engleski

Gangliosides of Adult Human Brain Precentral and Postcentral Gyrus: a Chip-Mass Spectrometry Based Composition and Structure Analysis

As plasma-membrane components, enriched in membrane microdomains (lipid rafts), and expressed as cell surface antigens, glycosphingolipids participate in vital processes and events of eukaryotic cells: cell-to-cell recognition/communication and cell signaling, growth, differentiation, apoptosis etc. Mammalian brain tissues, comparing to other tissue types, contain the highest concentrations of sialylated glycosphingolipids – gangliosides. Specific changes in their expression occur during brain development, maturation, aging, and due to diseases. Therefore, gangliosides represent important biomarkers able to provide information upon various processes/events in CNS in health and pathology. In this contribution, we report to our knowledge the first data describing ganglioside compositions in two functionally defined regions of adult human brain (20 and 17 years): the precentral gyrus (the location of primary motor cortex) and the postcentral gyrus (the location of primary somatosensory cortex). The comparative study was conducted employing advanced chip-mass spectrometry (MS) and high-performance thin-layer chromatography (HPTLC) methods. Dissected tissue samples were homogenized and total gangliosides were extracted and purified as native mixtures for analyses. HPTLC was used for both purposes: collection of compositional data following resorcinol-HCl staining of separated ganglioside patterns and preparative isolation of separated fractions for subsequent MS analysis. The MS screening and sequencing analyses were performed on a High Capacity Ion Trap Ultra (PTM discovery) mass spectrometer (Bruker Daltonics, Bremen, Germany) coupled, via mounting system, with a NanoMate robot incorporating ESI 400 Chip technology (Advion BioSciences, Ithaca, USA). Tandem MS was carried out by collision-induced dissociation. The resorcinol-HCl-stained HPTLC ganglioside patterns of both analyzed brain regions were basically similar, resembling the reference pattern of adult frontal cerebral cortex, but with slightly elevated domination of GM1-migrating fraction, almost equal relative proportions of GD1a and GD1b fractions, and slightly higher proportions of GM3, GQ1b and GX fractions. Comparative MS screening of the analyzed native mixtures revealed highly complex ganglioside compositions with more than 100 distinct species. Based on peak intensities of detected molecular ions in the negative ion mode, characteristic differences in relative abundances of individual species in precental vs. postcental gyrus were observed. High variability of ceramide portions was detected for the majority of ganglioside forms defined by oligosaccharide moieties. Besides mono- to polysialylated forms, both regions contained structures with fucosyl- or additional GalNAc-residue, as well as alkali-labile O-acetylated and lactonized gangliosides as minor components. Sequencing data allowing structural elucidation of some characteristic species will be presented.

adult human brain; precentral/postcentral gyrus; gangliosides; mass spectrometry

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