Cell surface proteoglycan that bears heparan sulfate. May fulfill a function related to the motile behaviors of developing neurons. Interacts (via heparan sulfate) with PTN; this interaction promotes neurite outgrowth through binding of PTN with chondroitin sulfate of proteoglycans, thereby releasing PTPRS of chondroitin sulfate proteoglycans (CSPGs) and leading to binding with heparan sulfate of GPC2. Interacts (heparan sulfate chain) with MDK; this interaction is inhibited by heparin followed by chondroitin sulfate E; this interaction induces GPC2 clustering through heparan sulfate chain; this interaction induces neuronal cell adhesion and neurite outgrowth (PubMed:12084985). Nervous system. Widely and transiently expressed by immature neurons, appearing around the time of final mitosis and disappearing after cell migration and axon outgrowth have been completed. Belongs to the glypican family.