Cell surface heparan sulfate proteoglycans are composed of a membrane-associated protein core substituted with a variable number of heparan sulfate chains. Members of the glypican-related integral membrane proteoglycan family (GRIPS) contain a core protein anchored to the cytoplasmic membrane via a glycosyl phosphatidylinositol linkage. These proteins may play a role in the control of cell division and growth regulation.

The GPC4 gene is adjacent to the 3' end of GPC3 and may also play a role in Simpson-Golabi-Behmel syndrome.The deduced 556-amino acid GPC4 protein is 93.5% identical to mouse K-glypican. Northern blot analysis detected 2 GPC4 transcripts of 2.9 kb and 4.3 kb in most human fetal and adult tissues tested.