TY - JOUR
T1 - Sterols in an intramolecular channel of Smoothened mediate Hedgehog signaling
AU - Qi, Xiaofeng
AU - Friedberg, Lucas
AU - De Bose-Boyd, Ryan
AU - Long, Tao
AU - Li, Xiaochun
N1 - Funding Information:
We thank D. Stoddard at the UT Southwestern Medical Center Cryo-EM Facility (funded in part by the CPRIT Core Facility Support Award no. RP170644) for assistance in data collection. We thank B. Kobilka for sharing the plasmids of Gi and scFv16; L. Beatty, L. Esparza and C. Lee for tissue culture; A. Lemoff at the UT Southwestern Proteomics Core for mass spectrometry identification; and M. Brown, B. Chen, E. Debler, J. Goldstein, J. Jiang, Y. Yu and C. Zhang for discussions. This work was supported by the Endowed Scholars Program in Medical Science of UT Southwestern Medical Center, NIH grant nos. P01 HL020948 and R01 GM135343 and the Welch Foundation (no. I-1957, to X.L.). X.Q. is the recipient of a DDBrown Fellow of the Life Sciences Research Foundation. X.L. is a Damon Runyon-Rachleff Innovator supported by the Damon Runyon Cancer Research Foundation (no. DRR-53-19) and a Rita C. and William P. Clements, Jr Scholar in Biomedical Research at UT Southwestern Medical Center.
Publisher Copyright:
© 2020, The Author(s), under exclusive licence to Springer Nature America, Inc.
PY - 2020/12
Y1 - 2020/12
N2 - Smoothened (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, SMOD384R and SMOG111C/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. [Figure not available: see fulltext.]
AB - Smoothened (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, SMOD384R and SMOG111C/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. [Figure not available: see fulltext.]
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U2 - 10.1038/s41589-020-0646-2
DO - 10.1038/s41589-020-0646-2
M3 - Article
C2 - 32929279
AN - SCOPUS:85090947295
VL - 16
SP - 1368
EP - 1375
JO - Nature Chemical Biology
JF - Nature Chemical Biology
SN - 1552-4450
IS - 12
ER -