Cartilage oligomeric matrix protein (COMP, thrombospondin-5) is a 524-kDa pentameric glycoprotein expressed primarily in cartilage, tendon, ligament and synovium. In adult cartilage, COMP has been shown to be located primarily in the inter-territorial matrix between chondrocytes (Murphy et al. 1999). The mature protein is pentameric with each monomer linked to its neighbour by a disulphide bond, located at the amino terminus of the protein (Hedbom et al. 1992, Morgelin et al. 1992).
COMP binds integrin alpha5beta1 (Chen et al. 2005), integrin alphaVbeta3 (Neidhart et al.2005) and CD47 (also known as integrin-associated peptide or IAP, Rock et al. 2010) on the cell surface of chondrocytes and fibroblasts.