Fig. 5.
Crosstalk between autophagy and apoptosis in mammalian cells. (A) In a cell, the same stress induces both autophagy and apoptosis as independent processes (top). A stress can also induce autophagy, which then inhibits apoptosis (middle) or, alternatively, a stress induces autophagy, which can be the trigger of apoptosis (bottom). (B) Both autophagy and apoptosis are negatively regulated by Bcl-2, Bcl-xL and Flip. (C) Autophagy proteins Atg5, beclin 1 and Atg4D function in autophagy in their unmodified form, but also have a role in apoptosis after cleavage by either calpains, which target Atg5 and give rise to 24 K Atg5, or caspase 3, which cleaves beclin 1, resulting in a C-terminal fragment of beclin 1 (Beclin 1-C), and Atg4D, truncating it at the canonical caspase cleavage sequence (DEVD63K) to ΔN63 Atg4D.