Inhibition of the ER Ca2+ pump forces multidrug-resistant cells deficient in Bak and Bax into necrosis

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Item Type:	Article
Title:	Inhibition of the ER Ca2+ pump forces multidrug-resistant cells deficient in Bak and Bax into necrosis
Creators Name:	Janssen, K., Horn, S., Niemann, M.T., Daniel, P.T., Schulze-Osthoff, K. and Fischer, U.
Abstract:	Tumor cells deficient in the proapoptotic proteins Bak and Bax are resistant to chemotherapeutic drugs. Here, we demonstrate that murine embryonic fibroblasts deficient for both Bak and Bax are, however, efficiently killed by thapsigargin, a specific inhibitor of ER Ca(2+) pumps that induces ER stress by depleting ER Ca(2+) stores. In the presence of Bak and Bax, thapsigargin eliminates cells by release of mitochondrial cytochrome c and subsequent caspase activation, which leads to the proteolytic inactivation of the molecular necrosis switch PARP-1 and results in apoptosis. By contrast, in the absence of Bak and Bax, a failure to activate caspases results in PARP-1-mediated ATP depletion. The subsequent necrosis is not prevented by autophagy as an alternative energy source. Moreover, in cells deficient for both Bak and Bax, thapsigargin induces permanent mitochondrial damage by Ca(2+) overload, permeability transition and membrane rupture. Thus, even though deficiency in Bak and Bax protects these cells against apoptosis, it does not compromise necrosis induced by SERCA inhibitors. Importantly, thapsigargin induces caspase-independent cell death also in colon and prostate carcinoma cells deficient in Bak and Bax expression. Therefore, targeted application of ER stressors such as thapsigargin might be a promising approach for the treatment of Bak- and Bax-deficient, drug-resistant tumors.
Keywords:	ER Stress, PARP, SERCA, Bak, Bax, Necrosis, Multidrug Resistance, UPR, Autophagy, Ire1, Animals, Mice
Source:	Journal of Cell Science
ISSN:	0021-9533
Publisher:	Company of Biologists
Volume:	122
Number:	Pt 24
Page Range:	4481-4491
Date:	15 December 2009
Official Publication:	https://doi.org/10.1242/jcs.055772
PubMed:	View item in PubMed

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