Activation of Nrf2 and accumulation of ubiquitinated A170 by arsenic in osteoblasts.
Sub-lethal levels of arsenic induce upregulation of stress proteins. We here report for the first time that inorganic arsenic activates the transcription factor Nrf2, which controls the expression of oxidative stress-induced proteins. Treatment of cultured MC3T3-E1 osteoblasts with arsenite or arsenate induced increase of Nrf2, followed by transcriptional activation of target genes encoding HO-1, Prx I, and A170. We found that arsenate (200-800 micro M) only slightly increased the normal 60kDa A170 protein but markedly increased higher molecular mass forms of A170 (HMM-A170) that appeared as smeared bands. Arsenate also markedly increased ubiquitin-conjugated cellular proteins, suggesting that HMM-A170 was one of the poly-ubiquitinated proteins. Arsenite (50-100 micro M) also induced accumulation of HMM-A170 and ubiquitin-conjugated proteins. These results provide the first direct evidence that toxic arsenics impair the normal function of A170. Our findings provide a potential diagnostic tool for monitoring biotoxicity in cells and tissues in response to arsenic compounds.
Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
Junko
J
Aono
Toru
T
Yanagawa
Ken
K
Itoh
Baojie
B
Li
Hiroshi
H
Yoshida
Yoshito
Y
Kumagai
Masayuki
M
Yamamoto
Tetsuro
T
Ishii
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001149:Arsenates / Q000494:pharmacology; D001152:Arsenicals / Q000494:pharmacology*; D018053:Arsenites / Q000494:pharmacology; D002460:Cell Line; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D046911:Macromolecular Substances; D051379:Mice; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D051267:NF-E2-Related Factor 2; D010006:Osteoblasts / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D000071456:Sequestosome-1 Protein; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation; D014452:Ubiquitins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D001149:Arsenates; D001152:Arsenicals; D018053:Arsenites; D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D007976:Leupeptins; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D000071456:Sequestosome-1 Protein; C101343:Sqstm1 protein, mouse; D015534:Trans-Activators; D014452:Ubiquitins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C015001:arsenite; C025657:arsenic acid; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde