Apical integrins as a switchable target to regulate the epithelial barrier.

Tight junctions regulate epithelial barrier function and have been shown to be influenced by multiple classes of proteins. Apical integrins have been identified as potential regulators of epithelial barrier function, however, only indirect approaches have been used to measure integrin regulation of the epithelial barrier. Here, we used polymeric nanowires conjugated with anti-integrin β1 antibodies to specifically target apically localized integrins in either their closed or open conformation. Barrier regulation by apical integrins was found to be conformation specific. Nanowires targeting integrins in the closed conformation increased epithelial permeability and caused zonula occludens-1 (ZO-1) to change from a linear to a ruffled morphology. Claudin-2 and claudin-4 co-localized with ZO-1 and also was ruffled, however, claudin-1 and claudin-7 remained linear. Ruffling was myosin light chain (MLCK) and rho kinase (ROCK) dependent. Conversely, targeting integrins in the open conformation decreased epithelial permeability and made junctions more linearized. Anti-integrin β1 nanowires differentially affected actin and talin, depending on whether they contained activating or inhibitory antibodies. Thus, apical integrins can act as a conformation sensitive switch that regulates epithelial barrier function.