Figure 1.

Autophagy is induced despite Bcl-2 expression and contributes to both metabolism and apoptosis upon growth factor withdrawal. Bcl-2-expressing FL5.12 cells were deprived IL3 and imaged by electron microscopy. Autophagic vesicles were observed within hours of IL3 withdrawal (indicated by white arrows) showing that unlike in acute nutrient withdrawal, Bcl-2 does not effectively inhibit autophagy when cells are growth factor-deprived. Unexpectedly, autophagy both contributed to cell metabolism as a source of intracellular nutrients and sensitized cells to apoptosis, possibly to ensure only cells with high resistance to apoptosis can survive long-term using nutrients derived from autophagy.