Osteopontin (OPN), also known as bone sialoprotein I (BSP-1 or BNSP), early T-lymphocyte activation (ETA-1), secreted phosphoprotein 1 (SPP1), 2ar and Rickettsia resistance (Ric), is a human gene product,[1] which is also conserved in other species. Osteopontin is a SIBLING glycoprotein that was first identified in 1986 in osteoblasts.
The prefix of the word "osteo" indicates that the protein is expressed in bone, although it is also expressed in other tissues. The suffix "-pontin" is derived from "pons," the Latin word for bridge, and signifies osteopontin's role as a linking protein. Osteopontin is an extracellular structural protein and therefore an organic component of bone. Synonyms for this protein include sialoprotein I and 44K BPP (bone phosphoprotein).
Function: Binds tightly to hydroxyapatite. Appears to form an integral part of the mineralized matrix. Probably important to cell-matrix interaction
Function: Acts as a cytokine involved in enhancing production of interferon-gamma and interleukin-12 and reducing production of interleukin-10 and is essential in the pathway that leads to type I immunity (By similarity)