Cartilage oligomeric matrix protein

Cartilage oligomeric matrix protein (also known as COMP) is a protein that in humans is encoded by the COMP gene. COMP is a non-collagenous extracellular matrix (ECM) protein and is a prominent component of the cartilage ECM. It is part of the thrombospondin family and is known to interact with other ECM proteins such as collagen and fibronectin.

Structure

COMP is a pentameric glycoprotein with a molecular mass of approximately 524 kDa. Each subunit of the COMP protein is composed of four distinct domains: a N-terminal domain, four type II thrombospondin repeats, eight type III thrombospondin repeats, and a C-terminal domain. The type II and type III repeats are known to mediate protein-protein interactions.

Function

The primary function of COMP is to maintain the structural integrity of the cartilage by interacting with other ECM proteins. It has a high binding affinity for collagen type II and collagen type IX, which are the major collagens present in the cartilage. COMP also binds to other ECM proteins such as fibronectin and matrilin-3, facilitating the formation of a stable, interconnected ECM network.

Clinical significance

Mutations in the COMP gene are associated with several skeletal disorders, including pseudoachondroplasia and multiple epiphyseal dysplasia. These disorders are characterized by short stature and early-onset osteoarthritis. In addition, elevated levels of COMP have been found in the synovial fluid of patients with rheumatoid arthritis and osteoarthritis, suggesting that COMP may be involved in the pathogenesis of these diseases.

See also

• Extracellular matrix
• Thrombospondin
• Collagen
• Fibronectin
• Pseudoachondroplasia
• Multiple epiphyseal dysplasia