A biochemical screen for identification of small-molecule regulators of the Wnt pathway using Xenopus egg extracts.
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.
PubMed ID: 21859680
PMC ID: PMC3694444
Article link: J Biomol Screen.
Grant support: 1 R01 GM081635-01 NIGMS NIH HHS , 5 T 32 DK007563 NIDDK NIH HHS , 5 T32 GM007347 NIGMS NIH HHS , GM085442 NIGMS NIH HHS , P50 CA95103 NCI NIH HHS , T32 CA09592 NCI NIH HHS , T32 DK007563 NIDDK NIH HHS , R01 GM081635 NIGMS NIH HHS , T32 CA009592 NCI NIH HHS
Genes referenced: lrp6