PRG4

The protein encoded by this gene is a large proteoglycan specifically synthesized by chondrocytes located at the surface of articular cartilage, and also by some synovial lining cells. This protein contains both chondroitin sulfate and keratan sulfate glycosaminoglycans. It functions as a boundary lubricant at the cartilage surface and contributes to the elastic absorption and energy dissipation of synovial fluid. Mutations in this gene result in camptodactyly-arthropathy-coxa vara-pericarditis syndrome. Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq]

proteoglycan 4

Plays a role in boundary lubrication within articulating joints. Prevents protein deposition onto cartilage from synovial fluid by controlling adhesion-dependent synovial growth and inhibiting the adhesion of synovial cells to the cartilage surface.
Isoform F plays a role as a growth factor acting on the primitive cells of both hematopoietic and endothelial cell lineages.

Immune responseIEA:InterPro

Secreted

Camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP):
An autosomal recessive disorder characterized by the association of congenital or early-onset camptodactyly and non-inflammatory arthropathy with synovial hyperplasia. Individuals with CACP have normal appearing joints at birth but with advancing age develop joint failure, non-inflammatory synoviocyte hyperplasia and subintimal fibrosis of the synovial capsule. Some patients also manifest progressive coxa vara deformity and/or non-inflammatory pericardial or pleural effusions.

N-glycosylated (PubMed:16335952).
O-glycosylated; contains glycosaminoglycan chondroitin sulfate and keratan sulfate. O-glycosylated with sialylated oligosaccharides which are predominantly represented by the monosialylated core type I structure, NeuNAcalpha2-3Galbeta1-3GalNAc, with smaller amounts of disialylated O-glycans (PubMed:25187573).
The disulfide bond between Cys-1146 and Cys-1403 is essential for protein cleavage.
Proteolytically cleaved by cathepsin CTSG.