At least 150 human proteins are glycosylphosphatidylinositol-anchored proteins (GPI-APs).The protein moiety of GPI-APs lacking transmembrane domains is anchored to the plasma membrane with GPI covalently attached to the C-terminus.The GPI consists of the conserved core glycan, phosphatidylinositol and glycan side chains.The entire GPI-AP is anchored to the outer leaflet of the lipid bilayer by insertion of fatty chains of phosphatidylinositol.
Because of GPI-dependent membrane anchoring, GPI-APs have some unique characteristics.The most prominent feature of GPI-APs chrome cologne set is their association with membrane microdomains or membrane rafts.In the polarized cells such as epithelial cells, many GPI-APs are exclusively expressed in the apical surfaces, whereas some GPI-APs are preferentially expressed in the basolateral surfaces.Several GPI-APs act as transcytotic transporters carrying their ligands from one compartment to another.
Some GPI-APs are shed from the membrane after cleavage within the GPI by a GPI-specific phospholipase or happy camper dog shirt a glycosidase.In this review, I will summarize the current understanding of GPI-AP biosynthesis in mammalian cells and discuss examples of GPI-dependent functions of mammalian GPI-APs.