Mitochondrial Oxidative Stress Induces Rapid Intermembrane Space/Matrix Translocation of Apurinic/Apyrimidinic Endonuclease 1 Protein through TIM23 Complex.

Mitochondria are essential cellular organelles that import the majority of proteins to sustain their function in cellular metabolism and homeostasis. Due to their role in oxidative phosphorylation, mitochondria are constantly affected by oxidative stress. Stability of mitochondrial DNA (mtDNA) is essential for mitochondrial physiology and cellular well-being and for this reason mtDNA lesions have to be rapidly recognized and repaired. Base excision repair (BER) is the main pathway responsible for repairing non-helix distorting base lesions both into the nucleus and in mitochondria. Apurinic/Apyrimidinic Endonuclease 1 (APE1) is a key component of BER pathway and the only protein that can recognize and process an abasic (AP) site. Comprehensions of the mechanisms regulating APE1 intracellular trafficking are still fragmentary. In this study we focused our attention on the mitochondrial form of APE1 protein and how oxidative stress induces its translocation to maintain mtDNA integrity. Our data proved that: (i) the rise of mitochondrial ROS determines a very rapid translocation of APE1 from the intermembrane space (IMS) into the matrix; and (ii) TIM23/PAM machinery complex is responsible for the matrix translocation of APE1. Moreover, our data support the hypothesis that the IMS, where the majority of APE1 resides, could represent a sort of storage site for the protein.