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Alterations in monovalent cation transport in Sindbis virus-infected chick cells
Abstract:
Influx experiments using the potassium tracer 86Rb+ indicated that the activity of the Na+K+ ATPase, or sodium pump, was reduced 40-50% as a consequence of Sindbis virus infection of avian fibroblasts. The inhibition of this ouabain-sensitive, active transport system temporally correlated with a decrease in the intracellular K+ concentration and the termination of cellular protein synthesis. By contrast, the rate of influx facilitated by the furosemide-sensitive (Na+K+Cl-) cotransport system was only slightly depressed. Efflux experiments indicated that no alterations in the relative rate of nonspecific permeability or "leakage" of K+ could be detected in chick cells infected by Sindbis virus. The amount of [3H]ouabain bound to Sindbis virus-infected cells paralleled the reduction in Na+K+ ATPase activity. These binding studies revealed no difference in the number of Na+ pump sites. The Km of ouabain binding, however, increased approximately 3.5-fold in the virus-infected cells. No change in the apparent affinity of the Na+ pump for K+ could be detected, yet the Vmax for ouabain-sensitive K+ transport was decreased. These experiments suggest that a reduction in Na+K+ ATPase turnover results in the altered intracellular monovalent cation levels found in Sindbis virus-infected chick cells.
Insights
Sindbis virus infection reduces sodium-potassium adenosine triphosphatase (Na+K+ ATPase) activity in avian fibroblasts by 40-50%. This impacts intracellular potassium levels and protein synthesis, suggesting altered Na+K+ ATPase turnover is key.
Area of Science:
- Virology
- Cell Biology
- Biochemistry
Background:
- Sindbis virus infection affects cellular processes in avian fibroblasts.
- The Na+K+ ATPase (sodium pump) is crucial for maintaining intracellular ion balance.
- Understanding viral impact on ion transport is vital for cell function studies.
Purpose of the Study:
- To investigate the effect of Sindbis virus infection on Na+K+ ATPase activity in avian fibroblasts.
- To determine the impact of viral infection on intracellular potassium levels and protein synthesis.
- To elucidate the mechanism behind altered monovalent cation levels during infection.
Main Methods:
- Utilized 86Rb+ influx experiments to measure Na+K+ ATPase activity.
- Performed [3H]ouabain binding assays to assess pump site number and affinity.
- Analyzed intracellular K+ concentration and cellular protein synthesis rates.
- Conducted K+ efflux experiments to evaluate membrane permeability.
Main Results:
- Sindbis virus infection reduced Na+K+ ATPase activity by 40-50%.
- Inhibition correlated with decreased intracellular K+ and halted protein synthesis.
- Na+K+ pump site number remained unchanged, but Vmax decreased, indicating reduced turnover.
- Furosemide-sensitive cotransport and K+ leakage were minimally affected.
Conclusions:
- Sindbis virus infection impairs Na+K+ ATPase function in avian cells.
- Reduced Na+K+ ATPase turnover is responsible for altered intracellular cation levels.
- Viral infection significantly disrupts essential cellular ion transport mechanisms.