The Transmembrane Domain of Influenza Hemagglutinin Exhibits a Stringent Length Requirement to Support the Hemifusion to Fusion Transition

Armstrong, R. Todd; Kushnir, Anna; White, Judith M.

doi:10.1083/jcb.151.2.425

Cited by 193 publications

(200 citation statements)

References 63 publications

(101 reference statements)

Supporting

Mentioning

191

Contrasting

Order By: Relevance

“…In the absence of fusion proteins, the process of bilayer fusion is a physical process with multiple high-energy intermediates (77,78) corresponding to: (i) diffusion of the membranes together, (ii) dehydration of the bilayers as the headgroups of opposing bilayers come into still closer proximity, (iii) formation of a lipidic stalk, (iv) hemifusion, (v) pore formation and expansion. Viral fusion proteins and SNARE proteins utilize essentially irreversible, energetically favorable conformational transitions to lower the activation energy for membrane fusion (50,51,77,78). Thus, they are active participants that shape the energy landscape.…”

Section: Discussionmentioning

confidence: 99%

“…If indeed FPs adopt a TM orientation, then one might envision a mechanism akin to SNARE proteins (50)(51)(52)(53), in which both the target and vesicular proteins have TM helices that associate as membrane fusion progresses. Accordingly, we investigate herein a class I fusogenic protein, F, from parainfluenza virus 5 (PIV5), which, like influenza virus HA and HIV gp41, has an N-terminal FP in the mature, cleaved protein (3).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Transmembrane orientation and possible role of the fusogenic peptide from parainfluenza virus 5 (PIV5) in promoting fusion

Donald¹,

Zhang

Fiorin

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Membrane fusion is required for diverse biological functions ranging from viral infection to neurotransmitter release. Fusogenic proteins increase the intrinsically slow rate of fusion by coupling energetically downhill conformational changes of the protein to kinetically unfavorable fusion of the membrane-phospholipid bilayers. Class I viral fusogenic proteins have an N-terminal hydrophobic fusion peptide (FP) domain, important for interaction with the target membrane, plus a C-terminal transmembrane (C-term-TM) helical membrane anchor. The role of the water-soluble regions of fusogenic proteins has been extensively studied, but the contributions of the membrane-interacting FP and C-term-TM peptides are less well characterized. Typically, FPs are thought to bind to membranes at an angle that allows helix penetration but not traversal of the lipid bilayer. Here, we show that the FP from the paramyxovirus parainfluenza virus 5 fusogenic protein, F, forms an N-terminal TM helix, which self-associates into a hexameric bundle. This FP also interacts strongly with the C-term-TM helix. Thus, the fusogenic F protein resembles SNARE proteins involved in vesicle fusion by having water-soluble coiled coils that zipper during fusion and TM helices in both membranes. By analogy to mechanosensitive channels, the force associated with zippering of the water-soluble coiled-coil domain is expected to lead to tilting of the FP helices, promoting interaction with the C-term-TM helices. The energetically unfavorable dehydration of lipid headgroups of opposing bilayers is compensated by thermodynamically favorable interactions between the FP and C-term-TM helices as the coiled coils zipper into the membrane phase, leading to a pore lined by both lipid and protein.T he basic mechanisms of viral membrane fusion have been studied extensively, but major gaps remain in our understanding of the relative roles of lipidic intermediates and viral fusogenic proteins in lowering the energy barrier for the overall process (1-4). The most common mechanistic hypothesis concerning enveloped viral fusion is that fusogenic proteins primarily serve to bring the target cell and viral membranes into proximity. Fusion occurs in a multistep process, in which the virus first binds to a specific receptor; this event and/or other environmental cues then cause a conformational change in the protein, leading to a metastable state with an exposed hydrophobic fusion peptide (FP) that binds to the target membrane. Once engaged with the bilayer, a second energetically favorable conformational change in the fusogenic protein then exerts a force pulling the FP toward the viral membrane, in effect reeling the host and viral membranes together.The conformational changes involved in the water-soluble portions of viral fusogenic proteins have been largely elucidated, but the roles of the membrane-binding FP and the C-terminal transmembrane (C-term-TM) anchor are less clear. After the crystal structure of the prefusogenic form of influenza hemagglutinin (HA) was solved...

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Transmembrane orientation and possible role of the fusogenic peptide from parainfluenza virus 5 (PIV5) in promoting fusion

Donald¹,

Zhang

Fiorin

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…C9 and C45 are dispensable for receptor-triggered target membrane association, but they are stringently required for the lipid mixing stage of fusion. We envision two non-mutually exclusive roles for the cysteines flanking the EnvA fusion peptide: (i) to allow the EnvA TM subunit to fold back into a trimer of hairpins compact enough to mediate lipid mixing, perhaps involving interactions between the fusion loop and the pre-TM or TM regions (1,2,16,20) of EnvA or (ii) to allow the fusion peptide to remain tightly associated with the target membrane during the foldback stage of fusion. Our findings are likely relevant to structural requirements for other internal fusion peptides flanked by Cys residues, notably those of the Ebola virus and Marburg virus glycoproteins.…”

mentioning

confidence: 99%

Cysteines Flanking the Internal Fusion Peptide Are Required for the Avian Sarcoma/Leukosis Virus Glycoprotein To Mediate the Lipid Mixing Stage of Fusion with High Efficiency

Delos¹,

Brecher

Chen³

et al. 2008

J Virol

Self Cite

View full text Add to dashboard Cite

We previously showed that the cysteines flanking the internal fusion peptide of the avian sarcoma/leukosis virus subtype A (ASLV-A) Env (EnvA) are important for infectivity and cell-cell fusion. Here we define the stage of fusion at which the cysteines are required. The flanking cysteines are dispensable for receptor-triggered membrane association but are required for the lipid mixing step of fusion, which, interestingly, displays a high pH onset and a biphasic profile. Second-site mutations that partially restore infection partially restore lipid mixing. These findings indicate that the cysteines flanking the internal fusion peptide of EnvA (and perhaps by analogy Ebola virus glycoprotein) are important for the foldback stage of the conformational changes that lead to membrane merger.The avian sarcoma/leukosis virus (ASLV) Env protein is unusual among class I fusion proteins in that it contains an internal fusion peptide, a characteristic it shares with filovirus (Ebola virus and Marburg virus) glycoproteins. These fusion peptides are flanked by two Cys residues, which, based on structural and mutagenesis evidence, likely form a disulfide bond (9, 21). The ASLV fusion peptide contains one proline, and the filovirus fusion peptides contain two prolines, at their centers. Previous work has shown that these Pro residues are important for fusion (4,8). The fusion peptide of EnvA is operationally defined as residues 22 to 37 of the transmembrane (TM) subunit. We previously provided evidence that the Pro in the middle of this peptide (P29) requires a ␤-turn structure (4) at some stage of fusion. We subsequently showed that the two Cys residues (C9 and C45) that define the likely disulfide-bonded loop encompassing the fusion peptide are required for infectivity and cell-cell fusion (5). In this study, we identified the specific stage of fusion that requires the Cys residues that flank the EnvA fusion peptide.To begin our studies, we asked if the defect was in the first step of fusion: target membrane binding. Accordingly, we determined the ability of murine leukemia virus pseudotyped virions (10) bearing either wild-type EnvA or an EnvA harboring double Cys-to-Ser mutations at both positions 9 and 45 of the TM subunit (referred to below as EnvAC9,45S) to bind to target membranes in a receptor-dependent manner (6, 7, 15). As seen in Fig. 1, wild-type murine leukemia virus pseudovirions bound liposomes and floated to the top of the gradient when either the quail (lane 1) or the chicken (lane 5) form of the soluble Tva receptor (sTva) was used (7). In the absence of sTva, all of the pseudovirions remained at the bottom of the gradient (Fig. 1, lane 12). Similar receptor-dependent membrane association was observed for EnvAC9,45S (Fig. 1). These data show that the Cys residues (C9 and C45) that define the loop encompassing the fusion peptide are not required for receptor-triggered binding of EnvA-bearing virus particles to target membranes.We then asked whether the cysteines are required for EnvA to reach the lipid mixing ...

show abstract

“…Indeed, in the case of influenza virus, Judy White and coworkers have shown that the membrane-spanning domain exhibits a stringent length requirement to support the hemifusion to fusion transition [48]. Moreover, in the case of SIV, Eric Hunter and coworkers observed that progressive truncations C-terminal to the membrane-spanning domain of simian immunodeficiency virus Env reduce fusogenicity and increase concentration dependence of Env for fusion.…”

Section: Development Of Site-directed Photosensitized Labeling To Stumentioning

confidence: 99%

HIV-1 envelope glycoprotein-mediated fusion and pathogenesis: Implications for therapy and vaccine development

Jacobs

Garg

Viard

et al. 2008

Vaccine

View full text Add to dashboard Cite

Our overall goal is to understand how viral envelope proteins mediate membrane fusion and pathogenesis. Membrane fusion is a crucial step in the delivery of the viral genome into the cell resulting in infection. On the other hand, fusion activity of viral envelope glycoproteins expressed in infected cells may cause the demise of uninfected bystander cells by apoptosis. Our general approach is to kinetically resolve steps in the pathway of viral envelope glycoprotein-mediated membrane fusion and to uncover physical parameters underlying those steps using a variety of biochemical, biophysical, virological, and molecular and cell biological techniques. Since HIV fusion involves a complex cascade of interactions of the envelope glycoprotein with two receptors, membrane organization plays an important role and interfering with it may modulate entry. To study this phenomenon, we have either examined cell lines with differential expression of sphingolipids (such as GM3), or altered membrane organization by modifying levels of cholesterol, ceramides, or glycosphingolipids. We show that the localized plasma membrane lipid microenvironment (and not the specific membrane lipids) in the vicinity of CD4 controls receptor mobility and HIV-1 fusion. The complex cascade of conformational changes that must occur to allow virus entry is also a very important target for therapy and vaccine development. We have recently designed and tested peptide analogs composed of chemical spacers and reactive moieties positioned strategically to promote permanent attachment. Using a temperature-arrested state in vitro assay we show evidence for the trapping of a pre-six helix bundle fusion intermediate by a covalent reaction with the inhibitory reactive peptide. Also, using photo-reactive hydrophobic probes we have found ways to inactivate viral envelope glycoproteins while leaving their overall structures intact. Finally, in order to study the envelope glycoprotein effects on pathogenesis, we have used an in vitro model of co-culture of envelope-expressing cells as effectors and CD4+ T cells as targets. We delineated that apoptosis mediated by envelope glycoprotein in bystander cells correlates with transmembrane subunit (gp41)-induced hemifusion. The apoptotic pathway initiated by this interaction involves caspase-3-dependent mitochondrial depolarization and reactive oxygen species production, which depends on the phenotype of the envelope glycoprotein associated with the virus. Taken as a whole, our studies have many different important implications for anti-viral therapies and vaccine development.

show abstract

The Transmembrane Domain of Influenza Hemagglutinin Exhibits a Stringent Length Requirement to Support the Hemifusion to Fusion Transition

Cited by 193 publications

References 63 publications

Transmembrane orientation and possible role of the fusogenic peptide from parainfluenza virus 5 (PIV5) in promoting fusion

Transmembrane orientation and possible role of the fusogenic peptide from parainfluenza virus 5 (PIV5) in promoting fusion

Cysteines Flanking the Internal Fusion Peptide Are Required for the Avian Sarcoma/Leukosis Virus Glycoprotein To Mediate the Lipid Mixing Stage of Fusion with High Efficiency

HIV-1 envelope glycoprotein-mediated fusion and pathogenesis: Implications for therapy and vaccine development

Contact Info

Product

Resources

About