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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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Related in: MedlinePlus

The axonal localization of two capsid proteins does not require Us9. (A) Less than 10% of the neurons were infected for 12 h with the wild-type (a) or the Us9- virus (b) and then were fixed and permeabilized. An antibody that recognizes the major capsid protein VP5 was used to label capsids in the infected neurons. (B) Viruses that express a GFP capsid fusion (GFP–VP26) from the wild-type and Us9- viral genomes were used to infect all neurons in the culture for 17 h and then were fixed and permeabilized. Antibodies that recognize GFP-labeled capsids in the infected neurons. gE localization in the same fields is shown (c compared with d) and required Us9 to localize to axons. Bars: (A) 25 μm; (B) 150 μm.
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fig8: The axonal localization of two capsid proteins does not require Us9. (A) Less than 10% of the neurons were infected for 12 h with the wild-type (a) or the Us9- virus (b) and then were fixed and permeabilized. An antibody that recognizes the major capsid protein VP5 was used to label capsids in the infected neurons. (B) Viruses that express a GFP capsid fusion (GFP–VP26) from the wild-type and Us9- viral genomes were used to infect all neurons in the culture for 17 h and then were fixed and permeabilized. Antibodies that recognize GFP-labeled capsids in the infected neurons. gE localization in the same fields is shown (c compared with d) and required Us9 to localize to axons. Bars: (A) 25 μm; (B) 150 μm.

Mentions: The PRV capsid is an icosahedral structure that contains and delivers the viral genome to the nucleus of an infected cell. Early in the infection (∼4–8 h after infection), an antibody to the major capsid protein, VP5, stained the nucleus intensely with weaker staining of the cytoplasm. This observation is consistent with the initial synthesis of VP5 in the cytoplasm and subsequent transport to the nucleus where it assembles into capsids. Despite the significant localization of VP5 in the nucleus and cell body, VP5 was not detected in axons at this time (unpublished data). Approximately 8 h after infection, VP5 immunoreactivity was detected in the axons of neurons infected with the wild-type and Us9 mutants (Fig. 8 A, a and b). Wild-type levels of VP5 immunoreactivity was also found in axons of neurons infected with the Us9 missense mutants (unpublished data).


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 two capsid proteins does not require Us9. (A) Less than 10% of the neurons were infected for 12 h with the wild-type (a) or the Us9- virus (b) and then were fixed and permeabilized. An antibody that recognizes the major capsid protein VP5 was used to label capsids in the infected neurons. (B) Viruses that express a GFP capsid fusion (GFP–VP26) from the wild-type and Us9- viral genomes were used to infect all neurons in the culture for 17 h and then were fixed and permeabilized. Antibodies that recognize GFP-labeled capsids in the infected neurons. gE localization in the same fields is shown (c compared with d) and required Us9 to localize to axons. Bars: (A) 25 μm; (B) 150 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2196449&req=5

fig8: The axonal localization of two capsid proteins does not require Us9. (A) Less than 10% of the neurons were infected for 12 h with the wild-type (a) or the Us9- virus (b) and then were fixed and permeabilized. An antibody that recognizes the major capsid protein VP5 was used to label capsids in the infected neurons. (B) Viruses that express a GFP capsid fusion (GFP–VP26) from the wild-type and Us9- viral genomes were used to infect all neurons in the culture for 17 h and then were fixed and permeabilized. Antibodies that recognize GFP-labeled capsids in the infected neurons. gE localization in the same fields is shown (c compared with d) and required Us9 to localize to axons. Bars: (A) 25 μm; (B) 150 μm.
Mentions: The PRV capsid is an icosahedral structure that contains and delivers the viral genome to the nucleus of an infected cell. Early in the infection (∼4–8 h after infection), an antibody to the major capsid protein, VP5, stained the nucleus intensely with weaker staining of the cytoplasm. This observation is consistent with the initial synthesis of VP5 in the cytoplasm and subsequent transport to the nucleus where it assembles into capsids. Despite the significant localization of VP5 in the nucleus and cell body, VP5 was not detected in axons at this time (unpublished data). Approximately 8 h after infection, VP5 immunoreactivity was detected in the axons of neurons infected with the wild-type and Us9 mutants (Fig. 8 A, a and b). Wild-type levels of VP5 immunoreactivity was also found in axons of neurons infected with the Us9 missense mutants (unpublished data).

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