title: Phosphorylation of β-catenin at serine 663 regulates its transcriptional activity.
abstract: 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.
authors.affiliation: Department of Biochemistry, College of Medicine, Chungbuk National University, Cheongju, Republic of Korea.
authors.forename: Mee-Hee
authors.initials: MH
authors.lastname: Park
authors.forename: Duk-Joong
authors.initials: DJ
authors.lastname: Kim
authors.forename: Soon-Tae
authors.initials: ST
authors.lastname: You
authors.forename: Chan-Soo
authors.initials: CS
authors.lastname: Lee
authors.forename: Hyong Kyu
authors.initials: HK
authors.lastname: Kim
authors.forename: Seon Mee
authors.initials: SM
authors.lastname: Park
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Shin
authors.forename: Eung-Gook
authors.initials: EG
authors.lastname: Kim
mesh_terms: D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism; D045325:HCT116 Cells; D057809:HEK293 Cells; D006801:Humans; D010766:Phosphorylation; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D051820:TCF Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D051820:TCF Transcription Factors; D051176:beta Catenin; D012694:Serine; D054462:p21-Activated Kinases