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Published on: June 24, 2012
Effects of monensin on morphogenesis and infectivity of Friend murine leukemia virus
Abstract:
The transport of the gp70 glycoprotein to the cell surface and concomitant release of infectious virus was inhibited by treatment of Friend murine leukemia virus-infected Eveline cells with the sodium ionophore monensin. Virus yields were reduced more than 50-fold by 10(-5) M monensin, whereas particle production was reduced by 50% in monensin-treated cells. The resulting particles failed to incorporate newly synthesized gp70 and p15(E), whereas the other structural proteins, p30, p15, p12, and p10, were incorporated into virions. However, monensin did not inhibit the incorporation into virions of preformed gp70. A reduction in the efficiency of cleavage of the PrENV glycoprotein precursor and a defect in the processing of simple endo-H-sensitive to complex endo-H-resistant oligosaccharides suggest that intracellular transport of gp70 may be blocked before its entry into the Golgi apparatus. Fewer particles were found to bud from the cell surface, but intracellular vacuoles with budding virions were detected. Ferritin labeling and pulse-chase studies suggested a cell surface origin for these vacuoles. These experiments indicate that monensin inhibits the transport of Friend murine leukemia virus glycoproteins at an early stage, with a resultant block in the assembly and release of infectious virus.
Insights
Monensin treatment blocks Friend murine leukemia virus (FMLV) infection by inhibiting the transport of viral glycoproteins to the cell surface. This disruption prevents the assembly and release of infectious FMLV particles.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Friend murine leukemia virus (FMLV) infection involves the transport of viral glycoproteins to the cell surface for virus release.
- Understanding the intracellular trafficking of viral proteins is crucial for developing antiviral strategies.
Purpose of the Study:
- To investigate the effect of the sodium ionophore monensin on FMLV glycoprotein transport and virus release.
- To elucidate the stage at which monensin interferes with FMLV assembly and maturation.
Main Methods:
- Treatment of FMLV-infected Eveline cells with monensin.
- Analysis of viral particle production and protein incorporation using biochemical assays.
- Pulse-chase studies and ferritin labeling to track glycoprotein processing and intracellular transport.
Main Results:
- Monensin significantly reduced infectious virus yields and inhibited the incorporation of newly synthesized gp70 and p15(E) into virions.
- Monensin did not affect the incorporation of pre-existing gp70 or the assembly of other structural proteins.
- Evidence suggests monensin disrupts gp70 processing and intracellular transport before the Golgi apparatus, leading to fewer particles budding from the cell surface.
Conclusions:
- Monensin inhibits FMLV glycoprotein transport at an early intracellular stage, likely before Golgi entry.
- This blockade results in defective virion assembly and a significant reduction in infectious virus release.
- Monensin serves as a valuable tool for studying the early steps of retroviral assembly and maturation.
