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.
D'Souza
Theresa
T
Laboratory of Cellular and Molecular Biology, National Institute on Aging, Baltimore, MD 21224, USA.
Indig
Fred E
FE
Morin
Patrice J
PJ
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