Sphingolipid and cholesterol dependence of alphavirus membrane fusion. Lack of correlation with lipid raft formation in target liposomes.
Semliki Forest virus (SFV) and Sindbis virus (SIN) are enveloped viruses that infect their host cells by receptor-mediated endocytosis and subsequent fusion from within acidic endosomes. Fusion of the viral envelope requires the presence of both cholesterol and sphingolipids in the target membrane. This is suggestive of a possible involvement of sphingolipid-cholesterol microdomains, or "lipid rafts," in the membrane fusion and cell entry process of the virus. In this study, large unilamellar vesicles (LUVs) were prepared from synthetic sphingolipids and sterols that vary with respect to their capacity to promote microdomain formation, as assessed by gradient flotation analysis in the presence of Triton X-100. SFV and SIN fused with LUVs irrespective of the presence or absence of Triton X-100-insoluble microdomains. These results suggest that SFV and SIN do not require the presence of lipid rafts for fusion with target membranes. Furthermore, it is not necessary for sphingolipids to reside in a detergent-insoluble complex with cholesterol to promote SFV or SIN fusion.
Waarts
Barry-Lee
BL
University of Groningen and Academic Hospital, Department of Medical Microbiology, Molecular Virology Section, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands.
Bittman
Robert
R
Wilschut
Jan
J
D000818:Animals; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D006224:Cricetinae; D003902:Detergents / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology*; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism*; D017830:Octoxynol / Q000378:metabolism; D012672:Semliki forest virus / Q000378:metabolism*; D012845:Sindbis Virus / Q000378:metabolism*; D013107:Sphingolipids / Q000378:metabolism*
D003902:Detergents; D008081:Liposomes; D013107:Sphingolipids; D017830:Octoxynol; D002784:Cholesterol