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Structural and molecular basis of ZNRF3/RNF43 transmembrane ubiquitin ligase inhibition by the Wnt agonist R-spondin.

ABSTRACT: The four R-spondin (Rspo) proteins are secreted agonists of Wnt signalling in vertebrates, functioning in embryogenesis and adult stem cell biology. Through ubiquitination and degradation of Wnt receptors, the transmembrane E3 ubiquitin ligase ZNRF3 and related RNF43 antagonize Wnt signalling. Rspo ligands have been reported to inhibit the ligase activity through direct interaction with ZNRF3 and RNF43. Here we report multiple crystal structures of the ZNRF3 ectodomain (ZNRF3(ecto)), a signalling-competent Furin1-Furin2 (Fu1-Fu2) fragment of Rspo2 (Rspo2(Fu1-Fu2)), and Rspo2(Fu1-Fu2) in complex with ZNRF3(ecto), or RNF43(ecto). A prominent loop in Fu1 clamps into equivalent grooves in the ZNRF3(ecto) and RNF43(ecto) surface. Rspo binding enhances dimerization of ZNRF3(ecto) but not of RNF43(ecto). Comparison of the four Rspo proteins, mutants and chimeras in biophysical and cellular assays shows that their signalling potency depends on their ability to recruit ZNRF3 or RNF43 via Fu1 into a complex with LGR receptors, which interact with Rspo via Fu2.

SUBMITTER: Zebisch M

PROVIDER: S-EPMC3905715 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Structural and molecular basis of ZNRF3/RNF43 transmembrane ubiquitin ligase inhibition by the Wnt agonist R-spondin.

Zebisch Matthias M Xu Yang Y Krastev Christos C MacDonald Bryan T BT Chen Maorong M Gilbert Robert J C RJ He Xi X Jones E Yvonne EY

Nature communications 20130101

The four R-spondin (Rspo) proteins are secreted agonists of Wnt signalling in vertebrates, functioning in embryogenesis and adult stem cell biology. Through ubiquitination and degradation of Wnt receptors, the transmembrane E3 ubiquitin ligase ZNRF3 and related RNF43 antagonize Wnt signalling. Rspo ligands have been reported to inhibit the ligase activity through direct interaction with ZNRF3 and RNF43. Here we report multiple crystal structures of the ZNRF3 ectodomain (ZNRF3(ecto)), a signallin ...[more]

PMID: 24225776

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Project description:Loss-of-function mutations in RNF43 induce activation of Wnt ligand-dependent Wnt/β-catenin signaling through stabilization of the Frizzled receptor, which is often found in microsatellite instability (MSI)-type colorectal cancer (CRC) that develops from sessile serrated adenomas. However, the mechanism underlying how RNF43 mutations promote tumorigenesis remains poorly understood. In this study, we established nine human CRC-derived organoids and found that three organoid lines carried RNF43 frameshift mutations associated with MSI-high and BRAFV600E mutations, suggesting that these CRCs developed through the serrated pathway. RNF43 frameshift mutant organoids required both Wnt ligands and R-spondin for proliferation, indicating that suppression of ZNRF3 and retained RNF43 function by R-spondin are required to achieve an indispensable level of Wnt activation for tumorigenesis. However, active β-catenin levels in RNF43-mutant organoids were lower than those in APC two-hit mutant CRC, suggesting a lower threshold for Wnt activation in CRC that developed through the serrated pathway. Interestingly, transplantation of RNF43-mutant organoids with intestinal myofibroblasts accelerated the β-catenin nuclear accumulation and proliferation of xenograft tumors, indicating a key role of stromal cells in the promotion of the malignant phenotype of RNF43-mutant CRC cells. Sequencing of subcloned organoid cell-expressed transcripts revealed that two organoid lines carried monoallelic RNF43 cis-mutations, with two RNF43 frameshift mutations introduced in the same allele and the wild-type RNF43 allele remaining, while the other organoid line carried two-hit biallelic RNF43 trans-mutations. These results suggest that heterozygous RNF43 frameshift mutations contribute to CRC development via the serrated pathway; however, a second-hit RNF43 mutation may be advantageous in tumorigenesis compared with a single-hit mutation through further activation of Wnt signaling. Finally, treatment with the PORCN inhibitor significantly suppressed RNF43-mutant cell-derived PDX tumor development. These results suggest a novel mechanism underlying RNF43 mutation-associated CRC development and the therapeutic potential of Wnt ligand inhibition against RNF43-mutant CRC. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Dataset Information

Structural and molecular basis of ZNRF3/RNF43 transmembrane ubiquitin ligase inhibition by the Wnt agonist R-spondin.

Publications

Structural and molecular basis of ZNRF3/RNF43 transmembrane ubiquitin ligase inhibition by the Wnt agonist R-spondin.

Similar Datasets

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