Phosphorylation of BCL-2 regulates ER Ca2+ homeostasis and apoptosis.
Phosphorylation of BCL-2 within an unstructured loop inhibits its antiapoptotic effect. We found that phosphorylated BCL-2 predominantly localized to the endoplasmic reticulum (ER) and tested whether phosphorylation would control its activity at this organelle, where Ca(2+) dynamics serve as a critical control point for apoptosis. Phosphorylation greatly inhibits the ability of BCL-2 to lower [Ca(2+)](er) and protect against Ca(2+)-dependent death stimuli. Cells expressing nonphosphorylatable BCL-2(AAA) exhibited increased leak of Ca(2+) from the ER and further diminished steady-state [Ca(2+)](er) stores when compared to cells expressing BCL-2(wt). Consequently, when BCL-2 is phosphorylated, Ca(2+) discharge from the ER is increased, with a secondary increase in mitochondrial Ca(2+) uptake. We also demonstrate that phosphorylation of BCL-2 inhibits its binding to proapoptotic family members. This inhibitory mechanism manifested at the ER, where phosphorylated BCL-2 was unable to bind proapoptotic members. [Ca(2+)](er) proved coordinate with the capacity of BCL-2 to bind proapoptotic BH3-only members, further integrating the apoptotic pathway and Ca(2+) modulation. Unexpectedly, the regulation of ER Ca(2+) dynamics is a principal avenue whereby BCL-2 phosphorylation alters susceptibility to apoptosis.
Bassik
Michael C
MC
Department of Pathology and Medicine, Howard Hughes Medical Institute, Dana Farber Cancer Institute, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Scorrano
Luca
L
Oakes
Scott A
SA
Pozzan
Tullio
T
Korsmeyer
Stanley J
SJ
D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*
D019253:Proto-Oncogene Proteins c-bcl-2; D002118:Calcium