Neutrophil azurophilic granule glycoproteins are distinctively decorated by atypical pauci- and phosphomannose glycans

• Published in: Communications biology 2021-08, Vol.4 (1), p.1012-1012, Article 1012
• Main Authors: Reiding, Karli R., Lin, Yu-Hsien, van Alphen, Floris P. J., Meijer, Alexander B., Heck, Albert J. R.
• Format: Article
• Language: English
• Subjects: 631/1647/296; 631/45/221; 82/16; 82/58; 82/83; Autoimmune diseases; Biology; Biomedical and Life Sciences; Chromatography, Liquid; Cytoplasmic Granules - metabolism; Enzymatic activity; Glycoproteins; Glycoproteins - metabolism; Glycosylation; Humans; Immune system; Leukocytes (neutrophilic); Life Sciences; Lysates; Mannose; N-glycans; Neutrophils; Neutrophils - metabolism; Polysaccharides; Polysaccharides - metabolism; Post-translation; Proteins; Proteome - metabolism; Proteomes; Proteomics; Tandem Mass Spectrometry
• ISSN: 2399-3642; 2399-3642
• DOI: 10.1038/s42003-021-02555-7

While neutrophils are critical first-responders of the immune system, they also cause tissue damage and act in a variety of autoimmune diseases. Many neutrophil proteins are N -glycosylated, a post-translational modification that may affect, among others, enzymatic activity, receptor interaction, and protein backbone accessibility. So far, a handful neutrophil proteins were reported to be decorated with atypical small glycans (paucimannose and smaller) and phosphomannosylated glycans. To elucidate the occurrence of these atypical glycoforms across the neutrophil proteome, we performed LC-MS/MS-based (glyco)proteomics of pooled neutrophils from healthy donors, obtaining site-specific N -glycan characterisation of >200 glycoproteins. We found that glycoproteins that are typically membrane-bound to be mostly decorated with high-mannose/complex N -glycans, while secreted proteins mainly harboured complex N -glycans. In contrast, proteins inferred to originate from azurophilic granules carried distinct and abundant paucimannosylation, asymmetric/hybrid glycans, and glycan phosphomannosylation. As these same proteins are often autoantigenic, uncovering their atypical glycosylation characteristics is an important step towards understanding autoimmune disease and improving treatment. Reiding et al. performed conventional proteomics as well as glycoproteomics on protein extracts from lysates of pooled neutrophils obtained from ten healthy donors. They analyse and compare the glycan occupancy on membrane and secreted glycoproteins, which is helpful to reveal the relationship between neutrophil glycoproteins and their function.