Project description:Recent outbreaks of severe acute respiratory syndrome and Middle-East respiratory syndrome along with the threat of a future coronavirus pandemic underscore the importance of finding ways to neutralize these viruses. The trimeric spike transmembrane glycoprotein S mediates entry into host cells and is the major target of neutralizing antibodies. To understand the humoral immune response elicited upon natural infections with coronaviruses, we structurally characterized the SARS-CoV and MERS-CoV S glycoproteins in complex with neutralizing antibodies isolated from human survivors using cryo electron microscopy and characterized the site-specific N-linked glycan profile of the recombinant S proteins with LC-MS/MS using EThcD fragmentation. Although the two antibodies studied blocked attachment to the host cell receptor, only the anti-SARS-CoV S antibody triggered premature fusogenic conformational changes via receptor functional mimicry. These results provide a structural framework for understanding coronavirus neutralization by human antibodies and shed light on the coronavirus fusion activation pathway which appears to take place through a receptor-driven ratcheting mechanism.
Project description:This study designed to characterize the differences in N-glycan expressions between normal and breastcancer cells, MCF10A and MCF7. Permethylated N-glycans released by PNGase F were enriched and then analyzed by LC-ESI/MS. The in-house-developed software GlySeeker was used to search IDs of N-glycans.
Project description:Coronaviruses (CoVs) are enveloped pathogens causing multiple respiratory disorders in humans with varying severity. Spike protein is one of the major proteins expressed on coronavirus surface, which mediates coronavirus entry into host cells. Spike proteins are extensively glycosylated and the glycans displayed on spike proteins play a key role in host pathogenesis and immune evasion. In this study, we aim to investigate whether glycosylation patterns are conservative at certain glycosites across different coronaviruses and how different host cells impact on the glycosylation profile. We analyzed site-specific glycans of S1 subunit from SARS-CoV and MERS-CoV spike proteins using hydrophilic interaction chromatography (HILIC) and LC-MS/MS on an Orbitrap Eclipse Tribrid mass spectrometer. We also compared glycosylation of MERS-CoV spike protein derived from HEK293 and insect cells. Our results show that SARS-CoV S1 and MERS-CoV S1 N-glycosylation presents some common patterns and also reveals the similar O-glycosites locations. Consistent with published data, confirming glycan and glycan subtype in specific positions, our data support that some monoclonal antibodies recognize glycan as part of their target epitope and cross react between SARS Cov and SARS CoV2 spike. The coronavirus spike proteins are highly glycosylated. The glycosylation sites, within each virus, are conserved with few changes over time.
Project description:Severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) are zoonotic pathogens that can cause severe respiratory disease in humans. Identification of the host factors that are necessary for viral infection and virus-induced cell death is critical to our understanding of the viral life cycle and can potentially aid the development of new treatment options. Here, we report CRISPR screen results of both SARS-CoV and MERS-CoV infections in derivatives of the human hepatoma cell line Huh7. Our screens identified the known entry receptors ACE2 for SARS-CoV and DPP4 for MERS-CoV. Additionally, the SARS-CoV screen uncovered several components of the NF-κB signaling pathway (CARD10, BCL10, MALT1, MAP3K7, IKBKG), while the MERS-CoV screen revealed the polypyrimidine tract-binding protein PTBP1, the ER scramblase TMEM41B, furin protease and several transcriptional and chromatin regulators as candidate factors for viral replication and/or virus-induced cell death. Together, we present several known and unknown coronavirus host factors that are of interest for further investigation.
Project description:Insect cells are a convenient cell factory to produce recombinant glycoproteins. Their glycosylation potential is believed to be simple, needing primarily addition of glycosyltransferases to humanize the recombinant products. In this study, the native glycoproteome of Spodoptera frugiperda Sf9 and Trichoplusia ni High Five cells examined using an LC-MS/MS approach revealed not only which proteins are N-glycosylated, but that the reconstructed N-glycomes contain glucuronylated and phosphorylcholine-modified glycans in addition to the typical oligomannosidic and fucosylated structures, These data were corroborated by a parallel MALDI-TOF MS/MS analysis of N-glycosidase-released oligosaccharides. Molecular modelling analysis of one endogenous Sf9 glycoprotein correlated the occurrence of complex and oligomannosidic N-glycans with the accessibility of the occupied N-glycosylation sites. Further, we showed that the N-glycans of influenza haemagglutinins and SARS-CoV-2 spike glycoprotein produced in Spodoptera cells possess a number of glycan structures modified with phosphorylcholine, but core difucosylation was minimal; in contrast, the Trichoplusia-produced haemagglutinin had only traces of the former type, while the latter were dominant. Detection of phosphorylcholine on these glycoproteins correlated with binding to human C-reactive protein. In conclusion, not just oligomannosidic or truncated paucimannosidic N-glycans, but structures with non-human features occur on both natural and recombinant glycoproteins derived from insect cell lines.
Project description:Recent outbreaks of severe acute respiratory syndrome and Middle-East respiratory syndrome along with the threat of a future coronavirus pandemic underscore the importance of finding ways to neutralize these viruses. The trimeric spike transmembrane glycoprotein S mediates entry into host cells and is the major target of neutralizing antibodies. To understand the humoral immune response elicited upon natural infections with coronaviruses, we structurally characterized the SARS-CoV and MERS-CoV S glycoproteins in complex with neutralizing antibodies isolated from human survivors using cryo electron microscopy and characterized the site-specific N-linked glycan profile of the recombinant S proteins with LC-MS/MS using EThcD fragmentation. Although the two antibodies studied blocked attachment to the host cell receptor, only the anti-SARS-CoV S antibody triggered premature fusogenic conformational changes via receptor functional mimicry. These results provide a structural framework for understanding coronavirus neutralization by human antibodies and shed light on the coronavirus fusion activation pathway which appears to take place through a receptor-driven ratcheting mechanism.
Project description:Human serum IgM antibodies are composed of heavily glycosylated polymers with five glycosylation sites on the μ (heavy) chain and one glycosylation site on the J chain. In contrast to IgG glycans, which are vital for a number of biological functions, virtually nothing is known about structure-function relationships of IgM glycans. Natural IgM is the earliest immunoglobulin produced and recognizes multiple antigens with low affinity, whilst immune IgM is induced by antigen exposure and is characterized by a higher antigen specificity. Natural anti-lymphocyte IgM is present in the serum of healthy individuals and increases in inflammatory conditions. It is able to inhibit T cell activation, but the underlying molecular mechanism is not understood. Here we show, for the first time, that sialylated N-linked glycans induce the internalization of IgM by T cells, which in turn causes severe inhibition of T cell responses. The absence of sialic acid residues abolishes these inhibitory activities, showing a key role of sialylated N-glycans in inducing the IgM-mediated immune suppression.
Project description:Glycosylation, including N-glycosylation and O-glycosylation is generally characterized and controlled as a critical quality attribute for therapeutic glycoproteins because glycans can impact protein-based drug product efficacy, half-life, stability, and safety. Analytical procedures to characterize N-glycans are relatively well-established, but the characterization of O-glycans is challenging due to the complex workflows and lack of enzymatic tools. Here we present a simplified chemoenzymatic method to simultaneously profile N- and O-glycans from the same sample using a one-pot format by mass spectrometry (MS). N-glycans were first released by PNGase F, followed by O-glycopeptide generation by Proteinase K, selective N-glycan reduction, and O-glycan release by β-elimination during permethylation of both N- and O- glycans. Glycan structural assignments, and determination of N- to O-glycan ratio was obtained from the one-pot mass spectra. The streamlined, one-pot method is an accurate and reproducible approach that will facilitate advanced characterizations for quality assessments of therapeutic glycoproteins.
Project description:With PNGase F digestion, PGC enrichment,OVA N-glycans were analyzed using PGC nanoLC-ESI-MS/MS.Datasets were analyzed by the N-glycan database search engine called GlycanGoggle developed in our group.
Project description:Activation of murine CD4+ and CD8+ T lymphocytes leads to dramatic remodeling of N-linked glycans. Naïve and activated CD4 T cells, CD8 T cells and B cells were compared for their N-linked glycan structures by MALDI-TOF MS profiling and for expression of glycan transferase genes to assess the biosynthetic basis for any change observed. The major change observed in activated CD4 and CD8 T cells was dramatic reduction of sialylated bi-antennary N-glycans carrying the terminal NeuGc?2-6Gal sequence, and corresponding increase in glycans carrying the Gal?1-3Gal sequence. This change was accounted for by a decrease in the expression of the sialyltransferase ST6Gal, and increase in the expression of the galactosyltransferase ?1-3GalT. Conversely, in B cells no change in terminal sialylation of N-linked glycans was evident, and the expression of the same two glycosyltransferases were increased and decreased, respectively. Keywords = N-linked glycosylation, T cell, B cell, activation, glycosyltransferase, carbohydrate, glycomics, glycan, galactosyltransferase, sialyltransferase Keywords: other