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Assembly and architecture of the Wnt/?-catenin signalosome at the membrane.

ABSTRACT: Wnt/?-catenin signalling is initiated by a ternary Wnt-Frizzled (FZD)-LDL receptor-related protein (LRP) 5/6 binding event. The resulting conformational changes in the FZD and LRP5/6 receptors promote the assembly of an intracellular signalosome driven by Dishevelled and Axin co-polymerization. Recent evidence suggests that the FZD receptor and LRP5/6 participate in the assembly of this signalosome by forming regulatory scaffolds for stabilizing Dishevelled and Axin adapters. In this review, we focus on the contributions of Wnts and their receptors in the assembly of the signalosome. We present an emerging model, which unifies Wnt receptor oligomerization with intracellular signalosome formation, and then discuss how FZD receptors might be targeted to either disrupt or enhance their capacity as a dynamic sensor of Wnt binding. LINKED ARTICLES:This article is part of a themed section on WNT Signalling: Mechanisms and Therapeutic Opportunities. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.24/issuetoc.

SUBMITTER: DeBruine ZJ

PROVIDER: S-EPMC5727340 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Assembly and architecture of the Wnt/β-catenin signalosome at the membrane.

DeBruine Zachary J ZJ Xu H E HE Melcher Karsten K

British journal of pharmacology 20171018 24

Wnt/β-catenin signalling is initiated by a ternary Wnt-Frizzled (FZD)-LDL receptor-related protein (LRP) 5/6 binding event. The resulting conformational changes in the FZD and LRP5/6 receptors promote the assembly of an intracellular signalosome driven by Dishevelled and Axin co-polymerization. Recent evidence suggests that the FZD receptor and LRP5/6 participate in the assembly of this signalosome by forming regulatory scaffolds for stabilizing Dishevelled and Axin adapters. In this review, we ...[more]

PMID: 28941231

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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

Assembly and architecture of the Wnt/?-catenin signalosome at the membrane.

Publications

Assembly and architecture of the Wnt/β-catenin signalosome at the membrane.

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