Initial size and dynamics of viral fusion pores are a function of the fusion protein mediating membrane fusion.
BACKGROUND
Protein-mediated merger of biological membranes, membrane fusion, is an important process. To investigate the role of fusogenic proteins in the initial size and dynamics of the fusion pore (a narrow aqueous pathway, which widens to finalize membrane fusion), two different fusion proteins expressed in the same cell line were investigated: the major glycoprotein of baculovirus Autographa californica (GP64) and the HA (haemagglutinin) of influenza X31.


RESULTS
The host Sf9 cells expressing these viral proteins, irrespective of protein species, fused to human RBCs (red blood cells) upon acidification of the medium. A high-time-resolution electrophysiological study of fusion pore conductance revealed fundamental differences in (i) the initial pore conductance; pores created by HA were smaller than those created by GP64; (ii) the ability of pores to flicker; only HA-mediated pores flickered; and (iii) the time required for pore formation; HA-mediated pores took much longer to form after acidification.


CONCLUSIONS
HA and GP64 have divergent electrophysiological phenotypes even when they fuse identical membranes, and fusion proteins play a crucial role in determining initial fusion pore characteristics. The structure of the initial fusion pore detected by electrical conductance measurements is sensitive to the nature of the fusion protein.
Plonsky
Ilya
I
Laboratory of Cellular and Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1855, U.S.A.
Kingsley
David H
DH
Rashtian
Afshin
A
Blank
Paul S
PS
Zimmerberg
Joshua
J
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology*; D004594:Electrophysiology; D004912:Erythrocytes / Q000502:physiology; D006023:Glycoproteins / Q000502:physiology*; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000502:physiology; D006801:Humans; D007700:Kinetics; D008561:Membrane Fusion; D008954:Models, Biological; D018272:Porins / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D018411:Spodoptera; D014764:Viral Proteins / Q000502:physiology*
D006023:Glycoproteins; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D018272:Porins; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins