Different glycosphingolipid composition in human neutrophil subcellular compartments

The binding of a number of carbohydrate-recognizing ligands to glycosphingo lipids and polyglycosylceramides of human neutrophil subcellular fractions (plasma membranes/secretory vesicles of resting and ionomycin-stimulated ce lls, specific and azurophil granules) was examined using the chromatogram b inding assay. Several organelle-related differences in glycosphingolipid co ntent were observed. The most prominent difference was a decreased content of the GM3 ganglioside in plasma membranes of activated neutrophils. Gangli osides recognized by anti-VIM-2 antibodies were detected mainly in the acid fractions of azurophil and specific granules. Slow-migrating gangliosides and polyglycosylceramides with Helicobacter pylori-binding activity were fo und in all acid fractions. A non-acid triglycosylceramide, recognized by Ga l alpha 4Gal-binding Escherichia coli, was detected in the plasma membrane/ secretory vesicles but not in the azurophil and specific granules. Although no defined roles of glycosphingolipids have yet been conclusively establis hed with respect to neutrophil function, the fact that many of the identifi ed glycosphingolipids are stored in granules, is in agreement with their ro le as receptor structures that are exposed on the neutrophil cell surface u pon fusion of granules with the plasma membrane. Accordingly, we show that neutrophil granules store specific carbohydrate epitopes that are upregulat ed to the plasma membrane upon cell activation.