Glypicans - A Brief Review

Glypicans (GPCs) are a family of proteoglycans that are bound to the cell surface by a glycosyl-phosphatidylinositol anchor. Six glypicans have been found in the mammalian genome (GPC1 to GPC6). Glypicans can be released from the cell surface by a lipase called Notum, and most of them are subjected to endoproteolytic cleavage by furin-like convertases. In vivo evidence published so far indicates that the main function of membrane-attached glypicans is to regulate the signaling of Wnts, Hedgehogs, fibroblast growth factors and bone morphogenetic proteins (BMPs). Surprisingly, the regulatory activity of glypicans in the Wnt, Hedgehog and BMP signaling pathways is only partially dependent on the heparan sulfate chains. It is obvious that our knowledge of glypican functions is still very limited despite the recent advances. A better understanding of these functions will make a significant contribution to the study of signaling pathways that play a very important role in developmental morphogenesis and several human diseases, including cancer.