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The selenoproteome exhibits widely varying, tissue-specific dependence on selenoprotein P for selenium supply.

Hoffmann PR, Höge SC, Li PA, Hoffmann FW, Hashimoto AC, Berry MJ - Nucleic Acids Res. (2007)

Bottom Line: Thus, Se availability affects not only selenoprotein levels, but also the turnover of selenoprotein mRNAs via the nonsense-mediated decay pathway.Our findings present a comprehensive description of selenoprotein mRNA expression in the following murine tissues: brain, heart, intestine, kidney, liver, lung, spleen and testes.We also describe how abundance of selenoproteins and selenoprotein-synthesis factors are affected by genetic deletion of Sel P in some of these tissues, providing insight into how the presence of this selenoprotein influences selenoprotein mRNA levels, and thus, the selenoproteome.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, USA. peterh@pbrc.hawaii.edu

ABSTRACT
Selenoprotein P (Sel P) is a selenium-rich glycoprotein believed to play a key role in selenium (Se) transport throughout the body. Development of a Sel P knockout mouse model has supported this notion and initial studies have indicated that selenium supply to various tissues is differentially affected by genetic deletion of Sel P. Se in the form of the amino acid, selenocysteine, is incorporated into selenoproteins at UGA codons. Thus, Se availability affects not only selenoprotein levels, but also the turnover of selenoprotein mRNAs via the nonsense-mediated decay pathway. We investigated how genetic deletion of Sel P in mice affected levels of the mRNAs encoding all known members of the murine selenoprotein family, as well as three non-selenoprotein factors involved in their synthesis, selenophosphate synthetase 1 (SPS1), SECIS-binding protein 2 (SBP2) and SECp43. Our findings present a comprehensive description of selenoprotein mRNA expression in the following murine tissues: brain, heart, intestine, kidney, liver, lung, spleen and testes. We also describe how abundance of selenoproteins and selenoprotein-synthesis factors are affected by genetic deletion of Sel P in some of these tissues, providing insight into how the presence of this selenoprotein influences selenoprotein mRNA levels, and thus, the selenoproteome.

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Comparison of GPX1, GPX4, and Sel W levels in Sel P knockout versus wild-type mice. (A) Protein was extracted from heart, lung, brain and testes, which were then used for western blot analysis. Rabbit polyclonal antibodies were used to detect GPX1, GPX4 and Sel W for three Sel P knockout mice and three wild-type mice for each tissue. Equivalent protein loading was determined using α-tubulin for heart and lung and β-actin for brain and testes. (B) Densitometry was used to quantify western blot data as described in the Methods section. Results represent mean ±SE. Statistical significance was determined by student's t-test (*P < 0.05) Black and white bars represent wildtype (N=3) and knockout (N=3) mice, respectively.
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Figure 3: Comparison of GPX1, GPX4, and Sel W levels in Sel P knockout versus wild-type mice. (A) Protein was extracted from heart, lung, brain and testes, which were then used for western blot analysis. Rabbit polyclonal antibodies were used to detect GPX1, GPX4 and Sel W for three Sel P knockout mice and three wild-type mice for each tissue. Equivalent protein loading was determined using α-tubulin for heart and lung and β-actin for brain and testes. (B) Densitometry was used to quantify western blot data as described in the Methods section. Results represent mean ±SE. Statistical significance was determined by student's t-test (*P < 0.05) Black and white bars represent wildtype (N=3) and knockout (N=3) mice, respectively.

Mentions: As shown in Figure 3A, levels of all three proteins are decreased in brain and testes. Using densitometry to quantify the levels of proteins, we found significant reductions in GPX1 in brain and both GPX4 and Sel W in testes. These results are consistent with the mRNA results described above. The results from lung and heart tissue differ from brain and testes in several ways. First, the antibody that detects Sel W in brain and testes does not detect Sel W in lung and heart. This could be due to different isoforms of Sel W expressed in the different tissues, as mRNA levels for this selenoprotein were relatively high in heart and lung. A second feature that is evident from the western blot analyses is that the decreased levels of GPX1 and GPX4 detected in Sel P+/+ brain and testes tissues are not detected in lung and heart, which is consistent with the mRNA levels described above. In fact, GPX4 levels are significantly increased in heart tissue from Sel P−/− mice and GPX1 levels show a trend toward an increase in the knockout mice. These results are similar to those found at the mRNA level and raise the question of why these two members of the GPX family may increase in heart with the deletion of Sel P.Figure 3.


The selenoproteome exhibits widely varying, tissue-specific dependence on selenoprotein P for selenium supply.

Hoffmann PR, Höge SC, Li PA, Hoffmann FW, Hashimoto AC, Berry MJ - Nucleic Acids Res. (2007)

Comparison of GPX1, GPX4, and Sel W levels in Sel P knockout versus wild-type mice. (A) Protein was extracted from heart, lung, brain and testes, which were then used for western blot analysis. Rabbit polyclonal antibodies were used to detect GPX1, GPX4 and Sel W for three Sel P knockout mice and three wild-type mice for each tissue. Equivalent protein loading was determined using α-tubulin for heart and lung and β-actin for brain and testes. (B) Densitometry was used to quantify western blot data as described in the Methods section. Results represent mean ±SE. Statistical significance was determined by student's t-test (*P < 0.05) Black and white bars represent wildtype (N=3) and knockout (N=3) mice, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC1919489&req=5

Figure 3: Comparison of GPX1, GPX4, and Sel W levels in Sel P knockout versus wild-type mice. (A) Protein was extracted from heart, lung, brain and testes, which were then used for western blot analysis. Rabbit polyclonal antibodies were used to detect GPX1, GPX4 and Sel W for three Sel P knockout mice and three wild-type mice for each tissue. Equivalent protein loading was determined using α-tubulin for heart and lung and β-actin for brain and testes. (B) Densitometry was used to quantify western blot data as described in the Methods section. Results represent mean ±SE. Statistical significance was determined by student's t-test (*P < 0.05) Black and white bars represent wildtype (N=3) and knockout (N=3) mice, respectively.
Mentions: As shown in Figure 3A, levels of all three proteins are decreased in brain and testes. Using densitometry to quantify the levels of proteins, we found significant reductions in GPX1 in brain and both GPX4 and Sel W in testes. These results are consistent with the mRNA results described above. The results from lung and heart tissue differ from brain and testes in several ways. First, the antibody that detects Sel W in brain and testes does not detect Sel W in lung and heart. This could be due to different isoforms of Sel W expressed in the different tissues, as mRNA levels for this selenoprotein were relatively high in heart and lung. A second feature that is evident from the western blot analyses is that the decreased levels of GPX1 and GPX4 detected in Sel P+/+ brain and testes tissues are not detected in lung and heart, which is consistent with the mRNA levels described above. In fact, GPX4 levels are significantly increased in heart tissue from Sel P−/− mice and GPX1 levels show a trend toward an increase in the knockout mice. These results are similar to those found at the mRNA level and raise the question of why these two members of the GPX family may increase in heart with the deletion of Sel P.Figure 3.

Bottom Line: Thus, Se availability affects not only selenoprotein levels, but also the turnover of selenoprotein mRNAs via the nonsense-mediated decay pathway.Our findings present a comprehensive description of selenoprotein mRNA expression in the following murine tissues: brain, heart, intestine, kidney, liver, lung, spleen and testes.We also describe how abundance of selenoproteins and selenoprotein-synthesis factors are affected by genetic deletion of Sel P in some of these tissues, providing insight into how the presence of this selenoprotein influences selenoprotein mRNA levels, and thus, the selenoproteome.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, USA. peterh@pbrc.hawaii.edu

ABSTRACT
Selenoprotein P (Sel P) is a selenium-rich glycoprotein believed to play a key role in selenium (Se) transport throughout the body. Development of a Sel P knockout mouse model has supported this notion and initial studies have indicated that selenium supply to various tissues is differentially affected by genetic deletion of Sel P. Se in the form of the amino acid, selenocysteine, is incorporated into selenoproteins at UGA codons. Thus, Se availability affects not only selenoprotein levels, but also the turnover of selenoprotein mRNAs via the nonsense-mediated decay pathway. We investigated how genetic deletion of Sel P in mice affected levels of the mRNAs encoding all known members of the murine selenoprotein family, as well as three non-selenoprotein factors involved in their synthesis, selenophosphate synthetase 1 (SPS1), SECIS-binding protein 2 (SBP2) and SECp43. Our findings present a comprehensive description of selenoprotein mRNA expression in the following murine tissues: brain, heart, intestine, kidney, liver, lung, spleen and testes. We also describe how abundance of selenoproteins and selenoprotein-synthesis factors are affected by genetic deletion of Sel P in some of these tissues, providing insight into how the presence of this selenoprotein influences selenoprotein mRNA levels, and thus, the selenoproteome.

Show MeSH
Related in: MedlinePlus