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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 the tegument proteins UL25 and VP22 does not require Us9. Less than 10% of the neurons in the cultures were infected for 8 h with the wild-type (A) or the Us9- virus (C) and then were fixed and permeabilized. Antibodies that recognize UL25 (A and C) revealed the subcellular localization of this tegument protein in infected neurons. In a second series of experiments, <10% of the neurons in the cultures were infected for 12 h with the wild-type (B) or the Us9- virus (D) and then were fixed and permeabilized. The neurons were labeled with antibodies that recognize VP22 (B and D). Bar, 25 μm.
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fig7: The axonal localization of the tegument proteins UL25 and VP22 does not require Us9. Less than 10% of the neurons in the cultures were infected for 8 h with the wild-type (A) or the Us9- virus (C) and then were fixed and permeabilized. Antibodies that recognize UL25 (A and C) revealed the subcellular localization of this tegument protein in infected neurons. In a second series of experiments, <10% of the neurons in the cultures were infected for 12 h with the wild-type (B) or the Us9- virus (D) and then were fixed and permeabilized. The neurons were labeled with antibodies that recognize VP22 (B and D). Bar, 25 μm.

Mentions: We first focused on the localization of tegument proteins in infected neurons. The tegument is the collection of proteins just below the virus envelope and outside the capsid of a herpes virion (Roizman and Furlong, 1974). Early in the infection for the wild-type and Us9 mutants (∼4–8 h after infection), the tegument proteins VP22 and UL25 localized most strongly to the nucleus but also were observed throughout the cell body (unpublished data). Tegument proteins could not be detected in axons during these early stages of the infection. However, ∼8 h after infection immunoreactivity for tegument proteins in the nucleus decreased with a concomitant increase in antibody staining of infected axons during wild-type and Us9- infections (Fig. 7) . Both VP22 and UL25 also localized to axons during infections with Us9 missense mutants PRV 166, 172, and 173 (unpublished data). We conclude that Us9 is not required to localize the tegument proteins VP22 and UL25 to axons. Thus, the original hypothesis that Us9 is required for localization of fully assembled virions to the axon is not likely to be correct.


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 the tegument proteins UL25 and VP22 does not require Us9. Less than 10% of the neurons in the cultures were infected for 8 h with the wild-type (A) or the Us9- virus (C) and then were fixed and permeabilized. Antibodies that recognize UL25 (A and C) revealed the subcellular localization of this tegument protein in infected neurons. In a second series of experiments, <10% of the neurons in the cultures were infected for 12 h with the wild-type (B) or the Us9- virus (D) and then were fixed and permeabilized. The neurons were labeled with antibodies that recognize VP22 (B and D). Bar, 25 μm.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2196449&req=5

fig7: The axonal localization of the tegument proteins UL25 and VP22 does not require Us9. Less than 10% of the neurons in the cultures were infected for 8 h with the wild-type (A) or the Us9- virus (C) and then were fixed and permeabilized. Antibodies that recognize UL25 (A and C) revealed the subcellular localization of this tegument protein in infected neurons. In a second series of experiments, <10% of the neurons in the cultures were infected for 12 h with the wild-type (B) or the Us9- virus (D) and then were fixed and permeabilized. The neurons were labeled with antibodies that recognize VP22 (B and D). Bar, 25 μm.
Mentions: We first focused on the localization of tegument proteins in infected neurons. The tegument is the collection of proteins just below the virus envelope and outside the capsid of a herpes virion (Roizman and Furlong, 1974). Early in the infection for the wild-type and Us9 mutants (∼4–8 h after infection), the tegument proteins VP22 and UL25 localized most strongly to the nucleus but also were observed throughout the cell body (unpublished data). Tegument proteins could not be detected in axons during these early stages of the infection. However, ∼8 h after infection immunoreactivity for tegument proteins in the nucleus decreased with a concomitant increase in antibody staining of infected axons during wild-type and Us9- infections (Fig. 7) . Both VP22 and UL25 also localized to axons during infections with Us9 missense mutants PRV 166, 172, and 173 (unpublished data). We conclude that Us9 is not required to localize the tegument proteins VP22 and UL25 to axons. Thus, the original hypothesis that Us9 is required for localization of fully assembled virions to the axon is not likely to be correct.

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