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Structure of human SMO-Gi complex with 24(S),25-EC
Structural highlights
FunctionSMO_HUMAN G protein-coupled receptor that probably associates with the patched protein (PTCH) to transduce the hedgehog's proteins signal. Binding of sonic hedgehog (SHH) to its receptor patched is thought to prevent normal inhibition by patched of smoothened (SMO). Required for the accumulation of KIF7 and GLI3 in the cilia.[1] Publication Abstract from PubMedSmoothened (SMO), a class Frizzled G protein-coupled receptor (class F GPCR), transduces the Hedgehog signal across the cell membrane. Sterols can bind to its extracellular cysteine-rich domain (CRD) and to several sites in the seven transmembrane helices (7-TMs) of SMO. However, the mechanism by which sterols regulate SMO via multiple sites is unknown. Here we determined the structures of SMO-Gi complexes bound to the synthetic SMO agonist (SAG) and to 24(S),25-epoxycholesterol (24(S),25-EC). A novel sterol-binding site in the extracellular extension of TM6 was revealed to connect other sites in 7-TMs and CRD, forming an intramolecular sterol channel from the middle side of 7-TMs to CRD. Additional structures of two gain-of-function variants, SMO(D384R) and SMO(G111C/I496C), showed that blocking the channel at its midpoints allows sterols to occupy the binding sites in 7-TMs, thereby activating SMO. These data indicate that sterol transport through the core of SMO is a major regulator of SMO-mediated signaling. Sterols in an intramolecular channel of Smoothened mediate Hedgehog signaling.,Qi X, Friedberg L, De Bose-Boyd R, Long T, Li X Nat Chem Biol. 2020 Sep 14. pii: 10.1038/s41589-020-0646-2. doi:, 10.1038/s41589-020-0646-2. PMID:32929279[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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