Sonic hedgehog protein (SHH) is also known as HHG-1, which belongs to the hedgehog family. SHH is expressed in fetal intestine, liver, lung, and kidney and not expressed in adult tissues. Sonic hedgehog protein can be cleavage into sonic hedgehog protein N-product and sonic hedgehog protein C-product by autolysis. SHH binds to the patched (PTC) receptor, which functions in association with smoothened (SMO), to activate the transcription of target genes. In the absence of SHH, PTC represses the constitutive signaling activity of SMO. Also regulates another target, the gli oncogene. Intercellular signal essential for a variety of patterning events during development. The C-terminal domain displays an autoproteolysis activity and a cholesterol transferase activity. The N-product is the active species in both local and long-range signaling, whereas the C-product has no signaling activity.