Project description:The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus utilizes an extensively glycosylated spike protein that protrudes from the viral envelope to bind to angiotensin-converting enzyme-related carboxypeptidase (ACE2) as its primary receptor to mediate host-cell entry. Currently, the predominant recombinant spike protein production hosts are Chinese hamster ovary (CHO) and human embryonic kidney (HEK) cells. In this study, recombinant full-size spike protein was produced transiently in CHO and HEK cell suspensions. To further evaluate the sialic acid linkages presenting on spike glycans, a two-step amidation process, employing dimethylamine and ammonium hydroxide reactions in a solid support system, was developed to differentially modify the sialic acid linkages on glycans and glycopeptides from spike protein. We determined global and site-specific N-linked glycosylation patterns in soluble SARS-CoV-2 spike using MALDI-TOF and LC-MS/MS with electron-transfer/higher-energy collision dissociation (EThcD) fragmentation. We identified the glycan compositions at 21 and 19 out of the 22 predicted N-glycosylation sites of the SARS-CoV-2 spike proteins produced in CHO and HEK, respectively. The N-glycan site at 1158 position (N1158) and the N-glycan sites at 122 ,282 and 1158 positions (N122, N282 and N1158) were found to be unoccupied on spike secreted from CHO and HEK cells, respectively. The structural mapping of glycans of recombinant human spike proteins revealed that CHO-Spike presented more complex and higher sialylation (α2,3-linked) content while HEK-Spike displayed more high-mannose and minor content of α2,3- and α2,6-linked sialic acids. The N74 site represents the most heavily N-glycosylated site on both spike proteins while some high-mannose abundant sites (N17, N234, N343, N616, N709, N717, N801 and N1134) on HEK-Spike may differentially shield the virus compared to CHO-spike and provide a different host immune system interaction strategy. Collectively, these data underscore the importance of characterizing site-specific glycosylation on recombinant human spike protein from HEK and CHO cells in order to better understand the impact of the production host on this complex and important protein used in diagnostics and vaccines.
Project description:Spike (S) protein plays a key role in COVID-19 (SARS-CoV-2) infection and host-cell entry. Previous studies have systematically analyzed site-specific glycans compositions of S protein. Here, we further provide structure-clear N-glycosylation of S protein at site-specific level by using our recently developed structure- and site-specific N-glycoproteomics sequencing algorithm StrucGP. In addition to the common N-glycans as detected in previous studies, many uncommon glycosylation structures such as LacdiNAc structures, Lewis structures, Mannose 6-Phosphate (M6P) residues and bisected core structures were unambiguously mapped at a total of 20 glycosites in the S protein trimer and protomer. These data further supports the glycosylation structural-functional investigations of COVID-19 virus Spike.
Project description:A central tenet in the design of vaccines is the display of native-like antigens in the elicitation of protective immunity. The abundance of N-linked glycans across the SARS-CoV-2 spike protein is a potential source of heterogeneity between the many different vaccine candidates under investigation. Here, we investigate the glycosylation of recombinant SARS-CoV-2 spike proteins from five different laboratories and compare them against infectious virus S protein. We find patterns which are conserved across all samples and this can be associated with site-specific stalling of glycan maturation which act as a highly sensitive reporter of protein structure. Molecular dynamics (MD) simulations of a fully glycosylated spike support s a model of steric restrictions that shape enzymatic processing of the glycans. These results suggest that recombinant spike-based SARS-CoV-2 immunogen glycosylation reproducibly recapitulates signatures of viral glycosylation.
https://doi.org/10.1101/2021.03.08.433764
This folder contains the RAW MS files used in the glycopeptide analysis for recombinant SARS proteins from a range of different labs outlined in Figure 1 and 2 and additionally the analysis performed on monomeric RBD
Project description:Site-specific glycosylation analysis of the ChAdOx1 nCoV-19 derived Spike protein. Raw files for both the cleaved (S1/S2) and uncleaved (S0) protein are included.
Project description:We have characterized the site-specific glycosylation patterns of the HEK293 recombinant spike RBD and S1 domains as well as the intact spike derived from whole virus produced in Vero cells.
Project description:Analysis of the structures and distributions of native spike conformations on vitrified human coronavirus NL63 (HCoV-NL63) virions without chemical fixation by cryogenic electron tomography (cryoET) and subtomogram averaging, along with site-specific glycan composition and occupancy determined by mass spectroscopy
Project description:Recombinant PDCoV spike glycoprotein was produced from Drosophile S2 cells for structural characterization by cryo electron microscopy and mass spectrometry. MS was used to assess the N-linked glycosylation profile of the purified material. We used a multiple protease digestion in combination with RP-LC-MS/MS, EThcD fragmentation on Orbitrap Fusion to characterize intact glycopeptides.
Project description:Fusion proteins of the SARS-CoV-1 and SARS-CoV-2 spike receptor binding domain with a fluorescent protein were created in monomeric and trimeric form as tools for receptor binding studies in cultured cells and animal tissues. Here, site specific N-linked glycosylation in the proteins expressed from GnTI-/- cells is profiled with LC-MS/MS, using electron transfer high-energy collision dissociation
Project description:The spike protein of SARS-CoV-2, the virus responsible for the global pandemic of COVID-19, is an abundant, heavily glycosylated surface protein that plays a key role in receptor binding and host cell fusion, and is the focus of all current vaccine development efforts. Variants of concern are now circulating worldwide that exhibit mutations in the spike protein. Protein sequence and glycosylation variations of the spike may affect viral fitness, antigenicity, and immune evasion. Global surveillance of the virus currently involves genome sequencing, but tracking emerging variants should include quantitative measurement of changes in site-specific glycosylation as well. In this work, we used data-dependent acquisition (DDA) and data-independent acquisition (DIA) mass spectrometry to quantitatively characterize the five N-linked glycosylation sites of the glycoprotein standard alpha-1-acid glycoprotein (AGP), as well as the 22 sites of SARS-CoV-2 spike protein. We found that DIA compared favorably to DDA in sensitivity, resulting in more assignments of low abundance glycopeptides. However, the reproducibility across replicates of DIA-identified glycopeptides was lower than that of DDA, possibly due to the difficulty of reliably assigning low abundance glycopeptides confidently. The differences in the data acquired between the two methods suggest that DIA out-performs DDA in terms of glycoprotein coverage but that overall performance is a balance of sensitivity, selectivity, and statistical confidence in glycoproteomics. We assert that these analytical and bioinformatics methods for assigning and quantifying glycoforms would benefit the process of tracking viral variants as well as for vaccine development.