Surface-Associated Glycans as a Possible Distinct Factor for Establishing the Molecular Properties of Prostasomes

Abstract

Glycans, complex carbohydrates bound to lipids and proteins, play important roles in biological processes. Prostasomes, extracellular vesicles from prostate epithelial cells, have a glycan composition influenced by their cellular origin and by the composition of the seminal plasma into which they are secreted. We hypothesized that the membrane-associated glycans could be used as selective targets for separation of prostasomes and as relevant parameter for distinction of their populations. Prostasomes from seminal plasma of normozoospermic and oligozoospermic men were separated by ion-exchange- and lectin-affinity chromatography using concanavalin A (ConA) lectin, specific for mannosylated structures, and wheat germ agglutinin (WGA), specific for sialic acid. The presence of tetraspanins (CD63, CD9 and CD81), galectin-3 (gal-3) and gamma-glutamyl transferase (GGT) as known vesicle markers were monitored in association with distinct glycans. Their distribution was also analysed upon treatment of prostasomes with non-ionic detergent. Membrane-associated GGT in the context of Con A- and WGA-reactive glycans mark prostasome populations from normozoospermic and oligozoospermic men. The assembly of tetraspanins, gal-3, and distinct N-glycans defines the solubilisation signature of prostasomes. WGA-reactive glycoproteins co-localize with CD9 and gal-3 in detergent-resistant domains, whereas ConA-reactive glycoproteins were distributed in detergent-sensitive domains along with CD63 and GGT. Subtle differences in the composition/presentation of examined molecules made difference among vesicles sharing the same physical properties in each group as well as between them. The results obtained suggest the potential of glyco-parameters as reference markers for EVs populations.