Gene Summary: The protein encoded by COMP this gene is a noncollagenous extracellular matrix (ECM) protein. Cartilage Oligomeric Matrix Protein (COMP) consists of five identical glycoprotein subunits, each with EGF-like and calcium-binding (thrombospondin-like) domains. Oligomerization results from formation of a five-stranded coiled coil and disulfides. Binding to other ECM proteins such as collagen appears to depend on divalent cations. Mutations can cause the osteochondrodysplasias pseudochondroplasia (PSACH) and multiple epiphyseal dysplasia (MED).General information above from NCBI
Cofactor: Binds 11-14 calcium ions per subunit.
Subunit structure: Pentamer; disulfide-linked. Exists in a more compact conformation in the presence of calcium and shows a more extended conformation in the absence of calcium. Interacts with ITGB3, ITGA5 and FN1. Binding to FN1 requires the presence of divalent cations (Ca(2+), Mg(2+) or Mn(2+)). The greatest amount of binding is seen in the presence of Mn(2+). Interacts with MATN1, MATN3, MATN4 and ACAN. Binds heparin, heparan sulfate and chondroitin sulfate. EDTA dimishes significantly its binding to ACAN and abolishes its binding to MATN3, MATN4 and chondroitin sulfate. Interacts with collagen I, II and IX, and interaction with these collagens is dependent on the presence of zinc ions. Interacts with ADAMTS12. Interacts with ITGA7 (By similarity).
Domain: The cell attachment motif mediates the attachment to chondrocytes. It mediates the induction of both the IAP family of survival proteins and the antiapoptotic response.
The TSP C-terminal domain mediates interaction with FN1 and ACAN.
Each of the eight TSP type-3 repeats binds two calcium ions. The TSP C-terminal domain binds three calcium ions.
Subcellular location: Secreted, extracellular space, extracellular matrix.
Tissue specificity: Abundantly expressed in the chondrocyte extracellular matrix, and is also found in bone, tendon, ligament and synovium and blood vessels. Increased amounts are produced during late stages of osteoarthritis in the area adjacent to the main defect.
Developmental stage: Present during the earliest stages of limb maturation and is later found in regions where the joints develop.
Involvement in disease: Multiple epiphyseal dysplasia 1 (EDM1) [MIM:132400]: A generalized skeletal dysplasia associated with significant morbidity. Joint pain, joint deformity, waddling gait, and short stature are the main clinical signs and symptoms. Radiological examination of the skeleton shows delayed, irregular mineralization of the epiphyseal ossification centers and of the centers of the carpal and tarsal bones. Multiple epiphyseal dysplasia is broadly categorized into the more severe Fairbank and the milder Ribbing types. The Fairbank type is characterized by shortness of stature, short and stubby fingers, small epiphyses in several joints, including the knee, ankle, hand, and hip. The Ribbing type is confined predominantly to the hip joints and is characterized by hands that are normal and stature that is normal or near-normal. Note=The disease is caused by mutations affecting the gene represented in this entry.
Pseudoachondroplasia (PSACH) [MIM:177170]: A skeletal dysplasia usually manifesting in the second year of life and characterized by moderate to severe disproportionate short stature, deformity of the lower limbs, brachydactyly, ligamentous laxity, and degenerative joint disease. Note=The disease is caused by mutations affecting the gene represented in this entry.
Sequence similarity: Belongs to the thrombospondin family.
Contains 4 EGF-like domains.
Contains 1 TSP C-terminal (TSPC) domain.
Contains 8 TSP type-3 repeats.
General information above from UniProt