Intracellular transport of GPI-anchored proteins

In eukaryotic cells, a subset of proteins are attached to the external leaf let of the plasma membrane by a glycosylphosphatidylinositol (GPI) anchor. There is substantial evidence suggesting that these GPI-anchored proteins a re clustered in sphingolipid-sterol microdomains or rafts. Since the precur sors of these microdomain components are synthesized mainly in the endoplas mic reticulum, it is possible that microdomain assembly occurs during trans port along the exocytic route. A sorting mechanism for GPI-anchored protein s using sphingolipid microdomains as selective platforms for vesicle buddin g has been proposed to operate at different steps in the secretory pathway. Here, we discuss this sorting model in the context of the data obtained fr om different biological and artificial systems, in addition to other partic ularities of the intracellular transport of the GPI-anchored proteins.