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Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6

The Wnt/β-catenin signaling pathway plays essential roles in cell proliferation and differentiation, and deregulated β-catenin protein levels lead to many types of human cancers. On activation by Wnt, the Wnt co-receptor LDL receptor related protein 6 (LRP6) is phosphorylated at multiple conserved i...

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Autores principales: Wu, Geng, Huang, He, Abreu, Jose Garcia, He, Xi
Formato: Texto
Lenguaje:English
Publicado: Public Library of Science 2009
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2654145/
https://www.ncbi.nlm.nih.gov/pubmed/19293931
http://dx.doi.org/10.1371/journal.pone.0004926
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author Wu, Geng
Huang, He
Abreu, Jose Garcia
He, Xi
author_facet Wu, Geng
Huang, He
Abreu, Jose Garcia
He, Xi
author_sort Wu, Geng
collection PubMed
description The Wnt/β-catenin signaling pathway plays essential roles in cell proliferation and differentiation, and deregulated β-catenin protein levels lead to many types of human cancers. On activation by Wnt, the Wnt co-receptor LDL receptor related protein 6 (LRP6) is phosphorylated at multiple conserved intracellular PPPSPXS motifs by glycogen synthase kinase 3 (GSK3) and casein kinase 1 (CK1), resulting in recruitment of the scaffolding protein Axin to LRP6. As a result, β-catenin phosphorylation by GSK3 is inhibited and β-catenin protein is stabilized. However, how LRP6 phosphorylation and the ensuing LRP6-Axin interaction lead to the inhibition of β-catenin phosphorylation by GSK3 is not fully understood. In this study, we reconstituted Axin-dependent β-catenin phosphorylation by GSK3 and CK1 in vitro using recombinant proteins, and found that the phosphorylated PPPSPXS peptides directly inhibit β-catenin phosphorylation by GSK3 in a sequence and phosphorylation-dependent manner. This inhibitory effect of phosphorylated PPPSPXS motifs is direct and specific for GSK3 phosphorylation of β-catenin at Ser33/Ser37/Thr41 but not for CK1 phosphorylation of β-catenin at Ser45, and is independent of Axin function. We also show that a phosphorylated PPPSPXS peptide is able to activate Wnt/β-catenin signaling and to induce axis duplication in Xenopus embryos, presumably by inhibition of GSK3 in vivo. Based on these observations, we propose a working model that Axin recruitment to the phosphorylated LRP6 places GSK3 in the vicinity of multiple phosphorylated PPPSPXS motifs, which directly inhibit GSK3 phosphorylation of β-catenin. This model provides a possible mechanism to account, in part, for inhibition of β-catenin phosphorylation by Wnt-activated LRP6.
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spelling pubmed-26541452009-03-18 Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6 Wu, Geng Huang, He Abreu, Jose Garcia He, Xi PLoS One Research Article The Wnt/β-catenin signaling pathway plays essential roles in cell proliferation and differentiation, and deregulated β-catenin protein levels lead to many types of human cancers. On activation by Wnt, the Wnt co-receptor LDL receptor related protein 6 (LRP6) is phosphorylated at multiple conserved intracellular PPPSPXS motifs by glycogen synthase kinase 3 (GSK3) and casein kinase 1 (CK1), resulting in recruitment of the scaffolding protein Axin to LRP6. As a result, β-catenin phosphorylation by GSK3 is inhibited and β-catenin protein is stabilized. However, how LRP6 phosphorylation and the ensuing LRP6-Axin interaction lead to the inhibition of β-catenin phosphorylation by GSK3 is not fully understood. In this study, we reconstituted Axin-dependent β-catenin phosphorylation by GSK3 and CK1 in vitro using recombinant proteins, and found that the phosphorylated PPPSPXS peptides directly inhibit β-catenin phosphorylation by GSK3 in a sequence and phosphorylation-dependent manner. This inhibitory effect of phosphorylated PPPSPXS motifs is direct and specific for GSK3 phosphorylation of β-catenin at Ser33/Ser37/Thr41 but not for CK1 phosphorylation of β-catenin at Ser45, and is independent of Axin function. We also show that a phosphorylated PPPSPXS peptide is able to activate Wnt/β-catenin signaling and to induce axis duplication in Xenopus embryos, presumably by inhibition of GSK3 in vivo. Based on these observations, we propose a working model that Axin recruitment to the phosphorylated LRP6 places GSK3 in the vicinity of multiple phosphorylated PPPSPXS motifs, which directly inhibit GSK3 phosphorylation of β-catenin. This model provides a possible mechanism to account, in part, for inhibition of β-catenin phosphorylation by Wnt-activated LRP6. Public Library of Science 2009-03-18 /pmc/articles/PMC2654145/ /pubmed/19293931 http://dx.doi.org/10.1371/journal.pone.0004926 Text en Wu et al. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Wu, Geng
Huang, He
Abreu, Jose Garcia
He, Xi
Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6
title Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6
title_full Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6
title_fullStr Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6
title_full_unstemmed Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6
title_short Inhibition of GSK3 Phosphorylation of β-Catenin via Phosphorylated PPPSPXS Motifs of Wnt Coreceptor LRP6
title_sort inhibition of gsk3 phosphorylation of β-catenin via phosphorylated pppspxs motifs of wnt coreceptor lrp6
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2654145/
https://www.ncbi.nlm.nih.gov/pubmed/19293931
http://dx.doi.org/10.1371/journal.pone.0004926
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