Activator of the canonical Wnt signaling pathway by acting as a ligand for LGR4-6 receptors (PubMed:29769720). Upon binding to LGR4-6 (LGR4, LGR5 or LGR6), LGR4-6 associate with phosphorylated LRP6 and frizzled receptors that are activated by extracellular Wnt receptors, triggering the canonical Wnt signaling pathway to increase expression of target genes. Also regulates the canonical Wnt/beta-catenin-dependent pathway and non-canonical Wnt signaling by acting as an inhibitor of ZNRF3, an important regulator of the Wnt signaling pathway (PubMed:21727895, PubMed:21909076). Binds heparin (By similarity). Interacts with LGR4, LGR5 and LGR6. The FU repeat is required for activation and stabilization of beta-catenin. Tyr-112 may be phosphorylated; however as this position is probably extracellular, the vivo relevance is not proven. The disease is caused by variants affecting the gene represented in this entry. Belongs to the R-spondin family.