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Updated: May 30, 2026
Reconstitution Of β-catenin Degradation In Xenopus Egg Extract
Published on: June 17, 2014
A biochemical screen for identification of small-molecule regulators of the Wnt pathway using Xenopus egg extracts
Curtis A Thorne1, Bonnie Lafleur, Michelle Lewis
1Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-8240, USA.
Abstract:
Misregulation of the Wnt pathway has been shown to be responsible for a variety of human diseases, most notably cancers. Screens for inhibitors of this pathway have been performed almost exclusively using cultured mammalian cells or with purified proteins. We have previously developed a biochemical assay using Xenopus egg extracts to recapitulate key cytoplasmic events in the Wnt pathway. Using this biochemical system, we show that a recombinant form of the Wnt coreceptor, LRP6, regulates the stability of two key components of the Wnt pathway (β-catenin and Axin) in opposing fashion. We have now fused β-catenin and Axin to firefly and Renilla luciferase, respectively, and demonstrate that the fusion proteins behave similarly as their wild-type counterparts. Using this dual luciferase readout, we adapted the Xenopus extracts system for high-throughput screening. Results from these screens demonstrate signal distribution curves that reflect the complexity of the library screened. Of several compounds identified as cytoplasmic modulators of the Wnt pathway, one was further validated as a bona fide inhibitor of the Wnt pathway in cultured mammalian cells and Xenopus embryos. We show that other embryonic pathways may be amendable to screening for inhibitors/modulators in Xenopus egg extracts.
Insights
This study developed a high-throughput screening method using Xenopus egg extracts to identify Wnt pathway inhibitors. A novel compound was validated as a Wnt pathway inhibitor in both cell cultures and embryos.
Area of Science:
- Biochemistry
- Developmental Biology
- Molecular Biology
Background:
- The Wnt pathway is crucial in human diseases, particularly cancers.
- Previous inhibitor screens relied on mammalian cells or purified proteins.
- A Xenopus egg extract system was previously established to study Wnt pathway cytoplasmic events.
Purpose of the Study:
- To develop a high-throughput screening (HTS) system for Wnt pathway modulators using Xenopus egg extracts.
- To identify novel inhibitors of the Wnt pathway.
- To explore the utility of Xenopus egg extracts for screening other embryonic pathways.
Main Methods:
- Recombinant Wnt coreceptor LRP6 was used to study its effect on beta-catenin and Axin stability.
- Beta-catenin and Axin were fused to luciferase reporters for a dual-luciferase readout.
- The Xenopus egg extract system was adapted for HTS.
- Identified compounds were validated in mammalian cells and Xenopus embryos.
Main Results:
- Recombinant LRP6 differentially regulated beta-catenin and Axin stability.
- Fusion proteins behaved similarly to wild-type counterparts.
- HTS identified cytoplasmic modulators of the Wnt pathway.
- One compound demonstrated bona fide Wnt pathway inhibition in multiple models.
Conclusions:
- The Xenopus egg extract system with dual-luciferase reporters is effective for HTS of Wnt pathway modulators.
- This system can identify novel Wnt pathway inhibitors.
- Xenopus egg extracts show potential for screening inhibitors of other embryonic signaling pathways.
