Discovery
Osteopontin (OPN) is a highly phosphorylated glycoprotein
consisting of approximately 314 aa. It was first
identified in 1985 by Franzen and Heinegård as sialoprotein
isolated from bovine bone matrix.
Properties
A unit of mass of nascent OPN is 33kDa in humans
and 32kDa in mice.It is expressed as a sequence of about
300 aa (305 in zebrafish, 264 in chickens, 294 in mice, 314
in humans). However, the apparent molecular weight of
OPN according to SDS-PAGE can range from 45 to
75kDa because of posttranslational modifications such
as O-linked glycosylation, tyrosine sulfation and sialylation,
and multiple Ser/Thr phosphorylations. Those modifications
vary according to the cellular origin of OPN and
greatly affect the function of the protein.4 Basal pI 4.37. Soluble
in water. Stable in 1xPBS at 4°C within 2–4weeks.
Clinical implications
Increased OPN secretion has been correlated with cell
proliferation in various malignancies, including breast
and prostate cancer, squamous cell carcinoma, melanoma,
osteosarcoma, and glioblastoma.
Regulation of synthesis and release
OPN is constitutively expressed in many cells but is
upregulated under various conditions, particularly in
inflammation and cancer progression. The following
variants of growth factors and cytokines (including LPS,
NO, Ang II, IL-1b, IL-2, IL-3, IFN-γ, TNF-α, TGF-β) have
been reported to upregulate OPN expression.
Uses
OPN produced by tumor cells is structurally different
compared to that produced by normal cells. Therefore, it
has been reported that blocking the production of OPN
by using antibodies or synthetic peptides that recognize
specific epitopes of tumor-derived OPN may block cell
proliferation.
Uses
For research use only. Not for use in diagnostic procedures.
Please refer to the attached General ELISA KIT
Procedure (sandwich, competitive & Indirect ELISA)
General Description
The Human OPN ELISA (Enzyme-Linked Immunosorbent Assay) kit is an in vitro enzyme-linked immunosorbent assay for the quantitative measurement of human OPN in serum, plasma, cell culture supernatants and urine.
Biochem/physiol Actions
Osteopontin (OPN) is a secreted glycoprotein and is assumed to be associated with various cellular processes such as adhesion, migration, and biomineralization in diverse tissues. Osteopontin acts as a ligand to αvβ3 integrin and possibly other receptors. In addition to its involvement in mineralized matrix formation, osteopontin can also function as a cytokine that stimulates the release of IFNγ (interferon γ) and IL-12 (interleukin 12), while inhibiting the production of IL-10. Osteopontin is involved in inflammation and also regulates immunity against infectious diseases. It also co-stimulates T cell proliferation. Osteopontin has proinflammatory functions and is associated with multiple sclerosis. It participates in inflammation in Crohn′s Disease. Osteopontin plays a crucial role in bone remodelling and retards ectopic calcification by inhibiting the formation of hydroxyapatite. OPN is thought to prevent renal stone formation by suppressing nucleation, growth and aggregation of calcium oxalate crystals.
