Receptor for Dickkopf proteins. Cooperates with DKK1/2 to inhibit Wnt/beta-catenin signaling by promoting the endocytosis of Wnt receptors LRP5 and LRP6. In the absence of DKK1, potentiates Wnt-beta-catenin signaling by maintaining LRP5 or LRP6 at the cell membrane. Can trigger apoptosis in a Wnt-independent manner and this apoptotic activity is inhibited upon binding of the ligand DKK1. Plays a role in limb development; attenuates Wnt signaling in the developing limb to allow normal limb patterning and can also negatively regulate bone formation. Modulates cell fate decisions in the developing cochlea with an inhibitory role in hair cell fate specification. Forms a ternary complex with DKK1 and LRP6 (PubMed:27524201). Interacts with LRP6 in a DKK1-dependent manner. Interacts with DKK1 and RSPO1 (via FU repeats) (PubMed:17804805). The disease is caused by variants affecting the gene represented in this entry. Exon 1 splicing donor site is not canonical.