Figure 5. Mechanisms of mitochondrial quality improvement, from macro to micro.

At the top is PINK1/Parkin-mediated mitophagy of an intact organelle, as with the depolarized daughter of an asymmetric fission event (see Figure 3). To the left is bit-by-bit autophagy of localized mitochondrial damage, which is excised and engulfed by an autophagosome via Parkin activity. At the bottom is PINK1/Parkin-mediated formation of mitochondria-derived vesicle, incorporating damaged components into a vesicle that transports them to lysosomes. On the right is shown PINK1-Parkin independent proteasomal removal of outer mitochondrial membrane proteins, and protease-dependent degradation of internal mitochondrial proteins, the most selective of the quality improvement processes.