Work

Roles of protein–protein interactions and monolayer mechanics in tricellulin localization to tricellular tight junctions

Year: 2025

Type: article

Abstract: Tricellular tight junctions (tTJs) seal the space between three or more cells in epithelial monolayers. These specialized tight junctions have distinct protein components, including a transmembrane protein tricellulin. However, the mechanisms by which tricellulin localizes specifically to tTJs are incompletely understood. We demonstrate that tricellulin undergoes rapid lateral diffusion along bicellular junctions but is a very stable component of tTJs. BioID proteomics identified several proximity partners of tricellulin, and knockout studies on angulin-1/LSR, occludin and afadin provided evidence that these proteins control tricellulin accumulation to tTJs to different extents and mechanisms. Tricellulin localization was disrupted in afadin and angulin-1/LSR knockout cells, although these proteins did not display similar accumulation to tTJs, suggesting that they contribute to tricellulin localization through indirect or context-dependent mechanisms. Importantly, experiments on mixed cultures revealed that defects of tricellulin localization in occludin knockout cells were affected by the proximity of wild-type cells, and treatment of monolayers with myosin-II inhibitor resulted in displacement of tricellulin from tTJs. These results suggest that, in addition to protein-protein interactions, proper epithelial monolayer mechanics are essential for stabilizing tricellulin at tTJs.

Source: Biology Open

DOI: 10.1242/bio.061987