Claudin‐4 interacts with the small GTPase Rap1 and accelerates epithelial repair

Abstract

Epithelial repair is a requirement for recovery in patients with acute lung injury. In human lungs rejected for transplantation, higher cldn4 levels are associated with preserved epithelial barrier function, but the role of claudins in epithelial repair is uncertain. To determine if claudin‐4 is important to epithelial repair, we examined claudin‐4 expression and function in two in vitro model of epithelial repair: scratch wounding and tight junction resealing after calcium depletion. In both models, epithelial disruption was followed by an induction of claudin‐4. The increase in claudin‐4 was dependent of EGFR as inhibition with AG1478 prevented the increase in claudin‐4. Knock down of claudin‐4 with siRNA resulted in delayed epithelial repair in both models. To determine the contribution of claudin‐4 to repair we used an immuoprecipitation and mass spectrometry approach to identify potential claudin‐4 interaction partners in primary rat type 2 cells and the human airway cell line 16HBE. In wounded epithelial monolayers the small GTPase Rap1 was identified and this association was confirmed with co‐immuoprecipitation. Because Rap1 is known to mediate cell junction maturation, adhesion, and cell spreading, we hypothesize that claudin‐4 interacts with Rap1 to accelerate epithelial repair potentially by recruiting Rap1 to tight junctions. Funded by NIH/NHLBI HL88440 and T32 HL007185