Phosphorylation of claudin-4 by PKCepsilon regulates tight junction barrier function in ovarian cancer cells.
Claudin proteins belong to a large family of transmembrane proteins essential to the formation and maintenance of tight junctions (TJs). In ovarian cancer, TJ protein claudin-4 is frequently overexpressed and may have roles in survival and invasion, but the molecular mechanisms underlying its regulation are poorly understood. In this report, we show that claudin-4 can be phosphorylated by protein kinase C (PKC) at Thr189 and Ser194 in ovarian cancer cells and overexpression of a claudin-4 mutant protein mimicking the phosphorylated state results in the disruption of the barrier function. Furthermore, upon phorbol ester-mediated PKC activation of OVCA433 cells, TJ strength is decreased and claudin-4 localization is altered. Analyses using PKC inhibitors and siRNA suggest that PKCepsilon, an isoform typically expressed in ovarian cancer cells, may be important in the TPA-mediated claudin-4 phosphorylation and weakening of the TJs. Furthermore, immunofluorescence studies showed that claudin-4 and PKCepsilon are co-localized at the TJs in these cells. The modulation of claudin-4 activity by PKCepsilon may not only provide a mechanism for disrupting TJ function in ovarian cancer, but may also be important in the regulation of TJ function in normal epithelial cells.
Laboratory of Cellular and Molecular Biology, National Institute on Aging, Baltimore, MD 21224, USA.
Theresa
T
D'Souza
Fred E
FE
Indig
Patrice J
PJ
Morin
D045744:Cell Line, Tumor; D062506:Claudin-4; D005260:Female; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010051:Ovarian Neoplasms / Q000378:metabolism*; D010766:Phosphorylation; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000378:metabolism; D051744:Protein Kinase C-epsilon / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019108:Tight Junctions / Q000502:physiology*
C568157:CLDN4 protein, human; D062506:Claudin-4; D007211:Indoles; D008301:Maleimides; D008565:Membrane Proteins; D020033:Protein Isoforms; D051744:Protein Kinase C-epsilon; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate