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Regulation of the extracellular antioxidant selenoprotein plasma glutathione peroxidase (GPx-3) in mammalian cells.

ABSTRACT: Plasma glutathione peroxidase (GPx-3) is a selenocysteine-containing extracellular antioxidant protein that catalyzes the reduction of hydrogen peroxide and lipid hydroperoxides. Selenoprotein expression involves the alternate recognition of a UGA codon as a selenocysteine codon and requires signals in the 3'-untranslated region (UTR), including a selenocysteine insertion sequence (SECIS), as well as specific translational cofactors. To ascertain regulatory determinants of GPx-3 expression and function, we generated recombinant GPx-3 (rGPX-3) constructs with various 3'-UTR, as well as a Sec73Cys mutant. In transfected Cos7 cells, the Sec73Cys mutant was expressed at higher levels than the wild type rGPx-3, although the wild type rGPx-3 had higher specific activity, similar to plasma purified GPx-3. A 3'-UTR with only the SECIS was insufficient for wild type rGPx-3 protein expression. Selenocompound supplementation and co-transfection with SECIS binding protein 2 increased wild type rGPx-3 expression. These results demonstrate the importance of translational mechanisms in GPx-3 expression.

SUBMITTER: Ottaviano FG

PROVIDER: S-EPMC2693281 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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Regulation of the extracellular antioxidant selenoprotein plasma glutathione peroxidase (GPx-3) in mammalian cells.

Ottaviano Filomena G FG Tang Shiow-Shih SS Handy Diane E DE Loscalzo Joseph J

Molecular and cellular biochemistry 20090215 1-2

Plasma glutathione peroxidase (GPx-3) is a selenocysteine-containing extracellular antioxidant protein that catalyzes the reduction of hydrogen peroxide and lipid hydroperoxides. Selenoprotein expression involves the alternate recognition of a UGA codon as a selenocysteine codon and requires signals in the 3'-untranslated region (UTR), including a selenocysteine insertion sequence (SECIS), as well as specific translational cofactors. To ascertain regulatory determinants of GPx-3 expression and f ...[more]

PMID: 19219623

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Project description:A growing number of studies reveal that oxidative stress is associated with viral infections or cancer development. However, there are few reports assessing the relationships between oxidative stress, viral infection, and carcinogenesis. The present study analyzed the level of total antioxidant status (TAS) as well as the activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) in patients with oropharyngeal cancer both Epstein-Barr virus (EBV)-positive and EBV-negative in comparison with the control group. The correlations between these parameters and EBV type (wild-type LMP1 (wt-LMP1) or LMP1 with deletion (del-LMP1)), level of antibodies against EBV, the degree of tumor differentiation, and TNM classification were also investigated. Fresh frozen tumor tissue samples collected from 66 patients with oropharyngeal squamous cell carcinoma were tested using nested PCR assay for EBV DNA detection. Spectrophotometric methods were used to measure TAS values as well as SOD and GPx activities in homogenates of tissue, using diagnostic kits produced by Randox Laboratories. Sera from all individuals were investigated using ELISA method to detect the presence of Epstein-Barr virus capsid antigen (EBVCA) IgM and IgG, Epstein-Barr virus nuclear antigen (EBNA) IgG, and early antigen (EA) IgG antibodies. The level of TAS and activities of antioxidant enzymes (GPx and SOD) were significantly decreased in tissues with oropharyngeal cancer, particularly in EBV-positive cases. In 82.3% of patients, wt-LMP1 was detected. Significantly lower TAS, GPx, and SOD values were stated in patients infected with wild-type EBV. The presence of antibodies against early antigen (anti-EA) was detected in over 80% of patients, which suggests reactivation of EBV infection. The correlation between the degree of tumor differentiation and TN classification, especially in EBV-positive patients, was also observed. Determination of these parameters may be useful in evaluating tumor burden in patients with various stages of oropharyngeal cancer and could be an important prognostic factor. Future studies are needed to understand the role of EBV lytic reactivation induced by oxidative stress.

Dataset Information

Regulation of the extracellular antioxidant selenoprotein plasma glutathione peroxidase (GPx-3) in mammalian cells.

Publications

Regulation of the extracellular antioxidant selenoprotein plasma glutathione peroxidase (GPx-3) in mammalian cells.

Similar Datasets

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