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.
