Inhibition of Hedgehog signaling by direct binding of cyclopamine to Smoothened

• Published in: Genes & development 2002-11, Vol.16 (21), p.2743-2748
• Main Authors: Chen, James K, Taipale, Jussi, Cooper, Michael K, Beachy, Philip A
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Antineoplastic Agents - pharmacology; Antineoplastic Agents - toxicity; Binding Sites; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - physiology; Hedgehog Proteins; Mice; Protein Binding; Protein Conformation; Receptors, Cell Surface - chemistry; Receptors, Cell Surface - drug effects; Receptors, Cell Surface - physiology; Receptors, G-Protein-Coupled; Research Communication; Signal Transduction - drug effects; Smoothened Receptor; Teratogens - pharmacology; Teratogens - toxicity; Trans-Activators - physiology; Veratrum Alkaloids - chemistry; Veratrum Alkaloids - pharmacology; Veratrum Alkaloids - toxicity
• ISSN: 0890-9369; 1549-5477
• DOI: 10.1101/gad.1025302

The steroidal alkaloid cyclopamine has both teratogenic and antitumor activities arising from its ability to specifically block cellular responses to vertebrate Hedgehog signaling. We show here, using photoaffinity and fluorescent derivatives, that this inhibitory effect is mediated by direct binding of cyclopamine to the heptahelical bundle of Smoothened (Smo). Cyclopamine also can reverse the retention of partially misfolded Smo in the endoplasmic reticulum, presumably through binding-mediated effects on protein conformation. These observations reveal the mechanism of cyclopamine's teratogenic and antitumor activities and further suggest a role for small molecules in the physiological regulation of Smo.