Bcl-2 complexed with Beclin-1 maintains full anti-apoptotic function

Oncogene. 2009 May 28;28(21):2128-41. doi: 10.1038/onc.2009.60. Epub 2009 Apr 6.


The binding of Bcl-2 to Beclin-1 reduces Beclin-1's capacity to induce autophagy. Here, we have tested whether the interaction is reciprocated by loss of Bcl-2's anti-apoptotic function. We targeted Bcl-2 to mitochondria or endoplasmic reticulum (ER) and induced apoptosis using several apoptotic stimuli that initiate ER and/or mitochondrial signaling pathways (UV radiation, TNF and cycloheximide, staurosporine, thapsigargin and tunicamycin). When Beclin-1 and Bcl-2 were expressed together in HeLa cells, Beclin-1 (but not Beclin-1 lacking the Bcl-2-binding domain) followed Bcl-2 to the appropriate organelle with complete or near-complete overlap (comprising 60 and 30% of cells, respectively). The interaction between Beclin-1 and Bcl-2 was verified by immunoprecipitation, and a membrane-proximate localization of Beclin-1 was shown by immunoelectron microscopy. Apoptosis was followed by measuring changes in nuclear morphology, caspase-3 activity, poly-ADP-ribose polymerase cleavage or punctation of mRFP-Bax on mitochondria. Binding of Beclin-1 to Bcl-2 did not modify apoptosis irrespective of Bcl-2 concentration, location or apoptotic stimulus. A similar result was obtained in Atg5-/- cells that are autophagy-deficient, arguing against compensation for the loss of protection by Bcl-2 by autophagy-mediated survival induced by Beclin-1. Hence, although Beclin-1 contains a BH3-only motif typical of pro-apoptotic proteins, it is a negligible modulator of Bcl-2's anti-apoptotic function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism*
  • Apoptosis*
  • Beclin-1
  • Cells, Cultured
  • Gene Expression Regulation
  • Humans
  • Intracellular Space / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mice
  • Protein Binding
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*


  • Apoptosis Regulatory Proteins
  • BECN1 protein, human
  • Beclin-1
  • Membrane Proteins
  • Proto-Oncogene Proteins c-bcl-2