 Importantly, the cytoplasmic segments of the Frizzled-associated LRP5 and LRP6 proteins contain GSK3 pseudo-substrate sequences (Pro-Pro-Pro-Ser-Pro-x-Ser), appropriately "primed" (pre-phosphorylated) by CKI, as if it were a true substrate of GSK3.These false target sites greatly inhibit GSK3 activity in a competitive manner.This way receptor-bound "axin" will abolish mediating the phosphorylation of β-catenin.