TY - JOUR
T1 - Inhibition of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase by thapsigargin analogs induces cell death via ER Ca2+ depletion and the unfolded protein response
AU - Sehgal, Pankaj
AU - Szalai, Paula
AU - Olesen, Claus
AU - Praetorius, Helle A
AU - Nissen, Poul
AU - Christensen, Søren Brøgger
AU - Engedal, Nikolai
AU - Møller, Jesper Vuust
N1 - Copyright © 2017, The American Society for Biochemistry and Molecular Biology.
PY - 2017/12/1
Y1 - 2017/12/1
N2 - Calcium (Ca
2) is a fundamental regulator of cell signaling and function. Thapsigargin (Tg) blocks the sarco/endoplasmic reticulum (ER) Ca
2-ATPase (SERCA), disrupts Ca
2 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 Ca
2 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 Ca
2 stores. This Ca
2 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 Ca
2 levels. Moreover, knockdown of two key store-operated Ca
2 entry (SOCE) components, Orai1 and STIM1, did not reduce Tg cytotoxicity, indicating that SOCE and Ca
2 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 Ca
2 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 Ca
2 drainage and sustained unfolded protein response activation are key for initiation of apoptosis at low concentrations of Tg and Tg analogs, whereas high cytosolic Ca
2 levels and SOCE are not required.
AB - Calcium (Ca
2) is a fundamental regulator of cell signaling and function. Thapsigargin (Tg) blocks the sarco/endoplasmic reticulum (ER) Ca
2-ATPase (SERCA), disrupts Ca
2 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 Ca
2 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 Ca
2 stores. This Ca
2 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 Ca
2 levels. Moreover, knockdown of two key store-operated Ca
2 entry (SOCE) components, Orai1 and STIM1, did not reduce Tg cytotoxicity, indicating that SOCE and Ca
2 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 Ca
2 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 Ca
2 drainage and sustained unfolded protein response activation are key for initiation of apoptosis at low concentrations of Tg and Tg analogs, whereas high cytosolic Ca
2 levels and SOCE are not required.
KW - Journal Article
UR - http://www.scopus.com/inward/record.url?scp=85036463135&partnerID=8YFLogxK
U2 - 10.1074/jbc.M117.796920
DO - 10.1074/jbc.M117.796920
M3 - Journal article
C2 - 28972171
SN - 0021-9258
VL - 292
SP - 19656
EP - 19673
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 48
ER -