A Structurally Unresolved Head Segment of Defined Length Favors Proper Measles Virus Hemagglutinin Tetramerization and Efficient Membrane Fusion Triggering

Navaratnarajah, Chanakha K.; Rosemarie, Quincy; Cattaneo, Roberto

doi:10.1128/jvi.02253-15

Cited by 21 publications

(20 citation statements)

References 41 publications

(72 reference statements)

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“…Four blue hexameric heads represent the six-bladed ␤-propellers of the receptor-binding domains. The heads are connected to the stalk by flexible dimeric linkers (green/blue) and four monomeric connectors (purple) (133,134). The MeV F trimer ectodomain structure (PDB code 5YXW) (154) is shown on the right with monomers represented as blue, purple, and orange.…”

Section: Receptors Tropism and Pathogenesismentioning

confidence: 99%

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Receptor-mediated cell entry of paramyxoviruses: Mechanisms, and consequences for tropism and pathogenesis

Navaratnarajah

Generous

Yousaf

et al. 2020

Journal of Biological Chemistry

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Research in the last decade has uncovered many new paramyxoviruses, airborne agents that cause epidemic diseases in animals including humans. Most paramyxoviruses enter epithelial cells of the airway using sialic acid as a receptor and cause only mild disease. However, others cross the epithelial barrier and cause more severe disease. For some of these viruses, the host receptors have been identified, and the mechanisms of cell entry have been elucidated. The tetrameric attachment proteins of paramyxoviruses have vastly different binding affinities for their cognate receptors, which they contact through different binding surfaces. Nevertheless, all input signals are converted to the same output: conformational changes that trigger refolding of trimeric fusion proteins and membrane fusion. Experiments with selectively receptor-blinded viruses inoculated into their natural hosts have provided insights into tropism, identifying the cells and tissues that support growth and revealing the mechanisms of pathogenesis. These analyses also shed light on diabolically elegant mechanisms used by morbilliviruses, including the measles virus, to promote massive amplification within the host, followed by efficient aerosolization and rapid spread through host populations. In another paradigm of receptor-facilitated severe disease, henipaviruses, including Nipah and Hendra viruses, use different members of one protein family to cause zoonoses. Specific properties of different paramyxoviruses, like neurotoxicity and immunosuppression, are now understood in the light of receptor specificity. We propose that research on the specific receptors for several newly identified members of the Paramyxoviridae family that may not bind sialic acid is needed to anticipate their zoonotic potential and to generate effective vaccines and antiviral compounds.

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Section: Receptors Tropism and Pathogenesismentioning

confidence: 99%

“…The hydrophobic hinge maintains the H-protein in an autorepressed state prior to receptor binding (134). The head connectors govern proper H-protein tetramerization (133). According to the model, membranebound receptors pull on the heads (Fig.…”

Section: Membrane Fusion Mechanismsmentioning

confidence: 99%

Receptor-mediated cell entry of paramyxoviruses: Mechanisms, and consequences for tropism and pathogenesis

Navaratnarajah

Generous

Yousaf

et al. 2020

Journal of Biological Chemistry

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“…1A). Based on our current model of membrane fusion triggering, this region may require structural flexibility to enable receptor binding-induced conformational changes of H, leading to F activation and ensuing fusion pore formation (27,33).…”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, while the structure of the entire H-stalk linker module (aa 140 to 154) remains to be determined, the first part of the following MeV H connector domain was successfully crystalized and was shown to contain a short ␣-helix (H1) contacting the head domain (aa 155 to 166). Interestingly, the length of the following C-terminal unresolved segment (aa 167 to 183) was recently hypothesized to be crucial for the generation of productive H proteins by controlling proper tetrameric oligomerization (33). The most recent model of membrane fusion triggering indicates that CDV/MeV H-stalk, connector, and head domains fold into native structures that enable intracellular assembly of H/F complexes while temporarily inhibiting the constitutive F-protein activation domain in the central stalk region (referred to as the autorepressed state).…”

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confidence: 99%

Regulatory Role of the Morbillivirus Attachment Protein Head-to-Stalk Linker Module in Membrane Fusion Triggering

Herren

Shrestha

Wyss

et al. 2018

J Virol

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Morbillivirus (e.g., measles virus [MeV] and canine distemper virus [CDV]) host cell entry is coordinated by two interacting envelope glycoproteins, namely, an attachment (H) protein and a fusion (F) protein. The ectodomain of H proteins consists of stalk, connector, and head domains that assemble into functional noncovalent dimer-of-dimers. The role of the C-terminal module of the H-stalk domain (termed linker) and the connector, although putatively able to assume flexible structures and allow receptor-induced structural rearrangements, remains largely unexplored. Here, we carried out a nonconservative mutagenesis scan analysis of the MeV and CDV H-linker/connector domains. Our data demonstrated that replacing isoleucine 146 in H-linker (H-I146) with any charged amino acids prevented virus-mediated membrane fusion activity, despite proper trafficking of the mutants to the cell surface and preserved binding efficiency to the SLAM/CD150 receptor. Nondenaturing electrophoresis revealed that these charged amino acid changes led to the formation of irregular covalent H tetramers rather than functional dimer-of-dimers formed when isoleucine or other hydrophobic amino acids were present at residue position 146. Remarkably, we next demonstrated that covalent H tetramerization was not the only mechanism preventing F activation. Indeed, the neutral glycine mutant (H-I146G), which exhibited strong covalent tetramerization propensity, maintained limited fusion promotion activity. Conversely, charged H-I146 mutants, which additionally carried alanine substitution of natural cysteines (H-C139A and H-C154A) and thus were unable to form covalently linked tetramers, were fusion activation defective. Our data suggest a dual regulatory role of the hydrophobic residue at position 146 of the morbillivirus head-to-stalk H-linker module: securing the assembly of productive dimer-of-dimers and contributing to receptor-induced F-triggering activity. MeV and CDV remain important human and animal pathogens. Development of antivirals may significantly support current global vaccination campaigns. Cell entry is orchestrated by two interacting glycoproteins (H and F). The current hypothesis postulates that tetrameric H ectodomains (composed of stalk, connector, and head domains) undergo receptor-induced rearrangements to productively trigger F; these conformational changes may be regulated by the H-stalk C-terminal module (linker) and the following connector domain. Mutagenesis scan analysis of both microdomains revealed that replacing amino acid 146 in the H-linker region with nonhydrophobic residues produced covalent H tetramers which were compromised in triggering membrane fusion activity. However, these mutant proteins retained their ability to traffic to the cell surface and to bind to the virus receptor. These data suggest that the morbillivirus linker module contributes to the folding of functional pre-F-triggering H tetramers. Furthermore, such structures might be critical to convert receptor engagement into F activation.

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“…The forces responsible for coupling receptor binding by the head to F activation by the stalk have not been elucidated. However, recent work by Navaratnarajah et al (83) has indicated that the rigidity and length and of the measles H head-stalk linker segment influence H tetramerization and fusion promotion.…”

Section: Discussionmentioning

confidence: 99%

Flexibility of the Head-Stalk Linker Domain of Paramyxovirus HN Glycoprotein Is Essential for Triggering Virus Fusion

Adu-Gyamfi

Kim

Jardetzky

et al. 2016

J Virol

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The Paramyxoviridae comprise a large family of enveloped, negative-sense, single-stranded RNA viruses with significant economic and public health implications. For nearly all paramyxoviruses, infection is initiated by fusion of the viral and host cell plasma membranes in a pH-independent fashion. Fusion is orchestrated by the receptor binding protein hemagglutinin-neuraminidase (HN; also called H or G depending on the virus type) protein and a fusion (F) protein, the latter undergoing a major refolding process to merge the two membranes. Mechanistic details regarding the coupling of receptor binding to F activation are not fully understood. Here, we have identified the flexible loop region connecting the bulky enzymatically active head and the four-helix bundle stalk to be essential for fusion promotion. Proline substitution in this region of HN of parainfluenza virus 5 (PIV5) and Newcastle disease virus HN abolishes cell-cell fusion, whereas HN retains receptor binding and neuraminidase activity. By using reverse genetics, we engineered recombinant PIV5-EGFP viruses with mutations in the head-stalk linker region of HN. Mutations in this region abolished virus recovery and infectivity. In sum, our data suggest that the loop region acts as a "hinge" around which the bulky head of HN swings to-and-fro to facilitate timely HN-mediate F-triggering, a notion consistent with the stalk-mediated activation model of paramyxovirus fusion. IMPORTANCE Paramyxovirus fusion with the host cell plasma membrane is essential for virus infection. Membrane fusion is orchestrated via interaction of the receptor binding protein (HN, H, or G) with the viral fusion glycoprotein (F). Two distinct models have been suggested to describe the mechanism of fusion: these include "the clamp" and the "provocateur" model of activation. By using biochemical and reverse genetics tools, we have obtained strong evidence in favor of the HN stalk-mediated activation of paramyxovirus fusion. Specifically, our data strongly support the notion that the short linker between the head and stalk plays a role in "conformational switching" of the head group to facilitate F-HN interaction and triggering. The Paramyxoviridae comprise a large family of enveloped, negative sense, single-stranded RNA viruses that are responsible for many important human and other animal diseases. Among these viruses are mumps virus, measles virus, respiratory syncytial virus, canine distemper virus, Newcastle disease virus (NDV), and parainfluenza viruses 1 to 5 (PIV1-5), as well as the Hendra and Nipah viruses (1-13). Paramyxoviruses cause significant threat to public health and safety and an economic loss to agribusiness. For entry into cells, all paramyxoviruses require fusion of their membrane with their target host cell plasma membrane (4, 14-21). A detailed understanding of the fusion mechanism is key to the development of therapeutic and vaccine strategies to prevent outbreaks.Unlike enveloped viruses that require a single glycoprotein for fusion, such as influenza v...

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A Structurally Unresolved Head Segment of Defined Length Favors Proper Measles Virus Hemagglutinin Tetramerization and Efficient Membrane Fusion Triggering

Cited by 21 publications

References 41 publications

Receptor-mediated cell entry of paramyxoviruses: Mechanisms, and consequences for tropism and pathogenesis

Receptor-mediated cell entry of paramyxoviruses: Mechanisms, and consequences for tropism and pathogenesis

Regulatory Role of the Morbillivirus Attachment Protein Head-to-Stalk Linker Module in Membrane Fusion Triggering

Flexibility of the Head-Stalk Linker Domain of Paramyxovirus HN Glycoprotein Is Essential for Triggering Virus Fusion

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