Shuttling of PINK1 between Mitochondrial Microcompartments Resolved by Triple-Color Superresolution Microscopy

The cytosolic phosphatase and tensin homologue Pten-kinase PINK1 involved in mitochondrial quality control undergoes a proteolytic process inside mitochondria. It has been suggested that the protein is not fully imported into mitochondria during this maturation. Here, we have established live cell triple-color super-resolution microscopy by combining FPALM and tracking and localization microscopy (TALM) in order to unravel the spatiotemporal organization of the C-terminal kinase domain of PINK1 during this process. We find that the kinase domain is imported into active mitochondria and colocalizes with respiratory complex I at the inner mitochondrial membrane. When the processing step inside mitochondria is inhibited or mitochondria are de-energized, full length PINK1 distributes between the outer and the inner mitochondrial membranes, indicating a holdup of import. These findings give the molecular base for a dual role of PINK1-inside energized mitochondria and outside of de-energized mitochondria.