNA.
- Mitochondrial dysfunction resulting from aprataxin deficiency contributes to the pathogenesis of ataxia with oculomotor apraxia.
- The findings identify aprataxin as a key player in safeguarding mitochondrial genome integrity.
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