Bcl-2 inhibits hydrogen peroxide-induced ER Ca2+ pool depletion.
The mechanism by which Bcl-2 inhibits apoptosis is unknown. The Bcl-2 protein is localized to intracellular membranes, including the endoplasmic reticulum (ER). The ER is the major intracellular reservoir of Ca2+ in non-muscle cells, sequestering Ca2+ for use in intracellular signaling, and is a prime target of oxidative damage. Because of the recent suggestion that Bcl-2 acts in an antioxidant pathway, we wondered whether Bcl-2 might protect the ER Ca2+ pool in cells exposed to reactive oxygen species. To test this hypothesis, we assessed the effect of hydrogen peroxide (H2O2) treatment on the ER Ca2+ pool in WEH17.2 cells, which do not express Bcl-2, and two stable transfectants, W.Hb13 and W.Hb12. The Bcl-2 level by Western blotting is 4-fold higher in W.Hb12 cells compared to W.Hb13 cells. The ER Ca2+ pool in H2O2-treated and untreated cells was measured according to the amount of Ca2+ mobilized from the ER lumen into the cytoplasm by thapsigargin (TG), a selective inhibitor of the ER (Ca2+)-ATPase. H2O2 treatment produced a significant reduction in the TG-mobilizable Ca2+ pool in WEH17.2 and W.Hb13 cells, but not in W.Hb12 cells, indicating that overexpression of Bcl-2 preserves the integrity of the ER Ca2+ pool in cells exposed to reactive oxygen species.
Distelhorst
C W
CW
Department of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
Lam
M
M
McCormick
T S
TS
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D008223:Lymphoma / Q000235:genetics / Q000378:metabolism; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000975:Antioxidants; D004791:Enzyme Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D013729:Terpenes; D019284:Thapsigargin; D004247:DNA; D006861:Hydrogen Peroxide; D000252:Calcium-Transporting ATPases; D002118:Calcium