4UFS: Low Resolution Structure R-spondin-2 (fu1fu2) In Complex With The Ectodomains Of Lgr5 And Znrf3

The four secreted R-spondin (Rspo1-4) proteins of vertebrates function as stem cell growth factors and potentiate canonical Wnt signalling. Rspo proteins act by cross-linking members of two cell surface receptor families, complexing the stem cell markers LGR4-6 with the Frizzled-specific E3 ubiquitin ligases ZNRF3/RNF43. The consequent internalisation of the ternary LGR-Rspo-E3 complex removes the E3 ligase activity, which otherwise targets the Wnt receptor Frizzled for degradation, and thus enhances Wnt signalling. Multiple combinations of LGR4-6, Rspo1-4 and ZNRF3/RNF43 are possible, implying the existence of generic interaction determinants, but also of specific differences in complex architecture and activity. We present here a high resolution crystal structure of an ectodomain variant of human LGR5 (hLGR5ecto) complexed with a signalling competent fragment of mouse Rspo2 (mRspo2Fu1-Fu2). The structure shows that the particularly potent Rspo2 ligand engages LGR5 in a fashion almost identical to that reported for hRSPO1. Comparison of our hLGR5ecto structure with previously published structures highlights a surprising plasticity of the LGR ectodomains, characterised by a nearly 9 degrees or larger rotation of the N-terminal half of the horseshoe-like fold relative to the C-terminal half. We also report a low resolution hLGR5-mRspo2Fu1-Fu2-mZNRF3ecto ternary complex structure. This crystal structure confirms our previously suggested hypothesis, showing that Rspo proteins cross-link LGRs and ZNRF3 into a 2:2:2 complex, whereas a 1:1:1 complex is formed with RNF43.
PDB ID: 4UFSDownload
MMDB ID: 130686
PDB Deposition Date: 2015/3/18
Updated in MMDB: 2015/08
Experimental Method:
x-ray diffraction
Resolution: 4.8  Å
Source Organism:
Similar Structures:
Biological Unit for 4UFS: trimeric; determined by author and by software (PQS)
Molecular Components in 4UFS
Label Count Molecule
Proteins (3 molecules)
Leucine-rich Repeat-containing G-protein Coupled Receptor 5(Gene symbol: LGR5)
Molecule annotation
R-spondin-2(Gene symbol: Rspo2)
Molecule annotation
E3 Ubiquitin-protein Ligase Znrf3(Gene symbol: Znrf3)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

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