Dataset Information

Modulation of the beta-catenin signaling pathway by the dishevelled-associated protein Hipk1.

ABSTRACT: BACKGROUND:Wnts are evolutionarily conserved ligands that signal through beta-catenin-dependent and beta-catenin-independent pathways to regulate cell fate, proliferation, polarity, and movements during vertebrate development. Dishevelled (Dsh/Dvl) is a multi-domain scaffold protein required for virtually all known Wnt signaling activities, raising interest in the identification and functions of Dsh-associated proteins. METHODOLOGY:We conducted a yeast-2-hybrid screen using an N-terminal fragment of Dsh, resulting in isolation of the Xenopus laevis ortholog of Hipk1. Interaction between the Dsh and Hipk1 proteins was confirmed by co-immunoprecipitation assays and mass spectrometry, and further experiments suggest that Hipk1 also complexes with the transcription factor Tcf3. Supporting a nuclear function during X. laevis development, Myc-tagged Hipk1 localizes primarily to the nucleus in animal cap explants, and the endogenous transcript is strongly expressed during gastrula and neurula stages. Experimental manipulations of Hipk1 levels indicate that Hipk1 can repress Wnt/beta-catenin target gene activation, as demonstrated by beta-catenin reporter assays in human embryonic kidney cells and by indicators of dorsal specification in X. laevis embryos at the late blastula stage. In addition, a subset of Wnt-responsive genes subsequently requires Hipk1 for activation in the involuting mesoderm during gastrulation. Moreover, either over-expression or knock-down of Hipk1 leads to perturbed convergent extension cell movements involved in both gastrulation and neural tube closure. CONCLUSIONS:These results suggest that Hipk1 contributes in a complex fashion to Dsh-dependent signaling activities during early vertebrate development. This includes regulating the transcription of Wnt/beta-catenin target genes in the nucleus, possibly in both repressive and activating ways under changing developmental contexts. This regulation is required to modulate gene expression and cell movements that are essential for gastrulation.

SUBMITTER: Louie SH

PROVIDER: S-EPMC2629544 | biostudies-literature | 2009

REPOSITORIES: biostudies-literature

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Modulation of the beta-catenin signaling pathway by the dishevelled-associated protein Hipk1.

Louie Sarah H SH Yang Xiao Yong XY Conrad William H WH Muster Jeanot J Angers Stephane S Moon Randall T RT Cheyette Benjamin N R BN

PloS one 20090202 2

<h4>Background</h4>Wnts are evolutionarily conserved ligands that signal through beta-catenin-dependent and beta-catenin-independent pathways to regulate cell fate, proliferation, polarity, and movements during vertebrate development. Dishevelled (Dsh/Dvl) is a multi-domain scaffold protein required for virtually all known Wnt signaling activities, raising interest in the identification and functions of Dsh-associated proteins.<h4>Methodology</h4>We conducted a yeast-2-hybrid screen using an N-t ...[more]

PMID: 19183803

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Project description:Liver fibrosis is a common pathological process of various chronic liver diseases that can develop into liver cancer. MicroRNAs (miRNAs) are a king of non-coding RNA which are closely related to liver diseases. Thus, this research hope to explore the effect of miR-484 on liver fibrosis and reveal its mechanism. The miRNAs profiles were screened by microRNA sequencing and the location of miR-484 was identified by fluorescence in situ hybridization (FISH) in human liver fibrotic tissues. MiR-484 expression was detected by qRT-PCR in rat primary hepatic stellate cells (HSCs). Bioinformatics analysis and dual-luciferase reporter assay were performed to determine the target gene of miR-484. Liver fibrosis specific signatures were analyzed by qRT-PCR and western blot after miR-484 mimic/inhibitor transfection. The cell apoptosis was detected by Annexin V-FITC/PI double staining. The effect of miR-484 silencing on fibrosis in vivo was investigated in thioacetamide (TAA) induced mice model using the adeno-associated virus carrying miR-484 inhibitor. Enrichment of miR-484 was observed in human liver fibrosis tissues and activated rat primary HSCs. FISH showed that miR-484 was prominently located at fibrotic region and the cytoplasm of HSCs in human liver tissues. Dual-luciferase reporter assay verified that the homeodomain-interacting protein kinases 1 (HIPK1) was the direct target of miR-484. After transfecting miR-484 inhibitor into HSC-T6, HIPK1 were significantly up-regulated, and α-SMA, col1a1, Wnt-3a, Wnt-5a, β-catenin and p-β-catenin were down-regulated, suggesting the restrain effect of miR-484 knockdown on HSCs activation. Conversely, the results were opposite with miR-484 mimic transfection. In addition, the apoptosis of HSC-T6 altered significantly after miR-484 modulation. Moreover, adeno-associated virus carrying miR-484 inhibitor alleviated mice liver fibrosis induced by TAA. In conclusion, miR-484 knockdown ameliorates liver fibrosis by promoting the apoptosis and suppressing HSCs activation via blocking Wnt/β-catenin signaling pathway. MiR-484 and its downstream gene HIPK1 might be selected as novel therapeutic targets of liver fibrosis.

Project description:Salmonella infections can become chronic and increase the risk of cancer. The mechanisms by which specific Salmonella organisms contribute to cancer, however, are still unknown. Live and attenuated Salmonella are used as vectors to target cancer cells, but there have been no systematic studies of the oncogenic potential of chronic Salmonella infections in cancer models. AvrA, a pathogenic product of Salmonella, is inserted into host cells during infection and influences eukaryotic cell pathways. In the current study, we colonized mice with Salmonella AvrA-sufficient or AvrA-deficient Salmonella typhimirium strains and induced inflammation-associated colon cancer by azoxymethane/dextran sulfate sodium (AOM/DSS). We confirmed Salmonella persisted in the colon for up to 45 weeks. Salmonella was identified not only in epithelial cells on the colonic luminal surface and base of the crypts but also in invading tumors. Tumor incidence in the AvrA+infected group was 100% compared with 51.4% in the AOM/DSS group without bacterial gavage and 56.3% in mice infected with the AvrA- strain. Infection with AvrA+ strain also altered tumor distribution from the distal to proximal colon that might reflect changes in the microbiome. AvrA-expressing bacteria also upregulated beta-catenin signaling as assessed by decreased beta-catenin ubiquitination, increased nuclear beta-catenin and increased phosphorylated-beta-catenin (Ser552), a marker of proliferating stem-progenitor cells. Other β-catenin targets increased by AvrA included Bmi1, a cancer stem cell marker, matrix metalloproteinase-7, and cyclin D1. In summary, AvrA-expressing Salmonella infection activates β-catenin signals and enhances colonic tumorigenesis. Our findings provide important new mechanistic insights into how a bacterial protein targets proliferating stem-progenitor cells and contributes to cancer development. Our observations also raise a note of caution regarding the use of mutant Salmonella organisms as vectors for anti-cancer therapy. Finally, these studies could suggest biomarkers (such as AvrA level in gut) to assess cancer risk in susceptible individuals and infection-related dysregulation of β-catenin signaling in cancer.

Dataset Information

Modulation of the beta-catenin signaling pathway by the dishevelled-associated protein Hipk1.

Publications

Modulation of the beta-catenin signaling pathway by the dishevelled-associated protein Hipk1.

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