Glycophospholipid membrane anchoring provides clues to the mechanism of protein sorting in polarized epithelial cells.

The sorting signals that guide proteins to apical and basolateral surfaces of epithelial cells have remained elusive. Current evidence suggests a hierarchy of sorting information with multiple sorting signals (apical and basolateral) present in different domains of a given plasma membrane protein. The observation that covalently attached glycosyl-phosphatidylinositol (GPI) acts as a 'dominant' apical targeting signal is compatible with the involvement of glycolipids in epithelial protein sorting.