Glypicans [, ]are a group of heparan sulphate proteoglycans which are anchored to cell membranes by a glycosylphosphatidylinositol (GPI) linkage. Structurally, these proteins consist of three separate domains:a) A signal sequence;b) An extracellular domain of about 500 residues that contains 12 conserved cysteines probably involved in disulphide bonds and also contains the sites of attachment of the heparan sulphate glycosaminoglycan side chains;c) A C-terminal hydrophobic region that is post-translationally removed after formation of the GPI-anchor. Six members (GPC1-6) are known in vertebrates []. GPC3 encodes a putative extracellular proteoglycan, glypican 3 that is inferred to play an important role in growth control in embryonic mesodermal tissues in which it is selectively expressed. Initial western- and ligand-blotting experiments suggest that glypican 3 forms a complex with insulin-like growth factor 2 (IGF2), and might thereby modulate IGF2 action []. GPC3 gene defects in a wider range of overgrowth disorders []. GPC3 shares a number of features with the GPC1 [].
