title: Cholesterol promotes hemifusion and pore widening in membrane fusion induced by influenza hemagglutinin.
abstract: Cholesterol-specific interactions that affect membrane fusion were tested for using insect cells; cells that have naturally low cholesterol levels (< 4 mol %). Sf9 cells were engineered (HAS cells) to express the hemagglutinin (HA) of the influenza virus X-31 strain. Enrichment of HAS cells with cholesterol reduced the delay between triggering and lipid dye transfer between HAS cells and human red blood cells (RBC), indicating that cholesterol facilitates membrane lipid mixing prior to fusion pore opening. Increased cholesterol also increased aqueous content transfer between HAS cells and RBC over a broad range of HA expression levels, suggesting that cholesterol also favors fusion pore expansion. This interpretation was tested using both trans-cell dye diffusion and fusion pore conductivity measurements in cholesterol-enriched cells. The results of this study support the hypothesis that host cell cholesterol acts at two stages in membrane fusion: (1) early, prior to fusion pore opening, and (2) late, during fusion pore expansion.
authors.affiliation: Laboratory of Cellular and Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Subrata
authors.initials: S
authors.lastname: Biswas
authors.forename: Shu-Rong
authors.initials: SR
authors.lastname: Yin
authors.forename: Paul S
authors.initials: PS
authors.lastname: Blank
authors.forename: Joshua
authors.initials: J
authors.lastname: Zimmerberg
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002478:Cells, Cultured; D002784:Cholesterol / Q000737:chemistry* / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism / Q000821:virology; D005456:Fluorescent Dyes; D015870:Gene Expression; D005818:Genetic Engineering; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008561:Membrane Fusion; D009975:Orthomyxoviridae; D018408:Patch-Clamp Techniques; D018411:Spodoptera
chemical_list: D005456:Fluorescent Dyes; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D002784:Cholesterol