Tissue-Specific Glycosylation at the Glycopeptide Level

Abstract

This manuscript describes the enrichment and mass spectrometric analysis of intact glycopeptides from mouse liver, which yielded site-specific N-and O-glycosylation data for ϳ130 proteins. Incorporation of different sialic acid variants in both N-and O-linked glycans was observed, and the importance of using both collisional activation and electron transfer dissociation for glycopeptide analysis was illustrated. The N-glycan structures of predicted lysosomal, endoplasmic reticulum (ER), secreted and transmembrane proteins were compared. The data suggest that protein N-glycosylation differs depending on cellular location. The glycosylation patterns of several mouse liver and mouse brain glycopeptides were compared. Tissue-specific differences in glycosylation were observed between sites within the same protein: Some sites displayed a similar spectrum of glycan structures in both tissues, whereas for others no overlap was observed. We present comparative brain/liver glycosylation data on 50 N-glycosylation sites from 34 proteins and 13 O-glycosylation sites from seven proteins. Molecular

N-Glycopeptide Profiling in Arabidopsis Inflorescence

“…This large number of truncated structures is against conventional wisdom but is consistent with glycopeptide studies carried out by us and others (22,25,31). We believe that released glycan analysis misses these structures for a few reasons: 1) They mostly analyze glycans released from the plasma membrane, whereas our results are from the whole cell including compartments such as the ER and Golgi; 2) PNGase F is probably less efficient at cleaving truncated structures (it is known to FIG.…”

“…While we, and others, have observed nonconsensus glycosylation in other species (20,25,29,30), we believe this is the first confirmation that it also occurs naturally in plant proteins.…”

“…Precursor and fragment mass tolerances of 10 ppm and 0.6 Da were considered for ETD data. ETD data were initially searched using a mass modification strategy similar to that previously published (22,25), where any mass modification between 100 and 2500 Da on serine, threonines, or asparagine residues was considered. For subsequent searches, modifications were only considered on asparagine residues located within the glycosylation motif N-!P-S/T, a capability newly introduced in Protein Prospector version 5.14.20.…”

Protein-Specific Glycoprofiling for Patient Diagnostics

“…As an example, abnormal glycosylation of IgG was observed in GCS1-CDG patients with normal transferrin glycosylation (11 ), although GCS1 is ubiquitously expressed. New technologies for analysis of complex glycopeptide mixtures are emerging and show tissue-specific glycosylation profiles of individual proteins (12 ). Such technologies will pave the way to identify additional glycoproteins that can be used as biomarkers for CDG diagnostics and beyond.…”

Structural characterisation of glycosylation of paramyxovirus attachment and fusion proteins by mass spectrometry

“…Thus, the mature glycoproteins can bear a mixture of high mannose, hybrid or complex glycans. More recently, an unconventional glycan processing pathway has been described, prompted by the growing observation of truncated N-linked structures in mammals (19)(20)(21)(22)(23). These glycans stem from trimming of hybrid or complex glycans and the truncated N-glycans containing one to four mannose residues (Man 1-4 ) are described as paucimannose and those without Man residues are described as chitobiose core type glycans (19).…”