Tricellulin constitutes a novel barrier at tricellular contacts of epithelial cells

TLDR

For epithelia to function as barriers, the intercellular space must be sealed; while bicellular tight junctions are well described by claudins, tricellular contacts remain weak points where three cells meet. The study identifies tricellulin as the first integral membrane protein concentrated at the vertically oriented tight junction strands of tricellular contacts. RNA interference suppression of tricellulin disrupted epithelial barrier integrity and disorganized tricellular contacts and bicellular tight junctions. These results demonstrate tricellulin’s essential role in forming the epithelial barrier.

Abstract

For epithelia to function as barriers, the intercellular space must be sealed. Sealing two adjacent cells at bicellular tight junctions (bTJs) is well described with the discovery of the claudins. Yet, there are still barrier weak points at tricellular contacts, where three cells join together. In this study, we identify tricellulin, the first integral membrane protein that is concentrated at the vertically oriented TJ strands of tricellular contacts. When tricellulin expression was suppressed with RNA interference, the epithelial barrier was compromised, and tricellular contacts and bTJs were disorganized. These findings indicate the critical function of tricellulin for formation of the epithelial barrier.