Abstract
Activation of the Wnt signaling cascade provides key signals during development and in disease. Wnt signals are transduced by seven-transmembrane Frizzleds (Fzs) and the single transmembrane low density lipoprotein receptor-related proteins 5 or 6. In the course of the analysis of genes regulated by bone morphogenetic protein 2 in mesenchymal cells we found a significant induction of murine Frizzled-1 (mFz1) gene expression. Unexpectedly overexpression of mFz1 dramatically repressed the induction of alkaline phosphatase mediated by either bone morphogenetic protein 2 or Wnt3a in these cells. Moreover mFz1 overexpression significantly repressed both beta-catenin translocation into the nucleus and T cell factor signaling mediated by Wnt3a. Importantly microinjection of mFz1 transcript in Xenopus embryo inhibited the ability of Wnt1 to induce the expression of the Wnt/beta-catenin target gene Siamois in animal cap assay and secondary axis formation in whole embryo. By using chimeric constructs in which N- and C-terminal segments of mFz1 were replaced by the corresponding parts of Xfz3 we demonstrated that the antagonistic activity resides in the cysteine-rich domain of the N-terminal part. The antagonist activity of mFz1 could be prevented by overexpression of Galphaq-(305-359), which specifically uncouples Gq-coupled receptors, suggesting that Galphaq signaling contributes to the inhibition of Wnt/beta-catenin pathway by mFz1. This is the first time that a Frizzled receptor has been reported to antagonize Wnt/beta-catenin.
MeSH terms
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Active Transport, Cell Nucleus
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Alkaline Phosphatase / metabolism
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Animals
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Bone Morphogenetic Protein 2
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Bone Morphogenetic Proteins / metabolism
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COS Cells
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Cell Line
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Cell Nucleus / metabolism
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Culture Media, Conditioned / pharmacology
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Cystine / chemistry
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Cytoskeletal Proteins / antagonists & inhibitors*
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Enzyme Activation
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Frizzled Receptors
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GTP-Binding Protein alpha Subunits, Gq-G11 / metabolism
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Genetic Vectors
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Green Fluorescent Proteins
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Immunoblotting
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Luciferases / metabolism
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Luminescent Proteins / metabolism
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Mice
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Microscopy, Confocal
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Protein Structure, Tertiary
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Proteins / metabolism
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Proto-Oncogene Proteins / antagonists & inhibitors*
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Receptors, G-Protein-Coupled
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Receptors, Neurotransmitter / metabolism
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Receptors, Neurotransmitter / physiology*
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Recombinant Fusion Proteins / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Signal Transduction
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Time Factors
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Trans-Activators / antagonists & inhibitors*
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Transfection
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Transforming Growth Factor beta*
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Wnt Proteins
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Wnt1 Protein
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Wnt3 Protein
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Wnt3A Protein
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Xenopus
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Xenopus Proteins*
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Zebrafish Proteins*
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beta Catenin
Substances
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Bmp2 protein, mouse
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Bone Morphogenetic Protein 2
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Bone Morphogenetic Proteins
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CTNNB1 protein, Xenopus
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CTNNB1 protein, mouse
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Culture Media, Conditioned
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Cytoskeletal Proteins
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FZD1 protein, Xenopus
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Frizzled Receptors
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Fzd1 protein, mouse
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Luminescent Proteins
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Proteins
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Proto-Oncogene Proteins
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Receptors, G-Protein-Coupled
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Receptors, Neurotransmitter
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Recombinant Fusion Proteins
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Trans-Activators
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Transforming Growth Factor beta
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WNT1 protein, Xenopus
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WNT3A protein, Xenopus
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Wnt Proteins
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Wnt1 Protein
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Wnt1 protein, mouse
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Wnt3 Protein
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Wnt3A Protein
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Wnt3a protein, mouse
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Xenopus Proteins
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Zebrafish Proteins
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beta Catenin
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Green Fluorescent Proteins
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Cystine
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Luciferases
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Alkaline Phosphatase
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GTP-Binding Protein alpha Subunits, Gq-G11