Local Ca 2+ -ROS Cross Talk Between ER And Mitochondria

Mitochondria form junctions with the sarco/endoplasmic reticulum (SR/ER), which support many cell functions locally including calcium signaling, organellar dynamics and lipid biosynthesis. The SR/ER and mitochondrial membranes also host sources and targets of reactive oxygen species (ROS) but their local dynamics and relevance remained elusive because measurement and perturbation of ROS at the organellar interface has proven difficult. We will describe fluorescence based strategies to monitor the ROS fluctuations at the SR/ER-mitochondria interface and present evidence for spatially confined ROS fluctuations in association with calcium signal propagation from ER to the mitochondria and transient mitochondrial depolarizations referred as flickers. We will also offer some clues to the functional significance of the ER-mitochondrial nanodomains in regulating calcium signaling and mitochondrial activities.