Phosphorylation of claudin-4 by PKCepsilon regulates tight junction barrier function in ovarian cancer cells

Exp Cell Res. 2007 Sep 10;313(15):3364-75. doi: 10.1016/j.yexcr.2007.06.026. Epub 2007 Jul 13.


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.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Cell Line, Tumor
  • Claudin-4
  • Female
  • Humans
  • Indoles / pharmacology
  • Maleimides / pharmacology
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mutation
  • Ovarian Neoplasms / metabolism*
  • Phosphorylation
  • Protein Isoforms / antagonists & inhibitors
  • Protein Isoforms / metabolism
  • Protein Kinase C-epsilon / antagonists & inhibitors
  • Protein Kinase C-epsilon / metabolism*
  • Signal Transduction
  • Tetradecanoylphorbol Acetate / pharmacology
  • Tight Junctions / physiology*


  • CLDN4 protein, human
  • Claudin-4
  • Indoles
  • Maleimides
  • Membrane Proteins
  • Protein Isoforms
  • Protein Kinase C-epsilon
  • bisindolylmaleimide I
  • Tetradecanoylphorbol Acetate