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Release of Ca2+ from the endoplasmic reticulum and its subsequent influx into mitochondria trigger celastrol-induced paraptosis in cancer cells.

ABSTRACT: Celastrol, a triterpene extracted from the Chinese "Thunder of God Vine", is known to have anticancer activity, but its underlying mechanism is not completely understood. In this study, we show that celastrol kills several breast and colon cancer cell lines by induction of paraptosis, a cell death mode characterized by extensive vacuolization that arises via dilation of the endoplasmic reticulum (ER) and mitochondria. Celastrol treatment markedly increased mitochondrial Ca2+ levels and induced ER stress via proteasome inhibition in these cells. Both MCU (mitochondrial Ca2+ uniporter) knockdown and pretreatment with ruthenium red, an inhibitor of MCU, inhibited celastrol-induced mitochondrial Ca2+ uptake, dilation of mitochondria/ER, accumulation of poly-ubiquitinated proteins, and cell death in MDA-MB 435S cells. Inhibition of the IP3 receptor (IP3R) with 2-aminoethoxydiphenyl borate (2-APB) also effectively blocked celastrol-induced mitochondrial Ca2+ accumulation and subsequent paraptotic events. Collectively, our results show that the IP3R-mediated release of Ca2+ from the ER and its subsequent MCU-mediatedinflux into mitochondria critically contribute to celastrol-induced paraptosis in cancer cells.

SUBMITTER: Yoon MJ

PROVIDER: S-EPMC4196165 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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Release of Ca2+ from the endoplasmic reticulum and its subsequent influx into mitochondria trigger celastrol-induced paraptosis in cancer cells.

Yoon Mi Jin MJ Lee A Reum AR Jeong Soo Ah SA Kim You-Sun YS Kim Jin Yeop JY Kwon Yong-Jun YJ Choi Kyeong Sook KS

Oncotarget 20140801 16

Celastrol, a triterpene extracted from the Chinese "Thunder of God Vine", is known to have anticancer activity, but its underlying mechanism is not completely understood. In this study, we show that celastrol kills several breast and colon cancer cell lines by induction of paraptosis, a cell death mode characterized by extensive vacuolization that arises via dilation of the endoplasmic reticulum (ER) and mitochondria. Celastrol treatment markedly increased mitochondrial Ca2+ levels and induced E ...[more]

PMID: 25149175

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Project description:Phototransduction in Drosophila is mediated by phospholipase C (PLC) and Ca2+-permeable TRP channels, but the function of endoplasmic reticulum (ER) Ca2+ stores in this important model for Ca2+ signaling remains obscure. We therefore expressed a low affinity Ca2+ indicator (ER-GCaMP6-150) in the ER, and measured its fluorescence both in dissociated ommatidia and in vivo from intact flies of both sexes. Blue excitation light induced a rapid (tau ∼0.8 s), PLC-dependent decrease in fluorescence, representing depletion of ER Ca2+ stores, followed by a slower decay, typically reaching ∼50% of initial dark-adapted levels, with significant depletion occurring under natural levels of illumination. The ER stores refilled in the dark within 100-200 s. Both rapid and slow store depletion were largely unaffected in InsP3 receptor mutants, but were much reduced in trp mutants. Strikingly, rapid (but not slow) depletion of ER stores was blocked by removing external Na+ and in mutants of the Na+/Ca2+ exchanger, CalX, which we immuno-localized to ER membranes in addition to its established localization in the plasma membrane. Conversely, overexpression of calx greatly enhanced rapid depletion. These results indicate that rapid store depletion is mediated by Na+/Ca2+ exchange across the ER membrane induced by Na+ influx via the light-sensitive channels. Although too slow to be involved in channel activation, this Na+/Ca2+ exchange-dependent release explains the decades-old observation of a light-induced rise in cytosolic Ca2+ in photoreceptors exposed to Ca2+-free solutions.SIGNIFICANCE STATEMENT Phototransduction in Drosophila is mediated by phospholipase C, which activates TRP cation channels by an unknown mechanism. Despite much speculation, it is unknown whether endoplasmic reticulum (ER) Ca2+ stores play any role. We therefore engineered flies expressing a genetically encoded Ca2+ indicator in the photoreceptor ER. Although NCX Na+/Ca2+ exchangers are classically believed to operate only at the plasma membrane, we demonstrate a rapid light-induced depletion of ER Ca2+ stores mediated by Na+/Ca2+ exchange across the ER membrane. This NCX-dependent release was too slow to be involved in channel activation, but explains the decades-old observation of a light-induced rise in cytosolic Ca2+ in photoreceptors bathed in Ca2+-free solutions.

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Dataset Information

Release of Ca2+ from the endoplasmic reticulum and its subsequent influx into mitochondria trigger celastrol-induced paraptosis in cancer cells.

Publications

Release of Ca2+ from the endoplasmic reticulum and its subsequent influx into mitochondria trigger celastrol-induced paraptosis in cancer cells.

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