Nanotopography Enhances Dynamic Remodeling of Tight Junction Proteins through Cytosolic Liquid Complexes

Nanotopographic materials provide special biophysical stimuli that can regulate epithelial tight junctions and their barrier function. Through the use of total internal reflection fluorescence microscopy of live cells, we demonstrated that contact of synthetic surfaces with defined nanotopography at the apical surface of epithelial monolayers increased paracellular permeability of macromolecules. To monitor changes in tight junction morphology in live cells, we fluorescently tagged the scaffold protein zonula occludens-1 (ZO-1) through CRISPR/Cas9-based gene editing to enable live cell tracking of ZO-1 expressed at physiologic levels. Contact between cells and nanostructured surfaces destabilized junction-associated ZO-1 and promoted its arrangement into highly dynamic liquid cytosolic complexes with a 1-5 μm diameter. Junction-associated ZO-1 rapidly remodeled, and we observed the direct transformation of cytosolic complexes into junction-like structures. Claudin-family tight junction transmembrane proteins and F-actin also were associated with these ZO-1 containing cytosolic complexes. These data suggest that these cytosolic structures are important intermediates formed in response to nanotopographic cues that facilitate rapid tight junction remodeling in order to regulate paracellular permeability.