Heparan sulfate proteoglycans are complex molecules found on the cell surface and in the extracellular matrix. They consist of a core protein attached to long chains of heparan sulfate sugar molecules. These proteoglycans play a crucial role in cell signaling, cell adhesion, and tissue development. They interact with a variety of proteins, growth factors, and enzymes, helping to regulate processes such as cell growth, migration, and differentiation. Dysregulation of heparan sulfate proteoglycans has been linked to various diseases, including cancer, inflammation, and neurodegenerative disorders. Research in this area focuses on understanding the structure, function, and regulation of these molecules, as well as developing potential therapies targeting them.