Selenoprotein P. A selenium-rich extracellular glycoprotein

Area of Science:

• Biochemistry
• Molecular Biology
• Nutritional Science

Background:

• Selenoprotein P is a major selenium-binding glycoprotein found in plasma.
• Its concentration significantly decreases in selenium-deficient states.
• It contains multiple selenocysteine residues, crucial for its function.

Purpose of the Study:

• To characterize Selenoprotein P in rats and humans.
• To investigate its expression and regulation under selenium deficiency.
• To explore its potential role in extracellular oxidant defense.

Main Methods:

• Purification of Selenoprotein P from plasma.
• Biochemical analysis of selenium content.
• cDNA cloning and sequencing.
• Northern blot analysis of mRNA expression.
• Assessment of protection against diquat-induced toxicity.

Main Results:

• Selenoprotein P constitutes a large fraction of plasma selenium in replete rats.
• Its plasma concentration and half-life indicate rapid turnover.
• cDNA sequencing predicts 10 selenocysteine residues, though the protein appears modified.
• Selenoprotein P mRNA levels decrease in selenium deficiency, but less than glutathione peroxidase mRNA.
• Selenoprotein P presence correlates with protection against lipid peroxidation in deficient rats.

Conclusions:

• Selenoprotein P plays a significant role in selenium transport and metabolism.
• Its regulation is linked to selenium status, with distinct patterns compared to other selenoproteins.
• Evidence suggests Selenoprotein P functions as an extracellular antioxidant, protecting against oxidative damage.