proteoglykaanin

Proteoglykanin, also referred to as proteoglycan, is a type of molecule in which a core protein is covalently attached to one or more glycosaminoglycan (GAG) chains. These highly hydrated, negatively charged macromolecules are major components of the extracellular matrix and, in some cases, of the cell surface and basement membranes. The combination of a protein core with long GAG chains enables proteoglykanin to fill spaces in tissues, resist compression, and interact with a variety of signaling molecules.

The structure of proteoglykanin features a core protein to which one or more GAG chains are linked through a tetrasaccharide linker attached to specific serine residues. GAGs such as chondroitin sulfate, dermatan sulfate, heparan sulfate, keratan sulfate, and hyaluronic acid contribute to size, charge, and binding properties. Hyaluronic acid is not typically covalently bound to the core protein; instead, it forms large aggregates with certain proteoglykanin through link proteins and other interacting proteins. The sulfation pattern and chain length of GAGs determine the functional interactions of the molecule.

Biosynthesis occurs in the secretory pathway, with core proteins synthesized in the endoplasmic reticulum and modified in the Golgi apparatus. The resulting proteoglykanin can be secreted into the extracellular space or presented on the cell surface. In the extracellular matrix, proteoglykanin contribute to tissue hydration, elasticity, and the formation of a permeable gel that can trap growth factors, cytokines, and other bioactive molecules, thereby influencing cell behavior and tissue development.

Proteoglykanin are commonly classified into groups such as small leucine-rich proteoglycans (e.g., decorin, biglycan), large aggregating proteoglycans (e.g., aggrecan, versican), basement membrane proteoglycans (e.g., perlecan, agrin), and cell surface proteoglycans (e.g., syndecans, glypicans). Alterations in proteoglykanin structure or metabolism are linked to diseases including mucopolysaccharidoses, osteoarthritis, cancer progression, and inflammatory conditions, making them a focus of basic and clinical research.