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19561079
The thioxotriazole copper(II) complex A0 induces endoplasmic reticulum stress and paraptotic death in human cancer cells.

J Biol Chem, 2009/9/04;284(36):24306-19.

Tardito S[1], Isella C, Medico E, Marchiò L, Bevilacqua E, Hatzoglou M, Bussolati O, Franchi-Gazzola R

Affiliations

PMID: 19561079DOI: 10.1074/jbc.M109.026583

Abstract
The copper(II) complex A0 induces a type of non-apoptotic cell death also known as paraptosis. Paraptosis involves extensive endoplasmic reticulum vacuolization in the absence of caspase activation. A wide panel of human cancer cell lines was used to demonstrate differences in cytotoxicity by the paraptosis-inducing drug A0 and the metal-based pro-apoptotic drug cisplatin. Gene expression profiling of the human fibrosarcoma HT1080 cells showed that, while cisplatin induced p53 targets, A0 up-regulated genes involved in the unfolded protein response (UPR) and response to heavy metals. The cytotoxic effects of A0 were associated with inhibition of the ubiquitin-proteasome system and accumulation of ubiquitinylated proteins, in a manner dependent on protein synthesis. Cycloheximide inhibited the accumulation of ubiquitinylated proteins and hampered A0-induced cell death process. The occurrence of the UPR during A0-induced death process was shown by the increased abundance of spliced XBP1 mRNA, transient eIF2alpha phosphorylation, and a series of downstream events, including attenuation of global protein synthesis and increased expression of ATF4, CHOP, BIP, and GADD34. Mouse embryonic fibroblasts expressing a mutant eIF2alpha, which could not be phosphorylated, were more resistant to A0 than wild type cells, pointing to a pro-death role of eIF2alpha phosphorylation. A0 may thus represent the prototypical member of a new class of compounds that cause paraptotic cell death via mechanisms involving eIF2alpha phosphorylation and the UPR.
MeSH terms
Animals; Antineoplastic Agents; Apoptosis; Caco-2 Cells; Cisplatin; Copper; Drug Screening Assays, Antitumor; Endoplasmic Reticulum; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; HeLa Cells; Humans; Mice; Neoplasm Proteins; Neoplasms; Organometallic Compounds; Proteasome Endopeptidase Complex; Protein Folding; RNA, Messenger; Stress, Physiological; Ubiquitin; Ubiquitination
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