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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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Us9 is not involved in viral attachment, entry, or replication in SCG neurons. Neurons were infected with the wild-type and the Us9- virus such that every neuron was infected, and the amount of infectious virus (plaque forming units) produced at 1, 8, 16, and 24 h after infection was determined. Each sample was performed in triplicate for both viruses, and only the data for the cell-associated virus is shown in the graph.
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fig9: Us9 is not involved in viral attachment, entry, or replication in SCG neurons. Neurons were infected with the wild-type and the Us9- virus such that every neuron was infected, and the amount of infectious virus (plaque forming units) produced at 1, 8, 16, and 24 h after infection was determined. Each sample was performed in triplicate for both viruses, and only the data for the cell-associated virus is shown in the graph.

Mentions: Us9- mutants grow normally with no obvious defects in attachment, entry, or replication in nonneuronal cells (Brideau et al., 2000a). We observed that the Us9- mutant produced infectious virus at essentially the same rate and to the same extent as wild-type virus in SCG neurons (Fig. 9) . Wild-type and Us9- mutant viruses produced relatively few infectious particles per neuron compared with infection of nonneuronal cell lines such as PK15 cells. The quantity of infectious virus released into the medium was also low compared with nonneuronal cell lines. We note that measurement of released virus is likely to be an underestimate as virus can bind avidly to the poly-lysine substrate required for neuronal growth (unpublished data). Since there are no differences in rate and extent of infectious virus production among wild-type and Us9- viruses, we conclude that Us9 does not affect viral attachment, entry, or replication in SCG neurons during the duration of our experiments. Therefore, the Us9- phenotype is not due to a replication defect.


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

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

Us9 is not involved in viral attachment, entry, or replication in SCG neurons. Neurons were infected with the wild-type and the Us9- virus such that every neuron was infected, and the amount of infectious virus (plaque forming units) produced at 1, 8, 16, and 24 h after infection was determined. Each sample was performed in triplicate for both viruses, and only the data for the cell-associated virus is shown in the graph.
© Copyright Policy
Related In: Results  -  Collection

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

fig9: Us9 is not involved in viral attachment, entry, or replication in SCG neurons. Neurons were infected with the wild-type and the Us9- virus such that every neuron was infected, and the amount of infectious virus (plaque forming units) produced at 1, 8, 16, and 24 h after infection was determined. Each sample was performed in triplicate for both viruses, and only the data for the cell-associated virus is shown in the graph.
Mentions: Us9- mutants grow normally with no obvious defects in attachment, entry, or replication in nonneuronal cells (Brideau et al., 2000a). We observed that the Us9- mutant produced infectious virus at essentially the same rate and to the same extent as wild-type virus in SCG neurons (Fig. 9) . Wild-type and Us9- mutant viruses produced relatively few infectious particles per neuron compared with infection of nonneuronal cell lines such as PK15 cells. The quantity of infectious virus released into the medium was also low compared with nonneuronal cell lines. We note that measurement of released virus is likely to be an underestimate as virus can bind avidly to the poly-lysine substrate required for neuronal growth (unpublished data). Since there are no differences in rate and extent of infectious virus production among wild-type and Us9- viruses, we conclude that Us9 does not affect viral attachment, entry, or replication in SCG neurons during the duration of our experiments. Therefore, the Us9- phenotype is not due to a replication defect.

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