i(3)so3-galactosylceramide and Influenza--Human

Influenza A virus (IAV) recognizes terminal sialic acid of sialoglyco-conjugates on host cells through the viral envelope glycoprotein hemagglutinin (HA), followed by initiation of entry into the cells. Molecular species of sialic acid are largely divided into two moieties: N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc). A receptor for IAV infection generally means Neu5Ac. Almost all equine IAVs and some human, swine, and duck IAVs bind not only to Neu5Ac but also to Neu5Gc. In nonhuman animals, Neu5Gc has been detected in swine and equine tracheas and the duck colon, which are the main replication sites of mammalian and avian IAVs. Therefore, Neu5Gc in these sites has been suggested to be a functional receptor for IAV infection. Humans cannot synthesize Neu5Gc due to a genetic defect of the Neu5Gc-synthesizing enzyme. We evaluated the receptor function of Neu5Gc in IAV infection in human cells. Our results indicated that Neu5Gc expression on the surface of human cells is not a functional receptor for IAV infection and that it has a negative effect on infectivity of IAV possessing Neu5Gc binding ability. IAV also binds to non-sialo 3-O-sulfated galactosylceramide (sulfatide). Sulfatide has been suggested to be a functional receptor for IAV infection. However, we have shown that sulfatide is not a functional receptor for IAV infection and that the binding of HA with sulfatide enhances progeny virus production. It is expected that functions of these glyco-molecules can be used in prevention and development of new drugs against IAV.

Topics: Animals; Antiviral Agents; Drug Discovery; Galactosylceramides; Glycoconjugates; Humans; Influenza A virus; Influenza, Human; Molecular Targeted Therapy; N-Acetylneuraminic Acid; Neuraminic Acids; Receptors, Virus; Sulfoglycosphingolipids

Sulfatide is a 3-O-sulfated galactosylceramide that is abundantly expressed in the gastrointestinal tract, kidney, trachea, and particularly the central nervous system. Cellular sulfatide is mainly localized in the Golgi apparatus, cellular membrane, and lysosomes in cytosol. Since our earlier report showed that the influenza A virus specifically binds to sulfatide, we have investigated the roles of sulfatide in the influenza A virus lifecycle. The viral binding is independent of sialic acids, which function as virus receptors in virus attachment to the host cell surface. Sulfatide is recognized by the ectodomain of the viral envelope glycoprotein hemagglutinin (HA). Nascent HA is transported on the surface membrane of infected cells. The binding of HA with sulfatide on the cell surface induces apoptosis through potential loss of the mitochondrial membrane and nuclear translocation of apoptosis-inducing factor in mitochondria, where PB1-F2 peptide from the viral gene is accumulated. In the nucleus of infected cells, viral ribonucleoprotein (vRNP) complexes are formed from viral RNA genomes, viral nucleoprotein, and viral RNA polymerase subunits, and these complexes are selectively exported into cytosol through the nuclear membrane. The apoptosis significantly enhances the nuclear export of vRNP complexes, resulting in efficient formation of progeny viruses and facilitation of virus replication. At that time, activation of the Raf/mitogen-activated protein extracellular kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway through sulfatide is associated with virus replication. Our studies have demonstrated that sulfatide is not a viral receptor for virus infection, and that the binding of HA with sulfatide functions as an initiation switch for the formation of progeny viruses.

Topics: Apoptosis; Cell Membrane; Cell Nucleus; Extracellular Signal-Regulated MAP Kinases; Hemagglutinins; Humans; Influenza A virus; Influenza, Human; Mitochondria; Ribonucleoproteins; RNA, Viral; Sulfoglycosphingolipids; Viral Proteins; Virus Replication

3-O-sulfation synthesizes sulfatide in the galactose moiety of galactosylceramide. Sulfatide is expressed in many organs such as the gastrointestinal tract, trachea, kidney, and central nervous system. Influenza A virus binds not only to glycoconjugates terminally containing sialic acid as a viral binding receptor but also to sulfatide not containing sialic acid. On the surface of infected cells, the envelope glycoprotein hemagglutinin of influenza A virus interacts with sulfatide. This interaction enhances the nuclear export of viral ribonucleoprotein complexes, resulting in efficient progeny viruses. Inhibiting this interaction would be a new potent anti-influenza drug that suppresses the progeny virus production in the infected cells.

Topics: Galactose; Galactosylceramides; Glycoproteins; Hemagglutinins; Humans; Influenza A virus; Influenza, Human; N-Acetylneuraminic Acid; Receptors, Virus; Ribonucleoproteins; Sulfoglycosphingolipids

Association of sulphatide with influenza A virus (IAV) haemagglutinin (HA) delivered to the cell surface promotes progeny virus production. However, it is not known whether there is direct binding of HA to sulphatide. In this study, we found that recombinant HA, which was produced by a baculovirus protein expression system from the HA gene of A/duck/HK/313/4/78 (H5N3), bound to sulphatide in a dose-dependent manner and that the binding was inhibited by a specific antibody. Our results indicate that the recombinant HA is useful for elucidation of the binding domain of HA with sulphatide and for the development of new anti-IAV agents.

Topics: Animals; Antibodies, Monoclonal; Antibodies, Viral; Antibody Specificity; Antiviral Agents; Baculoviridae; Cell Line; Drug Discovery; Gangliosides; Genes, Viral; Globosides; Hemagglutinin Glycoproteins, Influenza Virus; Humans; Influenza A virus; Influenza, Human; Molecular Sequence Data; Protein Binding; Recombinant Fusion Proteins; Sulfoglycosphingolipids