Phospholipase A2-Induced Remodeling Processes on Liquid-Ordered/Liquid-Disordered Membranes Containing Docosahexaenoic or Oleic Acid: A Comparison Study.

Vesicle cycling, which is an important biological event, involves the interplay between membrane lipids and proteins, among which the enzyme phospholipase A2 (PLA2) plays a critical role. The capacity of PLA2 to trigger the budding and fission of liquid-ordered (L(o)) domains has been examined in palmitoyl-docosahexaenoylphosphatidylcholine (PDPC) and palmitoyl-oleoylphosphatidylcholine (POPC)/sphingomyelin/cholesterol membranes. They both exhibited a L(o)/liquid-disordered (L(d)) phase separation.

Role of Aminophospholipids in the Formation of Lipid Rafts in Model Membranes.

The phase separation of aminophospholipids in glycerophospholipid matrix and the effect of cholesterol were studied by means of fluorescence microscopy of giant unilamellar vesicles (GUV). GUVs were composed of binary mixtures, egg yolk phosphatidylcholine (eggPC)/egg yolk phosphatidylethanolamine (eggPE) and egg yolk phosphatidylcholine (eggPC)/brain phosphatidylserine (brainPS), and ternary ones with both aminophospholipids (eggPC/eggPE/brainPS). Gel/liquid-disordered phase coexistence was detected in these mixtures, where aminophospholipids segregate in gel leaf-like domains.

Resveratrol alters the lipid composition, metabolism and peroxide level in senescent rat hepatocytes.

Investigations were performed on the influence of resveratrol on the lipid composition, metabolism, fatty acid and peroxide level in plasma membranes of hepatocytes, isolated from aged rats. Hepatocytes were chosen due to the central role of the liver in lipid metabolism and homeostasis. The obtained results showed that the level of sphingomyelin (SM) and phosphatidylserine (PS) was augmented in plasma membranes of resveratrol-treated senescent hepatocytes.

Structural organization of plasma membrane lipids isolated from cells cultured as a monolayer and in tissue-like conditions.

Complementary biophysical approaches were used to study the structural organization of plasma membrane lipids obtained from fibroblasts cultured as two-dimensional (2D) monolayer and in tissue-like three-dimensional (3D) conditions. Fluorescence microscopy experiments demonstrated different domain patterns for 2D and 3D plasma membrane lipid extracts. ESR demonstrated that 3D lipid extract is characterized with lower order parameter than 2D in the deep hydrophobic core of the lipid bilayer.

Effect of sphingosine on domain morphology in giant vesicles.

Sphingosine is a bioactive molecule which is known to participate in the regulation of a number of cellular processes such as apoptosis, cell differentiation, growth, etc. Sphingosine was observed to exhibit different domain morphology depending on the surrounding lipid matrix in biomimetic systems such as giant vesicles. Our current results showed that in a glycerophospholipid matrix sphingosine segregated in gel leaf-like domains whereas cholesterol presence increased its miscibility by melting gel domains in a concentration-dependent manner.