Cell Biology

How Tight is Tight?

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Science  11 Apr 2003:
Vol. 300, Issue 5617, pp. 215-217
DOI: 10.1126/science.300.5617.215e

Epithelial cells in single (simple) and multiple (stratified) layers function as barriers that define internal fluid compartments, such as the intestine, or that protect the body from the external environment, such as the skin. The transcellular passage of small molecules across the lipid bilayer is facilitated by transport proteins. Similarly, the paracellular movement of ions is restricted by tight junctions, which appear as juxtaposed strands and consist primarily of the membrane protein claudin. By expressing a fluorescent claudin in fibroblasts, Sasaki et al. show that tight junction strands are dynamic structures that separate and come together even though the claudins within a strand appear to be stably associated. How the paracellular barrier is both maintained and regulated under these conditions will be of interest.—GJC

Proc. Natl. Acad. Sci. U.S.A.100, 3971 (2003).

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