Sialoprotein, bone

Bone sialoprotein Bone-specific. Heavily glycosylated, and sulfated on tyrosine. 

Recent interest has focused on acidic phosphoproteins, such as bone sialoprotein, acting as sites of nucleation. These proteins contain motifs (eg, poly-Asp and poly-Glu stretches) that bind calcium and may provide an initial scaffold for mineralization. Some macromolecules, such as certain proteoglycans and glycoproteins, can also act as inhibitors of nucleation. 

Helfrich MH, Nesbitt SA, Dorey EL, Horton MA (1992) Rat osteoclasts adhere to a wide range of RGD (Arg-Gly-Asp) peptide-containing proteins, including the bone sialoproteins and fibronectin, via a beta 3 integrin. J Bone Miner Res 7 335-343... 

Herring, G. M. Methods for the study of the glycoproteins and proteoglycans of bone using bacterial collagenase. Determination of bone sialoprotein and chondroitin sulphate. Calc. Tiss. Res. 24, 29 (1977)... 

Fig. 44. Diagram illustrating the structure of a section of (a) protein-polysaccharide molecule, and (b) bone sialoprotein (Herring414))...

Herring, G. M., Andrews, A. T. de B., and Chipperfield, A. R. Chemical structure of bone sialoprotein and a preliminary study of its calcium-binding properties. In Cellular mechanisms for calcium transfer and homeostasis (eds. G. Nichols, Jr. and R. H. Wasserman), pp. 63-73. New York and London Academic Press 1971. 

Increase expression of bone sialoprotein mRNA expression Kim et al., 2007... 

Kim DS, Takai H, Arai M, Araki S, Mezawa M, Kawai Y, Murota Y, Terao J, Ogata Y. 2007. Effect of quercetin and quercetin 3-glucuronide on the expression of bone sialoprotein gene. J Cell Biochem 101 790-800. 

Very little work has been reported on the role of oxidative stress in osteoblasts. However, osteoblasts can be induced to produce intracellular ROS (Cortizo et al., 2000 Liu et al., 1999), which can cause a decrease in alkalinephosphatase (ALP) activity that is partially inhibited by vitamin E and cause cell death (Cortizo et al., 2000 Liu et al., 1999). Treatment of rat osteosarcoma ROS 17/2.8 cells with tumor necrosis factor-alpha (TNF-a) suppressed bone sialoprotein (BSP) gene transcription through a tyrosine kinase-dependent pathway that generates ROS (Samoto et al., 2002). H202 modulated intracellular calcium (Ca2+) activity in osteoblasts by increasing Ca2+ release from the intracellular Ca2+ stores (Nam et al., 2002). 

Samoto, H., Shimizu, E., Matsuda-Honjo, Y., Saito, R., Yamazaki, M., Kasai, K., Furuyama, S., Sugiya, H., Sodek, J., and Ogata, Y. 2002. TNF-alpha suppresses bone sialoprotein (BSP) expression in ROS17/2.8 cells. J. Cell. Biochem. 87, 313-323. 

Bone sialoprotein, osteopontin, and osteocalcin are synthesized and deposited as the mineralization process begins and mineral nodules form (Stein and Lian, 1993). Bone sialoprotein contains the cell-adhesive arginine-glycine-aspartic acid peptide sequence and may thus mediate osteoblast adhesion on the extracellular matrix (Gehron-Robey, 1989). Osteocalcin, a calcium-binding protein, interacts with hydroxyapatite and is thought to mediate coupling of bone resorption (by osteoclasts) and bone formation (by osteoblasts and/or osteocytes) (Stein and Lian, 1993). 

Oldberg, A., Franzen, A., and Heinegard, D. (1986). Cloning and sequence analysis of rat bone sialoprotein (osteopontin) cDNA reveals an Arg-Gly-Asp cell-binding sequence. Proc. Natl Acad. Sci. USA 83, 8819-8823. 

Bone sialoprotein has a molecular weight of about 25,000. About 20% of the weight of the protein is sialic acid, an acidic sugar. The protein may aid in the formation of collagen fibers prior to the deposit of minerals. It is thought that osteonectin promotes the adhesion of osteoblasts to unmineralized surfaces. The protein component of the protein-chondroitin sulfate complex of bone has a molecular weight of 45,000, whereas the molecular weight of each of the associated chondroitin sulfate chains is 40,000. The complex, in bone, contains only one or two chains of chondroitin sulfate. 

Escarot-Charrier, B., Bouchard, F., and Delloye, C. (1989). Bone sialoprotein II synthesized by cultured osteoblasts contains tyrosine sulfate. /. Biol. Chem. 264, 20049-20053. 

Yamauchi, M., Ogata, Y., Kim, R. H., Li, J. J., Freedman, L. P., Sodek, J. (1996) AP-1 regulation of the rat bone sialoprotein gene transcription is mediated through a TPA response element within a glucocorticoid response unit in the gene promoter. Matrix Biol. 15, 119-130. 

Table 9. Amino acid composition of elastin and bone sialoprotein...

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