Different isolation approaches lead to diverse glycosylated extracellular vesicle populations

Extracellular vesicles (EVs) are a heterogeneous group of small secreted particles involved in inter-cellular communication and mediating a broad spectrum of biological functions. EVs cargo iscomposed of a large repertoire of molecules, including glycoconjugates. Herein, we report the firststudy on the impact of the isolation strategy on the EV populations’glycosylation profile. The use ofdifferent state-of-the-art protocols, namely differential ultracentrifugation (UC), total exosome isola-tion (TEI), OptiPrepTMdensity gradient (ODG) and size exclusion chromatography (SEC) resulted in EVpopulations displaying different sets of glycoconjugates. The EV populations obtained by UC, ODGand SEC methods displayed similar protein and glycan profiles, whereas TEI methodology isolated themost distinct EV population. In addition, ODG and SEC isolation protocols provided an enhanced EVglycoproteins detection. Remarkably, proteins displaying the tumour-associated glycan sialyl-Tn(STn) were identified as packaged cargo into EVs independently of the isolation methodology. STncarrying EV samples isolated by UC, ODG and SEC presented a considerable set of cancer-relatedproteins that were not detected in EVs isolated by TEI. Our work demonstrates the impact of usingdifferent isolation methodologies in the populations of EVs that are obtained, with consequences inthe glycosylation profile of the isolated population. Furthermore, our results highlight the importanceof selecting adequate EV isolation protocols and cell culture conditions to determine the structuraland functional complexity of the EV glycoconjugates.This work was funded by FEDER funds through theOperational Programme for Competitiveness Factors-COMPETE (POCI-01-0145-FEDER-016585; POCI-01-0145-FEDER-007274; POCI-01-0145-FEDER-028489) and NationalFunds through the Foundation for Science and Technology(FCT), under the projects: PTDC/BBB-EBI/0567/2014 (toCAR), PTDC/MED-ONC/28489/2017 (to AM) and UID/BIM/04293/2013; and the project NORTE-01-0145-FEDER-000029, supported by Norte Portugal Regional Programme(NORTE 2020), under the PORTUGAL 2020 PartnershipAgreement, through the European Regional DevelopmentFund (ERDF). DF acknowledges the FCT PhD Programmesand Programa Operacional Potencial Humano (POPH), speci-fically the Biotech Health Programme (Doctoral Programme onCellular and Molecular Biotechnology Applied to HealthSciences), with the reference PD/0016/2012 funded by FCTand the grant SFRH/BD/110636/2015 from FCT, POPH andFSE (Fundo Social Europeu); MB acknowledges the EuropeanUnion’s Horizon 2020 research and innovation programmeunder the Marie Sklodowska-Curie grant agreement No.748880; and JP acknowledges FCT (SFRH/BD/137319/2018).The authors acknowledge Rede Nacional de Espectrometria deMassa, ROTEIRO/0028/2013, ref. LISBOA-01-0145-FEDER-022125, supported by COMPETE and North PortugalRegional Operational Programme (Norte2020), under thePORTUGAL 2020 Partnership Agreement, through theEuropean Regional Development Fund (ERDF). SV acknowl-edges the Danish National Research Foundation (DNRF107)

Probing the O-glycoproteome of gastric cancer cell lines for biomarker discovery

Circulating O-glycoproteins shed from cancer cells represent important serum biomarkers for diagnostic and prognostic purposes. We have recently shown that selective detection of cancer-associated aberrant glycoforms of circulating O-glycoprotein biomarkers can increase specificity of cancer biomarker assays. However, the current knowledge of secreted and circulating O-glycoproteins is limited. Here, we used the COSMC KO "Simple- Cell" (SC) strategy to characterize the O-glycoproteome of two gastric cancer SimpleCell lines (AGS, MKN45) as well as a gastric cell line (KATO III) which naturally expresses at least partially truncated O-glycans. Overall, we identified 499 O-glycoproteins and 1236 O-glycosites in gastric cancer SimpleCells, and a total 47 O-glycoproteins and 73 O-glycosites in the KATO III cell line. We next modified the glycoproteomic strategy to apply it to pools of sera from gastric cancer and healthy individuals to identify circulating O-glycoproteins with the STn glycoform. We identified 37 O-glycoproteins in the pool of cancer sera, and only nine of these were also found in sera from healthy individuals. Two identified candidate O-glycoprotein biomarkers (CD44 and GalNAc-T5) circulating with the STn glycoform were further validated as being expressed in gastric cancer tissue. A proximity ligation assay was used to show that CD44 was expressed with the STn glycoform in gastric cancer tissues. The study provides a discovery strategy for aberrantly glycosylated O-glycoproteins and a set of O-glycoprotein candidates with biomarker potential in gastric cancer.This work was supported by The Danish Research Councils, The Mizutani Foundation, The Danish National Research Foundation (DNRF107) and Fundacão para a Ciência e a Tecnologia (FCT) and COMPETE (Programa Operacional Temático Factores de Competitividade, comparticipado pelo fundo comunitário europeu FEDER) in the framework of the projects: PTDC/BBB-EBI/0786/2012; EXPL/CTM-BIO/0762/2013. Grants were received from FCT (SFRH/BD/73717/2010 to DC), (SFRH/BPD/75871/2011 to AM), (SFRH/BPD/96510/2013 to CG) and (SFRH/BPD/66288/2009 to JAF). IPATIMUP is an Associate Laboratory of the Portuguese Ministry of Science, Technology and Higher Education, and is partially supported by FCT

Bioinformatics and molecular modeling in glycobiology

The field of glycobiology is concerned with the study of the structure, properties, and biological functions of the family of biomolecules called carbohydrates. Bioinformatics for glycobiology is a particularly challenging field, because carbohydrates exhibit a high structural diversity and their chains are often branched. Significant improvements in experimental analytical methods over recent years have led to a tremendous increase in the amount of carbohydrate structure data generated. Consequently, the availability of databases and tools to store, retrieve and analyze these data in an efficient way is of fundamental importance to progress in glycobiology. In this review, the various graphical representations and sequence formats of carbohydrates are introduced, and an overview of newly developed databases, the latest developments in sequence alignment and data mining, and tools to support experimental glycan analysis are presented. Finally, the field of structural glycoinformatics and molecular modeling of carbohydrates, glycoproteins, and protein–carbohydrate interaction are reviewed

Ion Mobility Mass Spectrometry for Ion Recovery and Clean-Up of MS and MS/MS Spectra Obtained from Low Abundance Viral Samples

Many samples of complex mixtures of N-glycans released from small amounts of material, such as glycoproteins from viruses, present problems for mass spectrometric analysis because of the presence of contaminating material that is difficult to remove by conventional methods without involving sample loss. This paper describes the use of ion mobility for extraction of glycan profiles from such samples and for obtaining clean CID spectra when targeted m/z values capture additional ions from those of the target compound. N-Glycans were released enzymatically from within SDSPAGE gels, from the representative glycoprotein, gp120 of the human immunodeficiency virus, and examined by direct infusion electrospray in negative mode followed by ion mobility with a Waters Synapt G2 mass spectrometer. Clean profiles of singly, doubly and triply charged N-glycans were obtained from samples in cases where the raw electrospray spectra displayed only a few glycan ions as the result of low sample concentration or the presence of contamination. Ion mobility also enabled uncontaminated CID spectra to be obtained from glycans when their molecular ions displayed coincidence with ions from fragments or multiply charged ions with similar m/z values. This technique proved to be invaluable for removing extraneous ions from many CID spectra. The presence of such ions often produces spectra that are difficult to interpret. Most CID spectra, even those from abundant glycan constituents, benefited from such clean-up showing that the extra dimension provided by ion mobility was invaluable for studies of this type