Journal
SCIENCE SIGNALING
Volume 7, Issue 317, Pages -Publisher
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/scisignal.2004985
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Funding
- Dutch Cancer Society [HUBR 2008-4114]
- Ministry of Education, Youth, and Sports of the Czech Republic [MSM0021622430]
- Czech Science Foundation [204/09/H058, 204/09/0498, 13-31488P]
- EMBO
- CEITEC-Central European Institute of Technology project from the European Regional Development Fund [CZ.1.05/1.1.00/02.0068]
- CEITEC open access project [LM2011020]
- Ministry of Education, Youth, and Sports of the Czech Republic
- Cancer Research UK
- Merck Serono
- Breast Cancer Campaign
- Tenovus
- Biotechnology and Biological Sciences Research Council [BB/D00117X/1] Funding Source: researchfish
- Cancer Research UK [15937] Funding Source: researchfish
- BBSRC [BB/D00117X/1] Funding Source: UKRI
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Wnt signaling plays a central role in development, adult tissue homeostasis, and cancer. Several steps in the canonical Wnt/beta-catenin signaling cascade are regulated by ubiquitylation, a protein modification that influences the stability, subcellular localization, or interactions of target proteins. To identify regulators of the Wnt/beta-catenin pathway, we performed an RNA interference screen in Caenorhabditis elegans and identified the HECT domain-containing ubiquitin ligase EEL-1 as an inhibitor of Wnt signaling. In human embryonic kidney 293T cells, knockdown of the EEL-1 homolog Huwe1 enhanced the activity of a Wnt reporter in cells stimulated with Wnt3a or in cells that overexpressed casein kinase 1 (CK1) or a constitutively active mutant of the Wnt co-receptor low-density lipoprotein receptor-related protein 6 (LRP6). However, knockdown of Huwe1 had no effect on reporter gene expression in cells expressing constitutively active beta-catenin, suggesting that Huwe1 inhibited Wnt signaling upstream of beta-catenin and downstream of CK1 and LRP6. Huwe1 bound to and ubiquitylated the cytoplasmic Wnt pathway component Dishevelled (Dvl) in a Wnt3a- and CK1 epsilon-dependent manner. Mass spectrometric analysis showed that Huwe1 promoted K63-linked, but not K48-linked, polyubiquitination of Dvl. Instead of targeting Dvl for degradation, ubiquitylation of the DIX domain of Dvl by Huwe1 inhibited Dvl multimerization, which is necessary for its function. Our findings indicate that Huwe1 is part of an evolutionarily conserved negative feedback loop in the Wnt/beta-catenin pathway.
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