Occludin modulates transepithelial migration of neutrophils

Neutrophils cross epithelial sheets to reach inflamed mucosal surfaces by m igrating along the paracellular route, To avoid breakdown of the epithelial barrier, this process requires coordinated opening and closing of tight ju nctions, the most apical intercellular junctions in epithelia. To determine the function of epithelial tight junction proteins in this process, we ana lyzed neutrophil migration across monolayers formed by stably transfected e pithelial cells expressing wild-type and mutant occludin, a membrane protei n of tight junctions with four transmembrane domains and both termini in th e cytosol, We found that expression of mutants with a modified N-terminal c ytoplasmic domain up-regulated migration, whereas deletion of the C-termina l cytoplasmic domain did not have an effect, The N-terminal cytosolic domai n was also found to be important for the linear arrangement of occludin wit hin tight junctions but not for the permeability barrier. Moreover, express ion of mutant occludin bearing a mutation in one of the two extracellular d omains inhibited neutrophil migration. The effects of transfected occludin mutants on neutrophil migration did not correlate with their effects on sel ective paracellular permeability and transepithelial electrical resistance. Hence, specific domains and functional properties of occludin modulate tra nsepithelial migration of neutrophils.