Phosphorylation of β-catenin at serine 663 regulates its transcriptional activity

Biochem Biophys Res Commun. 2012 Mar 16;419(3):543-9. doi: 10.1016/j.bbrc.2012.02.056. Epub 2012 Feb 17.


β-Catenin, a component of Wnt signaling, plays a key role in colorectal carcinogenesis. The phosphorylation status of β-catenin determines its fate and affects its cellular function, and serine 675 (S675) was previously identified as a common target of p21-activated kinase 1 (PAK1) and protein kinase A. In the present study, we explored the PAK1-specific phosphorylation site(s) in β-catenin. Active PAK1 T423E but not inactive PAK1 K299R interacted with and phosphorylated β-catenin. Mutagenesis followed by a kinase assay revealed that PAK1 phosphorylated S663 in addition to S675, and an anti-phospho-β-catenin(S663) antibody detected the phosphorylation of S663 downstream of PAK1 in various human colon cancer cells. Furthermore, the Wnt3a-stimulated S663 phosphorylation was inhibited by the PAK1-specific inhibitor, IPA-3, but not by H-89 or LY294002. The non-phosphorylatable mutant forms of β-catenin, S663A, S675A and S663/675A, showed similar defects in their PAK1-induced TCF/LEF transactivation, whereas the phosphomimetic form of β-catenin, S663D, demonstrated a transcriptional activity that was comparable to that of β-catenin S675D and β-catenin S663D/S675D. Taken together, these results provide evidence that PAK1 specifically phosphorylates β-catenin at S663 and that this phosphorylation is essential for the PAK1-mediated transcriptional activation of β-catenin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / metabolism
  • HCT116 Cells
  • HEK293 Cells
  • Humans
  • Phosphorylation
  • Serine / genetics
  • Serine / metabolism*
  • TCF Transcription Factors / metabolism
  • Transcription, Genetic
  • Transcriptional Activation*
  • beta Catenin / genetics
  • beta Catenin / metabolism*
  • p21-Activated Kinases / genetics
  • p21-Activated Kinases / metabolism*


  • TCF Transcription Factors
  • beta Catenin
  • Serine
  • p21-Activated Kinases