Wnt/β‐catenin signaling plays a critical role in metazoan development, stem cell maintenance, and human disease. The multicomponent β‐catenin destruction complex maintains low cellular β‐catenin in the absence of a signal and becomes inhibited in the presence of a Wnt ligand, allowing β‐catenin levels to rise. We have identified an FDA-approved drug, pyrvinium, as a potent inhibitor of Wnt signaling. We show pyrvinium binds CK1α, enhances kinase activity and CK1α knockdown abrogates the effects of pyrvinium on the Wnt pathway. In addition to effects on Axin and β‐catenin levels, pyrvinium promotes degradation of Pygopus, a Wnt transcriptional component. Pyrvinium treatment of colon cancer cells with mutation of Adenomatous Polyposis Coli or β‐catenin inhibits both Wnt signaling and proliferation. These findings reveal allosteric activation of CK1α as an effective mechanism to inhibit Wnt signaling.
We also performed biochemical studies that identified positive feedback within the β‐catenin destruction complex between essential components, Axin and GSK3. Theoretical modeling of this positive feedback loop predicts bistability in the activity of the β‐catenin destruction complex. Through single cell studies, we generated experimental evidence for our theoretical predictions. These findings elucidate molecular design features that convert gradients into discrete binary cell fate decisions.
In conclusion, this work combines chemical studies and systems-level analysis to uncover novel mechanisms of regulating the Wnt/β‐catenin pathway. Our findings highlight new strategies for targeted therapeutics directed against the Wnt pathway.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-07082010-093358 |
| Date | 15 July 2010 |
| Creators | Thorne, Curtis Andrew |
| Contributors | Guoqiang Gu, Michael Cooper, Albert Reynolds, Kathleen Gould, Ethan Lee |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu//available/etd-07082010-093358/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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