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Updated: Jun 10, 2026
Oxygen-Independent Assays to Measure Mitochondrial Function in Mammals
Published on: May 19, 2023
In vivo detection of oxidized proteins: a practical approach to tissue-derived mitochondria
Abstract:
Mitochondria are the major producers of free radical oxygen species (ROS) as well as the major target of oxidative damage. Defects in the mitochondrial respiratory chain complexes can increase ROS production and reduce ROS removal, leading to oxidative modification of proteins, lipids, and DNA. AAA proteases of the inner mitochondrial membrane, paraplegin and AFG3L2, participate in the biogenesis and maintenance of respiratory chain complexes. These proteins form hetero-oligomeric paraplegin/AFG3L2 and homo-oligomeric AFG3L2 complexes named m-AAA proteases. Inactivation of m-AAA proteases causes respiratory defects and altered mitochondrial morphology both in yeast and in mammals. In fact, mouse models defective for Afg3l2 display a very severe neurological syndrome and die within two weeks after birth. They display widespread morphological alterations of mitochondria in the central and peripheral nervous system and deficiencies in respiratory chain complex I and in complex III, which are major producers of ROS in physiological and especially in pathological conditions. Therefore, an efficient and reliable methodology to monitor the effect of increased ROS production is useful for accurately phenotyping cellular and animal models mutants in m-AAA. By measuring carbonyl formation as marker of protein oxidation, we have shown that respiratory defects cause oxidative damage in Afg3l2 mutants, indicating that oxidative stress is crucial in the pathogenesis of m-AAA deficiency.
Insights
Mitochondrial AAA proteases are crucial for respiratory chain function. Their inactivation causes oxidative stress and severe neurological defects, highlighting the role of oxidative damage in disease.
Area of Science:
- Cell Biology
- Neuroscience
- Biochemistry
Background:
- Mitochondria produce free radical oxygen species (ROS) and are susceptible to oxidative damage.
- Defects in mitochondrial respiratory chain complexes can exacerbate ROS production and lead to cellular damage.
- AAA proteases, paraplegin and AFG3L2, are vital for mitochondrial respiratory chain complex assembly and maintenance.
Purpose of the Study:
- To investigate the role of m-AAA proteases in mitochondrial function and oxidative stress.
- To establish a methodology for monitoring oxidative damage in m-AAA protease-deficient models.
- To understand the contribution of oxidative stress to the pathogenesis of m-AAA deficiency.
Main Methods:
- Studied mouse models with defects in the Afg3l2 gene, a component of m-AAA proteases.
- Assessed mitochondrial morphology and respiratory chain complex activity (Complex I and III).
- Measured protein oxidation by quantifying carbonyl formation as a marker of oxidative damage.
Main Results:
- Afg3l2-deficient mice exhibited severe neurological syndrome and early mortality.
- Mitochondria in these mutants showed morphological alterations and deficiencies in respiratory chain complexes I and III.
- Protein oxidation, indicated by carbonyl formation, was significantly increased in Afg3l2 mutants, correlating with respiratory defects.
Conclusions:
- Inactivation of m-AAA proteases leads to mitochondrial dysfunction and increased oxidative stress.
- Oxidative damage is a critical factor in the neurological pathology associated with m-AAA protease deficiency.
- Measuring protein oxidation provides a valuable method for phenotyping models of m-AAA protease dysfunction.
