The Experts below are selected from a list of 417 Experts worldwide ranked by ideXlab platform
Keith A Wharton - One of the best experts on this subject based on the ideXlab platform.
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drosophila Naked Cuticle nkd engages the nuclear import adaptor importin α3 to antagonize wnt β catenin signaling
Developmental Biology, 2008Co-Authors: Chihchiang Chan, Raphael Rousset, Shu Zhang, Keith A WhartonAbstract:Abstract Precise control of Wnt/β-catenin signaling is critical for animal development, stem cell renewal, and prevention of disease. In the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene limits signaling by the Wnt ligand Wingless (Wg) during embryo segmentation. Nkd is an intracellular protein that is composed of separable membrane- and nuclear-localization sequences (NLS) as well as a conserved EF-hand motif that binds the Wnt receptor-associated scaffold protein Dishevelled (Dsh), but the mechanism by which Nkd inhibits Wnt signaling remains a mystery. Here we identify a second NLS in Nkd that is required for full activity and that binds to the canonical nuclear import adaptor Importin-α3. The Nkd NLS is similar to the Importin-α3-binding NLS in the Drosophila heat-shock transcription factor (dHSF), and each Importin-α3-binding NLS required intact basic residues in similar positions for nuclear import and protein function. Our results provide further support for the hypothesis that Nkd inhibits nuclear step(s) in Wnt/β-catenin signaling and broaden our understanding of signaling pathways that engage the nuclear import machinery.
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Drosophila Naked Cuticle (Nkd) engages the nuclear import adaptor Importin-α3 to antagonize Wnt/β-catenin signaling
Developmental Biology, 2008Co-Authors: Chihchiang Chan, Raphael Rousset, Shu Zhang, Keith A WhartonAbstract:Abstract Precise control of Wnt/β-catenin signaling is critical for animal development, stem cell renewal, and prevention of disease. In the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene limits signaling by the Wnt ligand Wingless (Wg) during embryo segmentation. Nkd is an intracellular protein that is composed of separable membrane- and nuclear-localization sequences (NLS) as well as a conserved EF-hand motif that binds the Wnt receptor-associated scaffold protein Dishevelled (Dsh), but the mechanism by which Nkd inhibits Wnt signaling remains a mystery. Here we identify a second NLS in Nkd that is required for full activity and that binds to the canonical nuclear import adaptor Importin-α3. The Nkd NLS is similar to the Importin-α3-binding NLS in the Drosophila heat-shock transcription factor (dHSF), and each Importin-α3-binding NLS required intact basic residues in similar positions for nuclear import and protein function. Our results provide further support for the hypothesis that Nkd inhibits nuclear step(s) in Wnt/β-catenin signaling and broaden our understanding of signaling pathways that engage the nuclear import machinery.
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cell autonomous myristyl independent activity of the drosophila wnt wingless antagonist Naked Cuticle nkd
Developmental Biology, 2007Co-Authors: Chihchiang Chan, Shu Zhang, Tolga Cagatay, Keith A WhartonAbstract:Robust animal development, tissue homeostasis, and stem cell renewal requires precise control of the Wnt/β-catenin signaling axis. In the embryo of the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene attenuates signaling by the Wnt ligand Wingless (Wg) during segmentation. nkd mutants have been reported to exhibit abnormalities in wg transcription, Wg protein distribution and/or transport, and the intracellular response to Wg, but the relationship between each alteration and the molecular mechanism of Nkd action remains unclear. In addition, whether Nkd acts in a cell-autonomous or nonautonomous fashion in the embryo is not known. Mammalian Nkd homologs have N-terminal consensus sequences that direct the post-translational addition of a lipophilic myristoyl moiety, but fly and mosquito Nkd, while sharing N-terminal sequence homology, lack a myristoylation consensus sequence. Here we provide evidence that fly Nkd acts cell-autonomously in the embryo, with its N-terminus able to confer unique functional properties and membrane association that cannot be mimicked in vivo by heterologous myristoylation consensus sequences. In conjunction with our recent observation that Nkd requires nuclear localization for function, our data suggest that Nkd acts at more than one subcellular location within signal-receiving cells to attenuate Wg signaling.
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Cell-autonomous, myristyl-independent activity of the Drosophila Wnt/Wingless antagonist Naked Cuticle (Nkd).
Developmental Biology, 2007Co-Authors: Chihchiang Chan, Shu Zhang, Tolga Cagatay, Keith A WhartonAbstract:Robust animal development, tissue homeostasis, and stem cell renewal requires precise control of the Wnt/β-catenin signaling axis. In the embryo of the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene attenuates signaling by the Wnt ligand Wingless (Wg) during segmentation. nkd mutants have been reported to exhibit abnormalities in wg transcription, Wg protein distribution and/or transport, and the intracellular response to Wg, but the relationship between each alteration and the molecular mechanism of Nkd action remains unclear. In addition, whether Nkd acts in a cell-autonomous or nonautonomous fashion in the embryo is not known. Mammalian Nkd homologs have N-terminal consensus sequences that direct the post-translational addition of a lipophilic myristoyl moiety, but fly and mosquito Nkd, while sharing N-terminal sequence homology, lack a myristoylation consensus sequence. Here we provide evidence that fly Nkd acts cell-autonomously in the embryo, with its N-terminus able to confer unique functional properties and membrane association that cannot be mimicked in vivo by heterologous myristoylation consensus sequences. In conjunction with our recent observation that Nkd requires nuclear localization for function, our data suggest that Nkd acts at more than one subcellular location within signal-receiving cells to attenuate Wg signaling.
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Viable mice with compound mutations in the Wnt/Dvl pathway antagonists nkd1 and nkd2.
Molecular and Cellular Biology, 2007Co-Authors: Shu Zhang, Tolga Cagatay, Mei Zhang, Manami Amanai, Janine Kline, Diego H. Castrillon, Raheela Ashfaq, Orhan K. Öz, Keith A WhartonAbstract:Gradients of Wnt/β-catenin signaling coordinate development and physiological homeostasis in metazoan animals. Proper embryonic development of the fruit fly Drosophila melanogaster requires the Naked Cuticle (Nkd) protein to attenuate a gradient of Wnt/β-catenin signaling across each segmental anlage. Nkd inhibits Wnt signaling by binding the intracellular protein Dishevelled (Dsh). Mice and humans have two nkd homologs, nkd1 and nkd2, whose encoded proteins can bind Dsh homologs (the Dvl proteins) and inhibit Wnt signaling. To determine whether nkd genes are necessary for murine development, we replaced nkd exons that encode Dvl-binding sequences with IRES-lacZ/neomycin cassettes. Mutants homozygous for each nkdlacZ allele are viable with slightly reduced mean litter sizes. Surprisingly, double-knockout mice are viable, with subtle alterations in cranial bone morphology that are reminiscent of mutation in another Wnt/β-catenin antagonist, axin2. Our data show that nkd function in the mouse is dispensable for embryonic development.
Matthew P Scott - One of the best experts on this subject based on the ideXlab platform.
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zinc dependent interaction between dishevelled and the drosophila wnt antagonist Naked Cuticle
Journal of Biological Chemistry, 2002Co-Authors: Raphael Rousset, Keith A Wharton, Gregor Zimmermann, Matthew P ScottAbstract:Abstract During Drosophila development, theNaked Cuticle (nkd) gene attenuates wingless/Wnt signaling through a negative feedback loop mechanism. Fly and vertebrate Nkd proteins contain a putative calcium-binding EF-hand motif, the EFX domain, that interacts with the basic/PDZ region of the Wnt signal transducer, dishevelled (Dsh). Here we show that Dsh binding by Drosophila Nkd in vitro is mediated by the EFX domain as well as an adjacent C-terminal sequence. In vivo data suggest that both of these regions contribute to the ability of Nkd to antagonize Wnt signaling. Mutations in the Nkd EF-hand designed to eliminate potential ion binding affected Nkd-Dsh interactions in the yeast two-hybrid assay but not in the glutathioneS-transferase pull-down assay. Addition of the chelating agent EDTA abolished the in vitro Nkd-Dsh interaction. Surprisingly zinc, but not calcium, was able to restore Nkd-Dsh binding, suggesting a zinc-mediated interaction. Calcium 45- and zinc 65-blotting experiments show that Nkd is a zinc-binding metalloprotein. The results further clarify how Nkd may antagonize Wnt signaling via interaction with Dsh, and identify a novel zinc-binding domain in Drosophila Nkd that collaborates with the conserved EFX domain to bind Dsh.
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vertebrate proteins related to drosophila Naked Cuticle bind dishevelled and antagonize wnt signaling
Developmental Biology, 2001Co-Authors: Keith A Wharton, Raphael Rousset, Gregor Zimmermann, Matthew P ScottAbstract:Abstract Wnt signals control cell fate decisions and orchestrate cell behavior in metazoan animals. In the fruit fly Drosophila, embryos defective in signaling mediated by the Wnt protein Wingless (Wg) exhibit severe segmentation defects. The Drosophila segment polarity gene Naked Cuticle ( nkd ) encodes an EF hand protein that regulates early Wg activity by acting as an inducible antagonist. Nkd antagonizes Wg via a direct interaction with the Wnt signaling component Dishevelled (Dsh). Here we describe two mouse and human proteins, Nkd1 and Nkd2, related to fly Nkd. The most conserved region among the fly and vertebrate proteins, the EFX domain, includes the putative EF hand and flanking sequences. EFX corresponds to a minimal domain required for fly or vertebrate Nkd to interact with the basic/PDZ domains of fly Dsh or vertebrate Dvl proteins in the yeast two-hybrid assay. During mouse development, nkd1 and nkd2 are expressed in multiple tissues in partially overlapping, gradient-like patterns, some of which correlate with known patterns of Wnt activity. Mouse Nkd1 can block Wnt1-mediated, but not β-catenin-mediated, activation of a Wnt-dependent reporter construct in mammalian cell culture. Misexpression of mouse nkd1 in Drosophila antagonizes Wg function. The data suggest that the vertebrate Nkd-related proteins, similar to their fly counterpart, may act as inducible antagonists of Wnt signals.
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Naked Cuticle targets dishevelled to antagonize wnt signal transduction
Genes & Development, 2001Co-Authors: Raphael Rousset, Keith A Wharton, Judith A Mack, Jeffrey D Axelrod, Ken M Cadigan, Matt Fish, Roel Nusse, Matthew P ScottAbstract:In Drosophila embryos the protein Naked Cuticle (Nkd) limits the effects of the Wnt signal Wingless (Wg) during early segmentation. nkd loss of function results in segment polarity defects and embryonic death, but how nkd affects Wnt signaling is unknown. Using ectopic expression, we find that Nkd affects, in a cell-autonomous manner, a transduction step between the Wnt signaling components Dishevelled (Dsh) and Zeste-white 3 kinase (Zw3). Zw3 is essential for repressing Wg target-gene transcription in the absence of a Wg signal, and the role of Wg is to relieve this inhibition. Our double-mutant analysis shows that, in contrast to Zw3, Nkd acts when the Wg pathway is active to restrain signal transduction. Yeast two hybrid and in vitro experiments indicate that Nkd directly binds to the basic-PDZ region of Dsh. Specially timed Nkd overexpression is capable of abolishing Dsh function in a distinct signaling pathway that controls planar-cell polarity. Our results suggest that Nkd acts directly through Dsh to limit Wg activity and thus determines how efficiently Wnt signals stabilize Armadillo (Arm)/-catenin and activate downstream genes.
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Naked Cuticle encodes an inducible antagonist of wnt signalling
Nature, 2000Co-Authors: Wenlin Zeng, Keith A Wharton, Judith A Mack, Kevin C Wang, Matthew Gadbaw, Kaye Suyama, Peter S Klein, Matthew P ScottAbstract:During animal development, cells have to respond appropriately to localized secreted signals. Proper responses to Hedgehog, transforming growth factor-β, epidermal growth factor and fibroblast growth factor/Ras signals require cognate inducible antagonists such as Patched, Dad, Argos and Sprouty1. Wnt signals are crucial in development and neoplasia2. Here we show that Naked Cuticle (nkd), a Drosophila segment-polarity gene, encodes an inducible antagonist for the Wnt signal Wingless (Wg). In fly embryos and imaginal discs nkd transcription is induced by Wg. In embryos, decreased nkd function has an effect similar to excess Wg; at later stages such a decrease appears to have no effect. Conversely, overproduction of Nkd in Drosophila and misexpression of Nkd in the vertebrate Xenopus laevis result in phenotypes resembling those of loss of Wg/Wnt function. nkd encodes a protein with a single EF hand (a calcium-binding motif) that is most similar to the recoverin family of myristoyl switch proteins. Nkd may therefore link ion fluxes to the regulation of the potency, duration or distribution of Wnt signals. Signal-inducible feedback antagonists such as nkd may limit the effects of Wnt proteins in development and disease.
Raphael Rousset - One of the best experts on this subject based on the ideXlab platform.
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drosophila Naked Cuticle nkd engages the nuclear import adaptor importin α3 to antagonize wnt β catenin signaling
Developmental Biology, 2008Co-Authors: Chihchiang Chan, Raphael Rousset, Shu Zhang, Keith A WhartonAbstract:Abstract Precise control of Wnt/β-catenin signaling is critical for animal development, stem cell renewal, and prevention of disease. In the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene limits signaling by the Wnt ligand Wingless (Wg) during embryo segmentation. Nkd is an intracellular protein that is composed of separable membrane- and nuclear-localization sequences (NLS) as well as a conserved EF-hand motif that binds the Wnt receptor-associated scaffold protein Dishevelled (Dsh), but the mechanism by which Nkd inhibits Wnt signaling remains a mystery. Here we identify a second NLS in Nkd that is required for full activity and that binds to the canonical nuclear import adaptor Importin-α3. The Nkd NLS is similar to the Importin-α3-binding NLS in the Drosophila heat-shock transcription factor (dHSF), and each Importin-α3-binding NLS required intact basic residues in similar positions for nuclear import and protein function. Our results provide further support for the hypothesis that Nkd inhibits nuclear step(s) in Wnt/β-catenin signaling and broaden our understanding of signaling pathways that engage the nuclear import machinery.
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Drosophila Naked Cuticle (Nkd) engages the nuclear import adaptor Importin-α3 to antagonize Wnt/β-catenin signaling
Developmental Biology, 2008Co-Authors: Chihchiang Chan, Raphael Rousset, Shu Zhang, Keith A WhartonAbstract:Abstract Precise control of Wnt/β-catenin signaling is critical for animal development, stem cell renewal, and prevention of disease. In the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene limits signaling by the Wnt ligand Wingless (Wg) during embryo segmentation. Nkd is an intracellular protein that is composed of separable membrane- and nuclear-localization sequences (NLS) as well as a conserved EF-hand motif that binds the Wnt receptor-associated scaffold protein Dishevelled (Dsh), but the mechanism by which Nkd inhibits Wnt signaling remains a mystery. Here we identify a second NLS in Nkd that is required for full activity and that binds to the canonical nuclear import adaptor Importin-α3. The Nkd NLS is similar to the Importin-α3-binding NLS in the Drosophila heat-shock transcription factor (dHSF), and each Importin-α3-binding NLS required intact basic residues in similar positions for nuclear import and protein function. Our results provide further support for the hypothesis that Nkd inhibits nuclear step(s) in Wnt/β-catenin signaling and broaden our understanding of signaling pathways that engage the nuclear import machinery.
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an unconventional nuclear localization motif is crucial for function of the drosophila wnt wingless antagonist Naked Cuticle
Genetics, 2006Co-Authors: Sharon Waldrop, Wenlin Zeng, Raphael Rousset, Matt Fish, Chihchiang Chan, Shu Zhang, Tolga Cagatay, Judy Mack, Mei Zhang, Manami AmanaiAbstract:Wnt/β-catenin signals orchestrate cell fate and behavior throughout the animal kingdom. Aberrant Wnt signaling impacts nearly the entire spectrum of human disease, including birth defects, cancer, and osteoporosis. If Wnt signaling is to be effectively manipulated for therapeutic advantage, we first must understand how Wnt signals are normally controlled. Naked Cuticle (Nkd) is a novel and evolutionarily conserved inducible antagonist of Wnt/β-catenin signaling that is crucial for segmentation in the model genetic organism, the fruit fly Drosophila melanogaster. Nkd can bind and inhibit the Wnt signal transducer Dishevelled (Dsh), but the mechanism by which Nkd limits Wnt signaling in the fly embryo is not understood. Here we show that nkd mutants exhibit elevated levels of the β-catenin homolog Armadillo but no alteration in Dsh abundance or distribution. In the fly embryo, Nkd and Dsh are predominantly cytoplasmic, although a recent report suggests that vertebrate Dsh requires nuclear localization for activity in gain-of-function assays. While Dsh-binding regions of Nkd contribute to its activity, we identify a conserved 30-amino-acid motif, separable from Dsh-binding regions, that is essential for Nkd function and nuclear localization. Replacement of the 30-aa motif with a conventional nuclear localization sequence rescued a small fraction of nkd mutant animals to adulthood. Our studies suggest that Nkd targets Dsh-dependent signal transduction steps in both cytoplasmic and nuclear compartments of cells receiving the Wnt signal.
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An unconventional nuclear localization motif is crucial for function of the Drosophila Wnt/wingless antagonist Naked Cuticle.
Genetics, 2006Co-Authors: Sharon Waldrop, Wenlin Zeng, Raphael Rousset, Matt Fish, Chihchiang Chan, Shu Zhang, Tolga Cagatay, Judy Mack, Mei Zhang, Manami AmanaiAbstract:Wnt/β-catenin signals orchestrate cell fate and behavior throughout the animal kingdom. Aberrant Wnt signaling impacts nearly the entire spectrum of human disease, including birth defects, cancer, and osteoporosis. If Wnt signaling is to be effectively manipulated for therapeutic advantage, we first must understand how Wnt signals are normally controlled. Naked Cuticle (Nkd) is a novel and evolutionarily conserved inducible antagonist of Wnt/β-catenin signaling that is crucial for segmentation in the model genetic organism, the fruit fly Drosophila melanogaster. Nkd can bind and inhibit the Wnt signal transducer Dishevelled (Dsh), but the mechanism by which Nkd limits Wnt signaling in the fly embryo is not understood. Here we show that nkd mutants exhibit elevated levels of the β-catenin homolog Armadillo but no alteration in Dsh abundance or distribution. In the fly embryo, Nkd and Dsh are predominantly cytoplasmic, although a recent report suggests that vertebrate Dsh requires nuclear localization for activity in gain-of-function assays. While Dsh-binding regions of Nkd contribute to its activity, we identify a conserved 30-amino-acid motif, separable from Dsh-binding regions, that is essential for Nkd function and nuclear localization. Replacement of the 30-aa motif with a conventional nuclear localization sequence rescued a small fraction of nkd mutant animals to adulthood. Our studies suggest that Nkd targets Dsh-dependent signal transduction steps in both cytoplasmic and nuclear compartments of cells receiving the Wnt signal.
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zinc dependent interaction between dishevelled and the drosophila wnt antagonist Naked Cuticle
Journal of Biological Chemistry, 2002Co-Authors: Raphael Rousset, Keith A Wharton, Gregor Zimmermann, Matthew P ScottAbstract:Abstract During Drosophila development, theNaked Cuticle (nkd) gene attenuates wingless/Wnt signaling through a negative feedback loop mechanism. Fly and vertebrate Nkd proteins contain a putative calcium-binding EF-hand motif, the EFX domain, that interacts with the basic/PDZ region of the Wnt signal transducer, dishevelled (Dsh). Here we show that Dsh binding by Drosophila Nkd in vitro is mediated by the EFX domain as well as an adjacent C-terminal sequence. In vivo data suggest that both of these regions contribute to the ability of Nkd to antagonize Wnt signaling. Mutations in the Nkd EF-hand designed to eliminate potential ion binding affected Nkd-Dsh interactions in the yeast two-hybrid assay but not in the glutathioneS-transferase pull-down assay. Addition of the chelating agent EDTA abolished the in vitro Nkd-Dsh interaction. Surprisingly zinc, but not calcium, was able to restore Nkd-Dsh binding, suggesting a zinc-mediated interaction. Calcium 45- and zinc 65-blotting experiments show that Nkd is a zinc-binding metalloprotein. The results further clarify how Nkd may antagonize Wnt signaling via interaction with Dsh, and identify a novel zinc-binding domain in Drosophila Nkd that collaborates with the conserved EFX domain to bind Dsh.
Chihchiang Chan - One of the best experts on this subject based on the ideXlab platform.
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mutations in the human Naked Cuticle homolog nkd1 found in colorectal cancer alter wnt dvl β catenin signaling
PLOS ONE, 2009Co-Authors: Tolga Cagatay, Kaye Suyama, Chihchiang Chan, Guangjin Zhou, Shelby A Blythe, Li Zheng, Chiping Qian, Richard Hamelin, Stephen N ThibodeauAbstract:BACKGROUND: Mutation of Wnt signal antagonists Apc or Axin activates beta-catenin signaling in many cancers including the majority of human colorectal adenocarcinomas. The phenotype of apc or axin mutation in the fruit fly Drosophila melanogaster is strikingly similar to that caused by mutation in the segment-polarity gene, Naked Cuticle (nkd). Nkd inhibits Wnt signaling by binding to the Dishevelled (Dsh/Dvl) family of scaffold proteins that link Wnt receptor activation to beta-catenin accumulation and TCF-dependent transcription, but human NKD genes have yet to be directly implicated in cancer. METHODOLOGY/PRINCIPAL FINDINGS: We identify for the first time mutations in NKD1--one of two human nkd homologs--in a subset of DNA mismatch repair-deficient colorectal tumors that are not known to harbor mutations in other Wnt-pathway genes. The mutant Nkd1 proteins are defective at inhibiting Wnt signaling; in addition, the mutant Nkd1 proteins stabilize beta-catenin and promote cell proliferation, in part due to a reduced ability of each mutant Nkd1 protein to bind and destabilize Dvl proteins. CONCLUSIONS/SIGNIFICANCE: Our data raise the hypothesis that specific NKD1 mutations promote Wnt-dependent tumorigenesis in a subset of DNA mismatch-repair-deficient colorectal adenocarcinomas and possibly other Wnt-signal driven human cancers.
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Mutations in the Human Naked Cuticle Homolog NKD1 Found in Colorectal Cancer Alter Wnt/Dvl/β-Catenin Signaling
PLOS ONE, 2009Co-Authors: Tolga Cagatay, Kaye Suyama, Chihchiang Chan, Guangjin Zhou, Shelby A Blythe, Li Zheng, Chiping Qian, Richard HamelinAbstract:BACKGROUND: Mutation of Wnt signal antagonists Apc or Axin activates beta-catenin signaling in many cancers including the majority of human colorectal adenocarcinomas. The phenotype of apc or axin mutation in the fruit fly Drosophila melanogaster is strikingly similar to that caused by mutation in the segment-polarity gene, Naked Cuticle (nkd). Nkd inhibits Wnt signaling by binding to the Dishevelled (Dsh/Dvl) family of scaffold proteins that link Wnt receptor activation to beta-catenin accumulation and TCF-dependent transcription, but human NKD genes have yet to be directly implicated in cancer. METHODOLOGY/PRINCIPAL FINDINGS: We identify for the first time mutations in NKD1--one of two human nkd homologs--in a subset of DNA mismatch repair-deficient colorectal tumors that are not known to harbor mutations in other Wnt-pathway genes. The mutant Nkd1 proteins are defective at inhibiting Wnt signaling; in addition, the mutant Nkd1 proteins stabilize beta-catenin and promote cell proliferation, in part due to a reduced ability of each mutant Nkd1 protein to bind and destabilize Dvl proteins. CONCLUSIONS/SIGNIFICANCE: Our data raise the hypothesis that specific NKD1 mutations promote Wnt-dependent tumorigenesis in a subset of DNA mismatch-repair-deficient colorectal adenocarcinomas and possibly other Wnt-signal driven human cancers.
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drosophila Naked Cuticle nkd engages the nuclear import adaptor importin α3 to antagonize wnt β catenin signaling
Developmental Biology, 2008Co-Authors: Chihchiang Chan, Raphael Rousset, Shu Zhang, Keith A WhartonAbstract:Abstract Precise control of Wnt/β-catenin signaling is critical for animal development, stem cell renewal, and prevention of disease. In the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene limits signaling by the Wnt ligand Wingless (Wg) during embryo segmentation. Nkd is an intracellular protein that is composed of separable membrane- and nuclear-localization sequences (NLS) as well as a conserved EF-hand motif that binds the Wnt receptor-associated scaffold protein Dishevelled (Dsh), but the mechanism by which Nkd inhibits Wnt signaling remains a mystery. Here we identify a second NLS in Nkd that is required for full activity and that binds to the canonical nuclear import adaptor Importin-α3. The Nkd NLS is similar to the Importin-α3-binding NLS in the Drosophila heat-shock transcription factor (dHSF), and each Importin-α3-binding NLS required intact basic residues in similar positions for nuclear import and protein function. Our results provide further support for the hypothesis that Nkd inhibits nuclear step(s) in Wnt/β-catenin signaling and broaden our understanding of signaling pathways that engage the nuclear import machinery.
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Drosophila Naked Cuticle (Nkd) engages the nuclear import adaptor Importin-α3 to antagonize Wnt/β-catenin signaling
Developmental Biology, 2008Co-Authors: Chihchiang Chan, Raphael Rousset, Shu Zhang, Keith A WhartonAbstract:Abstract Precise control of Wnt/β-catenin signaling is critical for animal development, stem cell renewal, and prevention of disease. In the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene limits signaling by the Wnt ligand Wingless (Wg) during embryo segmentation. Nkd is an intracellular protein that is composed of separable membrane- and nuclear-localization sequences (NLS) as well as a conserved EF-hand motif that binds the Wnt receptor-associated scaffold protein Dishevelled (Dsh), but the mechanism by which Nkd inhibits Wnt signaling remains a mystery. Here we identify a second NLS in Nkd that is required for full activity and that binds to the canonical nuclear import adaptor Importin-α3. The Nkd NLS is similar to the Importin-α3-binding NLS in the Drosophila heat-shock transcription factor (dHSF), and each Importin-α3-binding NLS required intact basic residues in similar positions for nuclear import and protein function. Our results provide further support for the hypothesis that Nkd inhibits nuclear step(s) in Wnt/β-catenin signaling and broaden our understanding of signaling pathways that engage the nuclear import machinery.
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cell autonomous myristyl independent activity of the drosophila wnt wingless antagonist Naked Cuticle nkd
Developmental Biology, 2007Co-Authors: Chihchiang Chan, Shu Zhang, Tolga Cagatay, Keith A WhartonAbstract:Robust animal development, tissue homeostasis, and stem cell renewal requires precise control of the Wnt/β-catenin signaling axis. In the embryo of the fruit fly Drosophila melanogaster, the Naked Cuticle (nkd) gene attenuates signaling by the Wnt ligand Wingless (Wg) during segmentation. nkd mutants have been reported to exhibit abnormalities in wg transcription, Wg protein distribution and/or transport, and the intracellular response to Wg, but the relationship between each alteration and the molecular mechanism of Nkd action remains unclear. In addition, whether Nkd acts in a cell-autonomous or nonautonomous fashion in the embryo is not known. Mammalian Nkd homologs have N-terminal consensus sequences that direct the post-translational addition of a lipophilic myristoyl moiety, but fly and mosquito Nkd, while sharing N-terminal sequence homology, lack a myristoylation consensus sequence. Here we provide evidence that fly Nkd acts cell-autonomously in the embryo, with its N-terminus able to confer unique functional properties and membrane association that cannot be mimicked in vivo by heterologous myristoylation consensus sequences. In conjunction with our recent observation that Nkd requires nuclear localization for function, our data suggest that Nkd acts at more than one subcellular location within signal-receiving cells to attenuate Wg signaling.
Robert Tjian - One of the best experts on this subject based on the ideXlab platform.
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wnt signaling targets eto coactivation domain of taf4 tfiid in vivo
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Kevin J Wright, Robert TjianAbstract:Understanding the diverse activities of the multisubunit core promoter recognition complex TFIID in vivo requires knowledge of how individual subunits contribute to overall functions of this TATA box-binding protein (TBP)/TBP-associated factor (TAF) complex. By generating altered holo-TFIID complexes in Drosophila we identify the ETO domain of TAF4 as a coactivator domain likely targeted by Pygopus, a protein that is required for Wingless-induced transcription of Naked Cuticle. These results establish a coactivator function of TAF4 and provide a strategy to dissect mechanisms of TFIID function in vivo.
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Wnt signaling targets ETO coactivation domain of TAF4/TFIID in vivo
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Kevin J Wright, Robert TjianAbstract:Understanding the diverse activities of the multisubunit core promoter recognition complex TFIID in vivo requires knowledge of how individual subunits contribute to overall functions of this TATA box-binding protein (TBP)/TBP-associated factor (TAF) complex. By generating altered holo-TFIID complexes in Drosophila we identify the ETO domain of TAF4 as a coactivator domain likely targeted by Pygopus, a protein that is required for Wingless-induced transcription of Naked Cuticle. These results establish a coactivator function of TAF4 and provide a strategy to dissect mechanisms of TFIID function in vivo.
