title: Ouabain-induced alterations of the apical junctional complex involve α1 and β1 Na,K-ATPase downregulation and ERK1/2 activation independent of caveolae in colorectal cancer cells.
abstract: Studies have reported that Na,K-ATPase interacts with E-cadherin to stabilize (AJs) and regulate the expression of claudins, the main proteins present in the tight junction (TJ) in epithelial cells containing caveolae. However, the role of this ATPase in the regulation of the AJ and TJ proteins in colorectal cancer cells as well as the molecular events underlying this event in a caveolae-independent system remain undefined. In the present study, we used ouabain, a classic drug known to inhibit Na,K-ATPase, and Caco-2 cells, which are a well-established human colorectal cancer model that does not exhibit caveolae. We demonstrated that ouabain treatment resulted in a reduction of the β1 Na,K-ATPase protein and cell redistribution of the AJ proteins E-cadherin and β-catenin, as well as the α1 Na,K-ATPase subunit. Furthermore, ouabain increased claudin-3 protein levels, impaired the TJ barrier function and increased cell viability and proliferation during the early stages of treatment. Additionally, the observed ouabain-induced events were dependent on the activation of ERK1/2 signaling; but in contrast to previous studies, this signaling cascade was caveolae-independent. In conclusion, our findings strongly suggest that α1 and β1 Na,K-ATPase downregulation and ERK1/2 activation induced by ouabain are interlinked events that play an important role during cell-cell adhesion loss, which is an important step during the tumor progression of colorectal carcinomas.
authors.affiliation: Programa de Biologia Celular, Centro de Pesquisas, Instituto Nacional de Câncer, Rua André Cavalcanti, 37, 5° andar, Rio de Janeiro, RJ, 20231-050, Brazil.
authors.forename: Waldemir Fernandes
authors.initials: WF
authors.lastname: de Souza
authors.forename: Leandro Augusto
authors.initials: LA
authors.lastname: Barbosa
authors.forename: Lijun
authors.initials: L
authors.lastname: Liu
authors.forename: Wallace Martins
authors.initials: WM
authors.lastname: de Araujo
authors.forename: Julio Cesar Madureira
authors.initials: JC
authors.lastname: de-Freitas-Junior
authors.forename: Natalia
authors.initials: N
authors.lastname: Fortunato-Miranda
authors.forename: Carlos Frederico Leite
authors.initials: CF
authors.lastname: Fontes
authors.forename: José Andrés
authors.initials: JA
authors.lastname: Morgado-Díaz
mesh_terms: D022005:Adherens Junctions / Q000187:drug effects / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D021941:Caveolae / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D062465:Claudin-3; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology*; D015398:Signal Transduction; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism
chemical_list: D015820:Cadherins; D062465:Claudin-3; D010042:Ouabain; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000254:Sodium-Potassium-Exchanging ATPase