Project description:We analyzed the HILIC-enriched site-specific N-glycopeptides of human plasma by nano-reversed-phase liquid chromatography (nRPLC) coupled to MS with both HCD and CID-MS/MS fragmentation.
Project description:The human plasma glycoproteome holds enormous potential to identify personalized biomarkers to diagnose and understand disease. Recent advances in mass spectrometry and software development are opening novel avenues to mine the glycoproteome for protein- and site-specific glycosylation changes. Here, we describe a novel plasma N-glycoproteomics method for disease diagnosis and evaluated its clinical applicability by performing comparative glycoproteomics in blood plasma of 40 controls and a cohort of 74 patients with 13 different genetic diseases that directly impact the protein N-glycosylation pathway. The plasma glycoproteome yielded high-specificity biomarker signatures for each of the individual genetic defects. Bioinformatic analyses revealed site-specific glycosylation differences that could be explained by underlying glycobiology and in specific diseases by protein-intrinsic factors. Our work illustrates the strong potential of plasma glycoproteomics to significantly increase specificity of glycoprotein biomarkers with direct insights in site-specific glycosylation changes to better understand the mechanisms underlying human disease.
Project description:Human plasma fibronectin is an adhesive protein that plays a crucial role in wound healing. Many studies had indicated that glycans may mediate the expression and functions of fibronectin, yet a comprehensive understanding of its glycosylation is still missing. Here, we performed a comprehensive N- and O-glycosylation mapping of human plasma fibronectin, and quantified the occurrence of each glycoform in a site-specific manner. Intact N-glycopeptides were enriched by zwitterionic hydrophilic interaction chromatography, and N-glycosites sites were localized by the 18O-labeling method. O-glycopeptide enrichment and O-glycosite identification were achieved by an enzyme-assisted site-specific extraction method. An RP–LC–MS/MS system functionalized with Collision-Induced Dissociation and stepped normalized collision energy (sNCE)-HCD tandem mass was applied to analyze the glycoforms of fibronectin. A total of 6 N-glycosites and 53 O-glycosites were identified, which were occupied by 3842 N-glycoforms and 16 O-glycoforms, respectively. Furthermore, 81.4% of N-glycans were either fucosylated, sialylated, or with both modifications77.31% of N-glycans were sialylated, while O-glycosylation was dominated by the sialyl-T antigen. These site-specific glycosylation patterns on human fibronectin can facilitate functional analyses of fibronectin and therapeutics development.
Project description:Here, we report on the site-specific O-glycosylation analysis of human blood plasma glycoproteins. To this end pooled human blood plasma of healthy donors was digested non-specifically using Protein-ase K, followed by a precipitation step, as well as a glycopeptide enrichment and fractionation step via hydrophilic interaction liquid chromatography. Enriched glycopeptide fractions were subjected to mass spectrometric analysis using reversed-phase liquid chromatography coupled online to an ion trap mass spectrometer operated in positive-ion mode. Peptide identity and glycan composition were derived from low-energy collision-induced dissociation fragment spectra acquired in multistage mode. To pinpoint the O-glycosylation sites glyco�peptides were fragmented using electron transfer dissociation. Spectra were annotated by database searches as well as manually. Overall, 31 O-glycosylation sites and regions belonging to 22 proteins were identified. The majority of these proteins were acute-phase proteins. Strikingly, also 11 novel O-glycosylation sites and regions were identified. In total 23 O-glycosylation sites could be pinpointed. Interestingly, the use of Proteinase K proved to be particularly beneficial in this context. The identified O-glycan compositions most probably correspond to mono- and disialylated core-1 mucin-type O-glycans (T-antigen).
Project description:Monoclonal immunoglobulins (M-proteins) produced by clonal plasma cells are the main cause of multiple myeloma (MM), and hypocomplementemia is observed in some patients with MM. Previous studies have suggested that the glycosylation of immunoglobulins is associated with complement-mediated effector activities. However, the site-specific N-glycosylation of monoclonal immunoglobulins in MM and their effects on complement system activation remain unclear.
Project description:Fibrinogen is a major plasma glycoprotein involved in blood coagulation and inflammatory responses. Alterations in its glycosylation have been implicated in various pathological conditions, yet its site-specific N-glycosylation profile remains largely unexplored in a clinical context. Here, we present a high-throughput LC-MS workflow for site-specific analysis of fibrinogen N-glycosylation using a cost-effective ethanol precipitation enrichment method. The method demonstrated good intra- and inter-plate repeatability (CV: 5% and 12%, respectively) and was validated through the first assessment of intraindividual temporal stability in healthy individuals, revealing consistent glycosylation patterns within individuals. Application to 181 atrial fibrillation (AF) patients and 52 healthy controls identified three gamma chain glycoforms significantly associated with AF. Most notably, increased levels of the asialylated N4H5, known to enhance fibrin bundle thickness and promote clot formation, suggest a potential mechanism linking glycosylation changes to the prothrombotic state in AF. Furthermore, fibrinogen sialylation showed strong associations with cardiovascular risk factors, including triglycerides, BMI, and glucose levels. Longitudinal analysis of 108 AF patients six months post-catheter ablation showed stability in the AF-associated glycan profile. Our findings establish fibrinogen glycosylation as a potential biomarker for cardiovascular conditions and demonstrate the utility of site-specific glycosylation analysis for clinical applications.
Project description:HeLa cell line is frequently used in biomedical research, however little is known about N-glycan structures expressed on individual glycoproteins of this complex sample. We characterized site-specific N-glycosylation of HeLa N-glycoproteins using a complex workflow based on high and low energy tandem mass spectrometry experiments and rigorous data evaluation. The analyses revealed high amount of bovine serum contaminants compromising previous results focusing on released glycan analysis. We reliably identified 43 (human) glycoproteins, 69 N-glycosylation sites and 178 glycopeptides following an acetone precipitation based sample enrichment step. HeLa glycoproteins were found to be highly fucosylated and in several cases localization of the fucose (core or antenna) could also be determined based on low energy tandem mass spectra. High-mannose sugars were expressed in high amounts as expected in case of a cancer cell line. Our method enabled the detailed characterization of site-specific N-glycosylation of several glycoproteins expressed in HeLa. Furthermore, we were the first to experimentally prove the existence of 31 glycosylation sites, where previously presence of glycosylation was only predicted based on the existence of the consensus sequon.