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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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Axonal localization of viral membrane proteins promoted by Us9 missense mutants correlates with degree of anterograde spread in the rodent nervous system. Neurons were infected with PRV166 (L30L31 to AA) (A–C), PRV 172 (Y49Y50 to AA) (D–F), and PRV173 (S51S53 to AA) (G–I) such that every neuron was infected for 16 h and then were fixed and permeabilized. See legend to Fig. I for a more detailed description of the Us9 mutant viruses. Infected neurons were labeled with antibodies that recognize gB (A, D, and G), gC (B, E, and H), and gE (C, F, and I). Bar, 150 μm.
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fig5: Axonal localization of viral membrane proteins promoted by Us9 missense mutants correlates with degree of anterograde spread in the rodent nervous system. Neurons were infected with PRV166 (L30L31 to AA) (A–C), PRV 172 (Y49Y50 to AA) (D–F), and PRV173 (S51S53 to AA) (G–I) such that every neuron was infected for 16 h and then were fixed and permeabilized. See legend to Fig. I for a more detailed description of the Us9 mutant viruses. Infected neurons were labeled with antibodies that recognize gB (A, D, and G), gC (B, E, and H), and gE (C, F, and I). Bar, 150 μm.

Mentions: Brideau et al. (2000b) used alanine substitution mutagenesis to define residues of Us9 required to promote anterograde viral spread in the rat visual system (see Fig. 1 for the details of these mutant viruses). These Us9 mutants (PRV 166, 172, and 173) differ in the rate and extent of anterograde spread in vivo. We infected cultured superior cervical ganglia (SCG) neurons with these viruses to determine if the axonal localization of viral membrane proteins correlated with anterograde spread in vivo. PRV166 (L30L31 to AA) spreads through the rat visual system like a wild-type virus (Brideau et al., 2000b). Fig. 4, A–C, shows the results of SCG infection with PRV166. All viral membrane proteins examined (Fig. 5 A, gB; B, gC; and C, gE) localized to the axons of infected neurons. These infections were similar to the wild-type infections (Fig. 5, A–C, compared with Fig. 3 B, a–c). PRV173 (S51S53 to AA) is defective in rate but ultimately approximates wild-type extent of anterograde spread of infection in the rat visual system (Brideau et al., 2000b). Infection of cultured neurons with PRV173 led to an intermediate phenotype: all viral membrane proteins examined did localize to the axon (Fig. 5, G–I), but the extent was reduced compared with the wild-type infection (Fig. 5, G–I, compared with A–C). PRV172 (Y49Y50 to AA) has the Us9- phenotype (restricted anterograde spread) after infection of the rat visual system (Brideau et al., 2000b). Infections of cultured neurons with this mutant were identical to Us9- virus infections; viral membrane proteins were not found in axons, and only scattered vesicles were found near the cell body (Fig. 5, D–F). These data demonstrate that Us9-mediated membrane protein localization in axons correlates well with the anterograde spread of infection in the rat visual system.


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

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

Axonal localization of viral membrane proteins promoted by Us9 missense mutants correlates with degree of anterograde spread in the rodent nervous system. Neurons were infected with PRV166 (L30L31 to AA) (A–C), PRV 172 (Y49Y50 to AA) (D–F), and PRV173 (S51S53 to AA) (G–I) such that every neuron was infected for 16 h and then were fixed and permeabilized. See legend to Fig. I for a more detailed description of the Us9 mutant viruses. Infected neurons were labeled with antibodies that recognize gB (A, D, and G), gC (B, E, and H), and gE (C, F, and I). Bar, 150 μm.
© Copyright Policy
Related In: Results  -  Collection

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

fig5: Axonal localization of viral membrane proteins promoted by Us9 missense mutants correlates with degree of anterograde spread in the rodent nervous system. Neurons were infected with PRV166 (L30L31 to AA) (A–C), PRV 172 (Y49Y50 to AA) (D–F), and PRV173 (S51S53 to AA) (G–I) such that every neuron was infected for 16 h and then were fixed and permeabilized. See legend to Fig. I for a more detailed description of the Us9 mutant viruses. Infected neurons were labeled with antibodies that recognize gB (A, D, and G), gC (B, E, and H), and gE (C, F, and I). Bar, 150 μm.
Mentions: Brideau et al. (2000b) used alanine substitution mutagenesis to define residues of Us9 required to promote anterograde viral spread in the rat visual system (see Fig. 1 for the details of these mutant viruses). These Us9 mutants (PRV 166, 172, and 173) differ in the rate and extent of anterograde spread in vivo. We infected cultured superior cervical ganglia (SCG) neurons with these viruses to determine if the axonal localization of viral membrane proteins correlated with anterograde spread in vivo. PRV166 (L30L31 to AA) spreads through the rat visual system like a wild-type virus (Brideau et al., 2000b). Fig. 4, A–C, shows the results of SCG infection with PRV166. All viral membrane proteins examined (Fig. 5 A, gB; B, gC; and C, gE) localized to the axons of infected neurons. These infections were similar to the wild-type infections (Fig. 5, A–C, compared with Fig. 3 B, a–c). PRV173 (S51S53 to AA) is defective in rate but ultimately approximates wild-type extent of anterograde spread of infection in the rat visual system (Brideau et al., 2000b). Infection of cultured neurons with PRV173 led to an intermediate phenotype: all viral membrane proteins examined did localize to the axon (Fig. 5, G–I), but the extent was reduced compared with the wild-type infection (Fig. 5, G–I, compared with A–C). PRV172 (Y49Y50 to AA) has the Us9- phenotype (restricted anterograde spread) after infection of the rat visual system (Brideau et al., 2000b). Infections of cultured neurons with this mutant were identical to Us9- virus infections; viral membrane proteins were not found in axons, and only scattered vesicles were found near the cell body (Fig. 5, D–F). These data demonstrate that Us9-mediated membrane protein localization in axons correlates well with the anterograde spread of infection in the rat visual system.

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