Smoothened (smo), a G protein-coupled receptor, drives the Hedgehog signalling pathway and is involved in gene expression and Gli family transcription factors. The core members of the Smo signalling pathway include the ligand (Hedgehog, Hh), the receptor (Patched, Ptc), several transducers such as Smoothened (Smo) and the ytoplasmic complex formed by the kinesin-like protein Costal-2 (Cos2), the serine/threonine kinase Fused (Fu), the novel protein Suppressor of fused [Su(fu)], and the transcription factor Cubitus interruptus (Ci). SMO is classified as a proto-oncogene because the tumour suppressor PTCH represses signalling by SMO, and SHH relieves this repression.
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