Plasma membrane recruitment of dephosphorylated beta-catenin upon activation of the Wnt pathway

J Cell Sci. 2008 Jun 1;121(11):1793-802. doi: 10.1242/jcs.025536. Epub 2008 May 6.

Abstract

The standard model of Wnt signaling specifies that after receipt of a Wnt ligand at the membranous receptor complex, downstream mediators inhibit a cytoplasmic destruction complex, allowing beta-catenin to accumulate in the cytosol and nucleus and co-activate Wnt target genes. Unexpectedly, shortly after Wnt treatment, we detected the dephosphorylated form of beta-catenin at the plasma membrane, where it displayed a discontinuous punctate labeling. This pool of beta-catenin could only be detected in E-cadherin(-/-) cells, because in E-cadherin(+/+) cells Wnt-induced, membranous beta-catenin was concealed by a constitutive junctional pool. Wnt-signaling-dependent dephosphorylated beta-catenin colocalized at the plasma membrane with two members of the destruction complex -- APC and axin -- and the activated Wnt co-receptor LRP6. beta-catenin induced through the Wnt receptor complex was significantly more competent transcriptionally than overexpressed beta-catenin, both in cultured cells and in early Xenopus embryos. Our data reveal a new step in the processing of the Wnt signal and suggest regulation of signaling output beyond the level of protein accumulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenomatous Polyposis Coli Protein / metabolism
  • Animals
  • Axin Protein
  • Cadherins / metabolism
  • Cell Line
  • Cell Membrane / metabolism*
  • Cell Membrane / ultrastructure
  • Cells, Cultured
  • Enzyme Activation / physiology
  • Humans
  • Low Density Lipoprotein Receptor-Related Protein-6
  • Macromolecular Substances / metabolism
  • Mice
  • Mice, Knockout
  • Phosphorylation
  • Receptors, LDL / metabolism
  • Repressor Proteins / metabolism
  • Signal Transduction / physiology*
  • Transcriptional Activation / physiology
  • Up-Regulation / physiology
  • Wnt Proteins / metabolism*
  • Wnt3 Protein
  • Xenopus Proteins
  • Xenopus laevis
  • beta Catenin / genetics
  • beta Catenin / metabolism*

Substances

  • Adenomatous Polyposis Coli Protein
  • Axin Protein
  • Cadherins
  • LRP6 protein, human
  • Low Density Lipoprotein Receptor-Related Protein-6
  • Lrp6 protein, mouse
  • Macromolecular Substances
  • Receptors, LDL
  • Repressor Proteins
  • Wnt Proteins
  • Wnt3 Protein
  • Xenopus Proteins
  • axin1 protein, Xenopus
  • beta Catenin