Fusion of alphaviruses with liposomes is a non-leaky process.
It has been reported that low-pH-induced fusion of influenza virus with liposomes results in rapid and extensive release of both low- and high-molecular-weight substances from the liposomes [Günther-Ausborn et al., J. Biol. Chem. 270 (1995) 29279-29285; Shangguan et al., Biochemistry 35 (1996) 4956-4965]. Here, we demonstrate retention of encapsulated water-soluble compounds during fusion of Semliki Forest virus (SFV) or Sindbis virus with liposomes at low pH. Under conditions allowing complete fusion of the liposomes, a limited fluorescence dequenching of liposome-encapsulated calcein was observed, particularly for SFV. Also, radioactively labeled inulin or sucrose were largely retained. Freezing and thawing of the viruses in the absence of sucrose resulted in an enhanced leakiness of fusion. These results support the notion that the alphavirus fusion event per se is non-leaky and may well involve a discrete hemifusion intermediate.
Smit
Jolanda M
JM
Department of Medical Microbiology, Molecular Virology Section, University of Groningen and Academic Hospital, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands.
Li
Gang
G
Schoen
Pieter
P
Corver
Jeroen
J
Bittman
Robert
R
Lin
Ke-Chun
KC
Wilschut
Jan
J
D005452:Fluoresceins / Q000378:metabolism; D005615:Freezing; D007328:Insulin / Q000378:metabolism; D007553:Isotope Labeling; D050356:Lipid Metabolism; D008081:Liposomes / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology*; D012672:Semliki forest virus / Q000502:physiology*; D012845:Sindbis Virus / Q000502:physiology*; D013395:Sucrose / Q000378:metabolism; D014316:Tritium
D005452:Fluoresceins; D007328:Insulin; D008081:Liposomes; D014316:Tritium; D013395:Sucrose; C007740:fluorexon