What's new in tight junctions: a report on the 2002 ASCB Meeting, San Francisco, CA.

Abstract

Tight junctions (TJ) seal the apicolateral border of epithelial and endothelial cells, and control the diffusion of ions, molecules and cells through the space between cells (“barrier” function). Thus, TJ are responsible for the establishment and maintenance of compartments within organs, and allow epithelia to maintain ionic and molecular gradients crucial for a variety of important physiological processes, including sensation, absorption, secretion, and protection from pathogens. In addition, TJ define the border between apical and basolateral plasma membrane domains (“fence” function), and thus are a hallmark of polarized epithelial cells (Figure 1A and 1B). Despite their fundamental relevance in cell and tissue biology, vertebrate tight junctions have been out of the spotlight for many years, mostly because their molecular organization remained obscure. Not so now. We now know some three classes of transmembrane TJ proteins, and over 30 proteins associated with the cytoplasmic face of TJ, including proteins involved in scaffolding and signaling events, in the biogenesis of apico-basal polarity and in control of gene expression (Figure 1C). At the recent 42nd Annual Meeting of the American Society for Cell Biology (San Francisco, December 14–18, 2002), a Special Interest Subgroup Meeting entitled “Emerging Roles for the Tight Junction” was organized by James Anderson and Alan Fanning (University of North Carolina). The new results presented at this Subgroup Meeting, combined with those presented at Minisymposia and Poster Sessions, highlighted how TJ proteins play multiple roles in epithelial polarity and barrier function, signal transduction, scaffolding, human disease, and viral virulence.