ABSTRACT
AIM: To study the metalloproteome of DU-145 prostate carcinoma cells in comparison to prostate from control and selenium-deficient rats. MATERIALS AND METHODS: Total proteome of the samples was compared by two-dimensional electrophoresis (2-DE) and metalloproteome was analysed by size-exclusion chromatography coupled to inductively coupled plasma mass spectrometry (SEC-ICP/MS). Immunotests were used to quantify protein expression of superoxide dismutase, thioredoxin reductase and metallothionein. RESULTS: There was no general relation between protein expression and metal load. SEC-ICP/MS spectra for many metals varied significantly in terms of peak number and intensity between individuals of the same sample group. However, nickel and zinc peaks were consistently suppressed in DU-145 cells under selenium deficiency. Concurrent redistribution of cobalt binding to a low molecular weight fraction (presumably cobalamin) was observed. CONCLUSION: Metal load of proteins in comparison to their expression might point to yet unknown mechanisms of oncogenesis and may lead to new biomarkers of cancer.
Subject(s)
Health , Metals/metabolism , Prostate/metabolism , Proteome/metabolism , Animals , Cell Line, Tumor , Chromatography, Gel , Electrophoresis, Gel, Two-Dimensional , Humans , Immunohistochemistry , Male , Mass Spectrometry , Metallothionein/metabolism , Proteomics , Rats , Rats, Wistar , Superoxide Dismutase/metabolism , Thioredoxin-Disulfide Reductase/metabolismABSTRACT
BACKGROUND: Selenium (Se) is an essential element which is involved in various biological processes in nearly all tissues of animals and human, e.g. protection against oxidative stress in the cardiovascular system, and may play a role in cancer protection. It is incorporated in the proteome in the form of the genetically encoded amino acid selenocysteine, which is the characteristic component of the selenoproteins. MATERIALS AND METHODS: We investigated the expression of the selenoenzyme GPx-2 which is predominantly present in the tissues of the gastrointestinal tract such as the small intestine and therefore named gastrointestinal glutathione peroxidase. Rats were fed with a Se-adequate or Se-deficient diet and GPx-2 was assessed by means of enzyme activity with respect to the Se concentration in tissues of the colon and small intestine. Se quantification was carried out by means of graphite furnace atom absorption spectrometry and 2D-gel electrophoresis was applied to investigate the expression of the proteins of the small intestine tissue samples. RESULTS: Twenty-eight differences could be distinguished in the protein spot distribution of the 2D-gels of the homogenates. The GPx-2 activity in the Se-deficient rat colon samples was 6.8 fold lower than in the Se-adequate rats in contrast to 1.2 fold lower levels between the corresponding samples in the small intestine. CONCLUSION: This finding might explain the different susceptibility of the colon and the small intestine to cancer and support the theory of the protective effect of selenium in the gastrointestinal tract.
