The disruption of adherens junctions is associated with a decrease of E-cadherin phosphorylation by protein kinase CK2

Exp Cell Res. 2000 Jun 15;257(2):255-64. doi: 10.1006/excr.2000.4895.

Abstract

The down-regulation of E-cadherin is a common event in carcinogenesis. Phosphorylation/dephosphorylation is one posttranscriptional process which may regulate intercellular junctions. Here we show that in okadaic acid-treated keratinocytes, E-cadherin expression is shifted from the membrane to the cytoplasm, preventing cells from forming aggregates. These changes of E-cadherin localization and function are associated with a decrease in its phosphorylation state. The decrease in E-cadherin phosphorylation was essentially detected in okadaic acid-treated cell lysates isolated from 0.5% Triton-soluble fraction and not in the Triton-insoluble fraction linked to the cytoskeleton, suggesting a role of E-cadherin phosphorylation in cell-cell interactions. E-cadherin was markedly phosphorylated by CK2, either the purified recombinant enzyme or the endogenous enzyme. Using specific CK2 inhibitors such as heparin and 5, 6-dichloro-1-beta-d-ribofuranosylbenzimidazole, endogenous CK2 was confirmed as the main enzyme phosphorylating E-cadherin. The decrease in E-cadherin phosphorylation by endogenous CK2 was not restored by the addition of purified CK2, confirming that it is not due to a defect in CK2 expression or to its reduced activity, but rather to the incapacity of CK2 to phosphorylate E-cadherin. The co-immunoprecipitation and colocalization of E-cadherin and CK2 suggests that CK2 may play a critical role in the maintenance of epidermis cohesion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cadherins / metabolism*
  • Casein Kinase II
  • Cell Adhesion
  • Cells, Cultured
  • Enzyme Inhibitors / pharmacology
  • HeLa Cells
  • Humans
  • Intercellular Junctions / drug effects
  • Intercellular Junctions / physiology*
  • Keratinocytes / drug effects
  • Keratinocytes / metabolism
  • Keratinocytes / physiology
  • Okadaic Acid / pharmacology
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / isolation & purification
  • Protein-Serine-Threonine Kinases / metabolism*
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism

Substances

  • Cadherins
  • Enzyme Inhibitors
  • Recombinant Proteins
  • Okadaic Acid
  • Casein Kinase II
  • Protein-Serine-Threonine Kinases