Synchronized activation and refolding of influenza hemagglutinin in multimeric fusion machines

Markovic, Ingrid; Leikina, Eugenia; Zhukovsky, Mikhail A.; Zimmerberg, Joshua; Chernomordik, Leonid V.

doi:10.1083/jcb.200103005

Cited by 84 publications

(98 citation statements)

References 48 publications

(91 reference statements)

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“…In many experiments, HAb2 cells were pretreated with 9 mM sodium butyrate (NaBut) for 24 h to boost HA expression (7,8). If not stated otherwise, HA0 expressed at the cell surface was cleaved from HA0 to the fusioncompetent HA1-HA2 form by trypsin (5 g/ml, Fluka, Buchs, Switzerland) for 10 min at room temperature as described previously (9).…”

Section: Methodsmentioning

confidence: 99%

Influenza Hemagglutinins Outside of the Contact Zone Are Necessary for Fusion Pore Expansion

Leikina

Mittal

Cho

et al. 2004

Journal of Biological Chemistry

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Current models for membrane fusion in diverse biological processes are focused on the local action of fusion proteins present in the contact zone where the proteins anchored in one membrane might interact directly with the other membrane. Are the fusion proteins outside of the contact zone just bystanders? Here we assess the role of these "outsider" proteins in influenza virus hemagglutinin-mediated fusion between red blood cells and either hemagglutinin-expressing cells or viral particles. To selectively inhibit or enhance the actions of hemagglutinin outsiders, the antibodies that bind to hemagglutinin and proteases that cleave it were conjugated to polystyrene microspheres too large to enter the contact zone. We also involved hemagglutinin outsiders into interactions with additional red blood cells. We find the hemagglutinin outsiders to be necessary and sufficient for fusion. Interfering with the activity of the hemagglutinin outsiders inhibited fusion. Selective conversion of hemagglutinin outsiders alone into fusioncompetent conformation was sufficient to achieve fusion. The discovered functional role of fusion proteins located outside of the contact zone suggests a tempting analogy to mechanisms by which proteins mediate membrane fission from outside of the fission site.

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Section: Methodsmentioning

confidence: 99%

Influenza Hemagglutinins Outside of the Contact Zone Are Necessary for Fusion Pore Expansion

Leikina

Mittal

Cho

et al. 2004

Journal of Biological Chemistry

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“…[22,33,35,[43][44][45] The size of these ensembles varies: Some complexes are composed of two receptors while others contain thousands. Some receptors, [46][47][48] including the ryanodine receptor [40] and MCPs, [39] are so highly concentrated that they dominate certain subcellular regions. Unfortunately, little is known about the structures of these assemblies, where they are localized within the cells, and how their localization influences signaling.…”

Section: Signaling Complexesmentioning

confidence: 99%

Synthetic Multivalent Ligands as Probes of Signal Transduction

2006

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Cell surface receptors acquire information from the extracellular environment and coordinate intracellular responses. Evidence from biochemical and structural studies indicates that many receptors do not operate as individual entities, but rather as part of higher-order complexes (e.g. dimers and oligomers). Coupling the functions of multiple receptors may endow signaling pathways with the sensitivity and malleability required to govern cellular responses. Moreover, multireceptor signaling complexes may provide a means of spatially segregating otherwise degenerate signaling cascades. Despite the proposed importance of receptor-receptor processes in cellular signaling, questions concerning the mechanisms, extent, and consequences of receptor co-localization and interreceptor communication remain unanswered.Chemical synthesis can provide a variety of compounds with which to address the role of receptor assembly in signal transduction. The focus of this review is one such approach -the use of synthetic multivalent ligands to characterize receptor function. Multivalent ligands can be generated that possess a variety of sizes, shapes, valencies, orientations, and densities of binding elements. Their unique architectures imbue multivalent ligands with the ability to access binding modes not available to monovalent compounds. Multivalent ligands, therefore, are capable of illuminating aspects of inter-receptor processes that are not readily probed using conventional approaches. We suggest that, as focus shifts from investigations of the function of individual proteins and toward the analysis of multi-receptor signaling complexes, multivalent ligands will become even more valuable tools with which to ask sophisticated mechanistic questions. Further, multivalent ligands may provide new opportunities for manipulating receptor systems for the deconvolution of pathways, diagnosis, and, ultimately, the treatment of disease.

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“…Since this bond is accessible only in low-pH forms, the percentage of HA with the DTT-reducible bond reflects the percentage of low pH-activated HAs. The assay was performed as described in [39].…”

Section: Measuring Ha Activationmentioning

confidence: 99%

“…Putative acceleration of HA conformational changes by calcium can explain these phenomena. We hypothesize that calcium promotes the transition from early and reversible conformation(s) of low pH-activated HA towards an irreversible protein conformation that underlies both HA-mediated lipid mixing and HA inactivation [39,51].…”

Section: Putative Acceleration Of Ha Conformational Changes By Calciummentioning

confidence: 99%

“…The irreversible stage of HA restructuring involves lateral interactions between adjacent proteins. Such restructuring is facilitated at high densities of reversibly-activated HA molecules [39,51] and at high HA surface densities (HD-HA) can not be further significantly promoted by calcium. In contrast, at lower HA densities calcium might promote the shift to irreversible conformation thereby increasing the surface density of HA molecules in such conformation.…”

Section: Calcium Effects May Depend On Ha Surface Densitymentioning

confidence: 99%

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Influence of calcium on lipid mixing mediated by influenza hemagglutinin

Zhukovsky

Markovic

Bailey

2007

Archives of Biochemistry and Biophysics

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We studied the influence of calcium on lipid mixing mediated by influenza hemagglutinin (HA). Lipid mixing between HA-expressing cells and liposomes containing disialoganglioside, influenza virus receptor, was studied at 37°C and neutral pH after a low-pH pulse at 4°C. With DSPC/ cholesterol liposomes, calcium present after raising the temperature significantly promoted lipid mixing only when it was triggered by a short low-pH application. In case of DOPC/cholesterol liposomes, calcium promotion was observed regardless of the duration of the low-pH pulse. Calcium present during a short, but not long, low-pH application to HA-expressing cells with bound DSPC/ cholesterol liposomes at 4°C inhibited subsequent lipid mixing. We hypothesize that calcium influences lipid mixing because it binds to a vestigial esterase domain of hemagglutinin or causes expulsion of the fusion peptide from an electronegative cavity. We suggest that calcium promotes the transition from early and reversible conformation(s) of low pH-activated HA towards an irreversible conformation that underlies both HA-mediated lipid mixing and HA inactivation.

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Synchronized activation and refolding of influenza hemagglutinin in multimeric fusion machines

Cited by 84 publications

References 48 publications

Influenza Hemagglutinins Outside of the Contact Zone Are Necessary for Fusion Pore Expansion

Influenza Hemagglutinins Outside of the Contact Zone Are Necessary for Fusion Pore Expansion

Synthetic Multivalent Ligands as Probes of Signal Transduction

Influence of calcium on lipid mixing mediated by influenza hemagglutinin

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