Recombinant Mouse COMP/Thrombospondin-5 (Catalog # 8958-CP) induces adhesion of ATDC5 mouse chondrogenic cells. The ED50 for this effect is 0.15-0.9 μg/mL.
Cartilage Oligomeric Matrix Protein (COMP), also known as Thrombospondin-5, is a 110 kDa multidomain calcium binding protein that associates with other extracellular matrix molecules. Thrombospondin-1 and -2 constitute subgroup A and form homotrimers, whereas Thrombospondin-3, -4, and COMP constitute subgroup B and form homopentamers (1-4). Mouse COMP contains a non-collagenous coiled-coil domain, four EGF-like repeats, eight TSP type-3 repeats, and a globular TSP C-terminal domain (5). It shares 92% and 98% aa sequence identity with human and rat COMP, respectively. The coiled coil domain mediates the association of COMP into disulfide-linked homopentamers with a central hub and peripheral globular domains connected by flexible strands (6, 7). An axial pore is formed by the coiled coil assembly and binds vitamin D3 which is involved in bone and cartilage metabolism (8). An RGD sequence in the third TSP type-3 repeat mediates chondrocyte attachment via Integrin alpha 5 beta 1, although when reduced and in the absence of calcium, attachment is mediated via Integrin alpha V beta 3 (9). COMP is up-regulated in rheumatoid arthritis and osteoarthritis, hepatocellular carcinomas, chronic pancreatitis, and pancreatic carcinomas (10-12). Elevated circulating COMP levels are used as a biomarker for early onset of some skeletal disorders (10). Several mutations are associated with skeletal dysplasias, and the most common, a point mutation in the third TSP type-3 repeat, results in diminished calcium binding ability (13, 14).
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