35 Deficiency of the Planar Cell Polarity protein CELSR3 in CF bronchial epithelial cells increases susceptibility to epithelial–mesenchymal transition

Abstract

Objectives: Epithelial barrier function is impaired in CF airways as an indirect consequence of F508del-CFTR trafficking defect. The role of apico-basal polarity is crucial in the process but little is known about the influence of Planar Cell Polarity (PCP) which coordinates alignment of cell polarity across the tissue plane. Methods: Expression of several PCP proteins including atypical cadherin CELSR3 (Cadherin EGF LAG seven-pass G-type receptor 3) were quantified in normal and CF primary human bronchial epithelial (HBE) cells and HBE cell lines. To characterize the role of CELSR3 in epithelial polarity, CELSR3, epithelial and mesenchymal markers expression were quantified after inducing epithelial– mesenchymal transition (EMT) in HBEs monolayers with TGFb or cisplatin. To determine if CELSR3, suspected to undergo homophilic interactions to establish cell–cell interactions, is a key determinant of epithelial barrier function, transepithelial electric resistance (TEER) was measured after silencing CELSR3 expression in 16HBEs. Results: HBEs expressed several PCP proteins, including CELSR3 for which expression was downregulated in CF-HBEs compared to non-CF cells. Both TGFb and cisplatin induced concomitant loss of CELSR3 and epithelial marker ZO-1 and gain of mesenchymal (i.e. profibrotic) markers vimentin and fibronectin. CELSR3 siRNA in 16HBE cells enhanced TGFb-induced EMT. However, CELSR3 siRNA did not modulate TEER, indicating that CELSR3 is an epithelial marker but not a direct determinant of intercellular junction tightness. Conclusion: CELSR3 is an epithelial marker down-regulated in CF-HBEs. Loss of CELSR3 function may confer a profibrotic phenotype to CF-HBEs cells.