Oseteopontin is a extracellular linking protein which is also known by the names of bone sialoprotein I , early T-lymphocyte activation 1, secreted phosphoprotein 1, 2ar and Rickettsia resistance.
It is a glycoprotein that was first identified in 1986 in osteoblasts.
Apart from, the protein is also expressed in other tissues bone.
Osteopontin gene is located on the long arm of chromosome 4 region 13 (4q13). The protein is composed of ~300 amino acids residues and has ~30 carbohydrate residues attached including 10 sialic acid residues. The protein is rich in acidic residues: 30-36% are either aspartic or glutamic acid.
Osteopontin is synthesized in fibroblasts, preosteoblasts, osteoblasts, osteocytes, odontoblasts, some bone marrow cells, hypertrophic chondrocytes, dendritic cells, macrophages, smooth muscle, skeletal muscle, endothelial cells, and extraosseous cells in the inner ear, brain, kidney, and placenta.
Synthesis of osteopontin is stimulated by calcitriol. Regulation of the osteopontin gene is incompletely understood.
Osteopontin gene might find clinical application in wound healing, bone turnover, tumorigenesis, inflammation, ischemia and immune responses, allergy and asthma ad immune disorders