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Critical cysteine residues of Kelch-like ECH-associated protein 1 in arsenic sensing and suppression of nuclear factor erythroid 2-related factor 2.

Authors
He-X; Ma-Q
Source
J Pharmacol Exp Ther 2010 Jan; 332(1):66-75
NIOSHTIC No.
20036256
Abstract
Arsenic activates nuclear factor erythroid 2-related factor 2 (Nrf2) to induce phase II and antioxidative genes. Here we analyzed arsenic - Kelch-like ECH-associated protein 1 (Keap1) cysteine thiol interaction in Nrf2 activation. Arsenic-based Nrf2 activators, fluorescent biarsenical labeling reagent (FlAsH) and phenylarsine oxide (PAO), were used to probe binding of arsenic to Keap1. Strong fluorescence was observed on binding of FlAsH to purified Keap1. Pretreatment with arsenic, tertbutylhydroquinone (tBHQ), or 2,3-dimercaptopropanol significantly reduced the fluorescent signal. PAO affinity beads effectively pulled down Keap1 in vitro and from hepa1c1c7 cells. Arsenic, tBHQ, free PAO, or cadmium blocked Keap1 pulldown. Furthermore, arsenic and free PAO significantly reduced the free thiol contents of purified or endogenous Keap1. Thus, arsenic, FlAsH, and PAO, as well as tBHQ and cadmium, bind to Keap1 cysteine thiols in a similar fashion. All the domains of Keap1 bound PAO, and the linker region exhibited the highest binding activity. The function of arsenic-Keap1 interaction was evaluated in a reconstituted system that mimics endogenous Nrf2 regulation. Mutation of Cys273 or Cys288 in the linker region resulted in high level basal expression of Nrf2 protein. Mutation of Cys151 abolished Nrf2 activation by arsenic. Overexpression of C273A, C288A, or C151A altered the basal and arsenic-induced expression of Nrf2 target genes. The study shows an important role of Cys273 and Cys288 in the suppression of Nrf2 by Keap1 and a critical function of Cys151 in arsenic responsiveness. Our findings support a model in which arsenic binds to different sets of Keap1 cysteine residues to regulate divergent functions in Nrf2 signal transduction.
Keywords
Arsenic-compounds; Genes; Genotoxic-effects; Genotoxicity
Contact
Q. Ma, Receptor Biology Laboratory, TMBB/HELD/NIOSH/CDC, 1095 Willowdale Road, Morgantown, WV 26505
CODEN
JPETAB
CAS No.
7440-38-2
Publication Date
20100101
Document Type
Journal Article
Email Address
qam1@cdc.gov
Fiscal Year
2010
NTIS Accession No.
NTIS Price
Issue of Publication
1
ISSN
0022-3565
NIOSH Division
HELD
Priority Area
Manufacturing
Source Name
Journal of Pharmacology and Experimental Therapeutics
State
WV
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