Sulfatide with short fatty acid dominates in astrocytes and neurons

Abstract

Glycosphingolipids are located in cell membranes and the brain is especially enriched. We speculated that the subcellular location of glycosphingolipids depends on their fatty acid chain length because their sugar residues are constant, whereas fatty acid chain length can vary within the same molecule. To test this hypothesis we analysed the glycosphingolipid sulfatide, which is highly abundant in myelin and has mostly long fatty acids. We used a negative ion electrospray tandem mass spectrometry precursor ion scan to analyse the molecular species of sulfatide in cultured astrocytes and a mouse model of the human disease metachromatic leukodystrophy. In these arylsulfatase A (ASA)‐deficient mice sulfatide accumulates intracellularly in neurons and astrocytes. Immunocytochemistry was also performed on cultured astrocytes and analysed using confocal laser scanning microscopy. Analyses of the molecular species showed that cultured astrocytes contained sulfatide with a predominance of stearic acid (C18), which was located in large intracellular vesicles throughout the cell body and along the processes. The same was seen in ASA‐deficient mice, which accumulated a higher proportion (15 mol% compared with 8 mol% in control mice) of sulfatide with stearic acid. We conclude that the major fatty acid composition of sulfatide differs between white and grey matter, with neurons and astrocytes containing mostly short‐chain fatty acids with an emphasis on stearic acid. Based on our results, we speculate that the fatty acid chain length of sulfatide might determine its intracellular (short chain) or extracellular (long chain) location and thereby its functions.

Sulfatide Storage in Neurons Causes Hyperexcitability and Axonal Degeneration in a Mouse Model of Metachromatic Leukodystrophy

“…4 A, B, arrow), most likely GalCer. This is in agreement with neuronal GalCer production, because C18:0-fatty acid-containing ceramide is the predominant ceramide species in neurons, whereas oligodendrocytes synthesize ceramides containing mainly VLCFAs (C20 -C24) (Raghavan and Kanfer, 1972;Isaac et al, 2006).…”

“…These mice accumulate sulfolipids in neurons, microglia, and other glial cells, but also in non-neural tissues, such as kidney and gallbladder Schott et al, 2001;Sandhoff et al, 2002;Wittke et al, 2004;Isaac et al, 2006). The distribution of sulfolipid storage in these mice is very similar to that observed in MLD patients (von Figura et al, 2001).…”

Distribution of C16:0, C18:0, C24:1, and C24:0 sulfatides in central nervous system lipid rafts by quantitative ultra-high-pressure liquid chromatography tandem mass spectrometry

“…1). The functional significance of different sulfatide species is currently unknown, but recent studies suggest different roles in both neural and non-neural tissues [4,5].Sulfatides are particularly enriched in the brain, with different sulfatide species distributed in a tissue-and developmentdependent manner. For example, sulfatide species with short-chain fatty acids (e.g., C16:0 and C18:0) are more abundant in neurons and astrocytes, whereas long-chain fatty acid sulfatides (e.g., C24:1 and C24:0) are enriched in myelin [4].…”

Role of sulfatide in normal and pathological cells and tissues

“…Cultured astrocytes are capable of synthesizing small amounts of sulfatide ( 39,40 ). Low expression levels of both CGT and CST are detectable in various neurons.…”