Atg6/Beclin 1 is an evolutionarily conserved protein family that has been shown to function in vacuolar protein sorting (VPS) in yeast; in autophagy in yeast, Drosophila, Dictyostelium, C.elegans, ...

Bcl-2 was the first identified cellular protein that functions as an oncogene by blocking apoptotic cell death. Beclin 1, the first identified mammalian autophagy gene product, is a haploinsufficient tumor suppressor that was originally isolated as a Bcl-2-interacting protein. We recently showed that Bcl-2 negatively regulates Beclin 1-dependent autophagy and Beclin 1-dependent autophagic cell death. These findings raise the possibility that Bcl-2 family members may function as oncogenes not only by blocking apoptosis but also by blocking autophagy. (Cancer Res 2006; 66(6): 2885-8)

Macroautophagy is a vacuolar lysosomal catabolic pathway that is stimulated during periods of nutrient starvation to preserve cell integrity. Ceramide is a bioactive sphingolipid associated with a large range of cell processes. Here we show that short-chain ceramides (C₂-ceramide and C₆-ceramide) and stimulation of the de novo ceramide synthesis by tamoxifen induce the dissociation of the complex formed between the autophagy protein Beclin 1 and the anti-apoptotic protein Bcl-2. This dissociation is required for macroautophagy to be induced either in response to ceramide or to starvation. Three potential phosphorylation sites, Thr⁶⁹, Ser⁷⁰, and Ser⁸⁷, located in the non-structural N-terminal loop of Bcl-2, play major roles in the dissociation of Bcl-2 from Beclin 1. We further show that activation of c-Jun N-terminal protein kinase 1 by ceramide is required both to phosphorylate Bcl-2 and to stimulate macroautophagy. These findings reveal a new aspect of sphingolipid signaling in up-regulating a major cell process involved in cell adaptation to stress.