Coreceptor required for sonic hedgehog (SHH) handoff to its receptor: binds to the dually lipid-modified Sonic hedgehog protein N- product (ShhN) downstream of the CDON-BOC heterodimer and directly transfers ShhN to its patched receptor (PTCH1 or PTCH2), followed by activation of the smoothened signaling pathway (PubMed:35231446). Specifically recognizes and binds palmitate and cholesterol moieties in dually lipid-modified ShhN (PubMed:35231446). Binds 20(S)- hydroxycholesterol (20(S)-OHC) (By similarity). Acts as a growth arrest protein involved in growth suppression by blocking entry to S phase (PubMed:8127893). {ECO:0000250|UniProtKB:Q01721, ECO:0000269|PubMed:35231446, ECO:0000269|PubMed:8127893}. This is the function of ENSG00000180447 (GAS1, growth arrest specific 1).