Protein N-glycosylation is essential for SARS-CoV-2 infection

Abstract

SARS-CoV-2 extensively N-glycosylates its surface spike (S) proteins. This post-translational modification is essential to modulate protein conformation and host cell invasion. Each S monomer can be modified with up to 22 N-glycans. To meet the high demand of protein glycosylation during virus replication, SARS-CoV-2 upregulates the expression of host N-glycosylation genes. Although a substantial amount of detail is known about the structure of S protein N-glycans, the role of N-glycosylation in SARS-CoV-2 infection remains largely undetermined. Here, we investigated the essentiality of the host N-glycosylation pathway and viral N-glycans for SARS-CoV-2 infection. When either monkey or human cells were preincubated with glycosylation inhibitors, including FDA-approved iminosugars, virus infection was significantly reduced. This infection phenotype was confirmed after RNAi knockdown of several glycosylation genes. In addition, enzymatic deglycosylation of whole viral particles confirmed that accessible oligosaccharides on the SARS-CoV-2 surface are essential for host cell infection. Altogether, we show evidence that the normal functioning of the host N-glycosylation machinery is essential not only for SARS-CoV-2 to infect, but also to produce new functional virions. These findings open the door for developing new approaches targeting N-glycosylation against COVID-19.

SARS-CoV-2 activates ER stress and Unfolded protein response

“…Moreover, genetic ablation of this pathway using siRNAs and virions presenting N-glycosylation defects also reduced the infection rate 82 . Since we found that five enzymes involved in the glycosylation biosynthesis (CHST12, CHST14, B4GALT3, GCNT1 and MGAT2) were mainly up-regulated in the intermediate time-points, but down-regulated at 48 hpi, our data showed a complete remodeling of the N-linked protein glycosylation process.…”

Targeting conserved N-glycosylation blocks SARS-CoV-2 variant infection in vitro

“…NGI-1 disrupts oligosaccharyltransferase function by blocking the transfer of lipid-linked oligosaccharides to recipient glycoproteins, thereby inhibiting N-linked glycosylation [55]. Blocking N-linked but not O-linked glycosylation of S proteins by means of glycosylation inhibitors (such as NGI-1 and kifunensine) impedes viral entry [19,56]. Mutation of N-linked glycosylation sites in the RDB of S protein (N331 and N343) dramatically reduced viral infectivity [57], indicating that N-glycosylation of S protein is essential for viral infectivity.…”