Fusion between cell membrane and liposomes containing the glycoproteins of influenza virus

The Ratio of Plasma Membrane Cholesterol to Phospholipid and the Inhibition of Sindbis Virus Maturation by Low NaCl Medium

“…The enhanced fusion ofliposomes to infected cells may be a consequence of the fusogenic properties of the virus glycoproteins inserted in the plasma membrane. Previous studies have shown that incorporation of myxovirus or herpesvirus glycoproteins in liposomal membranes dramatically increases fusion with plasma membranes (Huang et al, 1980;Johnson et al, 1984). Using liposomes containing labelled cholesterol or oleic acid, we found that treatment of infected, sensitive cells (CE or BHK-S) with liposomes containing a high content of cholesterol resulted in sufficient incorporation of cholesterol to increase the ratio of cholesterol to phospholipid in the plasma membrane transiently to values comparable to those in BHK-R cells.…”

Involvement of Glycolipids in Myxovirus-induced Membrane Fusion (Haemolysis)

“…It is possible that these lipids are the natural reaction partners of the FI polypeptide of paramyxoviruses and the HA2 polypeptide of influenza virus, which contain similar hydrophobic N-terminal structures (Gething et al, 1978). The exposure of these hydrophobic peptides by proteolytic cleavage during the replication of myxoviruses is known to be essential for the fusion property of these viruses (Compans & Klenk, 1979;Huang et al, 1980b). Of late, evidence is mounting that several other enveloped viruses infect their host cells by membrane fusion (V/i~in/inen & Kii/iri~iinen, 1979; Helenius et al, 1980;Miller & Lenard, 1981) and it would be interesting for future investigation to see if a similar mechanism of membrane fusion operates in all these viruses.…”

“…The attachment occurs through a specific binding of neuraminic acid-containing receptors of cellular membrane with the haemagglutinin of influenza virus or the haemagglutinin-neuraminidase complex of paramyxovirus (Rott & Klenk, 1977;Compans & Klenk, 1979). The membrane fusion has been proposed to occur at the cellular surface (Dourmashkin & Tyrrell, 1974;Huang et al, 1980b or solely in the lysosomal milieu after endocytosis (White et al, 1981). The fusion process seems to be mediated by a lipophilic peptide segment of virus glycoproteins present in the amino-terminal region of the HA2 polypeptide of the haemagglutinin of influenza virus or the FI portion of the fusion protein of paramyxoviruses (Scheid et al, 1972;Klenk et al, 1975;Richardson et al, 1980).…”

Inhibition of proteolytic cleavage of the hemagglutinin of influenza virus by the calcium-specific ionophore A23187.

“…During transport the precursor HA undergoes post-translational proteolytic cleavage into the fragments HA1 and HA2. Cleavage which is a pre-condition for the fusion capacity of the hemagglutinin (Huang et al, 1980(Huang et al, , 1981Lenard and Miller, 1981;Maeda and Ohnishi, 1980;White et al, 1981) and, thus, for virus infectivity (Klenk et al, 1975;Lazarowitz and Choppin, 1975) involves the sequential action of a trypsin-like endoprotease and carboxypeptidase N which are both of host origin (Lazarowitz et al, 1973;Garten et al, 1981;Garten and Klenk, 1983). There is increasing evidence that structural differences at the cleavage site are important for the spread of infection and for pathogenicity (Bosch et al, 1979.…”