An Immunodominant N-Terminal Region of VP1 Protein of Poliovirion That Is Buried in Crystal Structure Can Be Exposed in Solution

Roivainen, Merja; Piirainen, Liisa; Rysä, T; Närvänen, Ale; Hovi, Tapani

doi:10.1006/viro.1993.1427

Cited by 79 publications

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“…6). In rhinovirus and related picornaviruses, this process can be attributed to the dynamic feature of the viral capsids (17,18,22), as well as the fragmented nature of the receptor binding site (4,11,16,28). Expansion of nonenveloped virus capsids catalyzed by receptor binding or other cellular factors could precede uncoating during virus entry into cells, as shown here for HRV and its ICAM-1 receptor.…”

Section: Discussionmentioning

confidence: 74%

“…Stable virus-receptor complexes (H3R C ) are formed at low temperatures by receptor binding to a close virus conformation, represented by the crystal structure (28). The capsid dynamics (or breathing) opens the interprotomer junction, so that the internal N-terminal regions of VP1 and VP4 (labeled as N-VP1-VP4) became exposed simultaneously at physiological temperatures (17,18,22). This expanded conformation is maintained by receptor binding between two adjacent protomers and to the exposed region of VP1, as shown by the cryo-EM H3R H structure.…”

Section: Discussionmentioning

confidence: 99%

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Structural Analysis of Human Rhinovirus Complexed with ICAM-1 Reveals the Dynamics of Receptor-Mediated Virus Uncoating

Casasnovas

Cheng

2003

J Virol

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Intercellular adhesion molecule 1 (ICAM-1) functions as the cellular receptor for the major group of human rhinoviruses, being not only the target of viral attachment but also the mediator of viral uncoating. The configurations of HRV3-ICAM-1 complexes prepared both at 4°C and physiological temperature (37°C) were analyzed by cryoelectron microscopy and image reconstruction. The particle diameters of two complexes (with and without RNA) representing uncoating intermediates generated at 37°C were each 4% larger than that of those prepared at 4°C. The larger virus particle arose by an expansive movement of the capsid pentamers along the fivefold axis, which loosens interprotomer contacts, particularly at the canyon region where the ICAM-1 receptor bound. Particle expansion required receptor binding and preceded the egress of the viral RNA. These observations suggest that receptor-mediated uncoating could be a consequence of restrained capsid motion, where the bound receptors maintain the viral capsid in an expanded open state for subsequent genome release.Human rhinoviruses (HRVs), a genus of the picornavirus family, are the major cause of the common cold in humans (25). They constitute a group of approximately 100 serotypes, all containing a single-stranded RNA genome encapsulated into an icosahedral capsid. Crystal structures of several rhinovirus serotypes demonstrated that the capsid is made of 60 protomers, each having a copy of four structural proteins (VP1 to VP4) (10, 24, 29). The three major proteins (VP1, VP2, and VP3) build the capsid shell. They have a central "jelly roll" structure, with their N-terminal regions being located close to the internal VP4 and RNA genome. Biochemical experiments showed that VP4 and internal N-terminal residues of VP1 were accessible to immobilized trypsin in HRV serotype 14 (HRV14), revealing that they became exposed spontaneously outside of the capsid (17). These findings demonstrated that the capsid shell of HRV is a dynamic, breathing entity.The most highly conserved structural feature among HRVs is a surface depression around the fivefold axes, the so-called canyon (25). The canyon is composed of the north wall (built by VP1) around the fivefold axis and the south wall (built mainly by VP2 and VP3). While the most accessible residues along the canyon walls are hypervariable, the less exposed residues in the canyon floor are conserved and used for receptor binding, as the strategy allowing the virus to escape antibody neutralization (23). There is a hydrophobic pocket in VP1 directly underneath the canyon floor. The pocket appears empty in HRV3 and HRV14 (29) but is filled with electron density resembling a fatty acid (pocket factor) in the structures of HRV2 and HRV16 (10, 27). The pocket factor stabilizes the virion during its cell-to-cell transit (19). Hydrophobic antiviral compounds (WIN compounds) were found to bind to the VP1 pocket and to inhibit capsid breathing (17).The major group of HRVs use the canyon region for binding to its cellular receptor, intercellula...

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Section: Discussionmentioning

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Structural Analysis of Human Rhinovirus Complexed with ICAM-1 Reveals the Dynamics of Receptor-Mediated Virus Uncoating

Casasnovas

Cheng

2003

J Virol

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“…Internal plasticity and motions of the capsid proteins can allow access to buried regions, which often play an important role in the viral life cycle [46]. Indeed, multiple antibodies against picornaviruses and flaviviruses that bind to normally inaccessible sites on the viral capsid were shown to be highly neutralizing [47][48][49][50][51][52]. For rhinoviruses and polioviruses, buried regions of internal VP4 protein are transiently exposed due to the capsid "breathing" and are targeted by neutralizing mAbs.…”

Section: Discussionmentioning

confidence: 99%

Nanobodies Targeting Norovirus Capsid Reveal Functional Epitopes and Potential Mechanisms of Neutralization

Koromyslova

Hansman

2018

Biophysical Journal

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Norovirus is the leading cause of gastroenteritis worldwide. Despite recent developments in norovirus propagation in cell culture, these viruses are still challenging to grow routinely. Moreover, little is known on how norovirus infects the host cells, except that histo-blood group antigens (HBGAs) are important binding factors for infection and cell entry. Antibodies that bind at the HBGA pocket and block attachment to HBGAs are believed to neutralize the virus. However, additional neutralization epitopes elsewhere on the capsid likely exist and impeding the intrinsic structural dynamics of the capsid could be equally important. In the current study, we investigated a panel of Nanobodies in order to probe functional epitopes that could trigger capsid rearrangement and/ or interfere with HBGA binding interactions. The precise binding sites of six Nanobodies (Nano-4, Nano-14, Nano-26, Nano-27, Nano-32, and Nano-42) were identified using X-ray crystallography. We showed that these Nanobodies bound on the top, side, and bottom of the norovirus protruding domain. The impact of Nanobody binding on norovirus capsid morphology was analyzed using electron microscopy and dynamic light scattering. We discovered that distinct Nanobody epitopes were associated with varied changes in particle structural integrity and assembly. Interestingly, certain Nanobody-induced capsid morphological changes lead to the capsid protein degradation and viral RNA exposure. Moreover, Nanobodies employed multiple inhibition mechanisms to prevent norovirus attachment to HBGAs, which included steric obstruction (Nano-14), allosteric interference (Nano-32), and violation of normal capsid morphology (Nano-26 and Nano-85). Finally, we showed that two Nanobodies (Nano-26 and Nano-85) not only compromised capsid integrity and inhibited VLPs attachment to HBGAs, but also recognized a broad panel of norovirus genotypes with high affinities. Consequently, Nano-26 and Nano-85 have a great potential to function as novel therapeutic agents against human noroviruses. PLOS Author summaryWe determined the binding sites of six novel human norovirus specific Nanobodies (Nano-4, Nano-14, Nano-26, Nano-27, Nano-32, and Nano-42) using X-ray crystallography. The unique Nanobody recognition epitopes were correlated with their potential neutralizing capacities. We showed that one Nanobody (Nano-26) bound numerous genogroup II genotypes and interacted with highly conserved capsid residues. Four Nanobodies (Nano-4, Nano-26, Nano-27, and Nano-42) bound to occluded regions on the intact particles and impaired normal capsid morphology and particle integrity. One Nanobody (Nano-14) bound contiguous to the HBGA pocket and interacted with several residues involved in binding HBGAs. We found that the Nanobodies delivered multiple inhibition mechanisms, which included steric obstruction, allosteric interference, and disruption of the capsid stability. Our data suggested that the HBGA pocket might not be an ideal target for drug development, since the surrounding regio...

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“…In the case of poliovirus, however, antibodies were raised against VP4 and the N termini of VP1 of poliovirus serotype I (15,21). It was shown that these antibodies are capable of neutralizing the virion despite the fact that those portions of the capsid protein are buried in the interior of the capsid at the capsid-RNA interface (8).…”

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confidence: 99%

Antibodies to the Buried N Terminus of Rhinovirus VP4 Exhibit Cross-Serotypic Neutralization

Katpally

Freed

et al. 2009

J Virol

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Development of a vaccine for the common cold has been thwarted by the fact that there are more than 100 serotypes of human rhinovirus (HRV). We previously demonstrated that the HRV14 capsid is dynamic and transiently displays the buried N termini of viral protein 1 (VP1) and VP4. Here, further evidence for this "breathing" phenomenon is presented, using antibodies to several peptides representing the N terminus of VP4. The antibodies form stable complexes with intact HRV14 virions and neutralize infectivity. Since this region of VP4 is highly conserved among all of the rhinoviruses, antiviral activity by these anti-VP4 antibodies is cross-serotypic. The antibodies inhibit HRV16 infectivity in a temperature-and time-dependent manner consistent with the breathing behavior. Monoclonal and polyclonal antibodies raised against the 30-residue peptide do not react with peptides shorter than 24 residues, suggesting that these peptides are adopting three-dimensional conformations that are highly dependent upon the length of the peptide. Furthermore, there is evidence that the N termini of VP4 are interacting with each other upon extrusion from the capsid. A Ser5Cys mutation in VP4 yields an infectious virus that forms cysteine cross-links in VP4 when the virus is incubated at room temperature but not at 4°C. The fact that all of the VP4s are involved in this cross-linking process strongly suggests that VP4 forms specific oligomers upon extrusion. Together these results suggest that it may be possible to develop a pan-serotypic peptide vaccine to HRV, but its design will likely require details about the oligomeric structure of the exposed termini.

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An Immunodominant N-Terminal Region of VP1 Protein of Poliovirion That Is Buried in Crystal Structure Can Be Exposed in Solution

Cited by 79 publications

References 0 publications

Structural Analysis of Human Rhinovirus Complexed with ICAM-1 Reveals the Dynamics of Receptor-Mediated Virus Uncoating

Structural Analysis of Human Rhinovirus Complexed with ICAM-1 Reveals the Dynamics of Receptor-Mediated Virus Uncoating

Nanobodies Targeting Norovirus Capsid Reveal Functional Epitopes and Potential Mechanisms of Neutralization

Antibodies to the Buried N Terminus of Rhinovirus VP4 Exhibit Cross-Serotypic Neutralization

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