Antagonizes canonical Wnt signaling by inhibiting LRP5/6 interaction with Wnt and by forming a ternary complex with the transmembrane protein KREMEN that promotes internalization of LRP5/6 (PubMed:18524778). Inhibits the pro-apoptotic function of KREMEN1 in a Wnt-independent manner, and has anti-apoptotic activity (PubMed:26206087). Plays a role in limb development; attenuates Wnt signaling in the developing limb to allow normal limb patterning (PubMed:18505822). Interacts (via the C-termianl Cys-rich domain) with LRP5 (via beta-propeller regions 3 and 4); the interaction, enhanced by MESD and or KREMEN, antagonizes Wnt-mediated signaling. Interacts with LRP6 (PubMed:18524778). Forms a ternary complex with LRP6 and KREM1. Interacts with KREM1 (By similarity). Expressed in the developing brain, cochlea and limb buds. The C-terminal cysteine-rich domain mediates interaction with LRP5 and LRP6. Triple knockout mice KREM1/KREM2/DKK1 exhibit enhanced growth of ectopic digits. Belongs to the dickkopf family.