Measurement of erythrocyte membrane mannoses to assess splenic function

Abstract

Summary Red blood cells (RBCs) lose plasma membrane in the spleen as they age, but the cells and molecules involved are yet to be identified. Sickle cell disease and infection by Plasmodium falciparum cause oxidative stress that induces aggregates of cross‐linked proteins with N‐linked high‐mannose glycans (HMGs). These glycans can be recognised by mannose‐binding lectins, including the mannose receptor (CD206), expressed on macrophages and specialised phagocytic endothelial cells in the spleen to mediate the extravascular haemolysis characteristic of these diseases. We postulated this system might also mediate removal of molecules and membrane in healthy individuals. Surface expression of HMGs on RBCs from patients who had previously undergone splenectomy was therefore assessed: high levels were indeed observable as large membrane aggregates. Glycomic analysis by mass spectrometry identified a mixture of Man5‐9GlcNAc2 structures. HMG levels correlated well with manual pit counts (r = 0.75–0.85). To assess further whether HMGs might act as a splenic reticuloendothelial function test, we measured levels on RBCs from patients with potential functional hyposplenism, some of whom exhibited high levels that may indicate risk of complications.

Glycoproteome remodelling and granule-specificN-glycosylation accompany neutrophil granulopoiesis

“…Finally, the Ge and Se granules each hosted ∼200 N -glycoproteins carrying predominantly oligomannosidic- and less sialylated/fucosylated complex-type N -glycans. While traditionally regarded as an intracellular glyco-feature pertaining to immaturely-processed N -glycoproteins trafficking the secretory machinery, oligomannosylation is increasingly reported i) on mature (fully processed) neutrophil glycoproteins as comprehensively reviewed 4,20 , ii) to decorate the surface of neutrophils 41 and other blood 42 and epithelial 43,44 cells, and iii) to be elevated in cancer 45,46 and other neutrophil-related diseases 47 . Our study supports that oligomannosylation is a prominent feature of the Ge and Se compartments.…”

Glycoproteome remodeling and organelle-specific N -glycosylation accompany neutrophil granulopoiesis

“…Finally, the Ge granules and Se vesicles each hosted ~200 N -glycoproteins carrying predominantly oligomannosidic- and less sialylated/fucosylated N -glycans. While traditionally regarded as an intracellular glycofeature pertaining to incompletely processed N -glycoproteins trafficking the secretory machinery, oligomannosylation is increasingly reported i) on mature (fully processed) neutrophil glycoproteins ( 4 , 19 ), ii) to decorate the surface of neutrophils ( 44 ) and other blood ( 45 ) as well as epithelial ( 46 , 47 ) cells, and iii) to be elevated in cancer ( 48 , 49 ) and other neutrophil-related diseases ( 50 ). Our study supports that oligomannosylation is a prominent feature of the Ge and Se compartments.…”