Quantitative analysis of the lipidomes of the influenza virus envelope and MDCK cell apical membrane.

The influenza virus (IFV) acquires its envelope by budding from host cell plasma membranes. Using quantitative shotgun mass spectrometry, we determined the lipidomes of the host Madin-Darby canine kidney cell, its apical membrane, and the IFV budding from it. We found the apical membrane to be enriched in sphingolipids (SPs) and cholesterol, whereas glycerophospholipids were reduced, and storage lipids were depleted compared with the whole-cell membranes.

Squalene-based oil-in-water emulsion adjuvants perturb metabolism of neutral lipids and enhance lipid droplet formation.

Oil-in-water emulsions are used as vaccine adjuvants, but the mechanism of action remains unknown. In this paper we used phagocytes (monocytes, macrophages, dendritic cells) and non-phagocytic cells (fibroblasts, skeletal muscle cells) to study internalization of emulsions in vitro, and to characterize the influence of emulsion uptake on cellular metabolism of neutral lipids. We found that all tested cell types endocytose the emulsion droplets, and that the uptake leads to an acute accumulation of neutral lipids in the form of cytoplasmic lipid droplets.

Order of lipid phases in model and plasma membranes.

Lipid rafts are nanoscopic assemblies of sphingolipids, cholesterol, and specific membrane proteins that contribute to lateral heterogeneity in eukaryotic membranes. Separation of artificial membranes into liquid-ordered (Lo) and liquid-disordered phases is regarded as a common model for this compartmentalization. However, tight lipid packing in Lo phases seems to conflict with efficient partitioning of raft-associated transmembrane (TM) proteins.

The lipidomes of vesicular stomatitis virus, semliki forest virus, and the host plasma membrane analyzed by quantitative shotgun mass spectrometry.

Although enveloped virus assembly in the host cell is a crucial step in the virus life cycle, it remains poorly understood. One issue is how viruses include lipids in their membranes during budding from infected host cells. To analyze this issue, we took advantage of the fact that baby hamster kidney cells can be infected by two different viruses, namely, vesicular stomatitis virus and Semliki Forest virus, from the Rhabdoviridae and Togaviridae families, respectively.

Age-dependent increase in desmosterol restores DRM formation and membrane-related functions in cholesterol-free DHCR24-/- mice.

Cholesterol is a prominent modulator of the integrity and functional activity of physiological membranes and the most abundant sterol in the mammalian brain. DHCR24-knock-out mice lack cholesterol and accumulate desmosterol with age. Here we demonstrate that brain cholesterol deficiency in 3-week-old DHCR24(-/-) mice was associated with altered membrane composition including disrupted detergent-resistant membrane domain (DRM) structure.

Lipids as modulators of proteolytic activity of BACE: involvement of cholesterol, glycosphingolipids, and anionic phospholipids in vitro.

The beta-secretase, BACE, is a membrane spanning aspartic protease, which cleaves the amyloid precursor protein (APP) in the first step of proteolytic processing leading to the formation of the neurotoxic beta-amyloid peptide (Abeta). Previous results have suggested that the regulation of beta-secretase and BACE access to APP is lipid dependent, and involves lipid rafts. Using the baculovirus expression system, we have expressed recombinant human full-length BACE in insect cells and purified milligram amounts to homogeneity.