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

• Published in: Biochemical and biophysical research communications 2012-03, Vol.419 (3), p.543-549
• Main Authors: Park, Mee-Hee, Kim, Duk-Joong, You, Soon-Tae, Lee, Chan-Soo, Kim, Hyong Kyu, Park, Seon Mee, Shin, Eun-Young, Kim, Eung-Gook
• Format: Article
• Language: English
• Subjects: beta Catenin - genetics; beta Catenin - metabolism; Colorectal Neoplasms - genetics; Colorectal Neoplasms - metabolism; HCT116 Cells; HEK293 Cells; Humans; p21-Activated kinase; p21-Activated Kinases - genetics; p21-Activated Kinases - metabolism; Phosphorylation; Serine - genetics; Serine - metabolism; TCF Transcription Factors - metabolism; Transcription; Transcription, Genetic; Transcriptional Activation; β-Catenin
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2012.02.056

► Active PAK1(T423E) but not inactive PAK1(K299R) interacted with and phosphorylated β-catenin. ► PAK1 phosphorylated β-catenin at serine 663 (S663) in addition to S675. ► S663 phosphorylation is observed in colon cancer cell lines which show a higher PAK1 activity. ► S663 phosphorylation was important in regulation of the transcriptional activity of β-catenin. 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-cateninS663 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.