FIG. 3.
A schematic illustration of the mitochondrion's life cycle and the roles of mitochondrial dynamics and autophagy in the segregation of dysfunctional mitochondria. The mitochondrion cyclically shifts between a postfusion state (networked) that lasts tens of seconds and a postfission state (solitary) that can last tens of minutes. Following a fission event, the mitochondrion can depolarize and restore an intact potential (thick arrow) or remain in a depolarized level. Sustained Δψm depolarization triggers cleavage of Opa1, accumulation of PINK1/Parkin, and reduction in mitofusin capacity. The mitochondrion may spend several hours in this preautophagic state before targeted by the autophagic machinery. Protein compositions during various steps along these pathways are indicated by a relevant close-up, which are also labeled with numbers, corresponding to their location in the scheme. (To see this illustration in color the reader is referred to the web version of this article at www.liebertonline.com/ars).