Members of the 'frizzled' gene family encode 7-transmembrane domain proteins that are receptors for Wnt signaling proteins. The Frizzled 5 protein is believed to be the receptor for the Wnt5A ligand. Frizzled 5 has been reported to be expressed in fetal kidney, fetal and adult liver, fetal lung, and adult pancreas. ESTs have been isolated from bone, liver spleen, placenta, and prostate libraries. Frizzled 5 was cloned from a retina cDNA library. Receptor for Wnt proteins. Component of the Wnt-Fzd-LRP5-LRP6 complex that triggers beta-catenin signaling through inducing aggregation of receptor-ligand complexes into ribosome-sized signalosomes. The beta-catenin canonical signaling pathway leads to the activation of disheveled proteins, inhibition of GSK-3 kinase, nuclear accumulation of beta-catenin and activation of Wnt target genes. A second signaling pathway involving PKC and calcium fluxes has been seen for some family members, but it is not yet clear if it represents a distinct pathway or if it can be integrated in the canonical pathway, as PKC seems to be required for Wnt-mediated inactivation of GSK-3 kinase. Both pathways seem to involve interactions with G-proteins. May be involved in transduction and intercellular transmission of polarity information during tissue morphogenesis and or in differentiated tissues. Coreceptor along with RYK of Wnt proteins, such as WNT1.
