Cryo-EM structure of oxysterol-bound human Smoothened coupled to a heterotrimeric Gi

Xiaofeng Qi, Heng Liu, Bonne Thompson, Jeffrey McDonald, Cheng Zhang, Xiaochun Li

Research output: Contribution to journalLetter

6 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
JournalNature
DOIs
StateAccepted/In press - Jan 1 2019

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G-Protein-Coupled Receptors
Oncogenes
GTP-Binding Proteins
Glioma
Ligands
Cryoelectron Microscopy
Heterotrimeric GTP-Binding Proteins
Oncogene Proteins
Signal Transduction
Proteins
Transcription Factors
Binding Sites
24,25-epoxycholesterol
Oxysterols
Neoplasms
In Vitro Techniques

ASJC Scopus subject areas

  • General

Cite this

Cryo-EM structure of oxysterol-bound human Smoothened coupled to a heterotrimeric Gi. / Qi, Xiaofeng; Liu, Heng; Thompson, Bonne; McDonald, Jeffrey; Zhang, Cheng; Li, Xiaochun.

In: Nature, 01.01.2019.

Research output: Contribution to journalLetter

Qi, Xiaofeng ; Liu, Heng ; Thompson, Bonne ; McDonald, Jeffrey ; Zhang, Cheng ; Li, Xiaochun. / Cryo-EM structure of oxysterol-bound human Smoothened coupled to a heterotrimeric Gi. In: Nature. 2019.
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