title: c-Jun N-terminal kinase mediates disassembly of apical junctions in model intestinal epithelia.
abstract: Dynamic remodeling of intercellular junctions is a critical determinant of epithelial barrier function in both physiological and pathophysiological states. While the disassembly of epithelial tight junctions (TJ) and adherens junctions (AJ) has been well-described in response to pathogens and other external stressors, the role of stress-related signaling in TJ/AJ regulation remains poorly understood. The aim of this study was to define the role of stress-activated c-Jun N-terminal kinase (JNK) in disruption of intercellular junctions in model intestinal epithelia. We show that rapid AJ/TJ disassembly triggered by extracellular calcium depletion of T84 and SK-CO15 cell monolayers was accompanied by activation (phosphorylation) of JNK, and prevented by pharmacological inhibitors of JNK. The opposite process, TJ/AJ reassembly, was accelerated by JNK inhibition and suppressed by the JNK activator anisomycin. JNK1 but not JNK2 was found to colocalize with intercellular junctions, and siRNA-mediated downregulation of JNK1 attenuated the TJ/AJ disruption caused by calcium depletion. JNK inhibition also blocked formation of characteristic contractile F-actin rings in calcium-depleted epithelial cells, suggesting that JNK regulates junctions by remodeling the actin cytoskeleton. In this role JNK acts downstream of the actin-reorganizing Rho-dependent kinase (ROCK), since ROCK inhibition abrogated JNK phosphorylation and TJ/AJ disassembly after calcium depletion. Furthermore, JNK acts upstream of F-actin-membrane linker proteins of the ERM (ezrin-radixin-moesin) family, but in a complex relationship yet to be fully elucidated. Taken together, our findings suggest a novel role for JNK in the signaling pathway that links ROCK and F-actin remodeling during disassembly of epithelial junctions.
authors.affiliation: Department of Medicine, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Nayden G
authors.initials: NG
authors.lastname: Naydenov
authors.forename: Ann M
authors.initials: AM
authors.lastname: Hopkins
authors.forename: Andrei I
authors.initials: AI
authors.lastname: Ivanov
mesh_terms: D000199:Actins / Q000378:metabolism; D022005:Adherens Junctions / Q000502:physiology*; D000841:Anisomycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D004847:Epithelial Cells / Q000201:enzymology / Q000502:physiology; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology* / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D048055:Mitogen-Activated Protein Kinase 8 / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000378:metabolism; D019108:Tight Junctions / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D004268:DNA-Binding Proteins; C086680:ETV5 protein, human; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D014157:Transcription Factors; D000841:Anisomycin; D054460:rho-Associated Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048055:Mitogen-Activated Protein Kinase 8; D002118:Calcium