Cell Biology

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Science  03 Aug 2007:
Vol. 317, Issue 5838, pp. 572-573
DOI: 10.1126/science.317.5838.572d

Epithelial cells provide a barrier function in tissues by establishing and maintaining a distinctive polarity with an apical surface that faces the lumen of the tissue and a basolateral surface that faces the blood. The maintenance of the two distinct membrane domains has been studied in great detail for many years, but how the polarity originates is much less clear. Nejsum and Nelson examined this process as epithelial cells in tissue culture generated a polarized cell layer and determined whether cell-cell adhesion and the generation of distinct membrane domains were linked. By looking at fluorescently tagged versions of two similar proteins, aquaporins 3 and 5, one of which (AQP3) is basolateral, the other (AQP5) apical, while simultaneously monitoring a component of the cell adhesion machinery, E-cadherin, they observed a precise correlation between the basolateral membrane protein and newly formed cell adhesions. It seems that during the establishment of polarity, newly synthesized basolateral membrane proteins leave the Golgi complex in vesicles that are specifically targeted to and fuse with the growing sites of cell adhesion, which are enriched for the docking and fusion machinery involved in basolateral membrane protein targeting. — SMH

J. Cell Biol. 178, 323 (2007).

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