Paracellular channels!
Wong, V.; Goodenough, D.A.
Science 285(5424): 62
1999
ISSN/ISBN: 0036-8075 PMID: 10428705 Document Number: 511077
In this issue, D. B. Simon and colleagues present the first report of a tight junction protein involved in paracellular ion conductance. Resorption in the human kidneys depends both on transcellular pathways, by which molecules and ions needed by the body are taken back through the cell cytoplasm via selective pumps and cotransporters on epithelial cell plasma membranes, and paracellular pathways, by which the materials travel through the intercellular space between cells. The latter pathways are regulated by tight junctions, intercellular structures in which the plasma membranes of neighboring cells are in very close contact. These junctions encompass the entire apical boundary of each cell and can be visualized by freeze-fracture as linear arrays of membrane proteins, including occludin and members of the claudin protein family. The researchers report that a claudin protein, paracellin-1, regulates the paracellular transport of magnesium ions in the kidney tubule.