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Media type:
E-Article
Title:
Activation of the glutathione peroxidase 2 (GPx2) promoter by β-catenin
Contributor:
Kipp, Anna;
Banning, Antje;
Brigelius-Flohé, Regina
Published:
Walter de Gruyter GmbH, 2007
Published in:
bchm, 388 (2007) 10, Seite 1027-1033
Language:
English
DOI:
10.1515/bc.2007.137
ISSN:
1437-4315;
1431-6730
Origination:
Footnote:
Description:
Abstract GPx2, formerly named gastrointestinal glutathione peroxidase, is highly expressed in the proliferative area of the intestinal crypt-to-villus axis and in Paneth cells. Additionally, GPx2 is transiently up-regulated during development of gastrointestinal adenocarcinomas. Because both normal proliferation and differentiation of intestinal epithelial cells as well as carcinogenesis are regulated by the Wnt pathway, it was tested whether GPx2 may be a target of the β-catenin/TCF complex which transfers Wnt signals. The GPx2 promoter contains five putative β-catenin/TCF binding sites. Accordingly, the promoter was active in two cell lines with a constitutively active Wnt pathway, HepG2 and SW480, but not in BHK-21 cells in which the pathway is silent. Overexpression of β-catenin/TCF activated the GPx2 promoter in all three cell lines. Overexpression of wild-type adenomatous polyposis coli (APC) in SW480 cells which harbor a mutated APC gene decreased basal GPx2 promoter activity. Truncation of the promoter identified one β-catenin/TCF binding site that was sufficient for activation. Mutation of this site reduced the response to β-catenin/TCF by more than 50%. These findings suggest a function of GPx2 in the maintenance of normal renewal of the intestinal epithelium. Whether up-regulation of GPx2 during carcinogenesis supports tumor growth or can rather be considered as a counteracting effect remains to be investigated.