title: Activation of ERK1/2 MAP kinase pathway induces tight junction disruption in human corneal epithelial cells.
abstract: Activation of protein kinase C (PKC) by exposure of cultured human corneal epithelial cells to phorbol 12-myristate 13-acetate (PMA) resulted in an increase in paracellular permeability as evidenced by a decrease in transepithelial electrical resistance (TER). A change in the membrane distribution of the tight junction protein ZO-1 was also observed in the PMA-treated cells. In contrast, when the cells were treated with PMA in the presence of PD98059, a specific inhibitor of mitogen-activated protein kinase (MAPK) kinase, all barrier characteristics were preserved, suggesting that PKC induces tight junction disruption through the activation of MAPK. The role of this signaling pathway in the regulation of epithelial permeability was further elucidated by the use of corneal epithelial-derived cell lines expressing constitutively activated (ca) or dominant-negative (dn) mutants of MAPK kinase-1 (MEK1). Transfectants of caMEK1, when compared to parental cells, had higher levels of phosphorylated extracellular regulated protein kinase (ERK), altered distribution of ZO-1 and occludin, and much reduced TER. On the other hand, dnMEK1 transfectants had lower but detectable levels of ERK phosphorylation, more flattened morphology, and, most importantly, significantly higher TER when compared to parental cells. Our study demonstrates that activation of PKC causes the disruption of tight junctions through activation of MAP kinase and that the MAP kinase signaling pathway plays a key role in the regulation of epithelial cell morphology and barrier function in the cornea.
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Xian-jin
authors.initials: XJ
authors.lastname: Yi
authors.forename: Fu-Shin X
authors.initials: FS
authors.lastname: Yu
mesh_terms: D002460:Cell Line; D002472:Cell Transformation, Viral; D017097:Electric Impedance; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000378:metabolism / Q000648:ultrastructure*; D005136:Eye Proteins / Q000032:analysis; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008565:Membrane Proteins / Q000032:analysis; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D062793:Occludin; D010750:Phosphoproteins / Q000032:analysis; D011493:Protein Kinase C / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019108:Tight Junctions / Q000648:ultrastructure*; D062826:Zonula Occludens-1 Protein
chemical_list: D004791:Enzyme Inhibitors; D005136:Eye Proteins; D005419:Flavonoids; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one