Dilation of the influenza hemagglutinin fusion pore revealed by the kinetics of individual cell-cell fusion events.
We have monitored kinetics of fusion between cell pairs consisting of a single influenza hemaglutinin (HA)-expressing cell and a single erythrocyte (RBC) that had been labeled with both a fluorescent lipid (Dil) in the membrane and a fluorescent solute (calcein) in the aqueous space. Initial fusion pore opening between the RBC and HA-expressing cell produced a change in RBC membrane potential (delta psi) that was monitored by a decrease in Dil fluorescence. This event was followed by two distinct stages of fusion pore dilation: the flux of fluorescent lipid (phi L) and the flux of a large aqueous fluorescent dye (phi s). We have analyzed the kinetics of events that occur as a result of transitions between a fusion pore (FP) and a solute permissive fusion pore (FPs). Our data are consistent with a fusion pore comprising six HA trimers.
Blumenthal
R
R
Section on Membrane Structure and Function, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA. blumen@helix.nih.gov
Sarkar
D P
DP
Durell
S
S
Howard
D E
DE
Morris
S J
SJ
D016475:3T3 Cells; D000818:Animals; D016466:CHO Cells; D002459:Cell Fusion; D006224:Cricetinae; D004910:Erythrocyte Membrane / Q000502:physiology*; D005452:Fluoresceins; D005456:Fluorescent Dyes; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008561:Membrane Fusion / Q000502:physiology*; D008564:Membrane Potentials; D051379:Mice; D018715:Microscopy, Video; D013696:Temperature
D005452:Fluoresceins; D005456:Fluorescent Dyes; D019267:Hemagglutinin Glycoproteins, Influenza Virus; C007740:fluorexon