Project description:The envelope glycoprotein GP of the ebolaviruses is essential for host cell attachment and entry. It is also the primary target of the protective and neutralizing antibody response in both natural infection and vaccination. GP is heavily glycosylated with up to 17 predicted N-linked sites, numerous O-linked glycans in its disordered mucin-like domain (MLD), and three predicted C-linked mannosylation sites. Glycosylation of GP is important for host cell attachment to cell-surface lectins, as well as GP stability and fusion activity. Moreover, it has been shown to shield GP from neutralizing activity of serum antibodies. Here, we use mass spectrometry-based glycoproteomics to profile the site-specific glycosylation patterns of ebolavirus GP, including N-, O-, and C-linked glycans.
Project description:Presentation of self- and foreign peptide antigens by human leukocyte antigen (HLA) complexes at the cell surface is a key process in our immune response. The alpha-chain, the part of the HLA class I complex that contains the peptide binding groove, is one of the most polymorphic proteins in the human proteome. All HLA class I alpha-chains carry a conserved N-glycosylation site, but little is known about its nature and function. Here, we report an in-depth characterization of the N-glycosylation features in HLA class I molecules. In three cell lines we observe that different HLA-A alpha-chains carry similar glycosylation, distinctly different from the HLA-B, HLA-C and HLA-F alpha-chains. HLA-B alpha-chains carry mostly mature glycans, HLA-C and HLA-F alpha-chains carry predominantly high-mannose, whereas HLA-A molecules display the broadest variety of glycan characteristics. We hypothesized that these glycosylation features are directly linked to the cellular localization of the HLA complexes. Analyzing HLA class I complexes from plasma and inner membrane enriched fractions revealed confirmed that most HLA-B complexes can be found in the plasma membrane, most HLA-C and HLA-F molecules reside in the ER and Golgi membrane and HLA-A molecules are more equally distributed over all these cellular compartments. As peptide-binding and specificity is cellular compartment dependent, we corroborate from our data that standard measurements of HLA peptide-antigens from whole cell extracts likely do not exclusively capture the antigen repertoires presented at the cell surface, but also those still within the cell. Our data indicate that standard protein quantification of HLA alpha-chains does not correlate with cell surface expression levels, while analysis of glycopeptides provides allotype and compartment specific quantification.
Project description:Comparison of the glycosylation profile of monoclonal anti-SARS-CoV-2 Spike IgG (87G7) produced in human or fungal expression platforms
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:Glycosylation reactions require activated glycosyl donors in form of nucleotide sugars to drive processes such as post-translational protein modifications, glycolipid and polysaccharide biosynthesis. Most of these reactions occur in the Golgi requiring cytosolic-derived nucleotide sugars, which are actively transferred into the Golgi lumen by nucleotide sugar transporters. Here we present the identification of the plant UDP-N-acetylglucosamine (UDP-GlcNAc) transporter (UGNT1) indispensable for the delivery of a substrate for maturation of N-glycans and glycosyl inositol phosphorylceramides (GIPCs). Profiles of N-glycopeptides revealed that UGNT1 loss-of-function mutants are devoid of complex and hybrid N-glycans. Instead, most of the glycol-N-peptide population contained high mannose structures, representing the structure prior to the addition of the first GlcNAc in the Golgi. Our findings emphasize that the reference plant Arabidopsis contains a single UDP-GlcNAc transporter responsible for the maturation of complex N-glycans in the Golgi lumen.
Project description:A workflow for differential analysis of the microheterogeneity of site-specific intact N-glycopeptides of serum haptoglobin between early hepatocellular carcinoma (HCC) and liver cirrhosis has been developed.
Project description:A comprehensive screening of site-specific N-glycopeptides in serum haptoglobin (Hp), a reporter molecule for aberrant glycosylation in HCC, has been performed to characterize glycopeptide markers for NASH-related HCCs.
Project description:Coronaviruses (CoVs) encompass many human pathogens such as HKU-1, OC43, NL63, SARS, MERS and, most recently, nCoV-2019. The spike (S) protein of CoVs has received much attention for its role in host tropism and immunity, but it is becoming increasingly clear that the haemagglutinin esterase (HE) also plays an important role in host adaptation by determining host receptor (sialic acid) specificity. We determined the structure of HKU1 HE by cryo electron microscopy and mapped site-specific N-linked glycosylation by LC-MS/MS of glycopeptides using electron transfer high-energy collision dissociation.
Project description:Here we show using mass photometry how proline substitutions, commonly used for SARS-CoV-2 spike stabilisation and vaccine design, directly impedes ACE2 receptor interactions via dynamics of open and closed states. Conformational changes and ACE2 binding were influenced by spike variant and temperature, but independent of site-specific N-glycosylation.
Project description:In this work, we performed a fully descriptive analysis N- and O- linked glycosylation of SARS-COV-2 S glycoprotein. We investigated that dual-functionalized Ti-IMAC material enable the simultaneous enrichment and separation of neutral and sialyl glycopeptides of a recombinant SARS-CoV-2 S glycoprotein from HEK293, which will eliminate the signal suppression of neutral glycopeptides to sialyl glycopeptides and improve the glycoform coverage of S protein. We have profiled 19 of its 22 potential N-glycosylated sites with 398 unique glycoforms in dual-functional Ti-IMIAC approach that is 1.6-fold of that in conventional HILIC method. We also identified O-linked glycosylation site that was not found in dual-functional Ti-IMIAC approach. In addition, we have also identified mannose-6-phosphate (M6P) glycosylation, which substantially expands the current knowledge of the spike protein’s glycosylation and enables the investigation of the influence of mannose-6-Phosphate on its cell entry.