Abstract
N-acetyl cysteine (NAC) and penicillamine (PEN) have been shown to induce apoptosis in multiple types of human cancer cells; however, the molecular mechanism underlying this activity is unclear. This study was designed to identify the genes responsible for apoptosis induction by NAC and PEN. We found that glucose-regulated protein 78 (GRP78) was upregulated in HeLa cells following treatment with NAC or PEN. GRP78 is a central regulator of endoplasmic reticulum (ER) stress and has been used as a marker of ER stress. Additionally, both the activating transcription factor 6 (ATF6) protein and X box-binding protein 1 (XBP1) mRNA were processed, which facilitates the expression of C/EBP homologous protein (CHOP), a key-signaling component of ER stress-induced apoptosis. Furthermore, the PERK-ATF4 pathway, which also induces the expression of CHOP, was activated in NAC-treated cells. The role of the ER stress pathway was further confirmed through the small interfering RNA (siRNA)-mediated knockdown of CHOP, which attenuated NAC and PEN-induced apoptosis. These results demonstrate that NAC- and PEN-induced apoptosis in HeLa cells is mediated by the ER stress pathway.
2009 Wiley-Liss, Inc.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Acetylcysteine / pharmacology*
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Activating Transcription Factor 4 / genetics
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Activating Transcription Factor 4 / metabolism
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Activating Transcription Factor 6 / genetics
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Activating Transcription Factor 6 / metabolism
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Apoptosis / drug effects*
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Blotting, Western
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Endoplasmic Reticulum / metabolism*
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Endoplasmic Reticulum Chaperone BiP
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Flow Cytometry
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HeLa Cells
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Heat-Shock Proteins / genetics
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Heat-Shock Proteins / metabolism
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Humans
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Penicillamine / pharmacology*
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RNA Interference
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Regulatory Factor X Transcription Factors
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Reverse Transcriptase Polymerase Chain Reaction
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Signal Transduction / drug effects*
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Transcription Factor CHOP / genetics
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Transcription Factor CHOP / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism
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X-Box Binding Protein 1
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eIF-2 Kinase / genetics
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eIF-2 Kinase / metabolism
Substances
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ATF4 protein, human
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ATF6 protein, human
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Activating Transcription Factor 6
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DDIT3 protein, human
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DNA-Binding Proteins
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Endoplasmic Reticulum Chaperone BiP
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HSPA5 protein, human
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Heat-Shock Proteins
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Regulatory Factor X Transcription Factors
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Transcription Factors
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X-Box Binding Protein 1
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XBP1 protein, human
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Activating Transcription Factor 4
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Transcription Factor CHOP
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PERK kinase
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eIF-2 Kinase
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Penicillamine
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Acetylcysteine