Homeodomain-interacting protein kinase 2 (HIPK2) targets beta-catenin for phosphorylation and proteasomal degradation.

The regulation of intracellular beta-catenin levels is central in the Wnt/beta-catenin signaling cascade and the activation of the Wnt target genes. Here, we show that homeodomain-interacting protein kinase 2 (HIPK2) acts as a negative regulator of the Wnt/beta-catenin pathway. Knock-down of endogenous HIPK2 increases the stability of beta-catenin and results in the accumulation of beta-catenin in the nucleus, consequently enhancing the expression of Wnt target genes and cell proliferation both in vivo and in cultured cells. HIPK2 inhibits TCF/LEF-mediated target gene activation via degradation of beta-catenin. HIPK2 phosphorylates beta-catenin at its Ser33 and Ser37 residues without the aid of a priming kinase. Substitutions of Ser33 and Ser37 for alanines abolished the degradation of beta-catenin associated with HIPK2. In ex vivo mouse model, HIPK2 knock-down resulted in accumulation of beta-catenin, thereby potentiated beta-catenin-mediated cell proliferation and tumor formation. Furthermore, the axis duplication induced by the ectopic expression of beta-catenin was blocked by co-injection of HIPK2 mRNAs into Xenopus embryos. Taken together, HIPK2 appears to function as a novel negative regulator of beta-catenin through its phosphorylation and proteasomal degradation.

[1]  H. Kwon,et al.  The Homeodomain Protein NK-3 Recruits Groucho and a Histone Deacetylase Complex to Repress Transcription* , 1999, The Journal of Biological Chemistry.

[2]  R. Nusse,et al.  The Wnt signaling pathway in development and disease. , 2004, Annual review of cell and developmental biology.

[3]  Wolfgang Driever,et al.  Repressor activity of Headless/Tcf3 is essential for vertebrate head formation , 2000, Nature.

[4]  M. Schmitz,et al.  Roles of HIPK1 and HIPK2 in AML1‐ and p300‐dependent transcription, hematopoiesis and blood vessel formation , 2006, The EMBO journal.

[5]  Cheol‐Hee Kim,et al.  Phosphorylation and Transactivation of Pax6 by Homeodomain-interacting Protein Kinase 2* , 2006, Journal of Biological Chemistry.

[6]  Stephen J. Elledge,et al.  The SCFβ-TRCP–ubiquitin ligase complex associates specifically with phosphorylated destruction motifs in IκBα and β-catenin and stimulates IκBα ubiquitination in vitro , 1999 .

[7]  Xiao Yong Yang,et al.  Modulation of the β-Catenin Signaling Pathway by the Dishevelled-Associated Protein Hipk1 , 2009, PloS one.

[8]  R. Schulz,et al.  Phosphorylation by the DHIPK2 Protein Kinase Modulates the Corepressor Activity of Groucho* , 2005, Journal of Biological Chemistry.

[9]  Ajamete Kaykas,et al.  WNT and β-catenin signalling: diseases and therapies , 2004, Nature Reviews Genetics.

[10]  Pablo Tamayo,et al.  CDK8 is a colorectal cancer oncogene that regulates β-catenin activity , 2008, Nature.

[11]  S. Swarup,et al.  Homeodomain-interacting protein kinases (Hipks) promote Wnt/Wg signaling through stabilization of β-catenin/Arm and stimulation of target gene expression , 2009, Development.

[12]  M. Schmitz,et al.  HIPK2, a Versatile Switchboard Regulating the Transcription Machinery and Cell Death , 2007, Cell cycle.

[13]  Yongsok Kim,et al.  Homeodomain-interacting Protein Kinases, a Novel Family of Co-repressors for Homeodomain Transcription Factors* , 1998, The Journal of Biological Chemistry.

[14]  A. Balmain,et al.  HIPK2 represses β-catenin-mediated transcription, epidermal stem cell expansion, and skin tumorigenesis , 2007, Proceedings of the National Academy of Sciences.

[15]  Haruhiko Koseki,et al.  Overlapping Roles for Homeodomain-Interacting Protein Kinases Hipk1 and Hipk2 in the Mediation of Cell Growth in Response to Morphogenetic and Genotoxic Signals , 2006, Molecular and Cellular Biology.

[16]  Frank McCormick,et al.  β-Catenin regulates expression of cyclin D1 in colon carcinoma cells , 1999, Nature.

[17]  S. Soddu,et al.  HIPK2: a multitalented partner for transcription factors in DNA damage response and development. , 2007, Biochemistry and cell biology = Biochimie et biologie cellulaire.

[18]  C. Albanese,et al.  The cyclin D1 gene is a target of the beta-catenin/LEF-1 pathway. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[19]  S. Elledge,et al.  The SCFbeta-TRCP-ubiquitin ligase complex associates specifically with phosphorylated destruction motifs in IkappaBalpha and beta-catenin and stimulates IkappaBalpha ubiquitination in vitro. , 1999, Genes & development.

[20]  Yukihiro Matsuda,et al.  Casein kinase I phosphorylates the Armadillo protein and induces its degradation in Drosophila , 2002, The EMBO journal.

[21]  M. Pagano,et al.  The human F box protein β-Trcp associates with the Cul1/Skp1 complex and regulates the stability of β-catenin , 1999, Oncogene.

[22]  C. Albanese,et al.  The cyclin D 1 gene is a target of the b-catenin y LEF-1 pathway , 1999 .

[23]  Teruaki Nomura,et al.  Wnt-1 signal induces phosphorylation and degradation of c-Myb protein via TAK1, HIPK2, and NLK. , 2004, Genes & development.

[24]  M. MacCoss,et al.  Wilms tumor suppressor WTX negatively regulates WNT/beta-catenin signaling. , 2007, Science.

[25]  E. Huang,et al.  Interaction of Brn3a and HIPK2 mediates transcriptional repression of sensory neuron survival , 2004, The Journal of cell biology.

[26]  Yongsok Kim,et al.  Differential interactions of the homeodomain‐interacting protein kinase 2 (HIPK2) by phosphorylation‐dependent sumoylation , 2005, FEBS letters.

[27]  Xi He,et al.  Control of β-Catenin Phosphorylation/Degradation by a Dual-Kinase Mechanism , 2002, Cell.

[28]  G. D’Orazi,et al.  Regulation of vascular endothelial growth factor expression by homeodomain-interacting protein kinase-2 , 2008, Journal of experimental & clinical cancer research : CR.