The thymus hypocholesterolemic factor (TphF): a bovine thymic superoxide dismutase active on HMG-CoA reductase

doi:10.1016/0305-0491(93)90358-C

Comparative Biochemistry and Physiology Part B: Comparative Biochemistry

Volume 104, Issue 1, January 1993, Pages 193-199

https://doi.org/10.1016/0305-0491(93)90358-C Get rights and content

Abstract

1.
1. This work describes the further biochemical characterization of a new calf thymus protein (TphF) and its primary structure.
2.
2. The amino acid sequences, obtained after sequence analysis of peptides derived from the endoproteinase Lys-C digestion, were subjected to a “Protein Data Bank Search” and were found to be identical with regions of bovine superoxide-dismutase (SOD).
3.
3. These data together with those showing the identical electrophoretic migration of SOD and TphF, their same isoelectric point and their immunoreactivity with anti-SOD antibodies, confirm the similarity of these two proteins.

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Corpus luteum derived copper, zinc-superoxide dismutase serves as a luteinizing hormone-release inhibiting factor in sheep
2003, Molecular and Cellular Endocrinology
In the present study, we report the purification and characterization of a polypeptide from the sheep corpus luteum of pregnancy with a potent luteinizing hormone-release inhibiting factor (LH-RIF) bioactivity that stained as a single band in SDS-PAGE with an apparent molecular mass of 16 000 Da. The amino acid sequences obtained after sequence analysis of peptides derived from the trypsin digestion of LH-RIF were subjected to a protein data bank search and were found to be identical with regions of sheep copper, zinc-superoxide dismutase (Cu,Zn-SOD). The measured mass of LH-RIF (15604.2±1.9 Da) was found to be similar to the theoretical mass of sheep Cu,Zn-SOD (15603.5 Da), with a disulfide bond and N acetylated alanine at the N-terminus. The inhibitory action of Cu,Zn-SOD on pulsatile LH secretion would suggest that this antioxidant may play an important role, either independently or in concert with some neurotransmitters, in the neuroendocrine regulation of sheep female reproductive function.
Effect of Cu,Zn superoxide dismutase on cholesterol metabolism in human hepatocarcinoma (HepG2) cells
2002, Biochemical and Biophysical Research Communications
The microsomal enzyme 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase and the low density lipoprotein (LDL) receptor pathway carry out a key role on cholesterol homeostasis in eucaryotic cells. The HMG-CoA reductase is sensitive to oxidative inactivation and to phosphorylation by many kinases that are able to inactivate the protein and increase its susceptibility to proteolysis. We previously demonstrated that a calf thymus Cu,Zn SOD affects cholesterol metabolism. This protein binds with rat hepatocyte cell membrane by a specific surface membrane receptor. The involvement of Cu,Zn SOD in cholesterol metabolism is confirmed further by the presence of this antioxidant enzyme in circulating serum lipoproteins. We studied the effect of native human Cu,Zn SOD, metal-free SOD (apo SOD), and SOD-inactivated with hydrogen peroxide on cholesterol metabolism in human hepatocarcinoma HepG2 cells. Results showed that all forms of SODs used, at the concentration of 150 ng/ml, are able to affect cholesterol metabolism decreasing both HMG-CoA reductase activity and its protein levels; this inhibitory effect is accompanied by reduced cholesterol synthesis measured as [¹⁴C]acetate incorporation into [¹⁴C]cholesterol and by an increased [¹²⁵I]LDL binding to HepG2 cells. Furthermore, the inhibitory effect of Cu,Zn SOD on cholesterol synthesis was completely abolished when the cells were incubated with Cu,Zn SOD in the presence of bisindoilmaleimide (BDM), an inhibitor of protein kinase C (PKC); moreover, we demonstrated that Cu,Zn SOD as well as apo SOD was able to increase PKC activity. Overall, data demonstrate that Cu,Zn SOD affects cholesterol metabolism independently from its dismutase activity and its metal content and that the inhibitory action on cholesterol synthesis is mediated by an activation of protein kinase C.
Thymosin α<inf>1</inf> protects liver and aorta from oxidative damage in atherosclerotic rabbits
1996, Life Sciences
The thymus hormones were reported to be effective on lipid peroxidation and the antioxidant system. Thymus plays a broader role than just regulating the immune system. Thymosin α₁ is the first subgroup extracted from thymosin F5 and has higher biological activity than thymosin F5. In the present study, we have examined the effects of thymosin α₁ on lipid levels and lipid peroxidation and glutathione (GSH) content in the plasma, liver and aorta tissues of atherosclerotic rabbits. At the end of thymosin α₁ treatment, we determined the lipid levels and lipid peroxidation of the plasma, liver and aorta tissues and hepatic subcellular fractions in these rabbits. Our results demonstrated that thymosin α₁ might normalize changed lipid levels and increased lipid peroxides and also elevate decreased GSH in the plasma, liver and aorta tissues of atherosclerotic rabbits. Results of this study suggest that thymosin a, may be beneficial to prevent and/or to treat atherosclerosis.
Evidence for secretion of cytosolic CuZn superoxide dismutase by Hep G2 cells and human fibroblasts
1996, International Journal of Biochemistry and Cell Biology
The role so far ascribed to intracellular CuZn superoxide dismutase is that of an intracellular scavenger of oxygen radicals. However, other functions of cytosolic CuZn superoxide dismutase have been hypothesized. For example, CuZn superoxide dismutase incubated with rat hepatocyte cells in culture inhibits 3-hydroxy-3methylglutaryl CoA reductase, thereby reducing cholesterol synthesis. We recently demonstrated the presence of surface membrane receptors for CuZn superoxide dismutase, suggesting possible autocrine or paracrine activities. The aim of the present study was to investigate whether cytosolic CuZn superoxide dismutase can be secreted by human hepatocarcinoma and fibroblast cells lines. Proteins in human hepatocellular carcinoma (Hep G2) cells and human fibroblasts were biosynthetically labelled with [³⁵S]-cysteine; then cell lysates and media were immunoprecipitated with rabbit polyclonal anti-human CuZn superoxide dismutase antibodies and separated by 12% polyacrylamide gel electrophoresis. Both Hep G2 cells and human fibroblasts produce and secrete CuZn superoxide dismutase which was detectable in cells and medium as a single protein band with the same electrophoretic mobility as human erythrocyte CuZn superoxide dismutase. These data suggest that CuZn superoxide dismutase, an enzyme thus far considered to be located exclusively intracellularly is secreted by at least two cell lines. This is consistent with autocrine or paracrine roles for CuZn superoxide dismutase.
The calf superoxide dismutase receptor of rat hepatocytes
1994, Comparative Biochemistry and Physiology -- Part B: Biochemistry and
The presence of a specific SOD surface membrane receptor in rat hepatocyte cells was investigated using ligand blot analysis of the SOD receptor with ¹²⁵I-SOD, and binding studies with iodinated and fluorescinated SOD. A specific SOD receptor with a molecular weight of about 320 kDa was identified. We suggest that the modulatory role of SOD on HMG-CoA reductase is exerted through this specific receptor.
The calf thymus superoxide dismutase: a protein active on cholesterol metabolism
1993, Comparative Biochemistry and Physiology -- Part B: Biochemistry and
- 1.
  1. Recent studies on the new aspects of thymus physiology describing the correlation between thymus hormones and pituitary hormone secretion, are illustrated.
- 2.
  2. Subsequently, results of a series of experiments showing the effect of a calf thymus protein on cholesterol synthesis in rat hepatocyte cells are discussed.
- 3.
  3. The last part of this review is focused on the biochemical characteristics of this calf thymus protein that revealed an amino acid sequence that was found to be identical with regions of bovine erythrocyte superoxide dismutase. New perspectives of studies, focused on the isolation of possible superoxide dismutase membrane receptors, are described at the end of this review.

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The thymus hypocholesterolemic factor (TphF): a bovine thymic superoxide dismutase active on HMG-CoA reductase

Abstract

J. biol. Chem.

J. biol. Chem.

J. biol. Chem.

J. Biol. Chem.

Int. J. Biochem.

Int. J. Biochem.

Comp. Biochem. Physiol.

Comp. Biochem. Physiol.

J. biol. Chem.