Cellular Redox Compartments.

Although initially considered as harmful, reactive oxygen species (ROS) are now also recognized as important signaling molecules affecting various cellular processes. For example, they contribute to the response to hormones, growth factors, or hypoxia, and defense reactions against mechanical or chemical stress. Therefore, different ROS-generating, ROS-utilizing, and ROS-degrading systems in different intracellular compartments play an important role. On the one hand, this leads to a functional specialization wherein proteins, which participate in a specific ROS-regulated pathway in one compartment, may have another ROS-unrelated specific function in another compartment. On the other hand, this also adds a layer of protection by keeping unwanted side reactions to a minimum. Accordingly, the intracellular communication between different cellular compartments is an important mechanism to achieve proper responses and adaptations at the cellular level.