title: Interplay between RAGE, CD44, and focal adhesion molecules in epithelial-mesenchymal transition of alveolar epithelial cells.
abstract: Fibrosis of the lung is characterized by the accumulation of myofibroblasts, a key mediator in the fibrogenic reaction. Cumulative evidence indicates that epithelial-mesenchymal transition (EMT), a process whereby epithelial cells become mesenchyme-like, is an important contributing source for the myofibroblast population. Underlying this phenotypical change is a dramatic alteration in cellular structure. The receptor for advanced glycation end-products (RAGE) has been suggested to maintain lung homeostasis by mediating cell adhesion, while the family of ezrin/radixin/moesin (ERM) proteins, on the other hand, serve as an important cross-linker between the plasma membrane and cytoskeleton. In the present investigation, we tested the hypothesis that RAGE and ERM interact and play a key role in regulating EMT-associated structural changes in alveolar epithelial cells. Exposure of A549 cells to inflammatory cytokines resulted in phosphorylation and redistribution of ERM to the cell periphery and localization with EMT-related actin stress fibers. Simultaneously, blockade of Rho kinase (ROCK) signaling attenuated these cytokine-induced structural changes. Additionally, RAGE expression was diminished after cytokine stimulation, with release of its soluble isoform via a matrix metalloproteinase (MMP)-9-dependent mechanism. Immunofluorescence microscopy and coimmunoprecipitation revealed association between ERM and RAGE under basal conditions, which was disrupted when challenged with inflammatory cytokines, as ERM in its activated state complexed with membrane-linked CD44. Dual-fluorescence immunohistochemistry of patient idiopathic pulmonary fibrosis (IPF) tissues highlighted marked diminution of RAGE in fibrotic samples, together with enhanced levels of CD44 and double-positive cells for CD44 and phospho (p)ERM. These data suggest that dysregulation of the ERM-RAGE complex might be an important step in rearrangement of the actin cytoskeleton during proinflammatory cytokine-induced EMT of human alveolar epithelial cells.
authors.affiliation: School of Pharmacy and Pharmaceutical Sciences, Trinity College Dublin, Dublin, Ireland.
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Buckley
authors.forename: Carlos
authors.initials: C
authors.lastname: Medina
authors.forename: Michael
authors.initials: M
authors.lastname: Kasper
authors.forename: Carsten
authors.initials: C
authors.lastname: Ehrhardt
mesh_terms: D000199:Actins / Q000378:metabolism; D056809:Alveolar Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D045744:Cell Line, Tumor; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D018836:Inflammation Mediators / Q000494:pharmacology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D008954:Models, Biological; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011658:Pulmonary Fibrosis / Q000378:metabolism / Q000473:pathology; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000378:metabolism*; D012995:Solubility / Q000187:drug effects; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000099149:Ezrin
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D018960:Hyaluronan Receptors; D018836:Inflammation Mediators; D020780:Matrix Metalloproteinase 9; D008565:Membrane Proteins; D008840:Microfilament Proteins; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; D053773:Transforming Growth Factor beta1; D054460:rho-Associated Kinases; D000099149:Ezrin; C497483:CD44 protein, human; C071058:moesin; C071776:radixin