Proteoglykanen

Proteoglykanen, in English known as proteoglycans, are a family of glycoproteins composed of a core protein covalently attached to one or more glycosaminoglycan (GAG) chains. They are major components of the extracellular matrix and cell surfaces in animals. They are distinguished from many glycoproteins by their high content of sulfated GAGs and a generally negative charge, which attracts water and ions.

GAG chains, such as chondroitin sulfate, dermatan sulfate, heparan sulfate, and keratan sulfate, are long, unbranched polysaccharides. They attach to specific serine residues on the core protein via a common tetrasaccharide linker formed in the Golgi apparatus. Proteoglycans may be secreted into the extracellular matrix or anchored to the cell surface as membrane proteoglycans. The sulfation patterns of GAGs create diverse interactions with proteins and ions, influencing binding properties and signaling.

In tissues, proteoglycans interact with collagen, hyaluronan, and other matrix components to form hydrated gels that resist compression and regulate molecular diffusion. Examples include aggrecan in cartilage and perlecan in basement membranes. Proteoglycans also bind growth factors and chemokines, modulating signaling and sometimes acting as co-receptors, thereby shaping cell behavior during development, wound healing, and tissue homeostasis.

Abnormal proteoglycan metabolism is linked to diseases such as mucopolysaccharidoses, osteoarthritis, and certain cancers. Therapeutic strategies focus on ECM remodeling and enzyme-based approaches, while proteoglycans are widely used in tissue engineering and regenerative medicine to tailor matrix properties.