Trimeric G protein-dependent signaling by Frizzled receptors in animal development

Receptors of the Frizzled family transduce important signals during animal development and are conserved from sponges to humans. Frizzled receptors belong to the superfamily of G protein-coupled receptors (GPCRs), but until recently were considered G protein-independent in their signaling. In the present article we review the extensive knowledge demonstrating the functions of trimeric G proteins in Frizzled signal transduction in vertebrates and lower animals. Other structural and functional similarities of Frizzled receptors and the GPCRs are also discussed.