Protocadherin-1 Localization and Cell-Adhesion Function in Airway Epithelial Cells in Asthma.

Grissel Faura Tellez,Susan Nijboer-Brinksma,Brigitte W M Willemse,John W Holloway,Natalie P Smithers,Martijn C Nawijn,Karl Vandepoele,Wim Timens,Maaike De Vries,Dirkje S Postma,Jacobien A Noordhoek,Gerard H Koppelman,Uilke Brouwer,Frans Van Roy,Irene Heijink,Peter M Lackie,Laura Wiffen

doi:10.1371/journal.pone.0163967

Abstract

BackgroundThe asthma gene PCDH1 encodes Protocadherin-1, a putative adhesion molecule of unknown function expressed in the airway epithelium. Here, we characterize the localization, differential expression, homotypic adhesion specificity and function of PCDH1 in airway epithelial cells in asthma.MethodsWe performed confocal fluorescence microscopy to determine subcellular localization of PCDH1 in 16HBE cells and primary bronchial epithelial cells (PBECs) grown at air-liquid interface. Next, to compare PCDH1 expression and localization in asthma and controls we performed qRT-PCR and fluorescence microscopy in PBECs and immunohistochemistry on airway wall biopsies. We examined homotypic adhesion specificity of HEK293T clones overexpressing fluorescently tagged-PCDH1 isoforms. Finally, to evaluate the role for PCDH1 in epithelial barrier formation and repair, we performed siRNA knockdown-studies and measured epithelial resistance.ResultsPCDH1 localized to the cell membrane at cell-cell contact sites, baso-lateral to adherens junctions, with increasing expression during epithelial differentiation. No differences in gene expression or localization of PCDH1 isoforms expressing the extracellular domain were observed in either PBECs or airway wall biopsies between asthma patients and controls. Overexpression of PCDH1 mediated homotypic interaction, whereas downregulation of PCDH1 reduced epithelial barrier formation, and impaired repair after wounding.ConclusionsIn conclusion, PCDH1 is localized to the cell membrane of bronchial epithelial cells baso-lateral to the adherens junction. Expression of PCDH1 is not reduced nor delocalized in asthma even though PCDH1 contributes to homotypic adhesion, epithelial barrier formation and repair.

Highlights

In 2009, our group identified Protocadherin 1 (PCDH1) as a susceptibility gene for bronchial hyperresponsiveness (BHR) and asthma [1]
PCDH1 localized to the cell membrane at cell-cell contact sites, baso-lateral to adherens junctions, with increasing expression during epithelial differentiation
PCDH1 is localized to the cell membrane of bronchial epithelial cells basolateral to the adherens junction

Summary

Introduction

In 2009, our group identified Protocadherin 1 (PCDH1) as a susceptibility gene for bronchial hyperresponsiveness (BHR) and asthma [1]. Since different PCDH1 gene variants were associated with specific asthma phenotypes including BHR positive [1], early onset [4], and non-allergic asthma [3], we proposed that PCDH1 may contribute to disease pathogenesis in subgroups of asthma patients [5]. We identified a shorter third isoform which lacks the extracellular domain yet contains the intracellular tail and hypothesized that this isoform 3 may act as a signaling molecule. Kozu et al found that siRNA silencing of PCDH1 increased epithelial permeability in 16HBE cells suggesting that PCDH1 is important for the physical barrier of the airway epithelium [9]. The asthma gene PCDH1 encodes Protocadherin-1, a putative adhesion molecule of unknown function expressed in the airway epithelium. We characterize the localization, differential expression, homotypic adhesion specificity and function of PCDH1 in airway epithelial cells in asthma

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