Effects of a -Maleimide-derivatized Phosphatidylethanolamine on the Architecture and Properties of Lipid Bilayers.

-maleimide-derivatized phospholipids are often used to facilitate protein anchoring to membranes. In autophagy studies, this is applied to the covalent binding of Atg8, an autophagy protein, to a phosphatidylethanolamine (PE) in the nascent autophagosome. However, the question remains on how closely the -maleimide PE derivative (PE-mal) mimicks the native PE in the bilayer.

Lipids in Mitochondrial Macroautophagy: Phase Behavior of Bilayers Containing Cardiolipin and Ceramide.

Cardiolipin (CL) is a key lipid for damaged mitochondrial recognition by the LC3/GABARAP human autophagy proteins. The role of ceramide (Cer) in this process is unclear, but CL and Cer have been proposed to coexist in mitochondria under certain conditions. Varela et al.

Phase behaviour of C18-N-acyl sphingolipids, the prevalent species in human brain.

Lipidomic analysis of the N-acyl components of sphingolipids in different mammalian tissues had revealed that brain tissue differed from all the other samples in that SM contained mainly C18:0 and C24:1N-acyl chains, and that the most abundant Cer species was C18:0. Only in the nervous system was C18:0 found in sizable proportions. The high levels of C18:0 and C16:0, respectively in brain and non-brain SM, were important because SM is by far the most abundant sphingolipid in the plasma membrane.

Exploring polar headgroup interactions between sphingomyelin and ceramide with infrared spectroscopy.

Ceramide is a major actor in the sphingolipid signaling pathway elicited by various kinds of cell stress. Under those conditions ceramide (Cer) is produced in the plasma membrane as a product of sphingomyelin (SM) hydrolysis, and this may lead to apoptosis. Thus, SM and Cer coexist in the membrane for some time, and they are known to separate laterally from the (more abundant) glycerolipids, giving rise to highly rigid domains or platforms.

C24:0 and C24:1 sphingolipids in cholesterol-containing, five- and six-component lipid membranes.

The biophysical properties of sphingolipids containing lignoceric (C24:0) or nervonic (C24:1) fatty acyl residues have been studied in multicomponent lipid bilayers containing cholesterol (Chol), by means of confocal microscopy, differential scanning calorimetry and atomic force microscopy. Lipid membranes composed of dioleoyl phosphatidylcholine and cholesterol were prepared, with the addition of different combinations of ceramides (C24:0 and/or C24:1) and sphingomyelins (C24:0 and/or C24:1). Results point to C24:0 sphingolipids, namely lignoceroyl sphingomyelin (lSM) and lignoceroyl ceramide (lCer), having higher membrane rigidifying properties than their C24:1 homologues (nervonoyl SM, nSM, or nervonoyl Cer, nCer), although with a similar strong capacity to induce segregated gel phases.

Mixing brain cerebrosides with brain ceramides, cholesterol and phospholipids.

The properties of bilayers composed of pure brain cerebroside (bCrb) or of binary mixtures of bCrb with brain ceramide, cholesterol, egg phosphatidylcholine or brain sphingomyelin have been studied using a combination of physical techniques. Pure bCrb exhibits a rather narrow gel-fluid transition centred at ≈65 °C, with a half-width at half-height T ≈ 3 °C. bCrb mixes well with both fluid and gel phospholipids and ceramide, and it rigidifies bilayers of egg phosphatidylcholine or brain sphingomyelin when the latter are in the fluid state.

Homogeneous and Heterogeneous Bilayers of Ternary Lipid Compositions Containing Equimolar Ceramide and Cholesterol.

Cell membranes have been proposed to be laterally inhomogeneous, particularly in the case of mammalian cells, due to the presence of "domains" enriched in sphingolipids and cholesterol (Chol). Among membrane sphingolipids, sphingomyelin (SM) in the cell plasma membrane is known to be degraded to ceramide (Cer) by acid sphingomyelinases under stress conditions. Since cholesterol (Chol) is abundant in the plasma membrane, the study of ternary mixtures SM:Chol:Cer is interesting from the point of view of membrane biophysics, and it might be physiologically relevant.

Pb(II) Induces Scramblase Activation and Ceramide-Domain Generation in Red Blood Cells.

The mechanisms of Pb(II) toxicity have been studied in human red blood cells using confocal microscopy, immunolabeling, fluorescence-activated cell sorting and atomic force microscopy. The process follows a sequence of events, starting with calcium entry, followed by potassium release, morphological change, generation of ceramide, lipid flip-flop and finally cell lysis. Clotrimazole blocks potassium channels and the whole process is inhibited.

Phase behavior of palmitoyl and egg sphingomyelin.

Despite the biological significance of sphingomyelins (SMs), there is far less structural information available for SMs compared to glycerophospholipids. Considerable confusion exists in the literature regarding even the phase behavior of SM bilayers. This work studies both palmitoyl (PSM) and egg sphingomyelin (ESM) in the temperature regime from 3 °C to 55 °C using X-ray diffraction and X-ray diffuse scattering on hydrated, oriented thick bilayer stacks.

Complex Effects of 24:1 Sphingolipids in Membranes Containing Dioleoylphosphatidylcholine and Cholesterol.

The effects of C24:1 sphingolipids have been tested in phospholipid bilayers containing cholesterol. Confocal microscopy, differential scanning calorimetry, and atomic force microscopy imaging and force curves have been used. More precisely, the effects of C24:1 ceramide (nervonoyl ceramide, nCer) were evaluated and compared to those of C16:0 ceramide (palmitoyl ceramide, pCer) in bilayers composed basically of dioleoylphosphatidylcholine, sphingomyelin (either C24:1, nSM or C16:0, pSM) and cholesterol.