title: Protein kinase D promotes airway epithelial barrier dysfunction and permeability through down-regulation of claudin-1.
abstract: At the interface between host and external environment, the airway epithelium serves as a major protective barrier. In the present study we show that protein kinase D (PKD) plays an important role in the formation and integrity of the airway epithelial barrier. Either inhibition of PKD activity or silencing of PKD increased transepithelial electrical resistance (TEER), resulting in a tighter epithelial barrier. Among the three PKD isoforms, PKD3 knockdown was the most efficient one to increase TEER in polarized airway epithelial monolayers. In contrast, overexpression of PKD3 wild type, but not PKD3 kinase-inactive mutant, disrupted the formation of apical intercellular junctions and their reassembly, impaired the development of TEER, and increased paracellular permeability to sodium fluorescein in airway epithelial monolayers. We further found that overexpression of PKD, in particular PKD3, markedly suppressed the mRNA and protein levels of claudin-1 but had only minor effects on the expression of other tight junctional proteins (claudin-3, claudin-4, claudin-5, occludin, and ZO-1) and adherent junctional proteins (E-cadherin and β-catenin). Immunofluorescence study revealed that claudin-1 level was markedly reduced and almost disappeared from intercellular contacts in PKD3-overexpressed epithelial monolayers and that claudin-4 was also restricted from intercellular contacts and tended to accumulate in the cell cytosolic compartments. Last, we found that claudin-1 knockdown prevented TEER elevation by PKD inhibition or silencing in airway epithelial monolayers. These novel findings indicate that PKD negatively regulates human airway epithelial barrier formation and integrity through down-regulation of claudin-1, which is a key component of tight junctions.
authors.affiliation: From the Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas 75708 and.
authors.forename: Huachen
authors.initials: H
authors.lastname: Gan
authors.forename: Guibo
authors.initials: G
authors.lastname: Wang
authors.forename: Qin
authors.initials: Q
authors.lastname: Hao
authors.forename: Q Jane
authors.initials: QJ
authors.lastname: Wang
authors.forename: Hua
authors.initials: H
authors.lastname: Tang
mesh_terms: D015824:Blood-Air Barrier / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D062445:Claudin-1 / Q000096:biosynthesis* / Q000235:genetics; D015536:Down-Regulation; D017097:Electric Impedance; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D055785:Gene Knockdown Techniques; D006801:Humans; D010539:Permeability; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020545:Respiratory Mucosa / Q000378:metabolism* / Q000473:pathology; D019108:Tight Junctions / Q000235:genetics / Q000378:metabolism* / Q000473:pathology
chemical_list: C568108:CLDN1 protein, human; D062445:Claudin-1; D012333:RNA, Messenger; C089212:protein kinase D; D011493:Protein Kinase C
keywords: Cell Junctions; Claudin-1; Epithelial Cell; Permeability; Protein Kinase D (PKD); Tight Junctions