Membrane fusion mechanisms: the influenza hemagglutinin paradigm and its implications for intracellular fusion.
The mechanism of membrane fusion induced by the influenza virus hemagglutinin (HA) has been extensively characterized. Fusion is triggered by low pH, which induces conformational changes in the protein, leading to insertion of a hydrophobic 'fusion peptide' into the viral membrane and the target membrane for fusion. Insertion perturbs the target membrane, and hour glass-shaped lipidic fusion intermediates, called stalks, fusing the outer monolayers of the two membranes, are formed. Stalk formation is followed by complete fusion of the two membranes. Structures similar to those formed by HA at the pH of fusion are found not only in many other viral fusion proteins, but are also formed by SNAREs, proteins involved in intracellular fusion. Substances that inhibit or promote HA-induced fusion because they affect stalk formation, also inhibit or promote intracellular fusion, cell-cell fusion and even intracellular fission similarly. Therefore, the mechanism of influenza HA-induced fusion may be a paradigm for many intracellular fusion events.
Stegmann
T
T
Institut de Pharmacologie et de Biologie Structurale, CNRS UPR 9062, 205 Route de Narbonne, 31077 Toulouse, France. Stegmann@ipbs.fr
D000818:Animals; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D008561:Membrane Fusion / Q000502:physiology*; D008563:Membrane Lipids / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009975:Orthomyxoviridae / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport / Q000502:physiology*; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D008563:Membrane Lipids; D008565:Membrane Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins