Abstract.
The plasma membrane of epithelial cells and hepatocytes is divided into two separate membrane compartments, the apical and the basolateral domain. This polarity is maintained by intracellular machinery that directs newly synthesized material into the correct target membrane. Apical protein sorting and trafficking require specific signals and different intracellular routes to the cell surface. Some of them depend on the integrity of sphingolipid/cholesterol-enriched membrane microdomains named ‘lipid rafts’, others use separate transport platforms. Certain characteristics of the heterogeneous population of apical sorting signals are described in this review and cellular factors associated with sorting and transport mechanisms are discussed.
Keywords. Epithelial cells, apical sorting, protein trafficking, cytoskeleton, transport vesicles, membrane fusion
Footnotes
Received 5 May 2006; received after revision 12 June 2006; accepted 11 July 2006