Receptor for Dickkopf proteins. Cooperates with DKK1/2 to inhibit Wnt/beta-catenin signaling by promoting the endocytosis of Wnt receptors LRP5 and LRP6 (PubMed:12050670). In the absence of DKK1, potentiates Wnt-beta-catenin signaling by maintaining LRP5 or LRP6 at the cell membrane (By similarity). Can trigger apoptosis in a Wnt-independent manner and this apoptotic activity is inhibited upon binding of the ligand DKK1 (PubMed:26206087). 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 (PubMed:18505822). Modulates cell fate decisions in the developing cochlea with an inhibitory role in hair cell fate specification (PubMed:27550540). Forms a ternary complex with DKK1 and LRP6 (PubMed:12050670). Interacts with LRP6 in a DKK1-dependent manner. Interacts with DKK1 and RSPO1 (via FU repeats) (By similarity). In the adult, widely expressed with high levels in heart, lung, kidney, skeletal muscle and testis. Expressed in the developing cochlea. Expressed first in the prosensory domain and the expression is restricted to supporting cells as development proceeds (at protein level). In the embryo, expression is first detected on day 9 and increases up to day 18. Lower levels are found in adult. At 9.5 dpc, expression is localized to the apical ectodermal ridge (AER) of the developing fore- and hindlimb buds, the telencephalon and the first brachial arch. At 10.5 dpc, expression is also observed in the myotome and in sensory tissues such as the nasal pit and optic vesicle. Expressed in the developing brain and developing limb buds. Animals with a double knockout of KREM1 and KREM2 exhibit enhanced Wnt signaling accompanied by ectopic postaxial forelimb digits and expanded apical ectodermal ridges. They also exhibit increased bone volume and bone formation rates. Triple knockout mice KREM1/KREM2/DKK1 exhibit enhanced growth of ectopic digits.