title: Hydrostatic pressure induces the fusion-active state of enveloped viruses.
abstract: Enveloped animal viruses must undergo membrane fusion to deliver their genome into the host cell. We demonstrate that high pressure inactivates two membrane-enveloped viruses, influenza and Sindbis, by trapping the particles in a fusion-intermediate state. The pressure-induced conformational changes in Sindbis and influenza viruses were followed using intrinsic and extrinsic fluorescence spectroscopy, circular dichroism, and fusion, plaque, and hemagglutination assays. Influenza virus subjected to pressure exposes hydrophobic domains as determined by tryptophan fluorescence and by the binding of bis-8-anilino-1-naphthalenesulfonate, a well established marker of the fusogenic state in influenza virus. Pressure also produced an increase in the fusion activity at neutral pH as monitored by fluorescence resonance energy transfer using lipid vesicles labeled with fluorescence probes. Sindbis virus also underwent conformational changes induced by pressure similar to those in influenza virus, and the increase in fusion activity was followed by pyrene excimer fluorescence of the metabolically labeled virus particles. Overall we show that pressure elicits subtle changes in the whole structure of the enveloped viruses triggering a conformational change that is similar to the change triggered by low pH. Our data strengthen the hypothesis that the native conformation of fusion proteins is metastable, and a cycle of pressure leads to a final state, the fusion-active state, of smaller volume.
authors.affiliation: Programa de Biologia Estrutural, Departamento de Bioquimica Médica, Instituto de Ciências Biomédicas, Centro Nacional de Ressonância Magnética Nuclear de Macromoléculas, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, RJ, Brazil.
authors.forename: Luciane P
authors.initials: LP
authors.lastname: Gaspar
authors.forename: Ana C B
authors.initials: AC
authors.lastname: Silva
authors.forename: Andre M O
authors.initials: AM
authors.lastname: Gomes
authors.forename: Mônica S
authors.initials: MS
authors.lastname: Freitas
authors.forename: Ana P D
authors.initials: AP
authors.lastname: Ano Bom
authors.forename: Waleska D
authors.initials: WD
authors.lastname: Schwarcz
authors.forename: Jiri
authors.initials: J
authors.lastname: Mestecky
authors.forename: Miroslav J
authors.initials: MJ
authors.lastname: Novak
authors.forename: Débora
authors.initials: D
authors.lastname: Foguel
authors.forename: Jerson L
authors.initials: JL
authors.lastname: Silva
mesh_terms: D000818:Animals; D002460:Cell Line; D002642:Chick Embryo; D002645:Chickens; D002942:Circular Dichroism; D006224:Cricetinae; D004912:Erythrocytes / Q000378:metabolism; D006388:Hemagglutinins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006874:Hydrostatic Pressure; D008081:Liposomes / Q000378:metabolism; D008561:Membrane Fusion; D008954:Models, Biological; D009975:Orthomyxoviridae / Q000378:metabolism*; D011312:Pressure; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012845:Sindbis Virus / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014364:Tryptophan / Q000378:metabolism; D014760:Viral Fusion Proteins / Q000737:chemistry*; D018406:Virus Physiological Phenomena
chemical_list: D006388:Hemagglutinins; D008081:Liposomes; D011993:Recombinant Fusion Proteins; D014760:Viral Fusion Proteins; D014364:Tryptophan