Cysteine-mediated redox signalling in the mitochondria.

The mitochondria are critical mediators of cellular redox homeostasis due to their role in the generation and dissipation of reactive oxygen/nitrogen species (ROS/RNS). Modulations in ROS/RNS levels in the mitochondria are often reflected through oxidation/nitrosation of highly redox-sensitive cysteine residues within this organelle. Oxidation/nitrosation of functional cysteines on mitochondrial proteins serves to modulate protein activity, localization, and complexation in response to cellular stress, thereby controlling critical processes such as oxidative phosphorylation, apoptosis, and redox signalling. In this review, we describe mitochondrial sources of ROS/RNS, cysteine modifications that are triggered by increased mitochondrial ROS/RNS, and examples of key mitochondrial proteins that are regulated through cysteine-mediated redox signalling. We highlight recent advancements in proteomic methods to study cysteine posttranslational modifications. These tools will further aid in illuminating the important role of cysteine in maintaining and transducing redox signals in the mitochondria.