Transbilayer lipid distribution in nano scale

Abstract

There is a limited number of methods to examine transbilayer lipid distribution in biomembranes. We employed freeze-fracture replicalabelling immunoelectron microscopy in combination with lipidbinding proteins and a peptide to examine both transbilayer distribution and lateral distribution of various phospholipids in mammalian cells. Our results indicate that phospholipids are exclusively distributed either in the outer or inner leaflet of human red blood cell (RBC) membranes. In contrast, in nucleated cells, such as human skin fibroblasts and neutrophils, sphingomyelin was distributed in both leaflets while exhibiting characteristic lipid domains in the inner leaflet. Similar to RBCs, lipid asymmetry was maintained both in resting and thrombin-activated platelets. However, the microparticles released from thrombin-activated platelets lost membrane asymmetry. Our results suggest that the microparticles were shed from platelet plasma membrane domains enriched with phosphatidylserine and/or phosphatidylinositol at the outer leaflet. These findings underscore the strict regulation and cell-type specificity of lipid asymmetry in the plasma membrane.

Virion-associated phosphatidylethanolamine promotes TIM1-mediated infection by Ebola, dengue, and West Nile viruses

“…We have shown here that the PE-specific antibiotic agent Duramycin effectively inhibits the infection of many pathogenic viruses without any approved vaccines or treatments. Given the importance of PE in viral entry processes, the presumed high abundance of PE on the virions, the fact that it is not exposed on the surface of healthy cells (29), Duramycin and similar PE-binding compounds may make useful antiviral agents. Although Duramycin itself contains lanthionine and methyllantionine bridges, making it expensive to synthesize and difficult to improve, its ability to control the replication of major pathogens such as EBOV, DENV, and WNV suggests that PE is a promising target for the design of broad-spectrum antiviral therapies.…”

“…To further verify that the ability of TIM1 to bind PE contributes to its physiological functions, we investigated the role of PE in TIM1-mediated phagocytosis. Like PS, PE is mostly confined to the inner leaflet of the plasma membrane (28,29). To assess whether PE is exposed on the surface of apoptotic cells, we induced apoptosis in Jurkat cells by using the transcription inhibitor actinomycin D, and stained them with biotin-annexin A5 or biotin-Duramycin.…”

Phospholipase Cβ1 induces membrane tubulation and is involved in caveolae formation

“…Interestingly, PLCβ1b is enriched in the caveolae of cardiomyocytes (41). A recent freeze-fracture immunoelectron microscope study reported an association of both PIP 2 and PE to the edge of the caveolae at the plasma membrane (25). It is well established that the heterotrimeric G protein Gα q -subunit activates PLCβ-lipase (42,43).…”

“…PLCβ1b and G protein subunit Gαq, which directly activates PLCβ, are reported to localize to the caveolar fraction (37). Previously, we showed that PE and PIP 2 were accumulated at the cytoplasmic leaflet of the edge of caveolar membranes (25). To address the role of PLCβ1 in caveolae formation, we compared the ultrastructures of the plasma membrane in control and PLCβ1 knockdown Swiss 3T3 cells.…”

“…There is an energy barrier to bend the flat membrane to the curved shape, and the redistribution of lipids reduces the energy by its spontaneous curvature. In fact, PE is associated on the edge of caveolae (25), and the addition of PE to GUV increased tubulation efficiency (26). Liposomes.…”