Characterization of Cell Glycocalyx with Mass Spectrometry Methods

Abstract

The cell membrane plays an important role in protecting the cell from its extracellular environment. As such, extensive work has been devoted to studying its structure and function. Crucial intercellular processes, such as signal transduction and immune protection, are mediated by cell surface glycosylation, which is comprised of large biomolecules, including glycoproteins and glycosphingolipids. Because perturbations in glycosylation could result in dysfunction of cells and are related to diseases, the analysis of surface glycosylation is critical for understanding pathogenic mechanisms and can further lead to biomarker discovery. Different mass spectrometry-based techniques have been developed for glycan analysis, ranging from highly specific, targeted approaches to more comprehensive profiling studies. In this review, we summarized the work conducted for extensive analysis of cell membrane glycosylation, particularly those employing liquid chromatography with mass spectrometry (LC-MS) in combination with various sample preparation techniques.

Der Tumormarker Sialinsäure

“…Die relativ starken Sialinsäuren (vom Griechischen "sialos": Speichel) existieren in der Natur in vielen verschiedenen molekularen Formen und finden sich bei höheren Tierarten [28,34,37,42,43]. Die höchsten Konzentrationen treten in Plasmamembranen (65-70 % der Sialinsäuren) und zu einem niedrigen Anteil im glatten endoplasmatischen Retikulum auf [8,9,34,37].…”

“…Sialinsäuren spielen wichtige Rollen in vielen physiologischen und pathologischen Prozessen, z. B. zelluläre Wiedererkennung und Kommunikation, Zellzusammenschluss und -entwicklung, Kontrolle der Lebenszeit von Zuckerkonjugaten im Organismus, Vermittlung bakterieller und viraler Infektionen, Tumorwachstum und Metastasierung, in der Immunologie, in der Biologie des Mikrobioms, Reproduktions-und in der Neurobiologie [8,13,15,26,33,34,37,42,43].…”

“…Sialinsäuren sind essenzielle Bestandteile von vielen Glykoproteinen, -peptiden und -lipiden [8,15,33,37,42,43]. Diese ubiquitäre Verbreitung in Glykokonjugaten verschiedenen Ursprungs zeigt, dass eine Vielzahl von biologischen Funktionen mit diesem Zucker assoziiert sind [3,7,10,15,33,42,43].…”

“…Sialinsäuren liegen im menschlichen Körper entweder an Proteinen bzw. an Lipiden gebunden oder in freier Form vor [42,43].…”

SugarQuant: a streamlined pipeline for multiplexed quantitative site-specific N-glycoproteomics

“…Conventional analytical approaches often release the glycan moiety chemically or enzymatically from proteins before performing MS analysis of either the resulting oligosaccharides or the de-glycosylated peptides 3 , thus deliberately discarding information about site specificity. Instead, analysis of intact N-glycopeptides (i.e., peptides that derive from endoproteolytic digestion of glycosylated proteins, but still carry the intact glycan moieties) is essential to determine the linkage between protein and glycan, and to profile the micro-heterogeneity of glycosylation at each site 4,5 . Significant improvements have been made with regard to methods for intact glycopeptide characterization, including glycopeptide enrichment [6][7][8] , optimized MS acquisition strategies 8 , advanced fragmentation techniques 9, 10 and database search algorithms 11 .…”