Cholesterol Modification of Smoothened Is Required for Hedgehog Signaling

Abstract

Hedgehog (Hh) has been known as the only cholesterol-modified morphogen playing pivotal roles in development and tumorigenesis. A major unsolved question is how Hh signaling regulates the activity of Smoothened (SMO). Here, we performed an unbiased biochemical screen and identified that SMO was covalently modified by cholesterol on the Asp95 (D95) residue through an ester bond. This modification was inhibited by Patched-1 (Ptch1) but enhanced by Hh. The SMO(D95N) mutation, which could not be cholesterol modified, was refractory to Hh-stimulated ciliary localization and failed to activate downstream signaling. Furthermore, homozygous Smo (the equivalent residue in mouse) knockin mice were embryonic lethal with severe cardiac defects, phenocopying the Smo mice. Together, the results of our study suggest that Hh signaling transduces to SMO through modulating its cholesterylation and provides a therapeutic opportunity to treat Hh-pathway-related cancers by targeting SMO cholesterylation.

Rational Targeting of Cellular Cholesterol in Diffuse Large B-Cell Lymphoma (DLBCL) Enabled by Functional Lipoprotein Nanoparticles: A Therapeutic Strategy Dependent on Cell of Origin

“…These genes were selected given their role in the biosynthesis of cholesterol and their identification in previously reported studies connecting BCR signaling and cholesterol biosynthesis. 15, 39 Genes were considered altered if the fold expression change was ≥1.5 or ≤-1.5, with a corresponding p < 0.05. HDL NP treatment resulted in upregulation of the cholesterol biosynthesis genes ACAT2, SQLE, MSMO1, INSIG1, HMGCS1, DHCR7, LSS, and MVD in SUDHL4 cells, with no upregulation seen when human HDL was administered (Figure 2a, Supplemental Figure S5).…”

Common genetic causes of holoprosencephaly are limited to a small set of evolutionarily conserved driver genes of midline development coordinated by TGF-β, hedgehog, and FGF signaling

“…The details of classical hedgehog morphogen binding on the responding cells offers a similar complexity including the poorly understood inhibition of the seven-pass transmembrane GPCR-like signal transducer SMO by the 12-pass transmembrane receptor PTCH1, the unusual requirement for the cilium in transducing hedgehog signals, and finally the complex and elaborate molecular switch between GLI activators and repressors as the ultimate read out of hedgehog signaling strength (Goetz & Anderson, 2010;Ingham et al, 2011;Ryan & Chiang, 2012). Recent studies have identified cholesterol as a modulator of hedgehog signaling through the binding to the hedgehog receptor SMO suggesting a novel mechanism for hypocholesterolemia to contribute to HPE (Grover, Valadez, Bowman, & Cooper, 2011;Huang et al, 2016;Luchetti et al, 2016;Xiao et al, 2017).…”

NPC1 Deficiency in Mice is Associated with Fetal Growth Restriction, Neonatal Lethality and Abnormal Lung Pathology

“…For example, cholesterol functions in multiple aspects of the sonic hedgehog (SHH) pathway, which regulates numerous developmental processes [57][58][59][60][61][62]. Thus, an imbalance in cholesterol homeostasis resulting from reduced NPC1 protein could have subtle effects throughout development.…”