Functional divergence in the role of N-linked glycosylation in smoothened signaling

Marada, Suresh, Navarro, Gemma, Truong, Ashley, Stewart, Daniel P., Arensdorf, Angela M., Nachtergaele, Sigrid, Angelats, Edgar, Opferman, Joseph T., Rohatgi, Rajat, McCormick, Peter J. and Ogden, Stacey K. (2015) Functional divergence in the role of N-linked glycosylation in smoothened signaling. PLoS Genetics, 11 (8). ISSN 1553-7404

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Abstract

The G protein-coupled receptor (GPCR) Smoothened (Smo) is the requisite signal transducer of the evolutionarily conserved Hedgehog (Hh) pathway. Although aspects of Smo signaling are conserved from Drosophila to vertebrates, significant differences have evolved. These include changes in its active sub-cellular localization, and the ability of vertebrate Smo to induce distinct G protein-dependent and independent signals in response to ligand. Whereas the canonical Smo signal to Gli transcriptional effectors occurs in a G protein-independent manner, its non-canonical signal employs Gαi. Whether vertebrate Smo can selectively bias its signal between these routes is not yet known. N-linked glycosylation is a post-translational modification that can influence GPCR trafficking, ligand responsiveness and signal output. Smo proteins in Drosophila and vertebrate systems harbor N-linked glycans, but their role in Smo signaling has not been established. Herein, we present a comprehensive analysis of Drosophila and murine Smo glycosylation that supports a functional divergence in the contribution of N-linked glycans to signaling. Of the seven predicted glycan acceptor sites in Drosophila Smo, one is essential. Loss of N-glycosylation at this site disrupted Smo trafficking and attenuated its signaling capability. In stark contrast, we found that all four predicted N-glycosylation sites on murine Smo were dispensable for proper trafficking, agonist binding and canonical signal induction. However, the under-glycosylated protein was compromised in its ability to induce a non-canonical signal through Gαi, providing for the first time evidence that Smo can bias its signal and that a post-translational modification can impact this process. As such, we postulate a profound shift in N-glycan function from affecting Smo ER exit in flies to influencing its signal output in mice.

Item Type: Article
Additional Information: © 2015 Marada et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Faculty \ School: Faculty of Science > School of Pharmacy
Depositing User: Pure Connector
Date Deposited: 26 Aug 2015 13:30
Last Modified: 22 Jul 2020 00:21
URI: https://ueaeprints.uea.ac.uk/id/eprint/54169
DOI: 10.1371/journal.pgen.1005473

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