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. Author manuscript; available in PMC: 2015 Feb 1.
Published in final edited form as: Cancer Treat Rev. 2013 Aug 13;40(1):10.1016/j.ctrv.2013.08.003. doi: 10.1016/j.ctrv.2013.08.003

Figure 2. Primary cilia and Hedgehog signal transduction.

Figure 2

Sonic Hedgehog (Shh) ligand binds its receptor Patch (Ptch), which subsequently releases its inhibitory effect on quiescent Smoothened (Smo) contained in cytoplasmic vesicles. Activated Smo moves antegrade into the cilia along tracks comprised of acetylated tubulin coupled to ciliary proteins Bardet-Biedl syndrome proteins (BBS), intraflagellar transport protein (IFT) and kinesin proteins. At the vesicle tip activated Smo induces the release of Gli2 from the cilia. Ciliary proteins (BBS and IFT) plus dynein move cargo proteins retrograde into the cytoplasm. Once cytoplasmic, limited degradation directs the transcription factor to the nucleus to bind and induce Hh-regulated genes Gli1, Ptch and Hedgehog interacting protein (HhIP).