title: Selective induction of the tumor marker glutathione S-transferase P1 by proteasome inhibitors.
abstract: Exposure of cells to a wide variety of chemoprotective compounds confers resistance to a broad set of carcinogens. For a subset of the chemoprotective compounds, protection is generated by an increase in the abundance of phase 2 detoxification enzymes such as glutathione S-transferases (GSTs). Transcription factor Nrf2, which is sequestered in the cytoplasm by Keap1 (Kelch-like ECH-associated protein-1) under unstimulated conditions, regulates the induction of phase 2 enzymes. In this study, to explore the role of the proteasome in the detoxification response, we tested the effect of proteasome inhibitors such as MG132, clasto-lactacystin beta-lactone, and lactacystin on the induction of GST isozymes and found that these inhibitors selectively induced the class Pi GST isozyme (GST P1). Down-regulation of the proteasome by antisense oligonucleotides or RNA interference indeed resulted in significant up-regulation of GST P1, suggesting that a decline in the proteasome activity could be directly or indirectly linked to the induction of GST P1. From the functional analysis of various deletion constructs of the upstream regulatory region of the GST P1 promoter, GST P1 enhancer I was identified as the response element for proteasome inhibition. Overexpression of the wild-type and dominant-negative forms of Nrf2 and Keap1 had little effect on the induction of GST P1 not only by the proteasome inhibitor, but also by phase 2-inducing isothiocyanate, suggesting that there may be a process of GST P1 induction distinct from other phase 2 gene induction mechanisms. Because GST P1 is highly and specifically induced during early hepatocarcinogenesis as well as in hepatocellular carcinoma cells, these data may provide a potential critical role for the proteasome in the induction of a cellular defense program associated with carcinogenesis.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Usami
authors.forename: Yuri
authors.initials: Y
authors.lastname: Kusano
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kumagai
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Osada
authors.forename: Ken
authors.initials: K
authors.lastname: Itoh
authors.forename: Akira
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism*; D015153:Blotting, Western; D003545:Cysteine / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D005799:Genes, Dominant; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D007783:Lactones / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D051267:NF-E2-Related Factor 2; D016376:Oligonucleotides, Antisense / Q000737:chemistry; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation
chemical_list: D014408:Biomarkers, Tumor; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; C486610:KEAP1 protein, rat; D000072019:Kelch-Like ECH-Associated Protein 1; D007783:Lactones; D007976:Leupeptins; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; C495637:Nfe2l2 protein, rat; D016376:Oligonucleotides, Antisense; D061988:Proteasome Inhibitors; D020033:Protein Isoforms; D011506:Proteins; D034741:RNA, Small Interfering; D015534:Trans-Activators; C067713:lactacystin; C098869:clasto-lactacystin beta-lactone; D008156:Luciferases; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase; C496557:Gstp1 protein, mouse; C496558:Gstp1 protein, rat; D046988:Proteasome Endopeptidase Complex; D003545:Cysteine; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000111:Acetylcysteine