Lipid Transport from the Golgi to the Plasma Membrane of Epithelial Cells
The two plasma membrane domains of epithelial cells display unique protein and lipid compositions. The general feature of the lipid polarity appears to be an enrichment of glycosphingolipids on the apical, and of the phospholipid phosphatidylcholine, PC, on the basolateral surface. The difference is maintained by the tight junctions, the zone of cell-cell contacts that encircles the apex of each epithelial cell. This structure acts as a barrier to lipid diffusion in the outer leaflet of the plasma membrane (van Meer, 1989b). The differences in lipid composition must therefore reside in the outer leaflets of the apical and basolateral plasma membrane domain. While the compositional differences appear to be generated by sorting of newly synthesized lipids before they reach the cell surface, lipid sorting along the transcytotic route would also seem necessary to prevent lipid intermixing by that pathway.
KeywordsCholesterol Permeability Hydroxyl Luminal Galactose
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