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A conserved alpha-herpesvirus protein necessary for axonal localization of viral membrane proteins.

Tomishima MJ, Enquist LW - J. Cell Biol. (2001)

Bottom Line: We conclude that the Us9 membrane protein controls axonal localization of diverse viral membrane proteins but not that of capsid or tegument proteins.The data support a model where virion subassemblies but not complete virions are transported in the axon.Our results provide new insight into the process of virion assembly and exit from neurons that leads to directional spread of herpesviruses in the nervous system.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.

ABSTRACT
Pseudorabies virus, an alpha-herpesvirus, is capable of infecting the nervous system and spreading between synaptically connected neurons in diverse hosts. At least three viral membrane proteins (gE, gI, and Us9) are necessary for the spread of infection from presynaptic to postsynaptic neurons (anterograde spread) in infected rodents. To understand how these proteins effect anterograde spread between neurons, we analyzed the subcellular localization of viral proteins after infection of cultured rat sympathetic neurons with wild-type or mutant viruses. After Us9- mutant infections but not gE- mutant infections, only a subset of the viral structural proteins had entered axons. Surprisingly, capsid and tegument proteins but not viral membrane proteins were detected in axons. The spread of Us9 missense mutants in the rodent nervous system correlated with the amount of viral membrane proteins localized to axons. We conclude that the Us9 membrane protein controls axonal localization of diverse viral membrane proteins but not that of capsid or tegument proteins. The data support a model where virion subassemblies but not complete virions are transported in the axon. Our results provide new insight into the process of virion assembly and exit from neurons that leads to directional spread of herpesviruses in the nervous system.

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The axonal localization of viral membrane proteins requires Us9. (A) Neurons were infected with the wild-type (a, b, and c) and the Us9- virus PRV160 (d, e, and f) such that every neuron was infected for 16 h and then were fixed and permeabilized. Infected neurons were labeled with antibodies that recognize gB (a and d), gC (b and e), and gE (c and f). Arrows point to axons that are labeled with viral membrane proteins in the wild-type infections. (B) The same experiment as above but at lower magnification. Bars: (A) 25 μm; (B) 150 μm.
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fig3: The axonal localization of viral membrane proteins requires Us9. (A) Neurons were infected with the wild-type (a, b, and c) and the Us9- virus PRV160 (d, e, and f) such that every neuron was infected for 16 h and then were fixed and permeabilized. Infected neurons were labeled with antibodies that recognize gB (a and d), gC (b and e), and gE (c and f). Arrows point to axons that are labeled with viral membrane proteins in the wild-type infections. (B) The same experiment as above but at lower magnification. Bars: (A) 25 μm; (B) 150 μm.

Mentions: We next determined whether gC and gE, two abundant but nonessential virion membrane proteins, localize to axons in the absence of Us9 (Fig. 3) . The results were similar to those for gB described above: the amount of gC and gE and the distance the membrane proteins had traveled in the axon were dramatically reduced during Us9- mutant infections compared with wild-type infections. Thus, three diverse virion membrane proteins (gB, gC, and gE) required Us9 protein to localize to and fill axons, even though no obvious defect in the expression or localization of these glycoproteins within the cell body was apparent by confocal microscopy.


A conserved alpha-herpesvirus protein necessary for axonal localization of viral membrane proteins.

Tomishima MJ, Enquist LW - J. Cell Biol. (2001)

The axonal localization of viral membrane proteins requires Us9. (A) Neurons were infected with the wild-type (a, b, and c) and the Us9- virus PRV160 (d, e, and f) such that every neuron was infected for 16 h and then were fixed and permeabilized. Infected neurons were labeled with antibodies that recognize gB (a and d), gC (b and e), and gE (c and f). Arrows point to axons that are labeled with viral membrane proteins in the wild-type infections. (B) The same experiment as above but at lower magnification. Bars: (A) 25 μm; (B) 150 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196449&req=5

fig3: The axonal localization of viral membrane proteins requires Us9. (A) Neurons were infected with the wild-type (a, b, and c) and the Us9- virus PRV160 (d, e, and f) such that every neuron was infected for 16 h and then were fixed and permeabilized. Infected neurons were labeled with antibodies that recognize gB (a and d), gC (b and e), and gE (c and f). Arrows point to axons that are labeled with viral membrane proteins in the wild-type infections. (B) The same experiment as above but at lower magnification. Bars: (A) 25 μm; (B) 150 μm.
Mentions: We next determined whether gC and gE, two abundant but nonessential virion membrane proteins, localize to axons in the absence of Us9 (Fig. 3) . The results were similar to those for gB described above: the amount of gC and gE and the distance the membrane proteins had traveled in the axon were dramatically reduced during Us9- mutant infections compared with wild-type infections. Thus, three diverse virion membrane proteins (gB, gC, and gE) required Us9 protein to localize to and fill axons, even though no obvious defect in the expression or localization of these glycoproteins within the cell body was apparent by confocal microscopy.

Bottom Line: We conclude that the Us9 membrane protein controls axonal localization of diverse viral membrane proteins but not that of capsid or tegument proteins.The data support a model where virion subassemblies but not complete virions are transported in the axon.Our results provide new insight into the process of virion assembly and exit from neurons that leads to directional spread of herpesviruses in the nervous system.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.

ABSTRACT
Pseudorabies virus, an alpha-herpesvirus, is capable of infecting the nervous system and spreading between synaptically connected neurons in diverse hosts. At least three viral membrane proteins (gE, gI, and Us9) are necessary for the spread of infection from presynaptic to postsynaptic neurons (anterograde spread) in infected rodents. To understand how these proteins effect anterograde spread between neurons, we analyzed the subcellular localization of viral proteins after infection of cultured rat sympathetic neurons with wild-type or mutant viruses. After Us9- mutant infections but not gE- mutant infections, only a subset of the viral structural proteins had entered axons. Surprisingly, capsid and tegument proteins but not viral membrane proteins were detected in axons. The spread of Us9 missense mutants in the rodent nervous system correlated with the amount of viral membrane proteins localized to axons. We conclude that the Us9 membrane protein controls axonal localization of diverse viral membrane proteins but not that of capsid or tegument proteins. The data support a model where virion subassemblies but not complete virions are transported in the axon. Our results provide new insight into the process of virion assembly and exit from neurons that leads to directional spread of herpesviruses in the nervous system.

Show MeSH
Related in: MedlinePlus