Lateral mobility of both envelope proteins (F and HN) of Sendai virus in the cell membrane is essential for cell-cell fusion.
Fluorescence photobleaching recovery was employed to study the effects of specific immobilization of Sendai virus envelope glycoproteins (F, the fusion protein, and HN, the hemagglutinin-neuraminidase) on the virally mediated fusion of human erythrocytes. Lateral immobilization of varying fractions of F and/or HN (after virus adsorption and hemagglutination, but before fusion) was achieved by cross-linking them with succinyl concanavalin A (inhibiting both F and HN) or with specific rabbit IgG directed against either F or HN. Alternatively, agglutinated cells were treated with low concentrations of the above proteins (inducing only minor inhibition of either mobility or fusion), and immobilization of F and/or HN was induced by cross-linking with a secondary antibody; this protocol ensured a minimal contribution of direct binding to the viral proteins to the inhibition of fusion. Our results demonstrate that lateral immobilization of either F or HN results in a strong inhibition of cell-cell fusion and a much weaker inhibition of virus-cell fusion. The level of cell-cell fusion was directly correlated with the level of laterally mobile viral glycoproteins in the cell membrane (either F or HN). We conclude that lateral mobility of both F and HN in the red cell membrane is essential for cell-cell fusion and that not only F but also HN has a role in this fusion event. The possible reasons for the different dependence of cell-cell and virus-cell fusion on viral glycoprotein mobility are discussed.
Henis
Y I
YI
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Herman-Barhom
Y
Y
Aroeti
B
B
Gutman
O
O
D000214:Acyl Coenzyme A / Q000494:pharmacology; D002459:Cell Fusion / Q000187:drug effects / Q000502:physiology*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000502:physiology*; D004912:Erythrocytes / Q000502:physiology; D005453:Fluorescence; D005455:Fluorescent Antibody Technique; D015707:HN Protein / Q000276:immunology / Q000502:physiology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D010222:Parainfluenza Virus 1, Human / Q000502:physiology*; D010777:Photochemistry; D012235:Rhodamines; D014760:Viral Fusion Proteins / Q000276:immunology / Q000502:physiology*
D000214:Acyl Coenzyme A; D003432:Cross-Linking Reagents; D015707:HN Protein; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D012235:Rhodamines; D014760:Viral Fusion Proteins; C009434:tetramethylrhodamine isothiocyanate; C012046:succinyl-coenzyme A