engleski

Potentials of a Fully Automated Chip-Based Nanoelectrospray Ionization High Capacity Ion Trap Mass Spectrometry in Neuroglycolipidomics: Characterization of Ganglioside Composition Specificity in Selected Fetal Human Brain Regions

Sialylated glycosphingolipids, gangliosides, are primarily building components of the outer leaflet of plasma membranes of all mammalian cell types ; the highest concentrations are present in the brain cells. They participate in cell-to-cell communication and cell signaling. Involvement of certain ganglioside species have been reported in key brain developmental processes, such as neuritogenesis, directional motility, axon guidance, apoptosis, and neural cell-cell recognition1. Brain ganglioside composition shows regional, developmental, and ageing specificity, while characteristic changes of the normal pattern have been observed in various neuropathological conditions. Employing ultra-sensitive mass spectrometric approaches complemented with chromatographic and immunochemical methods, we documented that specific ganglioside patterns contain much larger number of individual species than previously described2, 3. Here, we report results of the composition and structure analysis of native ganglioside mixtures from selected fetal human brain regions obtained by a fully automated chip-based nanoelectrospray ionization high capacity ion trap mass spectrometry (MS) approach, recently established4 by our group. The analyzed ganglioside mixtures were purified from fetal brain precentral and postcentral gyrus (24 gestational weeks (g.w.)) and frontal neocortex (36 g.w.). The mass spectrometric analyses were performed on a High Capacity Ion Trap Ultra (HCT Ultra, PTM discovery) mass spectrometer (Bruker Daltonics, Bremen, Germany) that was, via an in-laboratory made mounting system, coupled with a NanoMate robot incorporating ESI 400 Chip technology (Advion BioSciences, Ithaca, USA). All mass spectra were acquired in the m/z range 100-3000, with a scan speed of 8000 m/z per second. Tandem MS was carried out by collision-induced dissociation using He as the collision gas. The spectra obtained under optimized conditions in the negative ion mode enabled detection of more than 100 individual species in each analyzed ganglioside mixture. The major found structural forms were GM4, GM3, GM2, GM1/nLM1/LM1, GD3, GD1/nLD1 and GT1 ; GD2 and GT3 were present with lower abundance. Polysialylated structures, considered as fetal brain markers, GQ1 and in particular GP1 were considerably more abundant than previously detected in adult human brain. Fucosylated as well as alkali-labile O-acetylated and lactonized gangliosides were also found with higher relative abundance than previously noticed in adult human brain, indicating their possible involvement in prenatal brain development. Almost all oligosaccharide portion-defined ganglioside forms were represented by several species differing by the composition of ceramide portion. The ganglioside compositions from three analyzed brain regions differed in relative abundance of individual species. The MS/MS sequencing patterns of selected precursor ions corresponding to polysialylated species allowed their structural characterization. The results and an ultra-high sensitivity of detection confirm the applied methodology as a powerful tool for determining ganglioside fingerprinting compositions and biomarker species related to normal vs. pathological changes in the brain.

gangliosides; fetal human brain; chip-based MS

nije evidentirano