Figure 3. A range of quality control mechanisms exist to deal with stress in the mitochondria.

The magnitude of these mechanisms ranges in accordance with the severity of the perceived stress. From lowest to highest magnitude of response, they include activation of the UPR^mt to initiate a transcriptional program to potentially relieve the stress; removal of part of the mitochondria into a mitochondrial-derived vesicle (MDV) in hopes of preserving the undamaged part; activation of mitophagy to remove the entire damaged mitochondria; and induction of cell death through apoptosis or necrosis to remove the entire damaged cell. As such, the magnitude of response can be titrated to the level of perceived stress.