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Alteration of intracellular monovalent cation concentrations by a poliovirus mutant which encodes a defective 2A
1Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112.
Abstract:
Poliovirus mutant 2A-1, which encodes a defective protease 2A, fails to inhibit translation of capped mRNAs selectively. Despite the failure of 2A-1 to inactivate cap-dependent translation, a reduction in the overall rate of protein synthesis, both virus and cell-specified, does occur after 2A-1 infection. This global reduction in protein synthesis is temporally correlated with an increase in [Na+]i and a decrease in [K+]i. The extensive global shutoff of protein synthesis is not observed in 2A-1 infected cells incubated in low NaCl medium or medium containing an elevated concentration of KCl which compensate for the virally-induced alterations in intracellular monovalent cation concentrations. Furthermore, 2A-1-specified protein synthesis is only partly resistant to hypertonic NaCl media which increase [Na+]i, in contrast to protein synthesis specified by wild-type poliovirus. These results suggest that shutoff of host and viral protein synthesis during infection by poliovirus mutant 2A-1 is a consequence of the virus-induced changes in intracellular monovalent cation concentrations.
Insights
Poliovirus mutant 2A-1 infection reduces protein synthesis globally. This shutoff is linked to altered intracellular sodium and potassium levels, not defective protease activity.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Poliovirus mutant 2A-1 possesses a defective protease 2A.
- This mutant fails to selectively inhibit the translation of capped messenger RNAs (mRNAs).
- Despite this, a general decrease in protein synthesis is observed post-infection.
Purpose of the Study:
- To investigate the mechanism behind the global reduction in protein synthesis during poliovirus mutant 2A-1 infection.
- To determine the role of intracellular monovalent cation concentrations in this phenomenon.
Main Methods:
- Infection of cells with poliovirus mutant 2A-1.
- Monitoring of overall protein synthesis rates.
- Measurement of intracellular sodium ([Na+]i) and potassium ([K+]i) concentrations.
- Incubation of infected cells in modified media (low NaCl, high KCl).
- Assessment of protein synthesis resistance to hypertonic NaCl.
Main Results:
- A global shutoff of protein synthesis, affecting both viral and host proteins, occurs after 2A-1 infection.
- This shutoff correlates with increased intracellular sodium and decreased intracellular potassium.
- Altering extracellular salt concentrations to normalize intracellular cations prevents the global shutoff.
- Protein synthesis specified by 2A-1 shows partial resistance to hypertonic NaCl, unlike wild-type poliovirus.
Conclusions:
- The global shutoff of protein synthesis during poliovirus mutant 2A-1 infection is primarily caused by virus-induced alterations in intracellular monovalent cation concentrations.
- Defective protease activity is not the direct cause of the global protein synthesis shutoff.