Visna virus-induced activation of MAPK is required for virus replication and correlates with virus-induced neuropathology.
It is well accepted that viruses require access to specific intracellular environments in order to proliferate or, minimally, to secure future proliferative potential as latent reservoirs. Hence, identification of essential virus-cell interactions should both refine current models of virus replication and proffer alternative targets for therapeutic intervention. In the present study, we examined the activation states of mitogen-activated protein kinases (MAPKs), ERK-1/2, in primary cells susceptible to visna virus and report that virus infection induces and sustains activation of the ERK/MAPK pathway. Treatment of infected cells with PD98059, a specific inhibitor of the ERK/MAPK pathway, abolishes visna virus replication, as evidenced by extremely low levels of Gag protein expression and reverse transcriptase activity in culture supernatants. In addition, although visna virus-induced activation of MAPK is detectable within 15 min, early events of viral replication (i.e., reverse transcription, integration, and transcription) are largely unaffected by PD98059. Interestingly, further examination demonstrated that treatment with PD98059 results in decreased cytoplasmic expression of gag and env, but not rev, mRNA, highly suggestive of an ERK/MAPK-dependent defect in Rev function. In vivo analysis of ERK-1/2 activation in brains derived from visna virus-infected sheep demonstrates a strong correlation between ERK/MAPK activation and virus-associated encephalitis. Moreover, double-labeling experiments revealed that activation of MAPK occurs not only in cells classically infected by visna virus (i.e., macrophages and microglia), but also in astrocytes, cells not considered to be major targets of visna virus replication, suggesting that activation of the ERK/MAPK pathway may contribute to the virus-induced processes leading to neurodegenerative pathology.
Barber
Sheila A
SA
Division of Comparative Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Bruett
Linda
L
Douglass
Brian R
BR
Herbst
David S
DS
Zink
M Christine
MC
Clements
Janice E
JE
D000818:Animals; D001253:Astrocytes / Q000201:enzymology / Q000821:virology; D001921:Brain / Q000201:enzymology / Q000473:pathology / Q000821:virology; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D018792:Encephalitis, Viral / Q000201:enzymology / Q000473:pathology / Q000821:virology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015686:Gene Products, env / Q000096:biosynthesis / Q000235:genetics; D015683:Gene Products, gag / Q000096:biosynthesis / Q000235:genetics; D015694:Gene Products, rev / Q000096:biosynthesis / Q000235:genetics; D006041:Goats / Q000821:virology; D007150:Immunohistochemistry; D048369:MAP Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008264:Macrophages / Q000201:enzymology / Q000821:virology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D012756:Sheep / Q000821:virology; D014774:Virulence; D014779:Virus Replication / Q000187:drug effects; D014790:Visna-maedi virus / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*
D002070:Butadienes; D004791:Enzyme Inhibitors; D005419:Flavonoids; D015686:Gene Products, env; D015683:Gene Products, gag; D015694:Gene Products, rev; D009570:Nitriles; D012367:RNA, Viral; C113580:U 0126; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one