Dataset Information

Chemical labeling for fine mapping of IgG N-glycosylation by ETD-MS

ABSTRACT: Immunoglobulin G (IgG), which contains four subclasses (IgG1-4), is one of the most important class of glycoproteins in immune system. Because of its importance in immune system, a steady increase of interest in developing IgG as biomarker or biotherapeutic agents for the treatment of diseases has been seen, as most therapeutic mAbs were IgG-based. N-glycosylation of IgG is crucial for its effector function and makes the IgG highly heterogeneous both in structure and function, although all four subclasses of IgG contain only a single N-glycosylation site in the Fc region with highly similar amino acid sequence. Therefore, fine mapping the IgG glycosylation is necessary for understanding the IgG function and avoiding aberrant glycosylation in mAbs. However, site-specific and comprehensive N-glycosylation analysis of IgG subclasses still cannot be achieved by MS alone due to the partial sequence coverage and loss of connections among glycosylation on protein sequence. We report here a chemical labeling strategy to improve the electron transfer dissociation efficiency in mass spectrometry analysis, which enable a 100% peptide sequence coverage of N-glycopeptides in all subclasses of IgG. Combining with high-energy collisional dissociation for the fragmentation of glycans, fine mapping of N-glycosylation profile of IgG is achieved. This comprehensive glycosylation analysis strategy for the first time allows the discrimination of IgG3 and IgG4 intact N-glycopeptides with high similarity in sequence without the antibody-based pre-separation. Using this strategy, aberrant serum IgG N-glycosylation for four IgG subclasses associated with cirrhosis and hepatocellular carcinoma were revealed. Moreover, this method identifies 5 times more intact glycopeptides from human serum than native-ETD method, implying that the approach can also accommodate for large-scale site-specific profiling of glycoproteomics.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Blood Cell, Blood Serum

DISEASE(S): Avian Influenza

SUBMITTER: zhang lei

LAB HEAD: haojie lu

PROVIDER: PXD014713 | Pride | 2019-08-26

REPOSITORIES: Pride

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Project description:Changes in IgG glycosylation have been reported to be associated with colorectal cancer (CRC), but the alteration in specific subclass of IgG is unknown. Herein, we optimized five common IgG glycopeptides enrichment methods to acquire comprehensive profiling of IgG glycoproteomics in CRC. Notably, incomplete tryptic digestion of IgG occurred when using ordinary ratio of protease to protein, which significantly impacted the final statistical analysis of association between IgG glycosylation and CRC. We introduced a method based on two-step enzymatic digestion, enabling the complete digestion of IgG glycopeptides and further improving the detection intensity of the target glycopeptides. By this approach, total 47 IgG glycopeptides can be identified by nanoLC-ESI-MS/MS. Following rapid and automatic data processing through the self-developed program, we observed that IgG1_H3N4F1 and IgG1_H3N4 were substantially increased in CRC, while IgG1_H5N5F1, IgG1_H5N4F1S1and IgG2_H5N4F1 were markedly decreased. Strikingly, these four glycopeptides were continually significantly changed in early and late stages of CRC. Further evaluation of the diagnostic performance showed they all obtained a fair performance in discriminating the patients from the normal. In terms of the glycan features, it demonstrated that CRC progression associates with the increased agalactosylation, and the decreased digalactosylation and galactosylation per antenna on diantennay glycans of IgG1 and IgG2. Concurrently, the decreased sialylation of IgG1 was strongly correlated with CRC. Moreover, tumor-specific glycosylation analysis showed that the alterations of subclass-specific IgG glycosylation were more significant in colon cancer, and no obvious difference between colon and rectal cancer was found. More importantly, all these findings were validated in an independent cohort. This two-step enzymatic approach is crucial to explore the relationship between the disease progression and IgG glycosylation.

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Chemical labeling for fine mapping of IgG N-glycosylation by ETD-MS

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