The role of Cdc42 Rho GTPase in the cystic fibrosis intestinal epithelial barrier
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Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. People with CF and CF mouse models experience increased intestinal permeability, but the molecular mechanisms linking CFTR dysfunction with intestinal barrier dysfunction are not well understood. Previously, we demonstrated that intracellular pH (pHi) is increased in Cftr KO mouse intestinal epithelium compared to wild-type (WT). Loss of Cftr-mediated Cl- and HCO3- conductance increased pHi and Dishevelled (Dvl)-mediated Wnt/β-catenin signaling and intestinal stem cell proliferation. Dvl also transduces the noncanonical Wnt/planar cell polarity (PCP) signaling pathway to activate the Rho GTPases RhoA, Rac1, and Cdc42 to regulate the cytoskeleton and tight junction remodeling during cell proliferation and migration. We hypothesized that Dvl-mediated transduction of the Wnt/PCP pathway in CF would lead to increased tight junction remodeling and paracellular permeability. In this study, we show that Cftr KO mouse enteroids have increased paracellular permeability in vitro, but not CFTR KO Caco-2 monolayers when compared to WT. Regardless, Cdc42 activity is increased in CF to maintain barrier function in the hyperproliferative CF intestinal epithelium.
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Ph. D.