Cilia-Associated Oxysterols Activate Smoothened

Abstract

Summary Primary cilia are required for Smoothened to transduce vertebrate Hedgehog signals, but how Smoothened accumulates in cilia and is activated is incompletely understood. Here, we identify cilia-associated oxysterols that promote Smoothened accumulation in cilia and activate the Hedgehog pathway. Our data reveal that cilia-associated oxysterols bind to two distinct Smoothened domains to modulate Smoothened accumulation in cilia and tune the intensity of Hedgehog pathway activation. We find that the oxysterol synthase HSD11β2 participates in the production of Smoothened-activating oxysterols and promotes Hedgehog pathway activity. Inhibiting oxysterol biosynthesis impedes oncogenic Hedgehog pathway activation and attenuates the growth of Hedgehog pathway-associated medulloblastoma, suggesting that targeted inhibition of Smoothened activating oxysterol production may be therapeutically useful for patients with Hedgehog-associated cancers.

Misactivation of Hedgehog signaling causes inherited and sporadic cancers

“…Consistently, statin medications, which inhibit cholesterol biosynthesis, may synergize with HH pathway inhibition for the treatment of medulloblastoma (110). Endogenous, cilia-associated oxysterols activate the HH pathway by interacting with two separate domains of SMO (111). An enzyme that participates in the production of SMOactivating oxysterols, HSD11β2, is dramatically enriched in HHassociated medulloblastoma, raising the possibility that inhibiting HSD11β2 may also be a strategy for inhibiting HH pathway activity in cancer (111).…”

“…Endogenous, cilia-associated oxysterols activate the HH pathway by interacting with two separate domains of SMO (111). An enzyme that participates in the production of SMOactivating oxysterols, HSD11β2, is dramatically enriched in HHassociated medulloblastoma, raising the possibility that inhibiting HSD11β2 may also be a strategy for inhibiting HH pathway activity in cancer (111). In support of this hypothesis, genetic inhibition of HSD11β2 in a mouse model of HH-associated medulloblastoma attenuates HH signal transduction and the growth of cancer, and blocking HSD11β2 with an active ingredient from licorice similarly inhibits medulloblastoma growth in mouse models (111).…”

Sphingomyelin suppresses Hedgehog signaling by restricting cholesterol accessibility at the ciliary membrane

“…In order to determine which lipids influence Hedgehog signaling, mouse-specific genes were manually curated into lists for each lipid metabolic pathway identified on the Kyoto Encyclopedia of Genes and genomes (KEGG) website ( Supplementary Table 4 ). Since oxysterol pathways are not a separate category in KEGG, manual curation of the literature was used to identify 34 oxysterol-related enzymes (see Supplementary Table 4 ), 6 of which were not found in the KEGG database (Sever et al 2016;Abdel-Khalik et al 2018;Raleigh et al 2018;Griffiths and Wang 2018;Griffiths et al 2017) . For each gene identified in KEGG or the oxysterol list, FDR-corrected p-values were extracted from the HiSHH-Bot10% screen ( Supplementary Table 2) as well as the LoSHH-Top5% screen ( Supplementary Table 3).…”

A NanoBRET-based binding assay for Smoothened allows real time analysis of small-molecule ligand binding and distinction of two separate ligand binding sites for BODIPY-cyclopamine

“…Cholesterol and other naturally occurring sterols are positive allosteric modulators and agonists of SMO in Gli-and G protein-dependent signaling (Nachtergaele et al, 2012;Qi, Liu, Thompson, McDonald, Zhang & Li, 2019;Raleigh et al, 2018;Sever et al, 2016). Due to the distinct link to human cancer and occurrence of several cancerassociated SMO mutations (e.g.…”