Participation of de novo sphingolipid biosynthesis in the regulation of autophagy in Kdo2‐Lipid A stimulated RAW264.7 macrophages
Kacee SimsChristopher A. HaynesSamuel KellyJeremy C. AllegoodElaine WangAmin A. MominMartina LeipeltDonna ReichartChristopher K. GlassM. Cameron SullardsAlfred H. Merrill
0
Citation
0
Reference
10
Related Paper
Abstract:
Activation of RAW264.7 cells with a lipopolysaccharide specific for the TLR4 receptor, Kdo 2 ‐Lipid A (KLA), causes a large increase in cellular sphingolipids‐‐from 1.5 to 2.6 × 109 molecules per cell in 24 h, based on the sum of subspecies analyzed by “lipidomic” mass spectrometry. Thus, this study asked: What is the cause of this increase, and is there a cell function connected with it? The sphingolipids arise primarily from de novo biosynthesis; with the exception of ceramide, which is also produced from pre‐existing sources. Nonetheless, the activated RAW264.7 cells have a higher number of sphingolipids per cell because KLA inhibits cell division, thus, the cells are larger and contain increased numbers of membrane vacuoles termed autophagosomes. Indeed, de novo biosynthesis of sphingolipids performs an essential structural and/or signaling function in autophagy because autophagosome formation was eliminated by ISP1 in KLA stimulated RAW264.7 cells; furthermore, an anti‐ceramide antibody co‐localizes with autophagosomes in activated RAW264.7 cells versus the Golgi in unstimulated or ISP1 inhibited cells. These findings establish that KLA induces profound changes in sphingolipid metabolism and content in this macrophage‐like cell line, apparently to produce sphingolipids that are necessary for formation of autophagosomes, which are thought to play important roles in the mechanisms of innate immunity.Keywords:
Sphingolipid
Lactosylceramide
Sphingolipid
Sphingomyelin phosphodiesterase
Catabolism
Cite
Citations (8)
Sphingolipid
Cite
Citations (8)
Sphingolipid
Second messenger system
Sphingomyelin phosphodiesterase
Platelet-activating factor
Cite
Citations (1)
Sphingolipid
Cite
Citations (84)
Sphingolipid
Sphingomyelin phosphodiesterase
Second messenger system
Lipid raft
Cite
Citations (86)
Abstract— Purified oligodendroglia isolated from bovine brain white matter were found to contain, in addition to galactosylceramide, sulfatide and sphingomyelin, significant quantities of glucosylcerai‐mide, dihexosylceramide and esterified galactosylceramide. These sphingolipids were isolated and quan‐titated and their fatty acid and long chain base patterns compared with those from sphingolipids isolated from bovine myelin, white matter and gray matter. The minor glycosphingolipids, glucosylceramide, dihexosylceramide and esterified galactosylceramide, constituted a higher percentage of glial lipids than of myelin lipids. Glucosylceramide accounted for 12% of the total glial monohexosylceramide fraction and 0.8% of total lipids; dihexosylceramide was 0.9% of total glial lipids. Both of these lipids had small quantities of α‐hydroxy fatty acids. The unsubstituted fatty acids of glucosylceramide were mostly short chain (16 and 18 carbons) and were different from those of the dihexosylceramides which were a mixture of short and long chain. The hydroxy acids of each of these lipids were, however, similar and resembled those of galactosylceramide. The fatty acid patterns of galactosylceramide, sulfatide and sphingomyelin from glial cells resembled those of the corresponding lipids from myelin and white matter. The amide‐linked acids of esterified galactosylceramide contained both unsubstituted and α‐hydroxy chains. Their patterns were not identical to those of galactosylceramide, but were similar in all brain fractions. With the exception of sphingomyelin and dihexosylceramide, which contained small amounts of C 20 ‐sphingosine, all sphingolipids analyzed contained mostly sphingosine and dihydrosphingosine. We conclude that the distribution of sphingolipids in the oligodendroglia is characteristic, but the lipophilic residues of these lipids are not cell‐specific.
Sphingolipid
Cite
Citations (24)
Sphingolipid
Cite
Citations (67)
Sphingolipids isolated from cerebral grey and white matter of two patients with Juvenile Amaurotic Idiocy (Spielmeyer-Vogt Type) were studied. A new analytical procedure was attempted for the determination of sphingolipids, i.e., cerebroside, sulfatide, sphingomyelin and gangliosides were subjected to ozonolysis and reduced with NaBH4. Fatty alcohols thus derived from the double bond-containing long chain bases of the sphingolipids were analyzed by GLC as their TMS-derivatives using an internal standard. The new procedure was suitable for the analysis of small amounts of sphingolipids and could determine the amounts of C18 and C20 sphingosines. It was found that all individual gangliosides in both cases gave lower proportions of C20 sphingosine to the total long chain bases. Sphingomyelin in normal human grey matter contained a small but significant amount of C20 sphingosine, while the sphingomyelin of the two patient brains indicated a much lower proportion of C20 sphingosine in comparison with those of age-matched controls. Thus, this disease seemed to be related to a genetical defect in the metabolic regulation of the long chain bases of gangliosides and grey matter sphingomyelin. On the other hand, it was noted that the ganglioside pattern of grey matter in case-1 was entirely different from that of case-2. The grey matter gangliosides in case-1 were composed of 1.78% of GM2, 81.19% of GM1 and 17.02% of GD1b by the amounts of long chain bases, while the grey matter gangliosides in case-2 seemed to be similar to those of normal human brains. Also, unusual fatty acid compositions of galactosphingolipids (cerebrosides and sulfatides) were observed to a somewhat extent in the grey matter of case-1.
Sphingolipid
Cerebroside
Grey matter
Ganglioside
Cite
Citations (7)
Abstract —Developmental changes in composition of sphingosine bases of cerebrosides, sulphatides and sphingomyelins were investigated in samples from brain stem or corpus callosum from premature infants and patients aged 14 months, 39 and 59 years who died of non‐neurological causes. Since insufficient material was obtainable from the premature brains, sulphatides were studied only in older cases. Individual sphingolipids were isolated by combinations of column chromatography and TLC, and were examined for purity by analytical TLC. Sphingosine bases were released by acid‐catalysed methanolysis, and analysed as aldehydes by GLC. Effectiveness and limitations of methods used for analyses of sphingosine bases were evaluated. In contrast to adult sphingolipids in which approximately 95 per cent of the sphingosine bases was 18: sphingosine, as much as 10 per cent of the total was 18: dihydrosphingosine in immature sphingolipids. A compound tentatively identified as 20: sphingosine was present in foetal, infant and adult sphingomyelin at 5, 3 and 1 per cent of the total, respectively. Composition of sphingosine bases of non‐ganglioside sphingolipids in human brain varies with age, presumably in a complex manner.
Sphingolipid
Ganglioside
Lactosylceramide
Cite
Citations (10)
In mammalian cells, ceramides are central lipids in sphingolipid metabolism and serve both as signaling lipids and as precursors for other bioactive sphingolipids, ranging from complex glycosphingolipids to “simpler” lipids such as ceramide-1-phosphate, sphingomyelin (SM), sphingosine and sphingosine-1-phosphate (S1P).
Sphingolipid
Cite
Citations (3)