Inhibition of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase by thapsigargin analogs induces cell death via ER Ca2+ depletion and the unfolded protein response

Pankaj Sehgal; Paula Szalai; Helle A Praetorius; Poul Nissen; Søren Brøgger Christensen; Nikolai Engedal; Jesper Vuust Møller

doi:10.1074/jbc.m117.796920

Inhibition of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase by thapsigargin analogs induces cell death via ER Ca2+ depletion and the unfolded protein response

Pankaj Sehgal, Paula Szalai, Helle A Praetorius, Poul Nissen, Søren Brøgger Christensen, Nikolai Engedal, Jesper Vuust Møller

54 Citations (Scopus)

Abstract

Calcium (Ca²) is a fundamental regulator of cell signaling and function. Thapsigargin (Tg) blocks the sarco/endoplasmic reticulum (ER) Ca²-ATPase (SERCA), disrupts Ca² homeostasis, and causes cell death. However, the exact mechanisms whereby SERCA inhibition induces cell death are incompletely understood. Here, we report that low (0.1 M) concentrations of Tg and Tg analogs with various long-chain substitutions at the O-8 position extensively inhibit SERCA1a-mediated Ca² transport. We also found that, in both prostate and breast cancer cells, exposure to Tg or Tg analogs for 1 day caused extensive drainage of the ER Ca² stores. This Ca² depletion was followed by markedly reduced cell proliferation rates and morphological changes that developed over 2– 4 days and culminated in cell death. Interestingly, these changes were not accompanied by bulk increases in cytosolic Ca² levels. Moreover, knockdown of two key store-operated Ca² entry (SOCE) components, Orai1 and STIM1, did not reduce Tg cytotoxicity, indicating that SOCE and Ca² entry are not critical for Tg-induced cell death. However, we observed a correlation between the abilities of Tg and Tg analogs to deplete ER Ca² stores and their detrimental effects on cell viability. Furthermore, caspase activation and cell death were associated with a sustained unfolded protein response. We conclude that ER Ca² drainage and sustained unfolded protein response activation are key for initiation of apoptosis at low concentrations of Tg and Tg analogs, whereas high cytosolic Ca² levels and SOCE are not required.

Original language	English
Journal	Journal of Biological Chemistry
Volume	292
Issue number	48
Pages (from-to)	19656-19673
ISSN	0021-9258
DOIs	https://doi.org/10.1074/jbc.m117.796920
Publication status	Published - 1 Dec 2017

Keywords

Faculty of Health and Medical Sciences

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1074/jbc.m117.796920

http://www.jbc.org/content/292/48/19656.full.pdfLicence: CC BY

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Sehgal, P., Szalai, P., Praetorius, H. A., Nissen, P., Christensen, S. B., Engedal, N., & Møller, J. V. (2017). Inhibition of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase by thapsigargin analogs induces cell death via ER Ca2+ depletion and the unfolded protein response. Journal of Biological Chemistry, 292(48), 19656-19673. https://doi.org/10.1074/jbc.m117.796920

Inhibition of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase by thapsigargin analogs induces cell death via ER Ca2+ depletion and the unfolded protein response. / Sehgal, Pankaj; Szalai, Paula; Praetorius, Helle A et al.

In: Journal of Biological Chemistry, Vol. 292, No. 48, 01.12.2017, p. 19656-19673.

Research output: Contribution to journal › Journal article › Research › peer-review

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title = "Inhibition of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase by thapsigargin analogs induces cell death via ER Ca2+ depletion and the unfolded protein response",

abstract = "Calcium (Ca2) is a fundamental regulator of cell signaling and function. Thapsigargin (Tg) blocks the sarco/endoplasmic reticulum (ER) Ca2-ATPase (SERCA), disrupts Ca2 homeostasis, and causes cell death. However, the exact mechanisms whereby SERCA inhibition induces cell death are incompletely understood. Here, we report that low (0.1 M) concentrations of Tg and Tg analogs with various long-chain substitutions at the O-8 position extensively inhibit SERCA1a-mediated Ca2 transport. We also found that, in both prostate and breast cancer cells, exposure to Tg or Tg analogs for 1 day caused extensive drainage of the ER Ca2 stores. This Ca2 depletion was followed by markedly reduced cell proliferation rates and morphological changes that developed over 2– 4 days and culminated in cell death. Interestingly, these changes were not accompanied by bulk increases in cytosolic Ca2 levels. Moreover, knockdown of two key store-operated Ca2 entry (SOCE) components, Orai1 and STIM1, did not reduce Tg cytotoxicity, indicating that SOCE and Ca2 entry are not critical for Tg-induced cell death. However, we observed a correlation between the abilities of Tg and Tg analogs to deplete ER Ca2 stores and their detrimental effects on cell viability. Furthermore, caspase activation and cell death were associated with a sustained unfolded protein response. We conclude that ER Ca2 drainage and sustained unfolded protein response activation are key for initiation of apoptosis at low concentrations of Tg and Tg analogs, whereas high cytosolic Ca2 levels and SOCE are not required.",

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AU - Szalai, Paula

AU - Praetorius, Helle A

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AU - Christensen, Søren Brøgger

AU - Engedal, Nikolai

AU - Møller, Jesper Vuust

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AB - Calcium (Ca2) is a fundamental regulator of cell signaling and function. Thapsigargin (Tg) blocks the sarco/endoplasmic reticulum (ER) Ca2-ATPase (SERCA), disrupts Ca2 homeostasis, and causes cell death. However, the exact mechanisms whereby SERCA inhibition induces cell death are incompletely understood. Here, we report that low (0.1 M) concentrations of Tg and Tg analogs with various long-chain substitutions at the O-8 position extensively inhibit SERCA1a-mediated Ca2 transport. We also found that, in both prostate and breast cancer cells, exposure to Tg or Tg analogs for 1 day caused extensive drainage of the ER Ca2 stores. This Ca2 depletion was followed by markedly reduced cell proliferation rates and morphological changes that developed over 2– 4 days and culminated in cell death. Interestingly, these changes were not accompanied by bulk increases in cytosolic Ca2 levels. Moreover, knockdown of two key store-operated Ca2 entry (SOCE) components, Orai1 and STIM1, did not reduce Tg cytotoxicity, indicating that SOCE and Ca2 entry are not critical for Tg-induced cell death. However, we observed a correlation between the abilities of Tg and Tg analogs to deplete ER Ca2 stores and their detrimental effects on cell viability. Furthermore, caspase activation and cell death were associated with a sustained unfolded protein response. We conclude that ER Ca2 drainage and sustained unfolded protein response activation are key for initiation of apoptosis at low concentrations of Tg and Tg analogs, whereas high cytosolic Ca2 levels and SOCE are not required.

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KW - Apoptosis

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Inhibition of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase by thapsigargin analogs induces cell death via ER Ca2+ depletion and the unfolded protein response

Abstract

Keywords

UN SDGs

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