Inhibition of SARS-CoV-2 viral entry upon blocking N- and O-glycan elaboration

• Main Authors: Qi Yang, Thomas A Hughes, Anju Kelkar, Xinheng Yu, Kai Cheng, Sheldon Park, Wei-Chiao Huang, Jonathan F Lovell, Sriram Neelamegham
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2020-10-01
• Series: eLife
• Subjects: SARS-CoV-2; COVID-19; glycoscience; furin; spike; kifunensine
• Online Access: https://elifesciences.org/articles/61552

The Spike protein of SARS-CoV-2, its receptor-binding domain (RBD), and its primary receptor ACE2 are extensively glycosylated. The impact of this post-translational modification on viral entry is yet unestablished. We expressed different glycoforms of the Spike-protein and ACE2 in CRISPR-Cas9 glycoengineered cells, and developed corresponding SARS-CoV-2 pseudovirus. We observed that N- and O-glycans had only minor contribution to Spike-ACE2 binding. However, these carbohydrates played a major role in regulating viral entry. Blocking N-glycan biosynthesis at the oligomannose stage using both genetic approaches and the small molecule kifunensine dramatically reduced viral entry into ACE2 expressing HEK293T cells. Blocking O-glycan elaboration also partially blocked viral entry. Mechanistic studies suggest multiple roles for glycans during viral entry. Among them, inhibition of N-glycan biosynthesis enhanced Spike-protein proteolysis. This could reduce RBD presentation on virus, lowering binding to host ACE2 and decreasing viral entry. Overall, chemical inhibitors of glycosylation may be evaluated for COVID-19.