Self-consumption: the interplay of autophagy and apoptosis

Autophagy and apoptosis control the turnover of organelles and proteins within cells, and of cells within organisms, respectively. It is now clear that these processes often occur sequentially, and that crosstalk between the signalling pathways regulating them generally enables autophagy to block the induction of apoptosis, whereas apoptosis-associated caspase activation shuts off autophagy. Autophagy and apoptosis control the turnover of organelles and proteins within cells, and of cells within organisms, respectively, and many stress pathways sequentially elicit autophagy, and apoptosis within the same cell. Generally autophagy blocks the induction of apoptosis, and apoptosis-associated caspase activation shuts off the autophagic process. However, in special cases, autophagy or autophagy-relevant proteins may help to induce apoptosis or necrosis, and autophagy has been shown to degrade the cytoplasm excessively, leading to 'autophagic cell death'. The dialogue between autophagy and cell death pathways influences the normal clearance of dying cells, as well as immune recognition of dead cell antigens. Therefore, the disruption of the relationship between autophagy and apoptosis has important pathophysiological consequences.