Autophagy: Removing dysfunctional components and organelles

Two distinct pathways for autophagy have been described. Bulk autophagy, which is activated in states of starvation and selective autophagy, when damaged organelles or large defective structures have to be degraded. It is a highly regulated process to remove damaged cellular content or provide energy and building blocks. For both pathways an isolation membrane, the phagophore expands and engulfs cargo in a double membrane structure, called autophagosome. Then, autophagosomes fuse with lysosomes leading to the degradation of their content. In bulk autophagy, cytoplasmic content is enclosed in a non-specific manner. During selective autophagy, specific cargo, such as damaged mitochondria (mitophagy), pathogens (xenophagy) or protein aggregates (aggrephagy) are marked and sequestered into autophagosomes for their degradation.

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