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Modification of membrane permeability in poliovirus-infected HeLa cells: effect of guanidine
Abstract:
A drastic modification in permeability to monovalent ions occurred in HeLa cells infected with poliovirus, starting in the period from the third to the fourth h post-infection. The bulk of poliovirus protein synthesis took place from the third to the sixth h in cells in which the concentration of monovalent ions in the cytoplasm had changed considerably compared to uninfected cells. Under our conditions of infection (HeLa cells grown in monolayer), poliovirus translation continued beyond the eighth h. Modification of permeability to 86Rb+ ions induced by poliovirus infection was prevented by the addition of 2 mM-guanidine at the time of infection. However, when poliovirus replication was allowed to take place for 1 h before addition of guanidine, the membrane did become modified to some extent. The degree of leakiness to 86Rb+ ions increased when guanidine was added later. The blockage of membrane leakiness by early addition of guanidine was overcome by the addition of choline. The inhibition of cellular protein synthesis, which occurred early in infection or in the presence of guanidine, did not coincide with the modification of permeability to 86Rb+ ions. Viral protein synthesis was necessary in order to modify the membrane late in infection, since addition of 10(-5) M-cycloheximide during the first 2 h of infection prevented the leakiness to 86Rb+ ions observed from the fourth h after infection. Membrane potential, as measured by the lipophilic cation TPP+ (tetraphenylphosphonium), dropped from the fourth h post-infection. This change in the membrane was also prevented when viral gene expression was inhibited by the presence of guanidine.
Insights
Poliovirus infection drastically alters HeLa cell membrane permeability to ions, beginning 3-4 hours post-infection. Viral protein synthesis is essential for this membrane modification, impacting cellular function.
Area of Science:
- Virology
- Cell Biology
- Membrane Biophysics
Background:
- Poliovirus infection is known to affect host cell physiology.
- Changes in cellular ion permeability can significantly impact cell function and viability.
Purpose of the Study:
- To investigate the temporal relationship between poliovirus infection, protein synthesis, and changes in HeLa cell membrane permeability.
- To identify the viral components or processes responsible for inducing membrane alterations.
Main Methods:
- HeLa cells were infected with poliovirus, and permeability to monovalent ions (86Rb+) was measured over time.
- Viral protein synthesis was assessed, and inhibitors like guanidine and cycloheximide were used to block viral replication and protein synthesis.
- Membrane potential was measured using the lipophilic cation tetraphenylphosphonium (TPP+).
Main Results:
- Poliovirus infection induced a significant increase in HeLa cell membrane permeability to monovalent ions starting 3-4 hours post-infection.
- Viral protein synthesis, but not host cell protein synthesis, was necessary for this membrane modification.
- Inhibiting viral gene expression with guanidine early in infection prevented the permeability changes, while later addition had less effect.
- Choline could overcome the protective effect of early guanidine addition.
- A drop in membrane potential was observed concurrently with the permeability changes.
Conclusions:
- Poliovirus infection actively modifies host cell membrane permeability to monovalent ions.
- Viral protein synthesis plays a crucial role in mediating these late-stage membrane alterations.
- The observed changes in membrane permeability and potential are significant events in poliovirus-induced cytopathology.