Polyunsaturated Fatty Acids Inhibit T Cell Signal Transduction by Modification of Detergent-insoluble Membrane Domains

Abstract

Polyunsaturated fatty acids (PUFAs) exert immunosuppressive effects, but the molecular alterations leading to T cell inhibition are not yet elucidated. Signal transduction seems to involve detergent-resistant membrane domains (DRMs) acting as functional rafts within the plasma membrane bilayer with Src family protein tyrosine kinases being attached to their cytoplasmic leaflet. Since DRMs include predominantly saturated fatty acyl moieties, we investigated whether PUFAs could affect T cell signaling by remodeling of DRMs. Jurkat T cells cultured in PUFA-supplemented medium showed a markedly diminished calcium response when stimulated via the transmembrane CD3 complex or glycosyl phosphatidylinositol (GPI)- anchored CD59. Immunofluorescence studies indicated that CD59 but not Src family protein tyrosine kinase Lck remained in a punctate pattern after PUFA enrichment. Analysis of DRMs revealed a marked displacement of Src family kinases (Lck, Fyn) from DRMs derived from PUFA-enriched T cells compared with controls, and the presence of Lck in DRMs strictly correlated with calcium signaling. In contrast, GPI-anchored proteins (CD59, CD48) and ganglioside GM1, both residing in the outer membrane leaflet, remained in the DRM fraction. In conclusion, PUFA enrichment selectively modifies the cytoplasmic layer of DRMs and this alteration could underlie the inhibition of T cell signal transduction by PUFAs.

Adipose tissue inflammation induced by high-fat diet in obese diabetic mice is prevented by n−3 polyunsaturated fatty acids

“…A variety of molecular mechanisms underlying the anti-inflammatory action of n−3 PUFA have been described, mostly in vitro, including altered synthesis of eicosanoids (prostaglandins, leukotrienes), activation or inhibition of nuclear receptors (e.g. peroxisome proliferator-activated receptor γ [PPARγ], liver X receptors) and alterations of membrane lipid rafts [15,18,34]. Despite anti-inflammatory effects of PPARγ agonists in obese animals and humans [8,10] there is no evidence for a selectivity of PPARγ for n−3 PUFA [35].…”

Polyunsaturated eicosapentaenoic acid changes lipid composition in lipid rafts

“…For modification of cellular lipids, the cells were cultured for 2 days in serum-free Iscove's modified Dulbecco's medium (no fatty acid detectable), supplemented with 0.4 % (w/v) bovine serum albumin (fraction V, containing less than 3 µmol/l total fatty acids), with addition of 50 µmol/l of either EPA (20:5 n-3) or stearic acid (18:0) from stock solutions in ethanol (final concentration ≤ 0.5 %). Stearic acid served as a control and previously this fatty acid was shown not to influence cellular PUFA content and membrane subdomain distribution of proteins compared with controls treated with vehicle only [14]. After having been treated with EPA for 2 days, cells were pelleted and lysed.…”

“…Lipid rafts were isolated from Jurkat T cells as previously described [14] by discontinuous sucrose density gradient ultracentrifugation. 2.5 ϫ10 7 cells per ml were washed in Hanks' balanced salt solution three times and lysed in TKM buffer (50 mmol/l Tris, pH 7.4, 25 mmol/l KCl, 5 mmol/l MgCl 2 , and 1 mmol/l EDTA) containing 1 % Brij58 and protease inhibitor cocktail tablets (0.12 mg antipain-HCl, 20 µg bestatin, 40 µg chymostatin, 0.12 mg E-64, 20 µg leupeptin, 20 µg pepstatin, 0.12 mg phosphoramidon, 0.8 mg pefabloc, 40 µg aprotinin).…”

“…Some results have also indicated that several proteins involved in signaling pathway via T-cell receptor (TCR), B-cell receptor (BCR), IgE receptor (FcεRI) are within lipid raft compartments [11][12][13]. In general, PUFAs supplementation inhibits T lymphocyte activation by modifying detergent-insoluble membrane domains and displacing these signaling proteins from lipid rafts [14,15].…”

From the ECM to the Cytoskeleton and Back: How Integrins Orchestrate T Cell Action

“…Despite evidence for actin cap formation by T cells placed on anti-CD3 coated plates (Holsinger et al, 1998) In many respects, SMACs are strikingly similar to focal adhesions created by integrins in adherent cell types (Guan, 1997) (Figure 2 Lipid rafts is a term used to define regions of the T cell membrane that consist of detergent-resistant zones enriched in cholesterol and sphingolipids, as well as a variety of key signaling proteins (Xavier et al, 1998;Moran and Miceli, 1998). Intact lipid rafts are required for efficient T cell signal transduction (Moran and Miceli, 1998;Xavier et al, 1998;Stulnig et al, 1999) and T cell stimulation with beads containing anti-CD3 and anti-CD28 mAbs results in polarization of lipid rafts to the point of contact between the T cell and the bead (Viola et al, 1999).…”