Figure 2.

Simplified scheme of Hh signaling in mammalian cells: (a) in the absence of Hedgehog ligand, patched 1 (Ptch) localizes to the primary cilium, where it prevents activation of smoothened (Smo); (b) Hh signaling is activated upon binding of the ligand to the Ptch receptor, which leaves the cilium, releases the inhibition of Smo and leads to glioma-associated (Gli) transcription factors’ translocation into the nucleus; (c) Gli activates the expression of target genes Gli1, Ptch and Hedgehog interacting protein (Hhip1); (d) the pathway can be inhibited at the level of Smo or Gli.