A major fraction of glycosphingolipids in model and cellular cholesterol-containing membranes is undetectable by their binding proteins.

Glycosphingolipids (GSLs) accumulate in cholesterol-enriched cell membrane domains and provide receptors for protein ligands. Lipid-based "aglycone" interactions can influence GSL carbohydrate epitope presentation. To evaluate this relationship, Verotoxin binding its receptor GSL, globotriaosyl ceramide (Gb(3)), was analyzed in simple GSL/cholesterol, detergent-resistant membrane vesicles by equilibrium density gradient centrifugation.

Fatty acid-dependent globotriaosyl ceramide receptor function in detergent resistant model membranes.

Glycosphingolipid (GSL) fatty acid strictly regulates verotoxin 1 (VT1) and the HIV adhesin, gp120 binding to globotriaosyl ceramide within Gb(3)/cholesterol detergent resistant membrane (DRM) vesicle constructs and in Gb(3) water-air interface monolayers in a similar manner. VT2 bound Gb(3)/cholesterol vesicles irrespective of fatty acid composition, but VT1 bound neither C18 nor C20Gb(3)vesicles. C18/C20Gb(3) were dominant negative in mixed Gb(3) fatty acid isoform vesicles, but including C24:1Gb(3) gave maximal binding.

Differential intracellular transport and binding of verotoxin 1 and verotoxin 2 to globotriaosylceramide-containing lipid assemblies.

Although verotoxin-1 (VT1) and verotoxin-2 (VT2) share a common receptor, globotriaosyl ceramide (Gb(3)), VT2 induces distinct animal pathology and is preferentially associated with human disease. Moreover VT2 cytotoxicity in vitro is less than VT1. We therefore investigated whether these toxins similarly traffic within cells via similar Gb(3) assemblies.

Laboratory and clinical Pseudomonas aeruginosa strains do not bind glycosphingolipids in vitro or during type IV pili-mediated initial host cell attachment.

The glycosphingolipids (GSLs) gangliotriaosylceramide (Gg(3)) and gangliotetraosylceramide (Gg(4)) have been implicated as receptors for type IV pili (T4P)-mediated Pseudomonas aeruginosa epithelial cell attachment. Since P. aeruginosa T4P are divided into five groups, the authors determined whether GSLs in general, and Gg(3) and Gg(4) in particular, are specifically bound and required for host epithelial cell attachment of clinical and laboratory strains within these groups.

Lipid rafts: structure, function and role in HIV, Alzheimer's and prion diseases.

The fluid mosaic model of the plasma membrane has evolved considerably since its original formulation 30 years ago. Membrane lipids do not form a homogeneous phase consisting of glycerophospholipids (GPLs) and cholesterol, but a mosaic of domains with unique biochemical compositions. Among these domains, those containing sphingolipids and cholesterol, referred to as membrane or lipid rafts, have received much attention in the past few years.

The virotoxin model of HIV-1 enteropathy: involvement of GPR15/Bob and galactosylceramide in the cytopathic effects induced by HIV-1 gp120 in the HT-29-D4 intestinal cell line.

Background: Malabsorption and diarrhea are common, serious problems in AIDS patients, and are in part due to the incompletely understood entity HIV enteropathy. Our prior in vitro work has shown that increased transepithelial permeability and glucose malabsorption, similar to HIV enteropathy, are caused by HIV surface protein gp120, although the mechanism remains unclear.

Results: We studied the effects of HIV surface protein gp120 on the differentiated intestinal cell line HT-29-D4, specifically the effects on microtubules, transepithelial resistance, and sodium glucose cotransport.

A novel soluble analog of the HIV-1 fusion cofactor, globotriaosylceramide (Gb(3)), eliminates the cholesterol requirement for high affinity gp120/Gb(3) interaction.

We have analyzed the interaction of adamantyl Gb(3) (adaGb(3)), a semi-synthetic soluble analog of Gb(3), with HIV-1 surface envelope glycoprotein gp120. In this analog, which was orginally designed to inhibit verotoxin binding to its glycolipid receptor, Gb(3), the fatty acid chain is replaced with a rigid globular hydrocarbon frame (adamantane). Despite its solubility, adaGb(3) forms monolayers at an air-water interface.

The mycotoxin deoxynivalenol affects nutrient absorption in human intestinal epithelial cells.

Deoxynivalenol (DON) is a mycotoxin belonging to the tricothecene family that has many toxic effects in animals, including diarrhea and weight loss. Using the human epithelial intestinal cell line HT-29-D4 as an in vitro model, we studied the effect of DON on the uptake of different classes of nutrients, including sugars, amino acids and lipids. At low concentrations (below 10 micro mol/L), DON selectively modulated the activities of intestinal transporters: the D-glucose/D-galactose sodium-dependent transporter (SGLT1) was strongly inhibited by the mycotoxin (50% inhibition at 10 micro mol DON, P < 0.

The mycotoxin patulin alters the barrier function of the intestinal epithelium: mechanism of action of the toxin and protective effects of glutathione.

Patulin is a mycotoxin mainly found in apple and apple products. In addition to being toxic for animals, mutagenic, carcinogenic and teratogenic, patulin induces intestinal injuries, including epithelial cell degeneration, inflammation, ulceration, and hemorrhages. In a study of the cellular mechanisms associated with the intestinal toxicity of patulin, two human epithelial intestinal cell lines (HT-29-D4 and Caco-2-14) were exposed to the mycotoxin.

Identification of a common sphingolipid-binding domain in Alzheimer, prion, and HIV-1 proteins.

The V3 loop of the human immunodeficiency virus (HIV)-1 surface envelope glycoprotein gp120 is a sphingolipid-binding domain mediating the attachment of HIV-1 to plasma membrane microdomains (rafts). Sphingolipid-induced conformational changes in gp120 are required for HIV-1 fusion. Galactosylceramide and sphingomyelin have been detected in highly purified preparations of prion rods, suggesting that the prion protein (PrP) may interact with selected sphingolipids.

pH-dependent interaction of fumonisin B1 with cholesterol: physicochemical and molecular modeling studies at the air-water interface.

Langmuir film balance technology was used to study the interaction between the mycotoxin fumonisin B1 (FB1) and cholesterol. FB1 was added in the aqueous subphase underneath a monomolecular film of cholesterol, and the interaction was measured as an increase in the surface pressure of the film. Above pH 9, a strong inhibition of the reaction was observed.