Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Selenoprotein P”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1984

Effect of dietary selenium on plasma selenoprotein P, selenoprotein P1 and glutathione peroxidase in the rat.

The purpose of this study was to determine the effect of dietary selenium on the abundance of selenium in plasma selenoprotein P, selenoprotein P1 and glutathione peroxidase. Weanling rats were provided water that contained 1.0, 0.1 or 0.01 ppm selenium and 75Se for 21 days. Gel filtration of denatured subunits was used to identify 75Se in the selenoproteins. Rats provided 1.0 ppm selenium accumulated 1.5 times more 75Se in liver cytosolic selenoprotein P1, but not in the two other selenoproteins, than did rats provided 0.1 ppm selenium. Most of the liver and blood selenium in rats provided 1.0 ppm selenium was insoluble and in an unknown chemical form. The tissue accumulation of unrecoverable selenium was apparently a response to the high dietary level of selenium. The proportion of selenium in plasma selenoprotein P, a putative selenium-transport protein, reflected the long-term selenium status of rats and varied from approximately 11-58% depending on the level of selenium supplementation. Turnover of selenium from this protein was affected by the dietary selenium of the rats. The results indicate that selenium incorporation into plasma selenoprotein P and selenoprotein P1 is affected by diet in ways that may reflect their importance to the rat.

Animals↗
PubMed2001

Heparin-binding histidine and lysine residues of rat selenoprotein P.

Selenoprotein P is a plasma protein that has oxidant defense properties. It binds to heparin at pH 7.0, but most of it becomes unbound as the pH is raised to 8.5. This unusual heparin binding behavior was investigated by chemical modification of the basic amino acids of the protein. Diethylpyrocarbonate (DEPC) treatment of the protein abolished its binding to heparin. DEPC and [(14)C]DEPC modification, coupled with amino acid sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry of peptides, identified several peptides in which histidine and lysine residues had been modified by DEPC. Two peptides from one region (residues 80-95) were identified by both methods. Moreover, the two peptides that constituted this sequence bound to heparin. Finally, when DEPC modification of the protein was carried out in the presence of heparin, these two peptides did not become modified by DEPC. Based on these results, the heparin-binding region of the protein sequence was identified as KHAHLKKQVSDHIAVY. Two other peptides (residues 178-189 and 194-234) that contain histidine-rich sequences met some but not all of the criteria of heparin-binding sites, and it is possible that they and the histidine-rich sequence between them bind to heparin under some conditions. The present results indicate that histidine is a constituent of the heparin-binding site of selenoprotein P. The presence of histidine, the pK(a) of which is 7.0, explains the release of selenoprotein P from heparin binding as pH rises above 7.0. It can be speculated that this property would lead to increased binding of selenoprotein P in tissue regions that have low pH.

Amino Acid Sequence↗
PubMed2005

Brainstem axonal degeneration in mice with deletion of selenoprotein p.

Selenoprotein P is an abundant extracellular protein that is expressed in liver, brain, and other tissues. Studies in mice with the selenoprotein P gene deleted (Sepp-/- mice) have implicated the protein in maintaining brain selenium. Sepp-/- mice fed a normal or low selenium diet develop severe motor impairment and die, but Sepp-/- mice fed a high selenium diet remain clinically unimpaired. As an initial step to evaluate the effect of selenoprotein P deletion on central nervous system architecture, the brains and cervical spinal cords of Sepp-/- and Sepp+/+ mice fed low or high selenium diets were examined by light and electron microscopy. Brains of Sepp-/- mice demonstrated no gross abnormalities. At the light microscopic level, however, Sepp-/- mice fed either the selenium deficient diet or the high selenium diet had enlarged dystrophic axons and degenerated axons in their brainstems and cervical spinal cords. No axonal lesions were observed in the Sepp+/+ mice fed either diet. Electron microscopy demonstrated that the enlarged axons in the Sepp-/- mice were packed with organelles, suggesting a deficit in fast axonal transport. The similar severity of axonal lesions observed in Sepp-/- mice fed the 2 diets suggests that axonal dystrophy is a common phenotype for deletion of selenoprotein P regardless of selenium intake and that additional studies will be required to determine the pathogenesis of the neurological signs and mortality observed in Sepp-/- mice fed a low selenium diet.

Animals↗
PubMedDate not supplied

Some properties of selenoprotein P.

Selenoprotein P is a newly characterized selenoprotein. It is the first protein described to contain multiple selenocysteines. It is secreted by the liver into the plasma and turns over rapidly. Its concentration is sensitive to the selenium status of the animal. Its function is unknown.

Animals↗
PubMed2000

Selenoprotein P.

Selenoprotein P (SeP) is an extracellular, monomeric glycoprotein containing up to 10 selenocysteine residues in the polypeptide chain. It is ubiquitously expressed in mammalian tissues, and in human plasma it accounts for at least 40% of the total selenium concentration. SeP binds to heparin and cell membranes, and is associated with endothelial cells. SeP in human plasma protects against peroxynitrite-mediated oxidation and reduces phospholipid hydroperoxide in vitro, in accordance with the presumption that it has a function as an extracellular oxidant defense. Immunochemical assays have demonstrated that its concentration in plasma varies much with selenium intake, but other factors also have an influence.

Aging↗
PubMed1997

Cloning and characterization of the human selenoprotein P promoter. Response of selenoprotein P expression to cytokines in liver cells.

We isolated an 18-kilobase (kb) genomic selenoprotein P clone from a human placenta library and cloned, sequenced, and characterized the 5'-flanking region of the human selenoprotein P gene. Sequence analysis revealed an intron between base pairs (bp) -13 and -14 upstream of the ATG codon and another one between bp 534 and 535 of the coding region. The major transcription start site of selenoprotein P in human HepG2 hepatocarcinoma cells was mapped to bp -70 by 5'-rapid amplification of cDNA ends and by primer extension. 1.8 kb of the 5'-flanking sequence were fused to a luciferase reporter gene. They exhibited functional promoter activity in HepG2 hepatocarcinoma and Caco2 colon carcinoma cells in transient transfection experiments. Treatment of transfected HepG2 cells with the cytokines interleukin 1beta, tumor necrosis factor alpha, and interferon gamma repressed promoter activity. Nuclear extracts of interferon gamma-treated cells bound to a signal transducer and activator of transcription response element of the promoter in gel retardation experiments. By transfection of promoter-deletion constructs, a TATA box and a putative SP1 site were identified to be necessary for selenoprotein P transcription. These data indicate that the human selenoprotein P gene contains a strong promoter that is cytokine responsive. Furthermore, selenoprotein P, secreted by the liver, might react as a negative acute phase protein.

Base Sequence↗
PubMed1999

Selenoprotein P in human plasma as an extracellular phospholipid hydroperoxide glutathione peroxidase. Isolation and enzymatic characterization of human selenoprotein p.

Selenoprotein P is an extracellular protein containing presumably 10 selenocysteines that are encoded by the UGA stop codon in the open reading frame of the mRNA. The function of selenoprotein P is currently unknown, although several indirect lines of evidence suggest that selenoprotein P is a free radical scavenger. We first developed a conventional procedure to isolate selenoprotein P from human plasma. Next, we investigated the reactivities of selenoprotein P against various hydroperoxides in the presence of glutathione. Although selenoprotein P reduces neither hydrogen peroxide nor tertiary butyl hydroperoxide, it does reduce phospholipid hydroperoxide such as 1-palmitoyl-2-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl)-3-phosphatidylcholine hydroperoxide. Kinetic analysis demonstrated a tert-uni ping-pong mechanism, similar to those described for classical glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase. Not only glutathione, but also dithiothreitol, mercaptoethanol, cysteine, and homocysteine, were effective as reducing substances, as in the case of phospholipid hydroperoxide glutathione peroxidase. These results show that selenoprotein P functions as a phospholipid hydroperoxide glutathione peroxidase in extracellular fluids.

Amino Acids↗
PubMed1990

Selenium and amino acid composition of selenoprotein P, the major selenoprotein in rat serum.

Selenoprotein P is the second plasma selenoprotein to be purified. It is a glycoprotein and has been shown to be distinct from plasma glutathione peroxidase. This study characterizes selenoprotein P further. Deglycosylation of the protein shifts its migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis from Mr 57,000 to Mr 43,000, indicating it has a substantial carbohydrate component. Measurement of selenium indicates a selenium content of 7.5 +/- 1.0 atoms/molecule based on a polypeptide weight of 43,000. Amino acid analysis accounts for all the selenium as selenocysteine. The protein is also rich in cysteine (17 residues) and histidine (23 residues). Fragmentation of selenoprotein P by trypsin and by cyanogen bromide produces peptides with varying selenium content. This indicates that selenium-rich regions of the protein exist. The concentration of selenoprotein P determined by radioimmunoassay in serum from control rats is 26.3 +/- 4.5 micrograms/ml and in serum from selenium-deficient rats it is 2.7 +/- 0.8 micrograms/ml. Depletion of selenoprotein P from control serum using an immunoaffinity column indicates that over 60% of serum selenium in the rat is contained in this protein. These results demonstrate that selenoprotein P is the major form of selenium in rat serum. It is the first selenoprotein described which has more than one selenium atom/polypeptide chain.

Amino Acids↗
PubMed2004

Domain structure of bi-functional selenoprotein P.

Human selenoprotein P (SeP), a selenium-rich plasma glycoprotein, is presumed to contain ten selenocysteine residues; one of which is located at the 40th residue in the N-terminal region and the remaining nine localized in the C-terminal third part. We have shown that SeP not only catalyses the reduction of phosphatidylcholine hydroperoxide by glutathione [Saito, Hayashi, Tanaka, Watanabe, Suzuki, Saito and Takahashi (1999) J. Biol. Chem. 274, 2866-2871], but also supplies its selenium to proliferating cells [Saito and Takahashi (2002) Eur. J. Biochem. 269, 5746-5751]. Treatment of SeP with plasma kallikrein resulted in a sequential limited proteolysis (Arg-235-Gln-236 and Arg-242-Asp-243). The N-terminal (residues 1-235) and C-terminal (residues 243-361) fragments exhibited enzyme activity and selenium-supply activity respectively. These results confirm that SeP is a bi-functional protein and suggest that the first selenocysteine residue is the active site of the enzyme and the remaining nine residues function as a selenium supplier.

Binding Sites↗
PubMed1989

Rat plasma selenoprotein P properties and purification.

A selenoprotein in rat plasma, selenoprotein P, was fractionated and characterized. Plasma collected from rats 3 h post injection of 75SeO3(2-) contained one 75Se-labeled protein, selenoprotein P. Selenoprotein P was fractionated using salt precipitation, Affi-Gel Blue, and DEAE chromatography. The 75Se-containing subunit of selenoprotein P was purified to 90% homogeneity using SDS-polyacrylamide gel electrophoresis followed by electroelution. This isolation resulted in an 850-fold purification of the 75Se-containing subunit of selenoprotein P with a 15% yield of 75Se radioactivity. The molecular weight of selenoprotein P in plasma was 98,000. The 75Se-containing subunit of selenoprotein P had a molecular mass of 57 kDa as determined by SDS-polyacrylamide gel electrophoresis. Isoelectric focusing under nondenaturing conditions resulted in a band of 75Se radioactivity at pH 5.4. A comparison of Coomassie Blue- and silver-staining properties of selenoprotein P in SDS-polyacrylamide gels was made. Reverse-phase HPLC and Sephadex G-50 chromatography of tryptic peptides of the 57 kDa subunit of selenoprotein P yielded several peaks of 75Se radioactivity. These results indicate that 75Se is present in several locations within the 57 kDa subunit of selenoprotein P.

Animals↗
PubMed2000

Synthesis and secretion of selenoprotein P by cultured rat astrocytes.

Selenoprotein P is an extracellular protein that has been postulated to have an oxidant defense function. It has survival-promoting properties for cultured neurons and its mRNA is present in the brain. This study sought to determine the primary structure of rat brain selenoprotein P and to assess its production by cultured brain cells. The cDNA of selenoprotein P was isolated from a rat brain cDNA library and was found to encode the same peptide sequence as rat liver cDNA. Thus the primary structure of brain selenoprotein P is the same as selenoprotein P from liver. Astrocytes and a cerebellar granule cell preparation (CGC) were obtained from rat brains and established in culture. The CGC was estimated to contain up to 5% glial cells. Both preparations were shown to contain selenoprotein P mRNA. During incubation with (75)Se-labeled selenite, both cell preparations secreted a (75)Se-labeled protein into the medium that corresponded in size to selenoprotein P. Also, the (75)Se-labeled protein could be precipitated from both media with an antiserum to selenoprotein P. This shows that astrocytes and the CGC secrete selenoprotein P. Selenoprotein P is made in the brain and may have an oxidant defense function there.

Animals↗
PubMed1994

Purification of selenoprotein P from human plasma.

Selenoprotein P was partially purified (> 1000-fold) from human plasma in four chromatographic steps using 75Se-labeled selenoprotein P secreted by HepG2 cells in culture as a marker. The purified preparation was injected into mice and monoclonal antibodies, which precipitated the labeled protein, were generated. Neither of two different monoclonal antibodies had cross-reactivity with plasma from five animal species. Antibodies were coupled to agarose, and selenoprotein P was purified from human plasma by immunoaffinity chromatography followed by chromatography on heparin agarose. With two different matrix-bound monoclonal antibodies, the purification procedure gave two bands on SDS-PAGE with mobilities corresponding to 61 and 55 kDa. Both bands stained for carbohydrate and showed increased electrophoretic mobility after enzymatic deglycosylation. Immunoaffinity chromatography removed approx. one-third of the selenium from plasma or 0.4 mumol Se/l at a total selenium concentration of 1.1 mumol/l, indicating that selenoprotein P constituted this proportion of total plasma selenium in healthy US blood donors.

Amino Acid Sequence↗
PubMed1993

Conserved nucleotide sequences in the open reading frame and 3' untranslated region of selenoprotein P mRNA.

Rat liver selenoprotein P contains 10 selenocysteine residues in its primary structure (deduced). It is the only selenoprotein characterized to date that has more than one selenocysteine residue. Selenoprotein P cDNA has been cloned from human liver and heart cDNA libraries and sequenced. The open reading frames are identical and contain a signal peptide, indicating that the protein is secreted by both organs and is therefore not exclusively produced in the liver. Ten selenocysteine residues (deduced) are present. Comparison of the open reading frame of the human cDNA with the rat cDNA reveals a 69% identity of the nucleotide sequence and 72% identity of the deduced amino acid sequence. Two regions in the 3' untranslated portion have high conservation between human and rat. Each of these regions contains a predicted stable stem-loop structure similar to the single stem-loop structures reported in 3' untranslated regions of type I iodothyronine 5'-deiodinase and glutathione peroxidase. The stem-loop structure of type I iodothyronine 5'-deiodinase has been shown to be necessary for incorporation of the selenocysteine residue at the UGA codon. Because only two stem-loop structures are present in the 3' untranslated region of selenoprotein P mRNA, it can be concluded that a separate stem-loop structure is not required for each selenocysteine residue.

Amino Acid Sequence↗
PubMed1996

Effect of selenium on selenoprotein P expression in cultured liver cells.

Selenoprotein P and glutathione peroxidase are selenoproteins that are synthesized by hepatocytes. The production of these selenoproteins by human and rat liver cell lines has been assessed at several levels of selenium supplementation and compared with one another. HepG2 and H4IIE cells were cultured in serum-free medium without selenium supplementation for 48 h; then sodium selenite was added to the medium to give final concentrations of 0, 1, 2.5, 5, or 10 ng selenium/ml medium. After 48 h, selenoprotein P concentration in the medium, cellular glutathione peroxidase activity, and the mRNA levels of the two selenoproteins were determined. Selenium deficiency caused a decrease in selenoprotein mRNA and protein levels. The extent of decrease depended on the cell line examined. In selenium-deprived HepG2 cells, selenoprotein P release decreased to 10% of the release by selenium-replete cells. Under the same conditions, cellular glutathione peroxidase activity decreased to 33%. H4IIE cells showed the opposite results with cellular glutathione peroxidase activity decreasing to 13% and selenoprotein P release decreasing to 40% of selenium-replete cells. The effect of dithiothreitol on secretion of selenoprotein P by H4IIE cells was examined. Selenoprotein P secretion was inhibited by dithiothreitol, suggesting that disulfide bond formation is necessary for secretion of the mature protein.

Animals↗
PubMedDate not supplied

Association of selenoprotein P with testosterone production in cultured Leydig cells.

Selenoprotein P, a plasma selenoprotein, is thought to act as an antioxidant in the testis, similar to glutathione peroxidase. mRNA encoding selenoprotein P was selectively expressed by Leydig cells, suggesting participation in testosterone production. On the other hand, testosterone production has been linked to O2 toxicity in cultured Leydig cells. The authors, therefore, examined changes in selenoprotein P mRNA expression and testosterone production following stimulation by a stable analog cyclic adenosine 3',5'-monophosphate (cAMP) in cultured Leydig cells (MLTC-1 cells) under normal O2 concentrations. Selenoprotein P mRNA was analyzed by Northern blotting, while testosterone concentration in culture medium was measured by radioimmunoassay. When cAMP was added to cultures at 0, 0.01, 0.1, or 1 mM, selenoprotein P mRNA expression showed dose-dependent stimulation. cAMP was added at 0.1 mM to cultures, and the selenoprotein P mRNA expression and testosterone concentration were evaluated after incubation times of 2, 5, 9, 15, or 24 h. Selenoprotein P mRNA expression was maximal at 9 h. Testosterone concentration in the medium also increased, becoming maximal at 15 h. Selenoprotein P induced in Leydig cells following cAMP stimulation may counteract O2 toxicity from cAMP-mediated increases in testosterone production.

Animals↗
PubMed1998

A novel method for the purification of selenoprotein P from human plasma.

Selenoprotein P was purified from human plasma using conventional chromatographic methods featuring metal-chelate-affinity chromatography as the final step. Two distinct isoforms with different selenium content were isolated and identified by N-terminal sequencing and immunoblot analysis. Their molecular mass is 61 and 51 kDa, respectively. Both isoforms could be detected in fresh plasma from five individuals. This rules out the possibility of the second isoform being an artifact which results from degradation of full-length selenoprotein P during purification.

Blood Proteins↗
PubMed1994

Selenoprotein P. A selenium-rich extracellular glycoprotein.

Selenoprotein P is a glycoprotein that has been purified from rat and human plasma. In selenium-replete rats it contains 65% of the plasma selenium and its concentration is 25-30 mg protein/L. In selenium-deficient rats its concentration is < 3 mg protein/L. The plasma half life of 75Se in selenoprotein P is 3 to 4 h, indicating a rapid turnover. Purified rat selenoprotein P contains 7.5 +/- 1 selenium atoms per molecule as selenocysteine. The sequence of the cloned cDNA predicts 10 selenocysteine residues, which suggests that the protein in plasma is a modification of the predicted one. Deduced amino acid sequence identity between rats and humans is 72%. The 3' untranslated region of selenoprotein P cDNA contains two predicted stem loops of the type essential for selenocysteine incorporation. Northern analysis indicates that selenoprotein P is expressed by many tissues. Hepatic selenoprotein P mRNA level, but not its transcription, decreases during selenium deficiency. The decrease is less than the decrease of glutathione peroxidase mRNA, however. Selenoprotein P is postulated to serve as an extracellular oxidant defense because its presence correlates with selenium protection of selenium-deficient rats against diquat-induced lipid peroxidation and liver necrosis. More research will be required to test this hypothesis and to establish the biochemical function of selenoprotein P.

Amino Acid Sequence↗
PubMed2000

Expression and characterization of nonmammalian selenoprotein P in the zebrafish, Danio rerio.

BACKGROUND: Selenoprotein P is a protein of considerable intrigue, due to its unusual composition and requirements for its biosynthesis. Whereas most selenoproteins contain a single selenocysteine residue, the human, bovine and rodent selenoprotein P genes encode proteins containing 10-12 selenocysteines. Selenoprotein P genes have, to date, only been reported in mammals, and the function of the protein remains elusive. RESULTS: Herein, we report the identification and characterization of nonmammalian selenoprotein P in the zebrafish Danio rerio. Sequencing of the cDNA revealed the presence of 17 selenocysteine codons, the highest number reported in any protein. Two histidine-rich regions present in the mammalian selenoprotein P sequences are conserved in the zebrafish protein, and two SECIS elements are present in the 3' untranslated region. Whole-mount in situ hybridization of zebrafish embryos revealed high levels of expression of selenoprotein P mRNA in fertilized eggs and in the yolk sac of developing embryos. Transient transfection of the cDNA in mammalian cells resulted in efficient expression of the full-length secreted selenoprotein. A single N-glycosylation site is predicted, and shown to be utilized. CONCLUSIONS: Discovery of selenoprotein P in the zebrafish opens a previously unavailable avenue for genetic investigation of the functions of this unusual protein.

Amino Acid Sequence↗