Evidence that BCL-2 represses apoptosis by regulating endoplasmic reticulum-associated Ca2+ fluxes

M. Lam, G. Dubyak, L. Chen, G. Nunez, R. L. Miesfeld, C. W. Distelhorst

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BCL-2 is a 26-kDa integral membrane protein that represses apoptosis by an unknown mechanism. Recent findings indicate that Ca2+ release from the endoplasmic reticulum (ER) mediates apoptosis in mouse lymphoma cells. In view of growing evidence that BCL-2 localizes to the ER, as well as mitochondria and the perinuclear membrane, we investigated the possibility that BCL-2 represses apoptosis by regulating Ca2+ fluxes through the ER membrane. A cDNA encoding BCL-2 was introduced into WEH17.2 cells and two subclones, W.Hb12 and W.Hb13, which express high and low levels of BCL-2 mRNA and protein, respectively, were isolated. WEH17.2 cells underwent apoptosis in response to treatment with the glucocorticoid hormone dexamethasone, whereas W.Hb12 and W.Hb13 cells were protected from apoptosis, revealing a direct relationship between the level of BCL-2 expression and the degree of protection. Significantly, BCL-2 also blocked induction of apoptosis by thapsigargin (TG), a highly specific inhibitor of the ER-associated Ca2+ pump. TG completely inhibited ER Ca2+ pumping in both WEH17.2 and W.Hb12 cells, but the release of Ca2+ into the cytosol after inhibition of ER Ca2+ pumping was significantly less in W.Hb12 cells than in WEH17.2 cells, indicating that BCL-2 reduces Ca2+ efflux through the ER membrane. By reducing ER Ca2+ efflux, BCL-2 interfered with a signal for 'capacitative' entry of extracellular Ca2+, preventing a sustained increase of cytosolic Ca2+ in TG-treated cells. These findings suggest that BCL-2 either directly or indirectly regulates the flux of Ca2+ across the ER membrane, thereby abrogating Ca2+ signaling of apoptosis.

Original languageEnglish (US)
Pages (from-to)6569-6573
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number14
StatePublished - 1994


  • calcium homeostasis
  • glucocorticosteroid
  • mouse lymphoma cell
  • programmed cell death
  • thapsigargin

ASJC Scopus subject areas

  • General


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