skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Cellular Cholesterol Directly Activates Smoothened in Hedgehog Signaling

Abstract

In vertebrates, sterols are necessary for Hedgehog signaling, a pathway critical in embryogenesis and cancer. Sterols activate the membrane protein Smoothened by binding its extracellular, cysteine-rich domain (CRD). Major unanswered questions concern the nature of the endogenous, activating sterol and the mechanism by which it regulates Smoothened. We report crystal structures of CRD complexed with sterols and alone, revealing that sterols induce a dramatic conformational change of the binding site, which is sufficient for Smoothened activation and is unique among CRD-containing receptors. We demonstrate that Hedgehog signaling requires sterol binding to Smoothened and define key residues for sterol recognition and activity. We also show that cholesterol itself binds and activates Smoothened. Furthermore, the effect of oxysterols is abolished in Smoothened mutants that retain activation by cholesterol and Hedgehog. We propose that the endogenous Smoothened activator is cholesterol, not oxysterols, and that vertebrate Hedgehog signaling controls Smoothened by regulating its access to cholesterol.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Institutes of Health (NIH)
OSTI Identifier:
1336817
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cell; Journal Volume: 166; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Huang, Pengxiang, Nedelcu, Daniel, Watanabe, Miyako, Jao, Cindy, Kim, Youngchang, Liu, Jing, and Salic, Adrian. Cellular Cholesterol Directly Activates Smoothened in Hedgehog Signaling. United States: N. p., 2016. Web. doi:10.1016/j.cell.2016.08.003.
Huang, Pengxiang, Nedelcu, Daniel, Watanabe, Miyako, Jao, Cindy, Kim, Youngchang, Liu, Jing, & Salic, Adrian. Cellular Cholesterol Directly Activates Smoothened in Hedgehog Signaling. United States. doi:10.1016/j.cell.2016.08.003.
Huang, Pengxiang, Nedelcu, Daniel, Watanabe, Miyako, Jao, Cindy, Kim, Youngchang, Liu, Jing, and Salic, Adrian. 2016. "Cellular Cholesterol Directly Activates Smoothened in Hedgehog Signaling". United States. doi:10.1016/j.cell.2016.08.003.
@article{osti_1336817,
title = {Cellular Cholesterol Directly Activates Smoothened in Hedgehog Signaling},
author = {Huang, Pengxiang and Nedelcu, Daniel and Watanabe, Miyako and Jao, Cindy and Kim, Youngchang and Liu, Jing and Salic, Adrian},
abstractNote = {In vertebrates, sterols are necessary for Hedgehog signaling, a pathway critical in embryogenesis and cancer. Sterols activate the membrane protein Smoothened by binding its extracellular, cysteine-rich domain (CRD). Major unanswered questions concern the nature of the endogenous, activating sterol and the mechanism by which it regulates Smoothened. We report crystal structures of CRD complexed with sterols and alone, revealing that sterols induce a dramatic conformational change of the binding site, which is sufficient for Smoothened activation and is unique among CRD-containing receptors. We demonstrate that Hedgehog signaling requires sterol binding to Smoothened and define key residues for sterol recognition and activity. We also show that cholesterol itself binds and activates Smoothened. Furthermore, the effect of oxysterols is abolished in Smoothened mutants that retain activation by cholesterol and Hedgehog. We propose that the endogenous Smoothened activator is cholesterol, not oxysterols, and that vertebrate Hedgehog signaling controls Smoothened by regulating its access to cholesterol.},
doi = {10.1016/j.cell.2016.08.003},
journal = {Cell},
number = 5,
volume = 166,
place = {United States},
year = 2016,
month = 8
}
  • The RAH/Smith-Lemli-Opitz syndrome (RAH/SLOS) is an autosomal recessive malformation syndrome associated with increased levels of 7-dehydrocholesterol (7-DHC) and a defect of cholesterol biosynthesis at the level of 3{beta}-hydroxy-steroid-{Delta}{sup 7}-reductase (7-DHC reductase). Because rats exposed to inhibitors of 7-DHC reductase during development have a high frequency of holoprosencephaly (HPE), we have undertaken a search for biochemical evidence of RSH/SLOS and other possible defects of sterol metabolism among patients with various forms of HPE. We describe 4 patients, one with semilobar HPE and three others with less complete forms of the HPE sequence, in whom we have made a biochemical diagnosis ofmore » RAH/SLOS. The clinical and biochemical spectrum of these and other patients with RAH/SLOS suggests a role of abnormal sterol metabolism in the pathogenesis of their malformations. The association of HPE and RAH/SLOS is discussed in light of the recent discoveries that mutations in the embryonic patterning gene, Sonic Hedgehog (SHH), can cause HPE in humans and that the sonic hedgehog protein product undergoes autoproteolysis to form a cholesterol-modified active product. These clinical, biochemical, and molecular studies suggest that HPE and other malformations in SLOS may be caused by incomplete or abnormal modification of the sonic hedgehog protein and, possibly, other patterning proteins of the hedgehog class, a hypothesis testable in somatic cell systems. 37 refs., 1 fig.« less
  • Glypicans are heparan sulfate proteoglycans that modulate the signaling of multiple growth factors active during animal development, and loss of glypican function is associated with widespread developmental abnormalities. Glypicans consist of a conserved, approximately 45-kDa N-terminal protein core region followed by a stalk region that is tethered to the cell membrane by a glycosyl-phosphatidylinositol anchor. The stalk regions are predicted to be random coil but contain a variable number of attachment sites for heparan sulfate chains. Both the N-terminal protein core and the heparan sulfate attachments are important for glypican function. We report here the 2.4-{angstrom} crystal structure of themore » N-terminal protein core region of the Drosophila glypican Dally-like (Dlp). This structure reveals an elongated, {alpha}-helical fold for glypican core regions that does not appear homologous to any known structure. The Dlp core protein is required for normal responsiveness to Hedgehog (Hh) signals, and we identify a localized region on the Dlp surface important for mediating its function in Hh signaling. Purified Dlp protein core does not, however, interact appreciably with either Hh or an Hh:Ihog complex.« less
  • Cited by 22
  • Cadmium (Cd) is both an environmental pollutant and a component of cigarette smoke. Although evidence demonstrates that adult exposure to Cd causes changes in the immune system, there are limited reports in the literature of immunomodulatory effects of prenatal exposure to Cd. The sonic hedgehog (Shh) and Wnt/beta-catenin pathways are required for thymocyte maturation. Several studies have demonstrated that Cd exposure affects these pathways in different organ systems. This study was designed to investigate the effect of prenatal Cd exposure on thymocyte development, and to determine if these effects were linked to dysregulation of Shh and Wnt/beta-catenin pathways. Pregnant C57Bl/6more » mice were exposed to an environmentally relevant dose (10 ppm) of Cd throughout pregnancy and effects on the thymus were assessed on the day of birth. Thymocyte phenotype was determined by flow cytometry. A Gli:luciferase reporter cell line was used to measure Shh signaling. Transcription of target genes and translation of key components of both signaling pathways were assessed using real-time RT-PCR and western blot, respectively. Prenatal Cd exposure increased the number of CD4{sup +} cells and a subpopulation of double-negative cells (DN; CD4{sup -}CD8{sup -}), DN4 (CD44{sup -}CD25{sup -}). Shh and Wnt/beta-catenin signaling were both decreased in the thymus. Target genes of Shh (Patched1 and Gli1) and Wnt/beta-catenin (c-fos, and c-myc) were affected differentially among thymocyte subpopulations. These findings suggest that prenatal exposure to Cd dysregulates two signaling pathways in the thymus, resulting in altered thymocyte development.« less