Chondroitin sulfate proteoglycan
Chondroitin sulfate proteoglycans (CSPGs) are proteoglycans consisting of a protein core and a chondroitin sulfate side chain. They are known to be structural components of a variety of human tissues, including cartilage, and also play key roles in neural development and glial scar formation. They are known to be involved in certain cell processes, such as cell adhesion, cell growth, receptor binding, cell migration, and interaction with other extracellular matrix constituents. They are also known to interact with laminin, fibronectin, tenascin, and collagen. CSPGs are generally secreted from cells. Importantly, CSPGs are known to inhibit axon regeneration after spinal cord injury. CSPGs contribute to glial scar formation post injury, acting as a barrier against new axons growing into the injury site. CSPGs play a crucial role in explaining why the spinal cord doesn't self-regenerate after an injury. Chondroitin sulfate proteoglycans are composed of a core protein and a sugar side chain. The core protein is generally a glycoprotein, and the side chains are glycosaminoglycan (GAG) sugar chains attached through a covalent bond. The GAG side chains are of different lengths depending on the CSPG. Each GAG chain consists of a linear pattern of alternating monosaccharide units: uronic acid and either N-acetylglucosamine or N-acetylgalactosamine. The following CSPGs have been identified: Aggrecan (CSPG1) Versican (CSPG2) Neurocan (CSPG3) CSPG4 (melanoma-associated chondroitin sulfate proteoglycan, NG2) CSPG5 SMC3 (CSPG6, structural maintenance of chromosomes 3) Brevican (CSPG7) CD44 (CSPG8, cluster of differentiation 44) Phosphacan Neurocan, brevican, versican, and aggrecan all share similar N-terminal and C-terminal domains. CSPGs play an active role in the neural development of postnatal babies. During development, CSPGs act as guidance cues for developing growth cones. CSPGs guide growth cones through the use of negative signals, as seen by the fact that growing axons avoid CSPG dense areas.
