PP2A regulates BCL-2 phosphorylation and proteasome-mediated degradation at the endoplasmic reticulum

J Biol Chem. 2006 Aug 11;281(32):23003-12. doi: 10.1074/jbc.M602648200. Epub 2006 May 22.


Anti-apoptotic activity of BCL-2 is mediated by phosphorylation at the endoplasmic reticulum (ER), but how this phosphorylation is regulated and the mechanism(s) by which it regulates apoptosis are unknown. We purified macromolecular complexes containing BCL-2 from ER membranes and found that BCL-2 co-purified with the main two subunits of the serine/threonine phosphatase, PP2A. The association of endogenous PP2A and BCL-2 at the ER was verified by co-immunoprecipitation and microcystin affinity purification. Knock down or pharmacological inhibition of PP2A caused degradation of phosphorylated BCL-2 and led to an overall reduction in BCL-2 levels. We found that this degradation was due to the action of the proteasome acting selectively at the ER. Conversely, overexpression of PP2A caused elevation in endogenous BCL-2. Most importantly, we found that PP2A knock down sensitized cells to several classes of death stimuli (including ER stress), but this effect was abolished in a genetic background featuring knock in of a non-phosphorylatable BCL-2 allele. These studies support the hypothesis that PP2A-mediated dephosphorylation of BCL-2 is required to protect BCL-2 from proteasome-dependent degradation, affecting resistance to ER stress.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apoptosis
  • Endoplasmic Reticulum / metabolism*
  • Gene Expression Regulation*
  • Humans
  • Jurkat Cells
  • Mice
  • Mice, Inbred C57BL
  • Molecular Sequence Data
  • Phosphoprotein Phosphatases / metabolism
  • Phosphoprotein Phosphatases / physiology*
  • Phosphorylation
  • Proteasome Endopeptidase Complex / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Sequence Homology, Amino Acid


  • Proto-Oncogene Proteins c-bcl-2
  • Phosphoprotein Phosphatases
  • Proteasome Endopeptidase Complex