Polyunsaturated Eicosapentaenoic Acid Displaces Proteins from Membrane Rafts by Altering Raft Lipid Composition

Department of Internal Medicine III, University of Vienna, A-1090 Vienna, Austria.
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2001; 276(40):37335-40. DOI: 10.1074/jbc.M106193200
Source: PubMed


Polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (20:5 (n-3)) inhibit T lymphocyte activation probably by displacing acylated signaling proteins from membrane lipid rafts. Under physiological conditions, saturated fatty acyl residues of such proteins partition into the cytoplasmic membrane lipid leaflet with high affinity for rafts that are enriched in saturated fatty acyl-containing lipids. However, the biochemical alteration causing displacement of acylated proteins from rafts in PUFA-treated T cells is still under debate but could principally be attributed to altered protein acylation or changes in raft lipid composition. We show that treatment of Jurkat T cells with polyunsaturated eicosapentaenoic acid (20:5 (n-3)) results in marked enrichment of PUFAs (20:5; 22:5) in lipids from isolated rafts. Moreover, PUFAs were significantly incorporated into phosphatidylethanolamine that predominantly resides in the cytoplasmic membrane lipid leaflet. Notably, palmitate-labeled Src family kinase Lck and the linker for activation of T cells (LAT) were both displaced from lipid rafts indicating that acylation by PUFAs is not required for protein displacement from rafts in PUFA-treated T cells. In conclusion, these data provide strong evidence that displacement of acylated proteins from rafts in PUFA-treated T cells is predominantly due to altered raft lipid composition.

  • Source
    • "Recently, it has been suggested a role for ω-3 PUFAs in reorganizing the composition of the mitochondrial membrane, while promoting improvements in ADP sensitivity, determined as mitochondrial responses during ADP titration (Herbst et al., 2014). Moreover, it is well known that saturated FA incorporation reduces membrane fluidity, whereas PUFA do not have such effect (Clamp et al., 1997;Stulnig et al., 2001;Holzer et al., 2011). Further studies are needed to elucidate these mechanisms. "
    [Show abstract] [Hide abstract]
    ABSTRACT: It has been suggested that skeletal muscle mitochondria play a key role in high fat diet induced insulin resistance. Two opposite views are debated on mechanisms by which mitochondrial function could be involved in skeletal muscle insulin resistance. In one theory, mitochondrial dysfunction is suggested to cause intramyocellular lipid accumulation leading to insulin resistance. In the second theory, excess fuel within mitochondria in the absence of increased energy demand stimulates mitochondrial oxidant production and emission, ultimately leading to the development of insulin resistance. Noteworthy, mitochondrial bioenergetics is strictly associated with the maintenance of normal mitochondrial morphology by maintaining the balance between the fusion and fission processes. A shift towards mitochondrial fission with reduction of fusion protein, mainly mitofusin 2, has been associated with reduced insulin sensitivity and inflammation in obesity and insulin resistance development. However, dietary fat source during chronic overfeeding differently affects mitochondrial morphology. Saturated fatty acids induce skeletal muscle insulin resistance and inflammation associated with fission phenotype, whereas ω-3 polyunsaturated fatty acids improve skeletal muscle insulin sensitivity and inflammation, associated with a shift toward mitochondrial fusion phenotype. The present minireview focuses on mitochondrial bioenergetics and morphology in skeletal muscle insulin resistance, with particular attention to the effect of different dietary fat sources on skeletal muscle mitochondria morphology and fusion/fission balance.
    Preview · Article · Jan 2016 · Frontiers in Physiology
  • Source
    • "This indicates that, at the sn-1 position of phospholipids, a 18:1 fatty acid is not, while a 16:0 or 18:0 fatty acid is, favorable for inclusion in DRMs. The data of Stulnig et al. (2001) show a similar enrichment of 16:0 and 18:0 fatty acids in the DRM fraction of Jurkat T cells, while 16:1 and 18:1 fatty acids were excluded from DRMs. Unfortunately, the position of the fatty acids was not determined. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Lipid rafts are micro-domains of ordered lipids (L o phase) in biological membranes. The L o phase of cellular membranes can be isolated from disordered lipids (L d phase) after treatment with 1 % Triton X-100 at 4 °C in which the L o phase forms the detergent-resistant membrane (DRM) fraction. The lipid composition of DRM derived from Madin-Darby canine kidney (MDCK) cells, McArdle cells and por-cine sperm is compared with that of the whole cell. Remarkably, the unsaturation and chain length degree of aliphatic chains attached to phospholipids is virtually the same between DRM and whole cells. Cholesterol and sphingomyelin were enriched in DRMs but to a cell-specific molar ratio. Sulfatides (sphingolipids from MDCK cells) were enriched in the DRM while a seminolipid (an alkylacylglycerolipid from sperm) was depleted from the DRM. Treatment with<5 mM methyl-ß-cy-clodextrin (MBCD) caused cholesterol removal from the DRM without affecting the composition and amount of the phospholipid while higher levels disrupted the DRM. The substantial amount of (poly)unsaturated phospholipids in DRMs as well as a low stoichiometric amount of cholesterol suggest that lipid rafts in biological membranes are more fluid and dynamic than previously anticipated. Using negative staining, ultrastructural features of DRM were monitored and in all three cell types the DRMs appeared as multi-lamellar vesicular structures with a similar morphology. The detergent resistance is a result of protein–cholesterol and sphingolipid interactions allowing a relatively passive attraction of phospholipids to maintain the L o phase. For this special issue, the relevance of our findings is discussed in a sperm physiological context.
    Full-text · Article · Sep 2015 · Cell and Tissue Research
  • Source
    • "One recent in vivo study demonstrated that a small fraction of n-3 PUFAs from dietary fish oil incorporated into sphingolipids of murine B cells (Rockett et al., 2012). These results were consistent with similar findings in cell culture with immortal T cells (Stulnig et al., 2001). A fourth possibility we propose is that n-3 PUFA acyl chains could become esterified to cholesterol to modify Figure 2 Potential mechanisms by which n-3 PUFAs could disrupt lipid microdomain distribution. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Increased consumption of long-chain marine n-3 polyunsaturated fatty acids (PUFA) has potential health benefits for the general population and for select clinical populations. However, several key limitations remain in making adequate dietary recommendations on n-3 PUFAs in addition to translating the fatty acids into clinical trials for select diseases. One major constraint is an incomplete understanding of the underlying mechanisms of action of n-3 PUFAs. In this review, we highlight studies to show n-3 PUFA acyl chains reorganize the molecular architecture of plasma membrane sphingolipid-cholesterol-enriched lipid rafts and potentially sphingolipid-rich cholesterol-free domains and cardiolipin-protein scaffolds in the inner mitochondrial membrane. We also discuss the possibility that the effects of n-3 PUFAs on membrane organization could be regulated by the presence of vitamin E (α-tocopherol), which is necessary to protect highly unsaturated acyl chains from oxidation. Finally, we propose the integrated hypothesis, based predominately on studies in lymphocytes, cancer cells, and model membranes, that the mechanism by which n-3 PUFAs disrupt signaling microclusters is highly dependent on the type of lipid species that incorporate n-3 PUFA acyl chains. The current evidence suggests that n-3 PUFA acyl chains disrupt lipid raft formation by incorporating primarily into phosphatidylethanolamines but can also incorporate into other lipid species of the lipidome. Copyright © 2015 Elsevier Inc. All rights reserved.
    Full-text · Article · May 2015 · Current Topics in Membranes
Show more