In Vivo Detection of Oxidized Proteins: A Practical Approach to Tissue-Derived Mitochondria - Protein Misfolding and Cellular Stress in Disease and Aging - page 246

Chapter 17
In Vivo Detection of Oxidized Proteins: A Practical
Approach to Tissue-Derived Mitochondria
Francesca Maltecca and Giorgio Casari
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 produc-
tion 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 mam-
mals. 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 accu-
rately 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.
Key words : Reactive oxygen species, Carbonylated proteins, Mitochondrial insults, Mitochondrial
AAA-protease, Neurological disease, Protein quality control
1. Introduction
Mitochondria are important physiologic generators of ROS for
cell signaling, but they can also be important contributors to oxi-
dative damage. They contain multiple electron carriers capable of
producing ROS, as well as an extensive network of antioxidant
defence. Mitochondrial insults, including oxidative damage itself,
can cause an imbalance between ROS production and removal,