THBS5

THBS5, also known as thrombospondin-5 or cartilage oligomeric matrix protein (COMP), is a secreted extracellular matrix glycoprotein and a member of the thrombospondin family.

The THBS5 gene encodes COMP, a protein predominantly produced by chondrocytes and other cells of the skeletal system. It is abundantly expressed in cartilage and also present in tendon, ligament, and synovial tissue, where it is incorporated into the extracellular matrix.

COMP is secreted as a homopentamer and functions within the ECM through multiple binding modules that mediate interactions with collagen and proteoglycans.

In cartilage and bone, COMP participates in collagen fibrillogenesis and matrix assembly, helping to organize the extracellular matrix and supporting tissue integrity. It also participates in cell–matrix signaling and may influence chondrocyte behavior.

Mutations in THBS5 cause skeletal dysplasias such as pseudoachondroplasia and multiple epiphyseal dysplasia, disorders marked by abnormal joint development and early osteoarthritis. Serum COMP levels are elevated in cartilage damage and are studied as a biomarker for osteoarthritis and related conditions. Other tissues may show altered COMP expression in disease, and research continues to clarify COMP's roles.