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Axin directly interacts with plakoglobin and regulates its stability
1Department of Biochemistry, Hiroshima University School of Medicine, 1-2-3, Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
The Journal of Biological Chemistry
|September 17, 1999
Summary
Axin, a Wnt pathway regulator, targets plakoglobin for degradation by promoting its phosphorylation. This suggests Axin influences plakoglobin stability similarly to beta-catenin.
Area of Science:
- Cell Biology
- Molecular Biology
- Signal Transduction
Background:
- Plakoglobin shares homology with beta-catenin, a key Wnt signaling component.
- Axin acts as a negative regulator in the Wnt pathway, promoting beta-catenin phosphorylation and degradation via GSK-3beta.
Purpose of the Study:
- To investigate the effect of Axin on plakoglobin stability.
- To determine if Axin interacts with and modifies plakoglobin phosphorylation.
Main Methods:
- Co-immunoprecipitation assays in COS and SW480 cells to detect protein complexes.
- In vitro binding assays to assess direct interactions between Axin and plakoglobin.
- Analysis of plakoglobin phosphorylation levels following Axin overexpression and GSK-3beta activity.
Main Results:
- Axin formed a complex with plakoglobin in cellular models.
- Direct binding of Axin to plakoglobin was observed, which was competitively inhibited by beta-catenin.
- Axin enhanced glycogen synthase kinase-3beta (GSK-3beta)-dependent phosphorylation of plakoglobin.
- Overexpression of Axin led to decreased plakoglobin levels in SW480 cells.
Conclusions:
- Axin regulates plakoglobin stability through GSK-3beta-mediated phosphorylation.
- Axin appears to modulate plakoglobin stability in a manner analogous to its regulation of beta-catenin.