Bcl-2 complexed with Beclin-1 maintains full anti-apoptotic function
- 6 April 2009
- journal article
- Published by Springer Science and Business Media LLC in Oncogene
- Vol. 28 (21), 2128-2141
- https://doi.org/10.1038/onc.2009.60
Abstract
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.This publication has 50 references indexed in Scilit:
- Silencing of Bcl-2 expression by small interfering RNA induces autophagic cell death in MCF-7 breast cancer cellsAutophagy, 2008
- BAC-mediated transgenic expression of fluorescent autophagic protein Beclin 1 reveals a role for Beclin 1 in lymphocyte developmentCell Death & Differentiation, 2008
- Molecular Links Between Autophagy and ApoptosisMethods in molecular biology (Clifton, N.J.), 2008
- Beclin 1-Independent Pathway of Damage-Induced Mitophagy and Autophagic Stress: Implications for Neurodegeneration and Cell DeathAutophagy, 2007
- Physiological functions of Atg6/Beclin 1: a unique autophagy-related proteinCell Research, 2007
- The Bcl-2 apoptotic switch in cancer development and therapyOncogene, 2007
- Mitochondria primed by death signals determine cellular addiction to antiapoptotic BCL-2 family membersCancer Cell, 2006
- Inhibition of Macroautophagy Triggers ApoptosisMolecular and Cellular Biology, 2005
- There is more to life and death than mitochondria: Bcl-2 proteins at the endoplasmic reticulumBiochimica et Biophysica Acta (BBA) - Molecular Cell Research, 2004
- Cloning and Genomic Organization of Beclin 1, a Candidate Tumor Suppressor Gene on Chromosome 17q21Genomics, 1999