Transcription factor Nrf1 negatively regulates the cystine/glutamate transporter and lipid-metabolizing enzymes.

Molecular and cellular biology (2014-08-06)
Tadayuki Tsujita, Vivian Peirce, Liam Baird, Yuka Matsuyama, Misaki Takaku, Shawn V Walsh, Julian L Griffin, Akira Uruno, Masayuki Yamamoto, John D Hayes
RESUMEN

Liver-specific Nrf1 (NF-E2-p45-related factor 1) knockout mice develop nonalcoholic steatohepatitis. To identify postnatal mechanisms responsible for this phenotype, we generated an inducible liver-specific Nrf1 knockout mouse line using animals harboring an Nrf1(flox) allele and a rat CYP1A1-Cre transgene (Nrf1(flox/flox)::CYP1A1-Cre mice). Administration of 3-methylcholanthrene (3-MC) to these mice (Nrf1(flox/flox)::CYP1A1-Cre+3MC mice) resulted in loss of hepatic Nrf1 expression. The livers of mice lacking Nrf1 accumulated lipid, and the hepatic fatty acid (FA) composition in such animals differed significantly from that in the Nrf1(flox/flox)::CYP1A1-Cre control. This change was provoked by upregulation of several FA metabolism genes. Unexpectedly, we also found that the level of glutathione was increased dramatically in livers of Nrf1(flox/flox)::CYP1A1-Cre+3MC mice. While expression of glutathione biosynthetic enzymes was unchanged, xCT, a component of the cystine/glutamate antiporter system x(c)(-), was significantly upregulated in livers of Nrf1(flox/flox)::CYP1A1-Cre+3MC mice, suggesting that Nrf1 normally suppresses xCT. Thus, stress-inducible expression of xCT is a two-step process: under homeostatic conditions, Nrf1 effectively suppresses nonspecific transactivation of xCT, but when cells encounter severe oxidative/electrophilic stress, Nrf1 is displaced from an antioxidant response element (ARE) in the gene promoter while Nrf2 is recruited to the ARE. Thus, Nrf1 controls both the FA and the cystine/cysteine content of hepatocytes by participating in an elaborate regulatory network.

MATERIALES
Referencia del producto
Marca
Descripción del producto

Sigma-Aldrich
L-Glutathione reduced, ≥98.0%
Sigma-Aldrich
L-Glutathione reduced, suitable for cell culture, BioReagent, ≥98.0%, powder
Supelco
Glutathione, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
L-Cystine, ≥98% (TLC), crystalline
Sigma-Aldrich
L-Glutathione reduced, BioXtra, ≥98.0%
Sigma-Aldrich
L-Cystine, from non-animal source, meets EP testing specifications, suitable for cell culture, 98.5-101.0%
Sigma-Aldrich
L-Cystine, ≥99.7% (TLC)
SAFC
L-Cystine
Glutathione, European Pharmacopoeia (EP) Reference Standard
SAFC
L-Cystine
Supelco
L-Cystine, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
L-Cystine, certified reference material, TraceCERT®
Cystine, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
L-Cystine, produced by Wacker Chemie AG, Burghausen, Germany, ≥98.5%