Clathrin-mediated endocytosis regulates occludin, and not focal adhesion, distribution during epithelial wound healing

BACKGROUND: Vesicle trafficking has long been suggested to play mechanistic roles in regulating directed cell migration. Recent evidence demonstrates that specific cell types and modes of migration involve transport of particular cargo through particular pathways. Epithelial wound healing is essential to tissue repair. However, investigations into the mechanisms regulating cell migration have mainly focused upon other models, such as fibroblast derived cells. Roles for vesicle trafficking pathways in regulating directed cell migration have been identified in recent studies, but mechanisms through which endocytosis might be involved in epithelial wound healing have not been as well studied. Therefore we analysed potential regulatory roles for endocytosis pathways during epithelial cell motility, with a particular focus on cell adhesion. RESULTS: Specifically, and in contrast to studies in fibroblasts, we find no evidence for a link between endocytosis and the distribution of focal adhesions. However, the localisation of occludin, an essential component of tight junctions is regulated through endocytosis. We identified epithelial monolayer wounding as a stimulus for endocytosis of occludin and have shown that internalisation of occludin from the wound edge occurs through clathrin-mediated endocytosis into a rab5 positive compartment. CONCLUSIONS: Thus, these studies have evaluated mechanistic roles for dynamin-dependant, clathrin-mediated and caveolar endocytosis during epithelial wound healing, and have provided contrasting observations between analyses of cell motility in fibroblast models and epithelial cells. In conclusion these studies have identified a novel mechanism for regulation of occludin during wound healing.