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The Ca 2+ concentration of the endoplasmic reticulum is a key determinant of ceramide‐induced apoptosis: significance for the molecular mechanism of Bcl‐2 action
Author(s) -
Pinton Paolo,
Ferrari Davide,
Rapizzi Elena,
Virgilio Francesco Di,
Pozzan Tullio,
Rizzuto Rosario
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.11.2690
Subject(s) - endoplasmic reticulum , ceramide , apoptosis , microbiology and biotechnology , cytosol , mitochondrion , hela , sphingolipid , biology , organelle , chemistry , biochemistry , cell , enzyme
The mechanism of action of the anti‐apoptotic oncogene Bcl‐2 is still largely obscure. We have recently shown that the overexpression of Bcl‐2 in HeLa cells reduces the Ca 2+ concentration in the endoplasmic reticulum ([Ca 2+ ] er ) by increasing the passive Ca 2+ leak from the organelle. To investigate whether this Ca 2+ depletion is part of the mechanism of action of Bcl‐2, we mimicked the Bcl‐2 effect on [Ca 2+ ] er by different pharmacological and molecular approaches. All conditions that lowered [Ca 2+ ] er protected HeLa cells from ceramide, a Bcl‐2‐sensitive apoptotic stimulus, while treatments that increased [Ca 2+ ] er had the opposite effect. Surprisingly, ceramide itself caused the release of Ca 2+ from the endoplasmic reticulum and thus [Ca 2+ ] increased both in the cytosol and in the mitochondrial matrix, paralleled by marked alterations in mitochondria morphology. The reduction of [Ca 2+ ] er levels, as well as the buffering of cytoplasmic [Ca 2+ ] changes, prevented mitochondrial damage and protected cells from apoptosis. It is therefore concluded that the Bcl‐2‐dependent reduction of [Ca 2+ ] er is an important component of the anti‐apoptotic program controlled by this oncogene.