TY - JOUR
T1 - Cryo-EM structure of oxysterol-bound human Smoothened coupled to a heterotrimeric Gi
AU - Qi, Xiaofeng
AU - Liu, Heng
AU - Thompson, Bonne
AU - McDonald, Jeffrey
AU - Zhang, Cheng
AU - Li, Xiaochun
N1 - Publisher Copyright:
© 2019, The Author(s), under exclusive licence to Springer Nature Limited.
PY - 2019/7/11
Y1 - 2019/7/11
N2 - The oncoprotein Smoothened (SMO), a G-protein-coupled receptor (GPCR) of the Frizzled-class (class-F), transduces the Hedgehog signal from the tumour suppressor Patched-1 (PTCH1) to the glioma-associated-oncogene (GLI) transcription factors, which activates the Hedgehog signalling pathway1,2. It has remained unknown how PTCH1 modulates SMO, how SMO is stimulated to form a complex with heterotrimeric G proteins and whether G-protein coupling contributes to the activation of GLI proteins3. Here we show that 24,25-epoxycholesterol, which we identify as an endogenous ligand of PTCH1, can stimulate Hedgehog signalling in cells and can trigger G-protein signalling via human SMO in vitro. We present a cryo-electron microscopy structure of human SMO bound to 24(S),25-epoxycholesterol and coupled to a heterotrimeric Gi protein. The structure reveals a ligand-binding site for 24(S),25-epoxycholesterol in the 7-transmembrane region, as well as a Gi-coupled activation mechanism of human SMO. Notably, the Gi protein presents a different arrangement from that of class-A GPCR–Gi complexes. Our work provides molecular insights into Hedgehog signal transduction and the activation of a class-F GPCR.
AB - The oncoprotein Smoothened (SMO), a G-protein-coupled receptor (GPCR) of the Frizzled-class (class-F), transduces the Hedgehog signal from the tumour suppressor Patched-1 (PTCH1) to the glioma-associated-oncogene (GLI) transcription factors, which activates the Hedgehog signalling pathway1,2. It has remained unknown how PTCH1 modulates SMO, how SMO is stimulated to form a complex with heterotrimeric G proteins and whether G-protein coupling contributes to the activation of GLI proteins3. Here we show that 24,25-epoxycholesterol, which we identify as an endogenous ligand of PTCH1, can stimulate Hedgehog signalling in cells and can trigger G-protein signalling via human SMO in vitro. We present a cryo-electron microscopy structure of human SMO bound to 24(S),25-epoxycholesterol and coupled to a heterotrimeric Gi protein. The structure reveals a ligand-binding site for 24(S),25-epoxycholesterol in the 7-transmembrane region, as well as a Gi-coupled activation mechanism of human SMO. Notably, the Gi protein presents a different arrangement from that of class-A GPCR–Gi complexes. Our work provides molecular insights into Hedgehog signal transduction and the activation of a class-F GPCR.
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U2 - 10.1038/s41586-019-1286-0
DO - 10.1038/s41586-019-1286-0
M3 - Article
C2 - 31168089
AN - SCOPUS:85066925844
SN - 0028-0836
VL - 571
SP - 279
EP - 283
JO - Nature
JF - Nature
IS - 7764
ER -