Molecular consequences of genetic variations in the glutathione peroxidase 1 selenoenzyme.
Accumulating data have implicated the selenium-containing cytosolic glutathione peroxidase, GPx-1, as a determinant of cancer risk and a mediator of the chemopreventive properties of selenium. Genetic variants of GPx-1 have been shown to be associated with cancer risk for several types of malignancies. To investigate the relationship between GPx-1 enzyme activity and genotype, we measured GPx-1 enzyme activity and protein levels in human lymphocytes as a function of the presence of two common variations: a leucine/proline polymorphism at codon 198 and a variable number of alanine-repeat codons. Differences in GPx activity among these cell lines, as well as in the response to the low-level supplementation of the media with selenium, indicated that factors other than just genotype are significant in determining activity. To restrict the study to genotypic effects, human MCF-7 cells were engineered to exclusively express allelic variants representing a combination of either a codon 198 leucine or proline and either 5 or 7 alanine-repeat codons following transfection of GPx-1 expression constructs. Transfectants were selected and analyzed for GPx-1 enzyme activity and protein levels. GPx-1 with 5 alanines and a leucine at codon 198 showed a significantly higher induction when cells were incubated with selenium and showed a distinct pattern of thermal denaturation as compared with GPx-1 encoded by the other examined alleles. The collective data obtained using both lymphocytes and MCF-7 indicate that both intrinsic and extrinsic factors cooperate to ultimately determine the levels of this enzyme available to protect cells against DNA damage and mutagenesis.
Zhuo
Pin
P
Department of Pathology, University of Illinois at Chicago, Illinois 60612, USA.
Goldberg
Marci
M
Herman
Lauren
L
Lee
Bao-Shiang
BS
Wang
Hengbing
H
Brown
Rhonda L
RL
Foster
Charles B
CB
Peters
Ulrike
U
Diamond
Alan M
AM
D000409:Alanine / Q000737:chemistry / Q000235:genetics; D000483:Alleles; D000975:Antioxidants / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics*; D003062:Codon / Q000235:genetics; D004249:DNA Damage; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D005838:Genotype; D005979:Glutathione Peroxidase / Q000235:genetics*; D006801:Humans; D007930:Leucine / Q000737:chemistry / Q000235:genetics; D008214:Lymphocytes / Q000187:drug effects / Q000201:enzymology*; D016296:Mutagenesis; D011110:Polymorphism, Genetic / Q000235:genetics*; D011392:Proline / Q000737:chemistry / Q000235:genetics; D012643:Selenium / Q000494:pharmacology*; D000094765:Glutathione Peroxidase GPX1
D000975:Antioxidants; D003062:Codon; D011392:Proline; D005979:Glutathione Peroxidase; D007930:Leucine; D012643:Selenium; D000409:Alanine; D000094765:Glutathione Peroxidase GPX1; C000722067:GPX1 protein, human