Mitogen-Activated Protein Kinases Promote WNT/β-Catenin Signaling via Phosphorylation of LRP6

ABSTRACT LDL-related protein 6 (LRP6) is a coreceptor of WNTs and a key regulator of the WNT/β-catenin pathway. Upon activation, LRP6 is phosphorylated within its intracellular PPPS/TP motifs. These phosphorylated motifs are required to recruit axin and to inhibit glycogen synthase kinase 3 (GSK3), two basic components of the β-catenin destruction complex. On the basis of a kinome-wide small interfering RNA (siRNA) screen and confirmative biochemical analysis, we show that several proline-directed mitogen-activated protein kinases (MAPKs), such as p38, ERK1/2, and JNK1 are sufficient and required for the phosphorylation of PPPS/TP motifs of LRP6. External stimuli, which control the activity of MAPKs, such as phorbol esters and fibroblast growth factor 2 (FGF2) control the choice of the LRP6-PPPS/TP kinase and regulate the amplitude of LRP6 phosphorylation and WNT/β-catenin-dependent transcription. Our findings suggest that cells not only recruit one dedicated LRP6 kinase but rather select their LRP6 kinase depending on cell type and the external stimulus. Moreover, direct phosphorylation of LRP6 by MAPKs provides a unique point for convergence between WNT/β-catenin signaling and mitogenic pathways.

[1]  C. Malbon,et al.  p38 mitogen-activated protein kinase regulates canonical Wnt–β-catenin signaling by inactivation of GSK3β , 2008, Journal of Cell Science.

[2]  Gustavo Pedraza-Alva,et al.  Phosphorylation by p38 MAPK as an Alternative Pathway for GSK3β Inactivation , 2008, Science.

[3]  M. Caron,et al.  G Protein-coupled Receptor Kinases Phosphorylate LRP6 in the Wnt Pathway , 2009, The Journal of Biological Chemistry.

[4]  Christof Niehrs,et al.  Wnt Induces LRP6 Signalosomes and Promotes Dishevelled-Dependent LRP6 Phosphorylation , 2007, Science.

[5]  R. Nusse,et al.  Wnt and FGF signals interact to coordinate growth with cell fate specification during limb development , 2008, Development.

[6]  S. Byers,et al.  Serine phosphorylation-regulated ubiquitination and degradation of beta-catenin. , 1997, The Journal of biological chemistry.

[7]  Walter Birchmeier,et al.  Balancing cell adhesion and Wnt signaling, the key role of beta-catenin. , 2006, Current opinion in genetics & development.

[8]  H. Schaeffer,et al.  MP1: a MEK binding partner that enhances enzymatic activation of the MAP kinase cascade. , 1998, Science.

[9]  H. Clevers Wnt/beta-catenin signaling in development and disease. , 2006, Cell.

[10]  Stephen W. Byers,et al.  Serine Phosphorylation-regulated Ubiquitination and Degradation of β-Catenin* , 1997, The Journal of Biological Chemistry.

[11]  Nam-Chul Ha,et al.  Direct Inhibition of GSK3β by the Phosphorylated Cytoplasmic Domain of LRP6 in Wnt/β-Catenin Signaling , 2008, PloS one.

[12]  H. Schaeffer,et al.  A proline-rich sequence unique to MEK1 and MEK2 is required for raf binding and regulates MEK function , 1995, Molecular and cellular biology.

[13]  A. Hampl,et al.  Increased apoptosis in differentiating p27-deficient mouse embryonic stem cells , 2004, Cellular and Molecular Life Sciences CMLS.

[14]  Philip R. Cohen,et al.  The substrate specificity and structure of mitogen-activated protein (MAP) kinase-activated protein kinase-2. , 1993, The Biochemical journal.

[15]  A. Ishimoto,et al.  Characterization of Mouse Dishevelled (Dvl) Proteins in Wnt/Wingless Signaling Pathway* , 1999, The Journal of Biological Chemistry.

[16]  R. Moon,et al.  Wnt and FGF pathways cooperatively pattern anteroposterior neural ectoderm in Xenopus , 1997, Mechanisms of Development.

[17]  J. Gutkind,et al.  Faculty Opinions recommendation of Phosphorylation by p38 MAPK as an alternative pathway for GSK3beta inactivation. , 2008 .

[18]  Christof Niehrs,et al.  Casein kinase 1 gamma couples Wnt receptor activation to cytoplasmic signal transduction. , 2005, Nature.

[19]  G. Schulte,et al.  Wnt-3a utilizes a novel low dose and rapid pathway that does not require casein kinase 1-mediated phosphorylation of Dvl to activate beta-catenin. , 2007, Cellular signalling.

[20]  N. Lemoine,et al.  FGF-1 and FGF-2 modulate the E-cadherin/catenin system in pancreatic adenocarcinoma cell lines , 2001, British Journal of Cancer.

[21]  M. Boutros,et al.  Cell cycle control of wnt receptor activation. , 2009, Developmental cell.

[22]  Xi He,et al.  A dual-kinase mechanism for Wnt co-receptor phosphorylation and activation , 2005, Nature.

[23]  Xi He,et al.  Wnt Signal Amplification via Activity, Cooperativity, and Regulation of Multiple Intracellular PPPSP Motifs in the Wnt Co-receptor LRP6* , 2008, Journal of Biological Chemistry.

[24]  Xi He,et al.  A mechanism for Wnt coreceptor activation. , 2004, Molecular cell.

[25]  C. Malbon,et al.  Gαo mediates WNT-JNK signaling through Dishevelled 1 and 3, RhoA family members, and MEKK 1 and 4 in mammalian cells , 2008, Journal of Cell Science.

[26]  Ethan Lee,et al.  LRP6 transduces a canonical Wnt signal independently of Axin degradation by inhibiting GSK3's phosphorylation of β-catenin , 2008, Proceedings of the National Academy of Sciences of the United States of America.

[27]  B. Williams,et al.  Multiple PPPS/TP motifs act in a combinatorial fashion to transduce Wnt signaling through LRP6 , 2008, FEBS letters.

[28]  Yoichi Kato,et al.  LDL-receptor-related proteins in Wnt signal transduction , 2000, Nature.

[29]  K. Aldape,et al.  EGF-induced ERK activation promotes CK2-mediated disassociation of alpha-Catenin from beta-Catenin and transactivation of beta-Catenin. , 2009, Molecular cell.

[30]  Christof Niehrs,et al.  Casein kinase 1 γ couples Wnt receptor activation to cytoplasmic signal transduction , 2005, Nature.

[31]  F. Brembeck,et al.  Essential role of BCL9-2 in the switch between beta-catenin's adhesive and transcriptional functions. , 2004, Genes & development.

[32]  J. Abreu,et al.  Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6 , 2009, PloS one.

[33]  Walter Birchmeier,et al.  Balancing cell adhesion and Wnt signaling, the key role of β-catenin , 2006 .

[34]  A. Hampl,et al.  FGF2 inhibits proliferation and alters the cartilage-like phenotype of RCS cells. , 2004, Experimental cell research.

[35]  Stuart A. Aaronson,et al.  A Novel Mechanism for Wnt Activation of Canonical Signaling through the LRP6 Receptor , 2003, Molecular and Cellular Biology.

[36]  P. Crespo,et al.  The small GTP-binding proteins Rac1 and Cdc42regulate the activity of the JNK/SAPK signaling pathway , 1995, Cell.

[37]  Chika Yokota,et al.  Initiation of Wnt signaling: control of Wnt coreceptor Lrp6 phosphorylation/activation via frizzled, dishevelled and axin functions , 2007, Development.

[38]  J. Graff,et al.  Casein kinase I transduces Wnt signals , 1999, Nature.