Differential cholesterol binding by class II fusion proteins determines membrane fusion properties.
The class II fusion proteins of the alphaviruses and flaviviruses mediate virus infection by driving the fusion of the virus membrane with that of the cell. These fusion proteins are triggered by low pH, and their structures are strikingly similar in both the prefusion dimer and the postfusion homotrimer conformations. Here we have compared cholesterol interactions during membrane fusion by these two groups of viruses. Using cholesterol-depleted insect cells, we showed that fusion and infection by the alphaviruses Semliki Forest virus (SFV) and Sindbis virus were strongly promoted by cholesterol, with similar sterol dependence in laboratory and field isolates and in viruses passaged in tissue culture. The E1 fusion protein from SFV bound cholesterol, as detected by labeling with photocholesterol and by cholesterol extraction studies. In contrast, fusion and infection by numerous strains of the flavivirus dengue virus (DV) and by yellow fever virus 17D were cholesterol independent, and the DV fusion protein did not show significant cholesterol binding. SFV E1 is the first virus fusion protein demonstrated to directly bind cholesterol. Taken together, our results reveal important functional differences conferred by the cholesterol-binding properties of class II fusion proteins.
Umashankar
M
M
Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
Sánchez-San Martín
Claudia
C
Liao
Maofu
M
Reilly
Brigid
B
Guo
Alice
A
Taylor
Gwen
G
Kielian
Margaret
M
D000524:Alphavirus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D006224:Cricetinae; D009033:Culicidae; D003716:Dengue Virus / Q000378:metabolism / Q000472:pathogenicity; D005416:Flavivirus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D008561:Membrane Fusion / Q000502:physiology*; D009154:Mutation; D012672:Semliki forest virus / Q000378:metabolism / Q000472:pathogenicity; D012845:Sindbis Virus / Q000378:metabolism / Q000472:pathogenicity; D014760:Viral Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D015005:Yellow fever virus / Q000378:metabolism / Q000472:pathogenicity
D014760:Viral Fusion Proteins; D002784:Cholesterol