Lin, Stephen S.Bassik, Michael C.Suh, HeikyungNishino, MariArroyo, Jason D.Hahn, William C.Korsmeyer, Stanley J.Roberts, Thomas M.2019-10-132006Lin, Stephen S., Michael C. Bassik, Heikyung Suh, Mari Nishino, Jason D. Arroyo, William C. Hahn, Stanley J. Korsmeyer, and Thomas M. Roberts. 2006. “PP2A Regulates BCL-2 Phosphorylation and Proteasome-Mediated Degradation at the Endoplasmic Reticulum.” Journal of Biological Chemistry 281 (32): 23003–12. doi:10.1074/jbc.M602648200.0021-92581083-351Xhttp://nrs.harvard.edu/urn-3:HUL.InstRepos:41542806Anti-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.en-USJournal Article2019-10-1310.1074/jbc.M602648200