Human Neutrophils Secrete Bioactive Paucimannosidic Proteins from Azurophilic Granules into Pathogen-Infected Sputum

Abstract

Background: Protein paucimannosylation is considered an important invertebrate-and plant-specific glycoepitope. Results: Azurophilic granule-specific human neutrophil proteins from pathogen-infected sputum displayed significant corefucosylated paucimannosylation generated by maturation-and granule-specific ␤-hexosaminidase A and were preferentially secreted from non-lysosomal origins into sputum upon P. aeruginosa stimulation. Conclusion: Human neutrophils produce, store, and selectively secrete bioactive paucimannosidic proteins. Significance: This work will aid in understanding the function(s) of human paucimannosylation in glycoimmunology.

Maturing Glycoproteomics Technologies Provide Unique Structural Insights into the N-glycoproteome and Its Regulation in Health and Disease

“…As described further below, deep glycoproteome profiling studies may also expand our understanding of the N-glycosylation machinery by identifying novel N-glycan structures that may only be present on a small subset of glycoproteins or restricted to specific tissues or physiological conditions. As such, deep site-specific glycoprotein profiling may ultimately provide new "structuredriven" insight into the capacity and regulatory mechanisms of the biosynthetic machinery (21).…”

“…However, as we discussed in a recent review (67), comparing the entire glycoform distribution (micro-heterogeneity) at individual glycosylation sites in separate conditions may be more informative in glycobiology. Both isotope-assisted quantitative glycoproteomics (46,105,108,164) and label-free (based on XIC area, precursor intensity or spectral count) quantitative glycoproteomics (21,104,106,159,165) can generate quantitative information of site micro-heterogeneity. Importantly, if the ambition is to understand the mechanisms driving alterations of the glycoproteome in specific conditions (see Fig.…”

“…The different programs utilize various strategies to identify N-glycopeptides including the use of characteristic Y 1 ions, oxonium ions, B/Y-and C/Z-type glycan fragment ion series, and b/y-and c/z-type peptide fragment ions (116,117). In order to limit the search space and enhance the detailed structural knowledge of the glycans encountered in a given glycoproteome, several studies have performed parallel N-glycome profiling (21,40,88,105,106,108,162). This so-called 'glycomics-assisted glycoproteomics' approach can also be complemented with quantitative proteome and de-N-glycoproteome profiling (mapping of formerly N-glycosylated peptides) (21, 46, 88, 103, 105-108, 135, 159, 162), which reduce the search space even further and provide supporting evidence to pinpoint the exact mechanism(s) driving the observed glycoproteome alterations.…”

“…B, Mammalian N-glycoproteins are typically divided into three main N-glycan classes: high mannose, hybrid, and complex type. Unusual paucimannosidic and chitobiose core type N-glycans arising from unconventional truncation pathways (dashed box) have been reported in specific cell types and physiological conditions (21). Monosaccharide residues are depicted according to the establish nomenclature (180) with residual monoisotopic masses provided.…”

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).…”