osteopontin; bone sialoprotein 1; urinary stone protein; secreted phosphoprotein 1; nephropontin; uropontin (SPP1, BNSP, OPN)

Function

• multifunctional protein:
• principal phosphorylated glycoprotein of bone
  • binds tightly to hydroxyapatite
  • appears to form an integral part of the mineralized matrix
  • probably important to cell-matrix interaction
• acts as a cytokine involved in enhancing production of interferon-gamma & interleukin-12 & reducing production of interleukin-10 & is essential in the pathway that leads to cellular immunity (putative)
• ligand of CD44
• ligand of integrin alpha-V/beta-3
• extensively phosphorylated on clustered serine residues
  • phosphorylation sites are present in the extracellular medium

Structure

• N-glycosylated & O-glycosylated
• belongs to the osteopontin family

Compartment

• constituent of amorphous material within normal elastic fibers in human skin & aorta

Alternative splicing

named isoforms=4

Expression

• expressed in brain by:
  • microvascular endothelial cells
  • microglia
  • reactive astrocytes
  • neurons
• expression induced by hypoxia

Pathology

• abundant in plaques of multiple sclerosis
• urinary stone protein

More general terms

• glycoprotein
• phosphoprotein
• secreted protein

Additional terms

• CD44; phagocytic glycoprotein I; PGP-1; HUTCH-I; extracellular matrix receptor-III; ECMR-III; GP90 lymphocyte homing/adhesion receptor; Hermes antigen; hyaluronate receptor; heparan sulfate proteoglycan; epican; CDw44 (LHR, MDU2, MDU3, MIC4)

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=6696
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:6696
• OMIM: https://mirror.omim.org/entry/166490
• UniProt: http://www.uniprot.org/uniprot/P10451.html