Abstract
Axin is a key scaffolding protein responsible for the formation of the β-catenin destruction complex. Stability of Axin protein is regulated by the ubiquitin-proteasome system, and modulation of cellular concentration of Axin protein has a profound effect on Wnt/β-catenin signaling. Although E3s promoting Axin ubiquitination have been identified, the deubiquitinase responsible for Axin deubiquitination and stabilization remains unknown. Here, we identify USP7 as a potent negative regulator of Wnt/β-catenin signaling through CRISPR screens. Genetic ablation or pharmacological inhibition of USP7 robustly increases Wnt/β-catenin signaling in multiple cellular systems. USP7 directly interacts with Axin through its TRAF domain, and promotes deubiquitination and stabilization of Axin. Inhibition of USP7 regulates osteoblast differentiation and adipocyte differentiation through increasing Wnt/β-catenin signaling. Our study reveals a critical mechanism that prevents excessive degradation of Axin and identifies USP7 as a target for sensitizing cells to Wnt/β-catenin signaling.
Highlights
Axin is a key scaffolding protein responsible for the formation of the β-catenin destruction complex
STF-GFP reporter cells were mutagenized by a pooled lenti-viral guide RNA library, treated with Wnt3a conditioned medium (CM) and subjected to FACS analysis
Since USP7 stabilizes its substrates through promoting their deubiquitination, we examined whether USP7 could affect ubiquitination of Axin
Summary
Axin is a key scaffolding protein responsible for the formation of the β-catenin destruction complex. Our study reveals a critical mechanism that prevents excessive degradation of Axin and identifies USP7 as a target for sensitizing cells to Wnt/β-catenin signaling. In the absence of Wnt, β-catenin is bound to the β-catenin destruction complex, which contains the scaffolding protein Axin, the tumor suppressor adenomatous polyposis coli (APC), glycogen synthase kinase 3 (GSK3) and casein kinase 1α (CK1α). In this complex, β-catenin is phosphorylated by CK1α and GSK3, and targeted for ubiquitin-dependent proteasomal degradation. USP7 regulates the stability, function, or localization of its substrates, and plays important roles in cancer development, cell signaling, DNA damage repair, epigenetic regulation, and immune responses (reviewed by[21]).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
