Mitochondrial proteolysis: Its emerging roles in stress responses

Background: Mitochondria are multifunctional organelles that not only serve as cellular energy stores but are also actively involved in several cellular stress responses, including apoptosis. In addition, mitochondria themselves are also continuously challenged by stresses such as reactive oxygen species (ROS), an inevitable by-product of oxidative phosphorylation. To exert various functions against these stresses, mitochondria must be equipped with appropriate stress responses that monitor and maintain their quality. Scope of review: Interestingly, increasing evidence indicates that mitochondrial proteolysis has important roles in mitochondrial and cellular stress responses. In this review, we summarize current advances in mitochondria(proteolysis-mediated stress responses. Major conclusions: Mitochondrial proteases do not only function as surveillance systems of protein quality control by degrading unfolded proteins but also regulate mitochondrial stress responses by processing specific mitochondrial proteins. General significance: Studies on the regulation of mitochondrial proteolysis-mediated stress responses will provide the novel mechanistic insights into the stress response research fields. (C) 2014 Elsevier B.V. All rights reserved.