Measles Virus Glycoprotein Complex Assembly, Receptor Attachment, and Cell Entry (original) (raw)
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Journal of Virology, 2008
Measles is one of the most contagious human infectious diseases and remains a major cause of childhood morbidity and mortality worldwide. The signaling lymphocyte activation molecule (SLAM), also called CD150, is a cellular receptor for measles virus (MV), presumably accounting for its tropism for immune cells and its immunosuppressive properties. On the other hand, pathological studies have shown that MV also infects epithelial cells at a later stage of infection, although its mechanism has so far been unknown. In this study, we show that wild-type MV can infect and produce syncytia in human polarized epithelial cell lines independently of SLAM and CD46 (a receptor for the vaccine strains of MV). Progeny viral particles are released exclusively from the apical surface of these polarized epithelial cell lines. We have also identified amino acid residues on the MV attachment protein that are likely to interact with a putative receptor on epithelial cells. All of these residues have aromatic side chains and may form a receptor-binding pocket located in a different position from the putative SLAM-and CD46-binding sites on the MV attachment protein. Thus, our results indicate that MV has an intrinsic ability to infect both polarized epithelial and immune cells by using distinctive receptorbinding sites on the attachment protein corresponding to each of their respective receptors. The ability of MV to infect polarized epithelial cells and its exclusive release from the apical surface may facilitate its efficient transmission via aerosol droplets, resulting in its highly contagious nature.
Cell Entry by Measles Virus: Long Hybrid Receptors Uncouple Binding from Membrane Fusion
1996
The pH-independent fusion of membranes induced by measles virus (MV) requires, in addition to the fusion-competent protein F, hemagglutinin (H), and on the target membrane, the virus receptor CD46. We constructed hybrid receptors composed of different numbers and combinations of the four CD46 short consensus repeat (SCR) domains, followed by immunoglobulin-like domains of another cell surface protein, CD4. Hybrid proteins containing SCRs I and II bound MV particles and conferred fusion competence to rodent cells. SCRs III and/or IV strengthened MV binding. Increasing the distance between the MV binding site and the transmembrane domain enhanced virus binding but reduced fusion efficiency. A hybrid protein predicted to be about 120 Å (12 nm) longer than the standard receptor lost fusion support function and was dominant negative over a functional receptor. These data indicate that receptor protein length influences virus binding and determines fusion efficiency.
Efficiency of Measles Virus Entry and Dissemination through Different Receptors
Journal of Virology, 2002
The efficiency with which different measles virus (MV) strains enter cells through the immune cell-specific protein SLAM (CD150) or other receptors, including the ubiquitous protein CD46, may influence their pathogenicity. We compared the cell entry efficiency of recombinant MV differing only in their attachment protein hemagglutinin (H). We constructed these viruses with an additional gene expressing an autofluorescent reporter protein to allow direct detection of every infected cell. A virus with a wild-type H protein entered cells through SLAM two to three times more efficiently than a virus with the H protein of the attenuated strain Edmonston, whereas cell entry efficiency through CD46 was lower. However, these subtle differences were amplified at the cell fusion stage because the wild-type H protein failed to fuse CD46-expressing cells. We also proved formally that a mutation in H protein residue 481 (asparagine to tyrosine) results in improved CD46-specific entry. To define the selective pressure exerted on that codon, we monitored its evolution in different H protein backgrounds and found that several passages in CD46-expressing Vero cells were necessary to shift it in the majority of the MV RNA. To verify the importance of these observations for human infections, we examined MV entry into peripheral blood mononuclear cells and observed that viruses with asparagine 481 H proteins infect these cells more efficiently.
Journal of Virology, 2008
The glycoprotein complex of paramyxoviruses mediates receptor binding and membrane fusion. In particular, the measles virus (MV) fusion (F) protein executes membrane fusion, after receptor binding by the hemagglutinin (H) protein. Structures and single amino acids influencing fusion function have been identified in the F-protein ectodomain and cytoplasmic tail, but not in its transmembrane (TM) region. Since this region influences function of the envelope proteins of other viruses, we examined its role in the MV F protein. Alanine-scanning mutagenesis revealed that an F protein with a single mutation of a central TM region leucine (L507A) was more fusogenic than the unmodified F protein while retaining similar kinetics of proteolytic processing. In contrast, substitution of residues located near the edges of the lipid bilayer reduced fusion activity. This was true not only when the mutated F proteins were coexpressed with H but also in the context of infections with recombinant viruses. Analysis of the H-F complexes with reduced fusion activities revealed that more precursor (F 0) than activated (F 1؉2) protein coprecipitated with H. In contrast, in complexes with enhanced fusion activity, including H-F L507A , the F 0 /F 1؉2 ratio shifted toward F 1؉2. Thus, fusion activity correlated with an active F-H protein complex, and the MV F protein TM region modulated availability of this complex.
Journal of Virology, 2004
expressed only in immune cells or through the ubiquitously expressed regulator of complement activation, CD46. To identify residues on the attachment protein hemagglutinin (H) essential for fusion support through either receptor, we devised a strategy based on analysis of morbillivirus H-protein sequences, iterative cycles of mutant protein production followed by receptor-based functional assays, and a novel MV H three-dimensional model. This model uses the Newcastle disease virus hemagglutinin-neuraminidase protein structure as a template. We identified seven amino acids important for SLAM-and nine for CD46 (Vero cell receptor)induced fusion. The MV H three-dimensional model suggests (i) that SLAM-and CD46-relevant residues are located in contiguous areas in propeller -sheets 5 and 4, respectively; (ii) that two clusters of SLAM-relevant residues exist and that they are accessible for receptor contact; and (iii) that several CD46-relevant amino acids may be shielded from direct receptor contacts. It appears likely that certain residues support receptorspecific H-protein conformational changes. To verify the importance of the H residues identified with the cell-cell fusion assays for virus entry into cells, we transferred the relevant mutations into genomic MV cDNAs. Indeed, we were able to recover recombinant viruses, and we showed that these replicate selectively in cells expressing SLAM or CD46. Selectively receptor-blind viruses will be used to study MV pathogenesis and may have applications for the production of novel vaccines and therapeutics.
The heads of the measles virus attachment protein move to transmit the fusion-triggering signal
Nature Structural & Molecular Biology, 2011
The measles virus entry system, constituted of attachment (hemagglutinin, H) and fusion proteins, operates based on a variety of natural and targeted receptors. However, the mechanism triggering fusion of the viral envelope with the plasma membrane is not understood. Here we tested a model considering that the two heads of an H-dimer, which are covalently linked at their base, after binding two receptor molecules, move relative to each other to transmit the fusion-triggering signal. Indeed, stabilizing the H-dimer interface by additional inter-molecular disulfide bonds prevented membrane fusion, an effect reversed by a reducing agent. Moreover, a membraneanchored designated receptor efficiently triggered fusion, provided it engaged the H-dimer at locations proximal to where the natural receptors bind, and distal to the H-dimer interface. We discuss how receptors may force H-heads to switch partners and transmit the fusion-triggering signal. Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Functional and structural interactions between measles virus hemagglutinin and CD46
Journal of Virology, 1995
We analyzed the roles of the individual measles virus (MV) surface glycoproteins in mediating functional and structural interactions with human CD46, the primary MV receptor. On one cell population, recombinant vaccinia virus vectors were used to produce the MV hemagglutinin (H) and fusion (F) glycoproteins. As fusion partner cells, various cell types were examined, without or with human CD46 (endogenous or recombinant vaccinia virus encoded). Fusion between the two cell populations was monitored by a quantitative reporter gene activation assay and by syncytium formation. MV glycoproteins promoted fusion with primate cells but not with nonprimate cells; recombinant CD46 rendered nonprimate cells competent for MV glycoprotein-mediated fusion. Markedly different fusion specificity was observed for another morbillivirus, canine distemper virus (CDV): recombinant CDV glycoproteins promoted fusion with primate and nonprimate cells independently of CD46. Fusion by the recombinant MV and C...
Functional and structural interaction between measles virus hemagglutinin and CD46
Journal of Virology
We analyzed the roles of the individual measles virus (MV) surface glycoproteins in mediating functional and structural interactions with human CD46, the primary MV receptor. On one cell population, recombinant vaccinia virus vectors were used to produce the MV hemagglutinin (H) and fusion (F) glycoproteins. As fusion partner cells, various cell types were examined, without or with human CD46 (endogenous or recombinant vaccinia virus encoded). Fusion between the two cell populations was monitored by a quantitative reporter gene activation assay and by syncytium formation. MV glycoproteins promoted fusion with primate cells but not with nonprimate cells; recombinant CD46 rendered nonprimate cells competent for MV glycoprotein-mediated fusion. Markedly different fusion specificity was observed for another morbillivirus, canine distemper virus (CDV): recombinant CDV glycoproteins promoted fusion with primate and nonprimate cells independently of CD46. Fusion by the recombinant MV and C...