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Nradd Acts as a Negative Feedback Regulator of Wnt/?-Catenin Signaling and Promotes Apoptosis.

ABSTRACT: Wnt/?-catenin signaling controls many biological processes for the generation and sustainability of proper tissue size, organization and function during development and homeostasis. Consequently, mutations in the Wnt pathway components and modulators cause diseases, including genetic disorders and cancers. Targeted treatment of pathway-associated diseases entails detailed understanding of the regulatory mechanisms that fine-tune Wnt signaling. Here, we identify the neurotrophin receptor-associated death domain (Nradd), a homolog of p75 neurotrophin receptor (p75^NTR), as a negative regulator of Wnt/?-catenin signaling in zebrafish embryos and in mammalian cells. Nradd significantly suppresses Wnt8-mediated patterning of the mesoderm and neuroectoderm during zebrafish gastrulation. Nradd is localized at the plasma membrane, physically interacts with the Wnt receptor complex and enhances apoptosis in cooperation with Wnt/?-catenin signaling. Our functional analyses indicate that the N-glycosylated N-terminus and the death domain-containing C-terminus regions are necessary for both the inhibition of Wnt signaling and apoptosis. Finally, Nradd can induce apoptosis in mammalian cells. Thus, Nradd regulates cell death as a modifier of Wnt/?-catenin signaling during development.

SUBMITTER: Ozalp O

PROVIDER: S-EPMC7828832 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Nradd Acts as a Negative Feedback Regulator of Wnt/β-Catenin Signaling and Promotes Apoptosis.

Ozalp Ozgun O Cark Ozge O Azbazdar Yagmur Y Haykir Betul B Cucun Gokhan G Kucukaylak Ismail I Alkan-Yesilyurt Gozde G Sezgin Erdinc E Ozhan Gunes G

Biomolecules 20210114 1

Wnt/β-catenin signaling controls many biological processes for the generation and sustainability of proper tissue size, organization and function during development and homeostasis. Consequently, mutations in the Wnt pathway components and modulators cause diseases, including genetic disorders and cancers. Targeted treatment of pathway-associated diseases entails detailed understanding of the regulatory mechanisms that fine-tune Wnt signaling. Here, we identify the neurotrophin receptor-associat ...[more]

PMID: 33466728

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Project description:BACKGROUND:Aberrant Wnt/?-catenin signaling is associated with breast cancer even though genetic mutations in Wnt signaling components are rare. We have previously demonstrated that Rad6B, an ubiquitin conjugating enzyme, stabilizes ?-catenin via polyubiqutin modifications that render ?-catenin insensitive to proteasomal degradation. Rad6B is a transcriptional target of ?-catenin, creating a positive feedback loop between Rad6B expression and ?-catenin activation. METHODS:To isolate subpopulations expressing high or low Rad6B levels, we transfected MDA-MB-231 or WS-15 human breast cancer cells with ZsGreen fluorescent reporter vector in which the expression of ZsGreen was placed under the control of Rad6B promoter. ZsGreenhigh and ZsGreenlow subpopulations, reflective of high and low Rad6B promoter activity, respectively, were isolated by FACS. To determine the relevance of Wnt signaling in Rad6B-mediated ?-catenin stabilization/activation, the ZsGreenhigh cells were transfected with signaling-defective Wnt coreceptor LRP6?173. Rad6B expression and promoter activity were determined by RT-PCR, Western blot and Rad6B promoter-mediated luciferase assays. ?-catenin levels and transcriptional activity were determined by Western blot and TOP/FOP Flash reporter assays. Tumor formation and morphologies of ZsGreenlow, ZsGreenhigh, and ZsGreenhigh/LRP6?173 cells compared to unsorted vector controls were evaluated in nude mice. Expression of Wnt signaling related genes was profiled using the Wnt signaling pathway RT2 Profiler PCR arrays. RESULTS:ZsGreenhigh subpopulations showed high Rad6B expression and Rad6B promoter activity as compared to ZsGreenlow cells. ZsGreenhigh (high Rad6B expressors) also showed elevated ?-catenin levels and TOP/Flash activity. Inhibiting Wnt signaling in the high Rad6B expressors decreased ZsGreen fluorescence, Rad6B gene expression, ?-catenin levels and TOP/Flash activity. Tumors derived from high Rad6B expressors were predominantly composed of cells with epithelial mesenchymal transition (EMT) phenotype as compared to control tumors that were composed of both cuboidal and EMT-type cells. Tumors derived from low Rad6B expressors lacked EMT phenotype. Inhibition of LRP6 function in the high Rad6B expressors abrogated the EMT phenotype. Gene expression profiling showed upregulation of several Wnt signaling pathway regulators in high Rad6B expressors that were downregulated by interference of Wnt signaling with mutant LRP6 or by Rad6B silencing. CONCLUSIONS:These data reveal a functional link between the canonical Wnt pathway and Rad6B in ?-catenin activation and breast cancer progression.

Dataset Information

Nradd Acts as a Negative Feedback Regulator of Wnt/?-Catenin Signaling and Promotes Apoptosis.

Publications

Nradd Acts as a Negative Feedback Regulator of Wnt/β-Catenin Signaling and Promotes Apoptosis.

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