ABSTRACT
Most enveloped viruses rely on the host cell endoplasmic reticulum (ER) quality control (QC) machinery for proper folding of glycoproteins. The key ER α-glucosidases (α-Glu) I and II of the ERQC machinery are attractive targets for developing broad-spectrum antivirals. Iminosugars based on deoxynojirimycin have been extensively studied as ER α-glucosidase inhibitors; however, other glycomimetic compounds are less established. Accordingly, we synthesized a series of N-substituted derivatives of valiolamine, the iminosugar scaffold of type 2 diabetes drug voglibose. To understand the basis for up to 100,000-fold improved inhibitory potency, we determined high-resolution crystal structures of mouse ER α-GluII in complex with valiolamine and 10 derivatives. The structures revealed extensive interactions with all four α-GluII subsites. We further showed that N-substituted valiolamines were active against dengue virus and SARS-CoV-2 in vitro. This study introduces valiolamine-based inhibitors of the ERQC machinery as candidates for developing potential broad-spectrum therapeutics against the existing and emerging viruses.
Subject(s)
Antiviral Agents/pharmacology , Glycoside Hydrolase Inhibitors/pharmacology , Imino Sugars/pharmacology , Inositol/analogs & derivatives , alpha-Glucosidases/metabolism , Animals , Antiviral Agents/chemical synthesis , Antiviral Agents/metabolism , Binding Sites , Chlorocebus aethiops , Crystallography, X-Ray , Dengue Virus/drug effects , Endoplasmic Reticulum/enzymology , Glycoside Hydrolase Inhibitors/chemical synthesis , Glycoside Hydrolase Inhibitors/metabolism , Humans , Imino Sugars/chemical synthesis , Imino Sugars/metabolism , Inositol/chemical synthesis , Inositol/metabolism , Inositol/pharmacology , Mice , Microbial Sensitivity Tests , Molecular Docking Simulation , Protein Binding , SARS-CoV-2/drug effects , Vero Cells , alpha-Glucosidases/chemistryABSTRACT
Severe acute respiratory syndrome coronavirus 2 is the causative pathogen of the COVID-19 pandemic which as of March 29, 2021, has claimed 2â¯776â¯175 lives worldwide. Vaccine development efforts focus on the viral trimeric spike glycoprotein as the main target of the humoral immune response. Viral spikes carry glycans that facilitate immune evasion by shielding specific protein epitopes from antibody neutralization, and antigen efficacy is influenced by spike glycoprotein production in vivo. Therefore, immunogen integrity is important for glycoprotein-based vaccine candidates. Here, we show how site-specific glycosylation differs between virus-derived spikes, wild-type, non-stabilized spikes expressed from a plasmid with a CMV promoter and tPA signal sequence, and commonly used recombinant, engineered spike glycoproteins. Furthermore, we show that their distinctive cellular secretion pathways result in different protein glycosylation and secretion patterns, including shedding of spike monomeric subunits for the non-stabilized wild-type spike tested, which may have implications for the resulting immune response and vaccine design.