Proteoglycans Classes Courses

Proteoglycans are specialized macromolecules found within cells, tissues and the extracellular matrix of all multicellular organisms, playing a critical role in a number of biological processes. Proteoglycans are composed of a protein core, to which one or more glycosaminoglycans (GAGs) are attached. Generally, proteoglycans are classified based on their GAG composition, which would indicate the manner in which the GAGs are joined to the protein core. While there is no universal classification system, GAG-linked proteoglycans can be generally classified into four major classes: lectican, symplecan, aggrecan, and syndecan. Lecticans are proteoglycans with two GAGs, chondroitin sulfate and dermatan sulfate, linked to the protein core at the same site. This type of proteoglycan is found in connective tissues of vertebrate animals, and are important in regulating cell adhesion and inflammation. Symplecans are similar to lecticans in that they have two GAGs, but they are bound at separate sites on the protein core. Symplecans provide a structure for cells and tissues, and are also involved in cell adhesion and signal transduction pathways. Aggrecan is a proteoglycan consisting of a single GAG molecule, chondroitin sulfate, bound to a core domain of the protein. Aggrecan is primarily found in the cartilage of vertebrates, where it provides mechanical protection and support to the joint and serves an important role in the inflammatory response. Finally, syndecans are a family of proteoglycans that have a single core protein and a variety of different GAGs bound at the same site on the protein. Syndecans are important in signal transduction, cell adhesion and the structure of the cell surface membrane.