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Independent regulation of reovirus membrane penetration and apoptosis by the mu1 phi domain.

Danthi P, Coffey CM, Parker JS, Abel TW, Dermody TS - PLoS Pathog. (2008)

Bottom Line: We found that mutations in phi diminish reovirus membrane penetration efficiency by preventing conformational changes that lead to generation of key reovirus entry intermediates.Independent of effects on membrane penetration, amino acid substitutions in phi affect the apoptotic potential of reovirus, suggesting that phi initiates apoptosis subsequent to cytosolic delivery.These results indicate that the phi domain of mu1 plays an important regulatory role in reovirus-induced apoptosis and disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, USA. pdanthi@indiana.edu

ABSTRACT
Apoptosis plays an important role in the pathogenesis of reovirus encephalitis. Reovirus outer-capsid protein mu1, which functions to penetrate host cell membranes during viral entry, is the primary regulator of apoptosis following reovirus infection. Ectopic expression of full-length and truncated forms of mu1 indicates that the mu1 phi domain is sufficient to elicit a cell death response. To evaluate the contribution of the mu1 phi domain to the induction of apoptosis following reovirus infection, phi mutant viruses were generated by reverse genetics and analyzed for the capacity to penetrate cell membranes and elicit apoptosis. We found that mutations in phi diminish reovirus membrane penetration efficiency by preventing conformational changes that lead to generation of key reovirus entry intermediates. Independent of effects on membrane penetration, amino acid substitutions in phi affect the apoptotic potential of reovirus, suggesting that phi initiates apoptosis subsequent to cytosolic delivery. In comparison to wild-type virus, apoptosis-defective phi mutant viruses display diminished neurovirulence following intracranial inoculation of newborn mice. These results indicate that the phi domain of mu1 plays an important regulatory role in reovirus-induced apoptosis and disease.

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Related in: MedlinePlus

Apoptosis-defective ϕ mutants display attenuated virulence.ND4 Swiss Webster mice were inoculated intracranially with 50 PFU of rsT3D or the indicated ϕ mutant. (A) Mice (18–20) were monitored for survival over 21 days. *, P<0.05 as determined by logrank test in comparison to rsT3D. (B) Brains from infected mice were resected at the times shown and homogenized by freeze-thaw and sonication. Viral titers in brain homogenates were determined by plaque assay. Results are expressed as the mean viral titer (for 6–12 animals). Error bars indicate SD.
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ppat-1000248-g006: Apoptosis-defective ϕ mutants display attenuated virulence.ND4 Swiss Webster mice were inoculated intracranially with 50 PFU of rsT3D or the indicated ϕ mutant. (A) Mice (18–20) were monitored for survival over 21 days. *, P<0.05 as determined by logrank test in comparison to rsT3D. (B) Brains from infected mice were resected at the times shown and homogenized by freeze-thaw and sonication. Viral titers in brain homogenates were determined by plaque assay. Results are expressed as the mean viral titer (for 6–12 animals). Error bars indicate SD.

Mentions: Intracranial inoculation of 2 d old mice with type 3 reovirus strains such as T3D at doses as low as 10 PFU produces lethal encephalitis [7]–[9]. To determine whether in vitro differences in the apoptosis-inducing capacity of ϕ mutants affect reovirus disease, we inoculated newborn mice intracranially with 50 PFU of either rsT3D or the apoptosis-defective ϕ mutants, K594D or I595K, and monitored mice for survival and signs of neurological disease for an interval of 21 d (Figure 6A). We noted a significant difference in the survival of mice infected with rsT3D and either K594D or I595K. The median survival for rsT3D-infected mice was 11 d. In contrast, median survival for K594- or I595K-infected mice was 13 d. Moreover, a substantially greater proportion of mice survived infection with the ϕ mutant viruses (∼30%) in comparison to those infected with rsT3D (∼15%). These data indicate that ϕ residues Lys594 and Ile595 influence reovirus neurovirulence.


Independent regulation of reovirus membrane penetration and apoptosis by the mu1 phi domain.

Danthi P, Coffey CM, Parker JS, Abel TW, Dermody TS - PLoS Pathog. (2008)

Apoptosis-defective ϕ mutants display attenuated virulence.ND4 Swiss Webster mice were inoculated intracranially with 50 PFU of rsT3D or the indicated ϕ mutant. (A) Mice (18–20) were monitored for survival over 21 days. *, P<0.05 as determined by logrank test in comparison to rsT3D. (B) Brains from infected mice were resected at the times shown and homogenized by freeze-thaw and sonication. Viral titers in brain homogenates were determined by plaque assay. Results are expressed as the mean viral titer (for 6–12 animals). Error bars indicate SD.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2600812&req=5

ppat-1000248-g006: Apoptosis-defective ϕ mutants display attenuated virulence.ND4 Swiss Webster mice were inoculated intracranially with 50 PFU of rsT3D or the indicated ϕ mutant. (A) Mice (18–20) were monitored for survival over 21 days. *, P<0.05 as determined by logrank test in comparison to rsT3D. (B) Brains from infected mice were resected at the times shown and homogenized by freeze-thaw and sonication. Viral titers in brain homogenates were determined by plaque assay. Results are expressed as the mean viral titer (for 6–12 animals). Error bars indicate SD.
Mentions: Intracranial inoculation of 2 d old mice with type 3 reovirus strains such as T3D at doses as low as 10 PFU produces lethal encephalitis [7]–[9]. To determine whether in vitro differences in the apoptosis-inducing capacity of ϕ mutants affect reovirus disease, we inoculated newborn mice intracranially with 50 PFU of either rsT3D or the apoptosis-defective ϕ mutants, K594D or I595K, and monitored mice for survival and signs of neurological disease for an interval of 21 d (Figure 6A). We noted a significant difference in the survival of mice infected with rsT3D and either K594D or I595K. The median survival for rsT3D-infected mice was 11 d. In contrast, median survival for K594- or I595K-infected mice was 13 d. Moreover, a substantially greater proportion of mice survived infection with the ϕ mutant viruses (∼30%) in comparison to those infected with rsT3D (∼15%). These data indicate that ϕ residues Lys594 and Ile595 influence reovirus neurovirulence.

Bottom Line: We found that mutations in phi diminish reovirus membrane penetration efficiency by preventing conformational changes that lead to generation of key reovirus entry intermediates.Independent of effects on membrane penetration, amino acid substitutions in phi affect the apoptotic potential of reovirus, suggesting that phi initiates apoptosis subsequent to cytosolic delivery.These results indicate that the phi domain of mu1 plays an important regulatory role in reovirus-induced apoptosis and disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, USA. pdanthi@indiana.edu

ABSTRACT
Apoptosis plays an important role in the pathogenesis of reovirus encephalitis. Reovirus outer-capsid protein mu1, which functions to penetrate host cell membranes during viral entry, is the primary regulator of apoptosis following reovirus infection. Ectopic expression of full-length and truncated forms of mu1 indicates that the mu1 phi domain is sufficient to elicit a cell death response. To evaluate the contribution of the mu1 phi domain to the induction of apoptosis following reovirus infection, phi mutant viruses were generated by reverse genetics and analyzed for the capacity to penetrate cell membranes and elicit apoptosis. We found that mutations in phi diminish reovirus membrane penetration efficiency by preventing conformational changes that lead to generation of key reovirus entry intermediates. Independent of effects on membrane penetration, amino acid substitutions in phi affect the apoptotic potential of reovirus, suggesting that phi initiates apoptosis subsequent to cytosolic delivery. In comparison to wild-type virus, apoptosis-defective phi mutant viruses display diminished neurovirulence following intracranial inoculation of newborn mice. These results indicate that the phi domain of mu1 plays an important regulatory role in reovirus-induced apoptosis and disease.

Show MeSH
Related in: MedlinePlus