Document text
Principal Investigator: James B Munro
Organization: UNIV OF MASSACHUSETTS MED SCH WORCESTER
Fiscal Year: 2022
Award: $502,500
Funding agency: National Institute of General Medical Sciences
SUMMARY
Influenza A virus (IAV) hemagglutinin (HA) is the canonical example of a class-I viral fusion protein, and thus
provides an ideal model system for understanding the fusion mechanisms of many different viruses. Numerous
other viral envelope glycoproteins, including the SARS-CoV-2 spike, are believed to mediate fusion by a
comparable mechanism. Our long-term goal is to establish a complete mechanistic framework of class-I viral
fusion. We further aim to identify conserved and divergent features of the fusion mechanisms of distinct viruses,
generating specific models that fit within the general framework. HA resides on the surface of the IAV virion and
facilitates attachment to the target cell surface through the receptor-binding domain (HA1) engaging SA moieties.
Following endocytosis and trafficking to the late endosome, HA promotes fusion of the viral and endosomal
membranes. The model of HA-mediated membrane fusion describes a “spring-loaded” metastable prefusion
conformation at neutral pH. Dissociation of HA1 from the fusion domain (HA2) allows HA2 to undergo a cascade
of conformational changes that drive membrane fusion. While extensive structural data exist for HA pre- and
postfusion, and alternative conformations have been visualized and inferred, the conformational trajectory that
leads to membrane fusion, including the adoption of anticipated intermediates, has never been explicitly
validated. Nor has the order and timing of conformational changes and membrane fusion been determined. Here,
we will utilize a multifaceted approach involving single-molecule Förster resonance energy transfer imaging,
single-virion fusion, cryoelectron tomography, and molecular dynamic simulation to directly visualize the
conformational trajectory undergone by HA during membrane fusion. We will explore the roles of virion
morphology, HA density and cooperativity, and target membrane lipid content in mediating HA conformational
changes and the mechanism of fusion. We will describe the allosteric connection between distal regions of HA
that regulate the timing of fusion, drawing comparison to SARS-CoV-2 S. Finally, we will biophysically
characterize the phenotypic differences between human and avian IAV strains to determine what prevents avian
IAV strains from entering the human population.
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glycoprotein><SARS-CoV2 spike protein><SARS-associated corona virus 2><SARS-associated coronavirus 2><SARS-coronavirus-2><SARS-related corona virus 2><SARS-related coronavirus 2><SARSCoV2><Severe Acute Respiratory Coronavirus 2><Severe Acute Respiratory Distress Syndrome CoV 2><Severe Acute Respiratory Distress Syndrome Corona Virus 2><Severe Acute Respiratory Distress Syndrome Coronavirus 2><Severe Acute Respiratory Syndrome CoV 2><Severe Acute Respiratory Syndrome-associated coronavirus 2><Severe Acute Respiratory Syndrome-related coronavirus 2><Severe acute respiratory syndrome associated corona virus 2><Severe acute respiratory syndrome corona virus 2><Severe acute respiratory syndrome coronavirus 2><Severe acute respiratory syndrome coronavirus 2 S protein><Severe acute respiratory syndrome coronavirus 2 spike glycoprotein><Severe acute respiratory syndrome coronavirus 2 spike protein><Severe acute respiratory syndrome related corona virus 2><Sialic Acids><Specificity><Structure><Surface><Testing><Therapeutic><Thermodynamic><Thermodynamics><Transmission><Type A Influenza><Viral><Viral Fusion Proteins><Virion><Virus><Virus Particle><Wuhan coronavirus><Zoonoses><Zoonotic><Zoonotic Infection><avian flu><avian flu virus><balance><balance function><biophysical analysis><biophysical characteristics><biophysical characterization><biophysical foundation><biophysical measurement><biophysical parameters><biophysical principles><biophysical properties><biophysical sciences><biophysical studies><bird flu virus><block viral entry><cold temperature><combat><conformation><conformational state><coronavirus disease 2019 S protein><coronavirus disease 2019 spike glycoprotein><coronavirus disease 2019 spike protein><coronavirus disease 2019 virus><coronavirus disease-19 virus><cryo-EM tomography><cryoEM tomography><cryoelectron tomography><data exchange><data transfer><data transmission><density><developmental><electron cryo-tomography><env 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tropism><trafficking><transmission process><viral entry blocker><viral entry inhibitor><virus envelope>