Analysis of bovine selenoprotein P-like protein gene and availability of metal responsive element (MRE) located in its promoter

Transcriptome profiling reveals the immune response of goose T cells under selenium stimuli

The goose is an economically important poultry species and a principal natural host of avian viruses. This study aimed to determine the effects of selenium on the immune response of geese. Under selenium stimulation, gene expression profiling was investigated using transcriptome sequencing. The selenoproteins were promoted by selenium stimulation, while the heat shock proteins, interleukin and interferons were mainly down-regulated. After comparison, 2228 differentially expressed genes were primarily involved in immune and environmental response, and infectious disease and genetic information processing related pathways were identified. Specifically, the enzymes of the lysosomes which acted as a safeguard in preventing pathogens were mostly up-regulated and six randomly selected differentially expressed genes were validated by quantitative polymerase chain reaction. In addition, the most proportional increased transcription factor family basic helix-loop-helix (bHLH) located in the 5' flank of selenoprotein P-like protein for selenium metabolism was identified by response to the selenium stimulation in this study. These analyses show that selenium can promote immune function by activating selenoproteins, transcript factors and lysosome pathway related genes, while weakening cytokine content genes in geese.

Multiple variant mRNAs with different length tandem repeats of (CAYYCC)n produced from bovine selenoprotein P-like protein gene

In contrast to selenoprotein Ps (SeIPs) from other animal species, bovine selenoprotein P-like-protein (SeIPLP) was found to contain a tandem repeat of (CAYYCC)(11). During an investigation into whether SeIPLP was a bovine substitute for SeIP or uniquely bovine, its mRNA was found to consist of multiple variants with different length tandem repeat, namely p(0) with (CAYYCC)(11), p(-4) lacking (CAYYCC)(4), p(-8) lacking (CAYYCC)(8), and p(-9) lacking (CAYYCC)(9). Although they were encoded on a single gene locus, neither classicalGT-AG: nor minor classAT-AC: donator-acceptor sequences for alternative splicing were identified. A subsequent S1 protection assay using oligonucleotides, whose sequence may occur as variants, performed against bovine poly(A)(+)RNA identified a total of nine variants. Judging from the sequence of these variants and the branch point mapping, the consensus sequence for recognition of the donator was CACCCCCAC: and of the acceptor and the branch point A nucleotide,ACCCC: CAT orACCCC: CATCCCCAT. Furthermore, when the p(0) insert mRNA was expressed in COS-7 cells derived from an African green monkey kidney, cDNAs corresponding to p(-8) and p(-9) could be isolated. Therefore, the bovine SeIPLP mRNAs consisted of multiple variants probably due to a novel splicing mechanism which was not bovine-specific but common to other mammals.

Selenium and selenoproteins in the brain and brain diseases

Over the past three decades, selenium has been intensively investigated as an antioxidant trace element. It is widely distributed throughout the body, but is particularly well maintained in the brain, even upon prolonged dietary selenium deficiency. Changes in selenium concentration in blood and brain have been reported in Alzheimer's disease and brain tumors. The functions of selenium are believed to be carried out by selenoproteins, in which selenium is specifically incorporated as the amino acid, selenocysteine. Several selenoproteins are expressed in brain, but many questions remain about their roles in neuronal function. Glutathione peroxidase has been localized in glial cells, and its expression is increased surrounding the damaged area in Parkinson's disease and occlusive cerebrovascular disease, consistent with its protective role against oxidative damage. Selenoprotein P has been reported to possess antioxidant activities and the ability to promote neuronal cell survival. Recent studies in cell culture and gene knockout models support a function for selenoprotein P in delivery of selenium to the brain. mRNAs for other selenoproteins, including selenoprotein W, thioredoxin reductases, 15-kDa selenoprotein and type 2 iodothyronine deiodinase, are also detected in the brain. Future research directions will surely unravel the important functions of this class of proteins in the brain.

Selenoprotein P expression, purification, and immunochemical characterization

Most selenoproteins contain a single selenocysteine residue per polypeptide chain, encoded by an in-frame UGA codon. Selenoprotein P is unique in that its mRNA encodes 10-12 selenocysteine residues, depending on species. In addition to the high number of selenocysteines, the protein is cysteine- and histidine-rich. The function of selenoprotein P has remained elusive, in part due to the inability to express the recombinant protein. This has been attributed to presumed inefficient translation through the selenocysteine/stop codons. Herein, we report for the first time the expression of recombinant rat selenoprotein P in a transiently transfected human epithelial kidney cell line, as well as the endogenously expressed protein from HepG2 and Chinese hamster ovary cells. The majority of the expressed protein migrates with the predicted 57-kDa size of full-length glycosylated selenoprotein P. Based on the histidine-rich nature of selenoprotein P, we have purified the recombinant and endogenously expressed proteins using nickel-agarose affinity chromatography. We show that the recombinant rat and endogenous human proteins react in Western blotting and immunoprecipitation assays with commercial anti-histidine antibodies. The ability to express, purify, and immunochemically detect the recombinant protein provides a foundation for investigating the functions and efficiency of expression of this intriguing protein.

Selenoproteins are expressed in fetal human osteoblast-like cells

Selenoproteins are involved in mechanisms of cell differentiation and defense. We investigated the expression of glutathione peroxidases, as well as other selenoproteins, in fetal human osteoblasts (hFOB-cells). Using 75-selenium metabolic labelling of viable hFOB-cells, we identified several selenoproteins in cell lysates of about 45-80 kDa and in the migration range of 14 kDa to 24 kDa. Cells expressed low mRNA levels of both cellular glutathione peroxidase and plasma glutathione peroxidase mRNA as analysed by Southern analysis of RT-PCR products. Basal cellular glutathione peroxidase enzyme activity in hFOB-cells (19.7 nmol NADPH oxidised per min and microg protein) was further increased 2.5-fold by the addition of 100 nM sodium selenite to the culture medium for 3 days. Furthermore, expression of selenoprotein P mRNA was demonstrated by RT-PCR. hFOB-cells did not show activities of the selenoproteins type I or type II 5'-deiodinase. In summary, we identified cellular glutathione peroxidase, plasma glutathione peroxidase and selenoprotein P among of a panel of several 75-selenium labelled proteins in human fetal osteoblasts. The expression of selenoproteins like glutathione peroxidases in hFOB-cells represents a new system of osteoblast antioxidative defense that may be relevant for the protection against hydrogen peroxide produced by osteoclasts during bone remodelling.