Thr160 of Axin1 is critical for the formation and function of the β-catenin destruction complex.
Upon binding of a Wnt ligand to the frizzled (FZD)-low density lipoprotein receptor related protein 5/6 (LRP5/6) receptor complex, the β-catenin destruction complex, composed of Axin1, adenomatous polyposis coli (APC), glycogen synthase kinase 3 (GSK3) and casein kinase 1 (CK1), is immediately inactivated, which causes β-catenin stabilization. However, the molecular mechanism of signal transduction from the receptor complex to the β-catenin destruction complex is controversial. Here we show that Wnt3a treatment promotes the dissociation of the Axin1-APC complex in glioblastoma cells cultured in serum-free medium. Experiments with the GSK3 inhibitor BIO suggest that Axin1-APC dissociation was controlled by phosphorylation. Introduction of a phosphomimetic mutation into Thr160 of Axin1, located in the APC-binding region RGS, abrogated the interaction of Axin1 with APC. Consistent with these observations, the Axin1 phosphomimetic mutant lost the ability to reduce β-catenin stability and to repress β-catenin/TCF-dependent transcription. Taken together, our results suggest a novel mechanism of Wnt signaling through the dissociation of the β-catenin destruction complex by Axin1 Thr160 modification.
Laboratory of Molecular Target Therapy for Cancer, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan. Electronic address: r-nasu@koto.kpu-m.ac.jp.
Ryo
R
Koyama-Nasu
Laboratory of Molecular and Genetic Information, Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
Tomoatsu
T
Hayashi
Laboratory of Molecular and Genetic Information, Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
Yukiko
Y
Nasu-Nishimura
Laboratory of Molecular and Genetic Information, Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
Tetsu
T
Akiyama
Laboratory of Molecular Target Therapy for Cancer, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan; Department of Medical Science, Graduate School of Nursing for Health Care Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan.
Ryuya
R
Yamanaka
D025601:Adenomatous Polyposis Coli Protein / Q000737:chemistry / Q000378:metabolism; D060466:Axin Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D060465:Axin Signaling Complex / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D040761:Biomimetic Materials / Q000737:chemistry / Q000378:metabolism; D047389:Casein Kinase I / Q000737:chemistry / Q000378:metabolism; D045744:Cell Line, Tumor; D005909:Glioblastoma / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000737:chemistry / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D060492:Low Density Lipoprotein Receptor-Related Protein-5 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D060488:Low Density Lipoprotein Receptor-Related Protein-6 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D055550:Protein Stability; D034741:RNA, Small Interfering / Q000235:genetics; D013912:Threonine / Q000737:chemistry; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000737:chemistry / Q000378:metabolism
C555337:APC protein, human; C555451:AXIN1 protein, human; D025601:Adenomatous Polyposis Coli Protein; D060466:Axin Protein; D060465:Axin Signaling Complex; C495270:CTNNB1 protein, human; C555482:LRP5 protein, human; C555475:LRP6 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D034741:RNA, Small Interfering; D051176:beta Catenin; D013912:Threonine; D047389:Casein Kinase I; D038362:Glycogen Synthase Kinase 3
APC; Axin1; Wnt signaling; β-catenin destruction complex