Phases and phase transitions of the sphingolipids

Koynova, Rumiana; Caffrey, Martin

doi:10.1016/0005-2760(94)00202-a

Cited by 157 publications

(99 citation statements)

References 139 publications

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“…This transition temperature range is comparable with the one determined by fluorescence polarization on MLVs made of sphingomyelin extracted from renal BBM (25). The presence of two distinct peaks, here located at 28.7 Ϯ 0.2°C and 34.6 Ϯ 0.2°C, and the enthalpy change associated to the gel to liquid crystalline transition (⌬H ϭ 7.8 Kcal/mol) are in agreement with previous studies (26,27). The gel to liquid crystalline transition of POPC liposomes (⌬H ϭ 5.8 Kcal/mol) occurs at Ϫ2.5°C (28).…”

Section: Thermotropic Properties Of Bbm Model Bilayers-becausesupporting

confidence: 80%

Cholesterol Is Not Crucial for the Existence of Microdomains in Kidney Brush-border Membrane Models

Milhiet¹,

Giocondi²,

Grimellec³

2002

Journal of Biological Chemistry

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The external membrane leaflet plays a key role in the organization of the cell plasma membrane as a mosaic of ordered microdomains enriched in sphingolipids and cholesterol and of fluid domains. In this study, the thermotropic behavior and the topology of bilayers made of a phosphatidylcholine/sphingomyelin mixture, which mimicks the lipid composition of the external leaflet of renal brush-border membranes, were examined by differential scanning calorimetry and atomic force microscopy. In the absence of cholesterol, a broad phase separation process occurred where ordered gel phase domains of size varying from the mesoscopic to the microscopic scale, enriched in sphingomyelin, occupied half of the bilayer surface at room temperature. Increasing amounts of cholesterol progressively decreased the enthalpy of the transition and modified the topology of membranes domains up to a concentration of 33 mol % for which no membrane domains were detected. These results strongly suggest that, in membranes highly enriched in sphingolipids like renal and intestinal brush borders, there is a threshold close to the physiological concentration above which cholesterol acts as a suppressor rather than as a promoter of membrane domains. They also suggest that cholesterol depletion does not abolish the lateral heterogenity in brush-border membranes.According to the current view, the plasma membrane of eucaryotic cells is organized in an in-plane mosaic of microdomains (1, 2). Rafts correspond to a category of microdomains, enriched in sphingolipids (SPL) 1 and cholesterol (Chl), which play a key role in the expression and regulation of the plasma membrane functions (3, 4). This conclusion was reached essentially through the use of two experimental procedures, the low temperature non-ionic detergent extraction (2) and the Chl depletion of cells (5, 6). The resistance to low temperature, non-ionic detergent extraction of numerous membrane proteins is associated to a liquid ordered (L o ) or to a gel ordered (L ␤ ) state of membrane lipids, which strongly suggests that the physical state of these membrane lipids is of primary importance in the formation of the membrane microdomains mosaic (7,8). Formation of the L o phase, or more precisely of the fluid liquid ordered L o␣ and gel liquid ordered L o␤ phases (9), depends on the presence of Chl (10, 11). SPL also appear to be determinant for the existence of eucaryotic plasma membrane rafts (3, 4), and this could be explained by the preferential interaction of Chl with SPL rather than with the other phospholipid species in natural phospholipid-Chl mixtures (10, 12, 13). Because SPL are essentially localized on the external leaflet of the plasma membrane (14), this strongly suggests that this membrane leaflet plays a crucial role in the existence of microdomains.Renal brush-border membranes (BBM), which constitute the apical membrane of the proximal tubule epithelial cells, are highly ordered structures, as shown by fluorescence polarization and ESR data (15). Their glycerophospholipid GPL...

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Section: Thermotropic Properties Of Bbm Model Bilayers-becausesupporting

confidence: 80%

Cholesterol Is Not Crucial for the Existence of Microdomains in Kidney Brush-border Membrane Models

Milhiet¹,

Giocondi²,

Grimellec³

2002

Journal of Biological Chemistry

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“…From a biophysical viewpoint, the involvement of SMs in sphingolipid-cholesterol-rich microdomains makes the situation even more intriguing because SMs are one of a few naturally occurring membrane lipids whose fluid-gel coexistence region encompasses mammalian physiological temperatures [for review, see Koynova and Caffrey (1995)]. Cholesterol could easily modulate the phase behavior of the SMs by altering the size and nature of the coexisting fluid-solid domains, a situation known to occur in model membranes [e.g.…”

Section: Physiological Implicationsmentioning

confidence: 99%

Cholesterol-Induced Interfacial Area Condensations of Galactosylceramides and Sphingomyelins with Identical Acyl Chains

et al. 1996

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The interfacial interactions occurring between cholesterol and either galactosylceramides (GalCers) or sphingomyelins (SMs) with identical acyl chains have been investigated using Langmuir film balance techniques. Included among the synthesized GalCers and SMs were species containing palmitoyl (16:0), stearoyl (18:0), oleoyl [18:1 ∆9(c) ], nervonoyl [24:1 ∆15(c) ], or linoleoyl [18:2 ∆9,12(c) ] acyl residues. The cholesterol-induced condensations in the average molecular areas of the monolayers were determined by classic mean molecular area vs composition plots as well as by expressing the changes in terms of sphingolipid cross-sectional area reduction over the surface pressure range from 1 to 40 mN/m (at 1 mN/m intervals). The results show that, at surface pressures approximating bilayer conditions (30 mN/m), acyl heterogeneity in naturally occurring SMs (bovine or egg SM) enhanced the area condensation induced by cholesterol compared to their predominant molecular species (e.g. 18:0 SM in bovine SM; 16:0 SM in egg SM). Nonetheless, cholesterol always had a greater condensing effect on SM compared to GalCer when these sphingolipids were acyl chain matched and in similar phase states (prior to mixing with cholesterol). Also, the cholesterol-induced area changes for a given sphingolipid type (e.g. SM or GalCer) were similar whether the acyl chains were saturated, cis-∆9-monounsaturated, or cis-∆9,12-diunsaturated if the sphingolipids were in similar phase states (prior to mixing with cholesterol) and compared at equivalent surface pressures. These results indicate that, under conditions where hydrocarbon structure is matched, the sphingolipid head group plays a dominant role in determining the extent to which cholesterol reduces sphingolipid cross-sectional area. Despite the larger cholesterol-induced area condensations observed in SMs compared to those in GalCers, the molecular-packing densities showed that equimolar GalCercholesterol films were generally packed as tight as or slightly tighter than those of the SMcholesterol films. The results are discussed in terms of a molecular model for sphingolipidcholesterol interactions. Our findings also not only raise questions as to whether cholesterolinduced condensation data provide a reliable measure of the affinity, i.e. interaction strength, between cholesterol and different lipids but also provide insight regarding the stability of sterol/ sphingolipid-rich microdomains thought to exist in caveolae and other cell membrane regions. † This investigation was supported by USPHS Grant GM45928 (R.E.B.) and the Hormel Foundation. The automated Langmuir film balance used in this study receives major support from USPHS Grants HL49180 and HL17371 (H. L. Brockman, P. I.).

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“…Liganding of GalCer by GLTP has been shown after incubation with pure GalCer films adsorbed to glass and submerged in aqueous solution [41]. The GalCer in such pure films is expected to be tightly packed because the main thermotropic transition temperature of GalCer occurs at approximately 80°C [42]. Human GLTP also interacts efficiently with ganglioside GM1 when it is dispersed directly into aqueous buffer lacking phosphoglyceride, showing that GLTP can acquire glycolipid from nonbilayer sources [41].…”

Section: Sphingomyelin Phosphatidylcholine and Cholesterol Effects Omentioning

confidence: 99%

Glycolipid transfer proteins

Brown

Mattjus

2007

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biolog

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Glycolipid transfer proteins (GLTPs) are small (24 kD), soluble, ubiquitous proteins characterized by their ability to accelerate the intermembrane transfer of glycolipids in vitro. GLTP specificity encompasses both sphingoid-and glycerol-based glycolipids, but with a strict requirement that the initial sugar residue be beta-linked to the hydrophobic lipid backbone. The 3D protein structures of GLTP reveal liganded structures with unique lipid binding modes. The biochemical properties of GLTP action at the membrane surface have been studied rather comprehensively, but the biological role of GLTP remains enigmatic. What is clear is that GLTP differs distinctly from other known glycolipid-binding proteins, such as nonspecific lipid transfer proteins, lysosomal sphingolipid activator proteins, lectins, lung surfactant proteins as well as other lipid binding/transfer proteins. Based on the unique conformational architecture that targets GLTP to membranes and enables glycolipid binding, GLTP is now considered the prototypical and founding member of a new protein superfamily in eukaryotes.

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Phases and phase transitions of the sphingolipids

Cited by 157 publications

References 139 publications

Cholesterol Is Not Crucial for the Existence of Microdomains in Kidney Brush-border Membrane Models

Cholesterol Is Not Crucial for the Existence of Microdomains in Kidney Brush-border Membrane Models

Cholesterol-Induced Interfacial Area Condensations of Galactosylceramides and Sphingomyelins with Identical Acyl Chains

Glycolipid transfer proteins

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