• β-catenin;
  • murine-mammary-tumour virus (MMTV);
  • subcellular localization;
  • T-cell factor (TCF);
  • wingless-type MMTV integration site family;
  • member 4 (Wnt4)

Background information. During embryonic development, β-catenin is central both to the transcriptional activation of Wnt [wingless-type MMTV (murine-mammary-tumour virus) integration site family] target genes and as a mediator of cell—cell adhesion. Signals that regulate its levels and subcellular localization are critical. One mechanism of Wnt signalling results in stabilization of β-catenin protein, which leads to its translocation into the nucleus, where it interacts with TCF (T-cell factor, HMG box) and activates transcription of target genes. Less well understood are mechanisms of Wnt signalling that do not involve β-catenin stabilization and result in inhibition of β-catenin-mediated transcription.

Results. Here, we show that a member of the Wnt protein family, Wnt4 (Wnt, member 4), regulates the subcellular localization of β-catenin, redirecting it to the cell membrane. Unique among Wnts, this action does not affect the stability of β-catenin but does prohibit its involvement in TCF gene transactivation.

Conclusions. This novel mechanism suggests that Wnt4 acts as a switch between the two modes of β-catenin function, transcriptional activation and cell—cell adhesion.