Sphingosine increases the permeability of model and cell membranes - PubMed (original) (raw)
Sphingosine increases the permeability of model and cell membranes
F-Xabier Contreras et al. Biophys J. 2006.
Abstract
Sphingosine, at 5-15 mol % total lipids, remarkably increases the permeability to aqueous solutes of liposomal and erythrocyte ghost membranes. The increased permeability cannot be interpreted in terms of leakage occurring at the early stages of a putative membrane solubilization by sphingosine, nor is it due to a sphingosine-induced generation of nonlamellar structures, or flip-flop lipid movement. Instead, sphingosine stabilizes (rigidifies) gel domains in membranes, raising their melting temperatures and increasing the transition cooperativity. Structural defects originating during the lateral phase separation of the "more rigid" and "less rigid" domains are likely sites for the leakage of aqueous solutes to the extravesicular medium. The presence of coexisting domains in the plasma membrane makes it a target for sphingosine permeabilization. The sphingosine-induced increase in rigidity and breakdown of the plasma membrane permeability barrier could be responsible for some of the physiological effects of sphingosine.
Figures
FIGURE 1
Sphingosine- and ceramide-induced efflux of vesicular aqueous contents. LUVs were prepared, composed of SM/PE/Ch (2:1:1, mol ratio) containing entrapped ANTS/DPX. Sphingosine or ceramide in ethanol were added at time 0. (A) Time course of efflux. (▴) Ethanol (control); (▪) + 10 mol % ceramide; (•) + 10 mol % sphingosine; and (○) + 15 mol % sphingosine. (B) Dose-response curves. Data at time = 6000 s. (▴) Ceramide; (•) sphingosine (average values ± SD, n = 3).
FIGURE 2
Sphingosine-induced release of ANTS/DPX from resealed erythrocyte ghosts. Sphingosine in ethanol (▴) or pure ethanol as a control (○) were added at time 0. Average values ± SD (n =3).
FIGURE 3
The effect of bilayer lipid composition on vesicle efflux induced by 10 mol % sphingosine. Vesicle composition was: (♦) egg PC/PE/Ch (2:1:1, mol ratio), (•) SM/PE/Ch (2:1:1, mol ratio), (Δ) DPPC/PE/Ch (2:1:1, mol ratio), and (▪) SM/Ch (80:20 mol ratio). (○) Control: effect of ethanol alone on SM/PE/Ch vesicles.
FIGURE 4
Temperature-composition diagram for DEPE/sphingosine in excess water, pH 7.4. (•, ○) Onset and completion temperatures of the gel-fluid lamellar phase transition, derived from DSC thermograms. (▾, ∇) Onset and completion temperatures of the lamellar-to-inverted hexagonal phase transition, also derived from DSC thermograms. L_β_, lamellar gel phase L_α_, lamellar fluid phase HII, and inverted hexagonal phase. Average of three measurements. The SD are about the size of the symbols.
FIGURE 5
Effect of sphingosine on the gel-fluid transition of different lipid mixtures. (A) DPPC/Ch (80:20, mol ratio) ± 20 mol % sphingosine. (B) SM/Ch (80:20, mol ratio) ± 20 mol % sphingosine. (C) SM/PE/Ch (2:1:1, mol ratio) ± 20 mol %sphingosine. Representative thermograms of the second or third scans.
FIGURE 6
Rigidifying effect of sphingosine on vesicle membranes. (A) DPH fluorescence polarization. Vesicles composed of SM/PE/Ch (2:1:1, mol ratio), containing DPH at a 1:250 DPH/lipid mol ratio, were incubated while DPH fluorescence polarization was continuously recorded. Sphingosine (10 mol %) was added at the point indicated by the arrow (time 0). (B) TEMPO quenching of DPH fluorescence emission. Vesicles composed of SM/PE/Ch (2:1:1, mol ratio), containing DPH as above, were incubated while DPH fluorescence emission intensity was recorded. The change in fluorescence is plotted as F/_F_o (fluorescence measured in the presence/in the absence of TEMPO). (Solid line) Experiment in the absence of sphingosine. (Dotted line) Experiment in the presence of 10 mol % sphingosine.
FIGURE 7
Parallel behavior of sphingosine-induced rigidification and vesicle efflux. (Solid line) DPH fluorescence polarization. (•) Vesicle efflux. The dotted lines are only meant to guide the eye. Vesicle composition was as follows: (A) DPPC/PE/Ch (2:1:1, mol ratio). (B) SM/Ch (80:20, mol ratio). (C) SM/PE/Ch (2:1:1, mol ratio).
References
- Hannun, Y. A., C. R. Loomis, A. H. Merrill Jr., and R. M. Bell. 1986. Sphingosine inhibition of protein kinase C activity and of phorbol dibutyrate binding in vitro and in human platelets. J. Biol. Chem. 261:12604–12609. - PubMed
- Gomez-Munoz, A., E. H. Hamza, and D. N. Brindley. 1992. Effects of sphingosine, albumin and unsaturated fatty acids on the activation and translocation of phosphatidate phosphohydrolases in rat hepatocytes. Biochim. Biophys. Acta. 1127:49–56. - PubMed
- Kolesnick, R. N., F. M. Goni, and A. Alonso. 2000. Compartmentalization of ceramide signaling: physical foundations and biological effects. J. Cell. Physiol. 184:285–300. - PubMed