Conformational Changes in the Capsid of a Calicivirus upon Interaction with Its Functional Receptor

Abstract

Nonenveloped viral capsids are metastable structures that undergo conformational changes during virus entry that lead to interactions of the capsid or capsid fragments with the cell membrane. For members of the Caliciviridae, neither the nature of these structural changes in the capsid nor the factor(s) responsible for inducing these changes is known. Feline junctional adhesion molecule A (fJAM-A) mediates the attachment and infectious viral entry of feline calicivirus (FCV). Here, we show that the infectivity of some FCV isolates is neutralized following incubation with the soluble receptor at 37°C. We used this property to select mutants resistant to preincubation with the soluble receptor. We isolated and sequenced 24 soluble receptor-resistant (srr) mutants and characterized the growth properties and receptor-binding activities of eight mutants. The location of the mutations within the capsid structure of FCV was mapped using a new 3.6-Å structure of native FCV. The srr mutations mapped to the surface of the P2 domain were buried at the protruding domain dimer interface or were present in inaccessible regions of the capsid protein. Coupled with data showing that both the parental FCV and the srr mutants underwent increases in hydrophobicity upon incubation with the soluble receptor at 37°C, these findings indicate that FCV likely undergoes conformational change upon interaction with its receptor. Changes in FCV capsid conformation following its interaction with fJAM-A may be important for subsequent interactions of the capsid with cellular membranes, membrane penetration, and genome delivery.The interactions between viruses and receptors on the surface of host cells strongly influence viral pathogenesis and regulate morbidity and mortality in the host. Virus-receptor interactions determine the types of cells that can be infected, the pathway of entry into the cell, and the efficiency of productive infection. Interactions between nonenveloped virus capsids and their receptor(s) trigger one or more steps required for infectious entry. These steps can include interaction with other receptors, exposure to low pH or endosomal proteases, or other factors. Ultimately, one or more of these interactions induce changes in capsid conformation that result in the exposure of hydrophobic regions or release of a lipidseeking factor that can interact with and disrupt the limiting cellular membrane to allow the capsid and/or the genome to be delivered to the interior of the cell (reviewed in reference 60).The Caliciviridae are small nonenveloped viruses containing a positive-sense RNA genome (ϳ7 to 8 kb). Several important disease-causing members of the Caliciviridae, including human noroviruses and rabbit hemorrhagic disease virus, cannot be propagated in tissue culture systems (19,56). This has slowed progress on studies of the mechanisms of cellular entry of these viruses. In contrast, feline caliciviruses (FCVs) propagate readily in tissue culture, and two cell surface receptor molecules, feline junctional adhesion molec...

Rhesus enteric calicivirus surrogate model for human norovirus gastroenteritis

“…The role of annexin A2 was indicated in cellular entry of the rabbit vesivirus (González-Reyes at al., 2009). Moreover, supporting our hypothesis, recent studies also suggested receptor-induced conformational changes during FCV entry (Ossiboff et al, 2010). Fig.…”

Epitope Insertion at the N-Terminal Molecular Switch of the Rabbit Hemorrhagic Disease Virus T=3 Capsid Protein Leads to Larger T=4 Capsids

“…High-resolution X-ray structures of several caliciviruses show that the CP three-domain organization (NTA-S-P) is conserved (9,34,37). The NTA are similar and have an important role in capsid assembly; they act as molecular switches that alter subunit interfaces and/or conformations needed to assemble the quasiequivalent Tϭ3 capsid.…”

“…X-ray structures of the norovirus Norwalk virus (NV) VLP (37) as well as San Miguel sea lion virus (SMSV) (9) and feline calicivirus (FCV) (34) virions (both vesiviruses) indicate that the virion comprises 90 CP dimers arranged with Tϭ3 symmetry to form 12 pentamers and 20 hexamers. Each monomer has three domains, an N-terminal arm (NTA), a shell (S) composed of an eight-stranded ␤-sandwich, and a flexible protruding domain (P), facilitating virus-host receptor interactions (27,47) at the outermost surface (6).…”

Characterization of Dengue Virus NS4A and NS4B Protein Interaction

“…An enzyme-linked immunosorbent assay (ELISA) was performed according to a previous report (38) with minor modifications. In brief, purified DENV-2 NS4A protein was diluted in coating buffer (50 mM carbonate/bicarbonate buffer, pH 9.6) and incubated in 96-well ELISA plates (Nunc) (250 ng/well) at 4°C overnight.…”