A large body of evidence from the past decade supports the existence of functional microdomains in membranes of animal and yeast cells, which play important roles in protein sorting, signal transduction, or infection by pathogens. They are based on the dynamic clustering of sphingolipids and cholesterol or ergosterol and are characterized by their insolubility, at low temperature, in nonionic detergents. Here we show that similar microdomains also exist in plant plasma membrane isolated from both tobacco leaves and BY2 cells. Tobacco lipid rafts were found to be greatly enriched in a sphingolipid, identified as glycosylceramide, as well as in a mixture of stigmasterol, sitosterol, 24-methylcholesterol, and cholesterol. Phospho-and glycoglycerolipids of the plasma membrane were largely excluded from lipid rafts. Membrane proteins were separated by oneand two-dimensional gel electrophoresis and identified by tandem mass spectrometry or use of specific antibody. The data clearly indicate that tobacco microdomains are able to recruit a specific set of the plasma membrane proteins and exclude others. We demonstrate the recruitment of the NADPH oxidase after elicitation by cryptogein and the presence of the small G protein NtRac5, a negative regulator of NADPH oxidase, in lipid rafts.A new aspect of the lipid bilayer organization has arisen from biophysical and biochemical studies performed with animal cells for several years. Indeed, lipids are not uniformly miscible, but lateral separation of specific lipid species leads to the formation of specialized phase domains also called "lipid rafts" (1). The main role in the process of domain organization is played by sterols and sphingolipids, these latter interacting together through weak interaction between aliphatic chains stabilized by the presence of saturated alkyl chains, voids between sphingolipids being filled by sterols (for a review, see Ref.2). The cholesterol-sphingolipid-enriched domain formation is also enhanced by the fact that sphingolipids have higher melting temperatures than phospholipids. Regions between rafts are occupied by phospholipids, with unsaturated fatty acids forming a liquid-crystalline phase, whereas lipid rafts that contain more saturated aliphatic chains form a liquidordered phase. In model and biological membranes, the formation of the liquid-ordered phase correlates with resistance to solubilization by nonionic detergent such as Triton X-100 at 4°C and buoyancy at specific density in a sucrose gradient (3). Thus, isolation of detergent-insoluble membranes (DIM) 1 or detergent-insoluble glycolipid-enriched membrane domains is one of the most widely used methods for studying lipid rafts.In animal cells, these membrane domains act, for example, as sorting devices for the accumulation of acylated, glycosylphosphatidylinositol-anchored, palmitoylated signaling molecules that selectively locate in these domains. Tyrosine kinases of the Src family protein, heterotrimeric and small G-proteins, as well as phosphoinositides have been proved to be...

Although the application of nanotechnologies to atherosclerosis remains a young field, novel strategies are needed to address this public health issue. In this context, the magnetic resonance imaging (MRI) approach has been gradually investigated in order to enable image-guided treatments. In this contribution, we report a new approach based on nucleoside-lipids allowing the synthesis of solid lipid nanoparticles (SLN) loaded with iron oxide particles and therapeutic agents. The insertion of nucleoside-lipids allows the formation of stable SLNs loaded with prostacycline (PGI2) able to inhibit platelet aggregation. The new SLNs feature better relaxivity properties in comparison to the clinically used contrast agent Feridex, indicating that SLNs are suitable for image-guided therapy.