Glycoproteins and glycoproteomics in pancreatic cancer

Aberrations in protein glycosylation and polysaccharides play a pivotal role in pancreatic tumorigenesis, influencing cancer progression, metastasis, immunoresponse and chemoresistance. Abnormal expression in sugar moieties can impact the function of various glycoproteins, including mucins, surface receptors, adhesive proteins, proteoglycans, as well as their effectors and binding ligands, resulting in an increase in pancreatic cancer invasiveness and a cancerfavored microenvironment. Recent advance in glycoproteomics, glycomics and other chemical biology techniques have been employed to better understand the complex mechanism of glycosylation events and how they orchestrate molecular activities in genomics, proteomics and metabolomics implicated in pancreatic adenocarcinoma. A variety of strategies have been demonstrated targeting protein glycosylation and polysaccharides for diagnostic and therapeutic development.

Mass spectrometry analysis of intact protein N-glycosylation signatures of cells and sera in pancreatic adenocarcinomas

Pancreatic cancer is among the most malignant cancers,and thus early intervention is the key to better survival outcomes.However,no methods have been derived that can reliably identify early precursors of development into malignancy.Therefore,it is urgent to discover early molecular changes during pancreatic tumorigenesis.As aberrant glycosylation is closely associated with cancer progression,numerous efforts have been made to mine glycosylation changes as biomarkers for diagnosis;however,detailed glycoproteomic information,especially site-specific N-glycosylation changes in pancreatic cancer with and without drug treatment,needs to be further explored.Herein,we used comprehensive solid-phase chemoenzymatic glycoproteomics to analyze glycans,glycosites,and intact glycopeptides in pancreatic cancer cells and patient sera.The profiling of N-glycans in cancer cells revealed an increase in the secreted glycoproteins from the primary tumor of MIA PaCa-2 cells,whereas human sera,which contain many secreted glycoproteins,had significant changes of glycans at their specific glycosites.These results indicated the potential role for tumor-specific glycosylation as disease biomarkers.We also found that AMG-510,a small molecule inhibitor against Kirsten rat sarcoma viral oncogene homolog(KRAS)G12C mutation,profoundly reduced the glycosylation level in MIA PaCa-2 cells,suggesting that KRAS plays a role in the cellular glycosylation process,and thus glycosylation inhibition contributes to the anti-tumor effect of AMG-510.

Application of StrucGP in medical immunology:site-specific N-glycoproteomic analysis of macrophages

The structure of N-glycans on specific proteins can regulate innate and adaptive immunity via sensing environmental signals.Meanwhile,the structural diversity of N-glycans poses analytical challenges that limit the exploration of specific glycosylation functions.In this work,we used THP-1-derived macrophages as examples to show the vast potential of a N-glycan structural interpretation tool StrucGP in N-glycoproteomic analysis.The intact glycopeptides of macrophages were enriched and analyzed using mass spectrometry(MS)-based glycoproteomic approaches,followed by the large-scale mapping of site-specific glycan structures via StrucGP.Results revealed that bisected GlcNAc,core fucosylated,and sialylated glycans(e.g.,HexNAc4Hex5Fuc1Neu5Ac1,N4H5F1S1)were increased in M1 and M2 macrophages,especially in the latter.The findings indicated that these structures may be closely related to macrophage polarization.In addition,a high level of glycosylated PD-L1 was observed in M1 macrophages,and the LacNAc moiety was detected at Asn-192 and Asn-200 of PD-L1,and Asn-200 contained Lewis epitopes.The precision structural interpretation of site-specific glycans and subsequent intervention of target glycoproteins and related glycosyltransferases are of great value for the development of new diagnostic and therapeutic approaches for different diseases.

Mass Spectrometry-based Proteomics and Glycoproteomics in COVID-19 Biomarkers Identification:A Mini-review

The first corona-pandemic,coronavirus disease 2019(COVID-19)caused a huge health crisis and incalculable damage worldwide.Knowledge of how to cure the disease is urgently needed.Emerging immune escaping mutants of the virus suggested that it may be potentially persistent in human society as a regular health threat as the flu virus.Therefore,it is imperative to identify appropriate biomarkers to indicate pathological and physiological states,and more importantly,clinic outcomes.Proteins are the performers of life functions,and their abundance and modification status can directly reflect the immune status.Protein glycosylation serves a great impact in modulating protein function.The use of both unmodified and glycosylated proteins as biomarkers has also been proved feasible in the studies of SARS,Zika virus,influenza,etc.In recent years,mass spectrometry-based glycoproteomics,as well as proteomics approaches,advanced significantly due to the evolution of mass spectrometry.We focus on the current development of the mass spectrometry-based strategy for COVID-19 biomarkers’investigation.Potential application of glycoproteomics approaches and challenges in biomarkers identification are also discussed.

Con A affinity glycoproteomics of normal human liver tissue

In order to establish the novel high throughput, high efficiency and low cost technological platform for the research of N-glycoproteomics, to resolve the significance of characteristic expression profile of glycoprotein and to find the proteins with biological functional importance, the glycoproteins with high-mannose core and the two antennary types were purified and enriched by the Con A affinity chromatography. Con A affinity protein expression profiles of normal human liver tissue were gener- ated by using SDS-PAGE, two-dimensional electrophoresis (2-DE) followed by fast fluorescence stain- ing based on multiplexed proteomics (MP) technology. 301 visible protein spots on the gel were de- tected and 85 of glycoproteins were further successfully identified via peptide mass fingerprinting (PMF) by a matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF- MS/MS) and annotated to IPI databases. Identified glycoproteins definitely take part in the regulation of cell cycle and metabolic processes. The glycosylation sites were predicted with NetNGlyc 1.0 and NetOGlyc 3.1 software, meanwhile they were classified according to the geneontology methods. The construction of Con A affinity glycoprotein database of normal human liver tissue would contribute to the subsequent research.