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Rapamycin and wortmannin enhance replication of a defective encephalomyocarditis virus
Y V Svitkin1, H Hahn, A C Gingras
1Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, Canada H3G 1Y6.
Abstract:
Inhibitors of the phosphatidylinositol 3-kinase (PI3 kinase)-FKBP-rapamycin-associated protein (FRAP) pathway, such as rapamycin and wortmannin, induce dephosphorylation and activation of the suppressor of cap-dependent translation, 4E-BP1. Encephalomyocarditis virus (EMCV) infection leads to activation of 4E-BP1 at the time of host translation shutoff. Consistent with these data, rapamycin mildly enhances the synthesis of viral proteins and the shutoff of host cell protein synthesis after EMCV infection. In this study, two defective EMCV strains were generated by deleting portions of the 2A coding region of an infectious cDNA clone. These deletions dramatically decreased the efficiency of viral protein synthesis and abolished the virus-induced shutoff of host translation after infection of BHK-21 cells. Both translation and processing of the P1-2A capsid precursor polypeptide are impaired by the deletions in 2A. The translation and yield of mutant viruses were increased significantly by the presence of rapamycin and wortmannin during infection. Thus, inhibition of the PI3 kinase-FRAP signaling pathway partly complements mutations in 2A protein and reverses a slow-virus phenotype.
Insights
Inhibiting the PI3 kinase-FRAP pathway with rapamycin or wortmannin aids Encephalomyocarditis virus (EMCV) replication. This pathway inhibition partially rescues EMCV strains with defective 2A proteins, reversing slow-virus phenotypes.
Area of Science:
- Virology
- Molecular Biology
- Cellular Signaling
Background:
- The phosphatidylinositol 3-kinase (PI3 kinase)-FRAP pathway regulates protein synthesis.
- Inhibitors like rapamycin activate 4E-BP1, a key translation repressor.
- Encephalomyocarditis virus (EMCV) infection triggers host translation shutoff via 4E-BP1 activation.
Purpose of the Study:
- To investigate the role of the PI3 kinase-FRAP pathway in EMCV infection.
- To examine the effect of pathway inhibition on EMCV strains with mutations in the 2A coding region.
- To determine if PI3 kinase-FRAP inhibition can rescue viral replication defects.
Main Methods:
- Generated two defective EMCV strains by deleting portions of the 2A coding region.
- Infected BHK-21 cells with wild-type and mutant EMCV strains.
- Treated infected cells with PI3 kinase-FRAP inhibitors (rapamycin, wortmannin) and assessed viral protein synthesis and host translation.
Main Results:
- Deletions in the EMCV 2A region impaired viral protein synthesis and abolished host translation shutoff.
- Treatment with rapamycin and wortmannin significantly increased translation and yield of mutant viruses.
- PI3 kinase-FRAP pathway inhibition partially complemented the 2A mutations, reversing a slow-virus phenotype.
Conclusions:
- The PI3 kinase-FRAP signaling pathway plays a significant role in EMCV replication and host translation control.
- Inhibition of this pathway can partially rescue the replication defects of EMCV strains with mutations in the 2A protein.
- Targeting the PI3 kinase-FRAP pathway offers a potential strategy to modulate EMCV infection outcomes.