Barrier function of the tight junction protein tricellulin

Abstract

Tricellulin is a tight junction protein localized in tricellular junctions (tTJ), the meeting points of three cells, but also in bicellular junctions (bTJ). The barrier function of tricellulin in bTJ and tTJ has been characterized by overexpression experiments in kidney tubule MDCK II cells. When expressed in the tTJ alone, tricellulin impeded the permability for macromolecules, while after expression in both, tTJ and bTJ, tricellulin impeded the permeability for macromolecules and also for ions. The surprising finding that in tTJ no changes in ion permeability occured is explained by the fact that tTJ central tubes are wide enough for macromolecular passage but too rare to contribute significantly to ion permeability. In conclusion, tricellulin forms a barrier against macromolecular passage in the tTJ and, if present there, also in the bTJ.