PRG4
Function
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.
Involvement in disease
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.
None
The disease is caused by variants affecting the gene represented in this entry.
Post-translational modifications
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.
Tissue Specificity
Highly expressed in synovial tissue, cartilage and liver and weakly in heart and lung. Isoform B is expressed in kidney, lung, liver, heart and brain. Isoform C and isoform D are widely expressed.
Cellular localization
- Secreted
Alternative names
MSF, SZP, PRG4, Proteoglycan 4, Lubricin, Megakaryocyte-stimulating factor, Superficial zone proteoglycan