Frizzled-9: Proteins and Enzymes

This group of G protein-coupled receptors consists of 10 structurally-related, seven transmembrane proteins with a divergent N-terminal signal peptide and a variable-length C-terminal tail. The Frizzled family proteins contain a highly conserved cysteine-rich domain and a variable length linker region. Frizzled proteins function as receptors for Wnt proteins and can activate canonical Wnt/beta-catenin signaling as well as non-canonical pathways (Planar Cell Polarity and Wnt/Ca²⁺ Pathways). Wnt/Frizzled signaling is involved in a variety of developmental processes including cell fate determination, cell polarity, tissue patterning, and control of cell proliferation. Activation of a given Wnt/Frizzled signaling cascade is dependent on the Wnt ligand and the cell context. Frizzled proteins also form co-receptor complexes with LRP, ROR, and Ryk molecules.