Negative regulator of the smoothened signaling pathway, which acts as a receptor for hedgehog (SHH, IHH and DHH) morphogens (PubMed:21537345, PubMed:29954986, PubMed:29995851, PubMed:30139912, PubMed:31127104, PubMed:31555730, PubMed:37611095, PubMed:40128518, PubMed:9811851). In absence of hedgehog, acts as an inhibitor of smoothened protein (SMO) by preventing SMO access to cholesterol: mechanistically, acts as a cholesterol transporter, which depeletes cholesterol from the outer leaflet of plasma membrane, thereby preventing cholesterol-binding to the extracellular CRD region of SMO (PubMed:31555730, PubMed:37611095). Hedgehog-binding inhibits PTCH1 cholesterol transporter activity, promoting SMO activation by cholesterol and transduction of the smoothened signaling pathway (PubMed:31548691). Molecular mechanism governing cholesterol transport are still unclear: may move cholesterol from the outer to the inner leaflet of the membrane in exchange for potassium or sodium ion export in the opposite direction (PubMed:37611095). Seems to have a tumor suppressor function, as inactivation of this protein is probably a necessary, if not sufficient step for tumorigenesis (PubMed:8658145). {ECO:0000269|PubMed:21537345, ECO:0000269|PubMed:29954986, ECO:0000269|PubMed:29995851, ECO:0000269|PubMed:30139912, ECO:0000269|PubMed:31127104, ECO:0000269|PubMed:31548691, ECO:0000269|PubMed:31555730, ECO:0000269|PubMed:37611095, ECO:0000269|PubMed:40128518, ECO:0000269|PubMed:8658145, ECO:0000269|PubMed:9811851}. This is the function of Ensembl gene identifier ENSG00000185920 (PTCH1, patched 1).