Acts as a receptor for sonic hedgehog (SHH), indian hedgehog (IHH) and desert hedgehog (DHH). Associates with the smoothened protein (SMO) to transduce the hedgehog's proteins signal. Seems to have a tumor suppressor function, as inactivation of this protein is probably a necessary, if not sufficient step for tumorigenesis. Interacts with SNX17 (By similarity). Interacts with IHH (PubMed:21537345). Interacts with G-protein coupled receptor GPR37L1 (PubMed:24062445). Detected in cerebellar Bergmann glia cells (at protein level) (PubMed:24062445). In the developing embryo, first detected within the ventral neural tube and later in the somites and limb buds (PubMed:8595881). Expression in the limb buds is restricted to the posterior ectoderm surrounding the zone of polarizing activity (PubMed:8595881). In the adult, expression is seen in brain, lung, liver, kidney and ocular tissues; lower levels in heart, skeletal muscle, and testis (PubMed:8595881). Expressed at very low levels at 7 dpc, is most strongly expressed between 11 and 15 dpc, and persists at moderate levels at 17 dpc (PubMed:8595881). Also expressed in the adult (PubMed:8595881). Activated by Sonic hedgehog. Glycosylation is necessary for SHH binding. In the absence of Hh ligands, ubiquitination by ITCH at Lys-1413 promotes endocytosis and both proteasomal and lysosomal degradation. Belongs to the patched family.