The ability of eukaryotic cells to engulf and degrade both intracellular and extracellular material is vital to the development and maintenance of healthy cells and organisms. These engulfment pathways underpin fundamental processes such as the generation of nutrients, clearance of damaged proteins and organelles, elimination of pathogens, antigen presentation, and the regulation of the immune response.
Conversely, dysregulation of these engulfment and degradative pathways are associated with a number of pathologies, including those associated with the ageing process, and diseases including cancer.
Autophagy is an important intracellular degradation pathway where parts of a cell are engulfed and sequestered in double-membrane compartments called autophagosomes, which then fuse to lysosomes where the contents are degraded and recycled.
Phagocytosis and macropinocytosis are examples of macro-scale endocytic processes where extracellular material is internalised into specialised single-membrane compartments (phagosomes, macropinosomes) that mature and fuse with lysosomes upon which their contents are degraded.